Characterize Eruptive Processes at Yucca Mountain, Nevada REV 02, ICN 00

ANL-MGR-GS-000002
  
September 2004 

 

1. PURPOSE 
The purpose of this scientific analysis report, Characterize Eruptive Processes at Yucca 
Mountain, Nevada, is to present information about natural volcanic systems and the parameters 
that can be used to model their behavior. This information is used to develop parameter-value 
distributions appropriate for analysis of the consequences of volcanic eruptions through a 
repository at Yucca Mountain. 
This scientific analysis report provides information to four other reports: Number of Waste 
Packages Hit by Igneous Intrusion, (BSC 2004 [DIRS 170001]); Atmospheric Dispersal and 
Deposition of Tephra from Potential Volcanic Eruption at Yucca Mountain, Nevada (BSC 2004 
[DIRS 170026]); Dike/Drift Interactions (BSC 2004 [DIRS 170028]); Development of 
Earthquake Ground Motion Input for Preclosure Seismic Design and Postclosure Performance 
Assessment of a Geologic Repository at Yucca Mountain, NV (BSC 2004 [DIRS 1700271], 
Section 6.5). 
This report is organized into seven major sections. This section addresses the purpose of this 
document. Section 2 addresses quality assurance, Section 3 the use of software, Section 4 
identifies the requirements that constrain this work, and Section 5 lists assumptions and their 
rationale. Section 6 presents the details of the scientific analysis and Section 7 summarizes the 
conclusions reached. 
Section 6 lists the parameters and values used to model processes of shallow subsurface and 
surface volcanic activity relevant to a repository at Yucca Mountain. Section 6.1 discusses the 
scientific approach, background, and data sources. Section 6.2 lists the features, events, and 
processes (FEPs) supported by the analyses. Section 6.3 discusses the analyses of the eruptive 
processes, which include: 
 
Geometry of volcanic feeder systems (conduits and dikes), which are of primary 
importance in modeling how much area and volume of the repository might be affected 
by an intrusion of a feeder system. 
 
Estimates of the maximum magnitude of dike-induced earthquakes. 
 
Description of the physical and chemical properties of the basaltic magma, which 
influence both eruptive styles and mechanisms for interaction with radioactive waste 
packages. 
 
Ascent velocity of magma at depth, onset of bubble nucleation and growth in the rising 
magmas, magma fragmentation, and velocity of the resulting gas-particle mixture. 
1 The six-digit numerical identifier in brackets next to each reference is the Yucca Mountain Projects (YMP) 
Document Input Reference System [DIRS] number, which is provided to assist the reader in locating a specific 
reference in the DIRS database. Within the reference list (Section 8), multiple sources by the same author and date 
(e.g., BSC 2002) are sorted alphabetically by title. 

 
Eruption volume, duration of eruptions, power output, and mass discharge rates. 
 
Results from field and laboratory studies on the natural processes of redistribution of ash 
after deposition of a basaltic tephra sheet from a hypothetical volcanic eruption near the 
site of the Yucca Mountain repository. Ash redistribution, if incorporating radioactive 
waste particles brought up during eruption directly through a repository, might be a 
contributor to dose to a potential receptor in areas removed from the initial ash 
deposition area. 
Appendix A establishes the quality of the data used in this analysis, including the qualification of 
data obtained from external sources. 
Appendix B identifies the Yucca Mountain Review Plan, Final Report (YMRP) (NRC 2003 
[DIRS 163274]) acceptance criteria applicable to this work, discusses how the criteria are 
addressed, and cites the relevant locations in this document for this information. Appendix B 
also discusses the Igneous Activity Key Technical Issue related to tephra (ash) redistribution 
requested by the U.S. Nuclear Regulatory Commission (NRC). 
Appendix C provides results of both the field work and laboratory analyses and the interpretation 
of eruptive scenarios for the Lathrop Wells volcano, which is a young cinder cone/tephra 
sheet/lava flow complex 18 km south of the repository site. Emphasis on the Lathrop Wells 
volcano is engendered by its young age and the cones excellent state of preservation, combined 
with active quarrying operations that expose some of the cone interiors. Additionally, the Final 
Report of the Igneous Activity Peer Review Panel (Detournay et al. 2003 [DIRS 169660], 
pp. 12-13) concurs with the earlier conclusion in Perry et al. (1998 [DIRS 144335], p. vi) that the 
younger post-Timber Mountain caldera basalts (less than ~5 million years [Ma] old) provide the 
critical basis for forecasting future possible magmatic activity in the Yucca Mountain region 
(YMR). The Lathrop Wells volcano retains many volcanic products and features of a young vent 
and, therefore, provides the best analog of a potential eruptive center. 

2. QUALITY ASSURANCE 
This work contributes to the analysis of data used to support performance assessment and is 
classified as importance to waste isolation, as defined in AP-2.22Q, Classification Criteria and 
Maintenance of the Monitored Geologic Repository Q-List. Consequently, importance to waste 
isolation aspects of this work are controlled via approved procedures. This analysis does not 
investigate potential impacts on any specific items or barriers, as listed on the Q-List (BSC 2004 
[DIRS 168361]). 
This report was prepared under procedure AP-SIII.9Q, Scientific Analyses. The revision to this 
scientific analysis report is conducted in accordance with the Technical Work Plan: Igneous 
Activity Assessment for Disruptive Events (BSC 2004 [DIRS 171403], Sections 1.2.3 and 2.2.2). 
The following deviations have been made from the work scope as described in the technical 
work plan: 
 
YMRP Acceptance Criteria listed in Table 4-3 and described in Appendix B do not 
address model uncertainties or model abstraction outputs contained in other reports. 
This report provides output model reports that support the TSPA-LA model. 
 
This report contains an update of FEPs from those listed in the technical work plan. The 
FEPs discussed in Section 6.2 of this report are the current FEPs being considered. 
In addition, the electronic management of data was accomplished in accordance with the controls 
specified in the aforementioned Technical Work Plan. Unqualified data are qualified within this 
report in accordance with AP-SIII.9Q (see Appendix A). 

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3. USE OF SOFTWARE 
Standard, built-in functions of Microsoft Excel X, Service Release 1, for the Macintosh and 
personal computers were used to calculate parameters. This software is exempt from the 
requirements of LP-SI.11Q-BSC, Software Management. All other calculations were done using 
a hand-held calculator. The output was visually checked for correctness, and results were 
spot-checked for accuracy and reasonableness using an electronic calculator. 
Standard functions of Microsoft Excel X for Macintosh running Mac OS X (V 10.2) were used 
to obtain averages, medians, modes, and standard deviations as listed in this report. 
Input for these standard functions consisted of subsets of sieve-fraction weight percent (wt%), 
microscopic grain counts for pyroclast types in samples, and counts of lithic clasts quantities and 
sizes as measured in outcrops at Lathrop Wells volcano. Outputs consisted of averages and 
medians along with the associated standard deviations and modes, depending on the type of 
statistical function required for sufficient description of the data distribution. 

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4. INPUTS 
4.1 DATA, PARAMETERS, AND OTHER INPUTS 
In this scientific analysis report, all available scientific literature is reviewed and from this data 
parameter values, distributions, and theoretical concepts are developed. This information is used 
to recommend parameter distributions for models and analyses that support the YMP total 
system performance assessment (TSPA) calculations. Parameter distributions are based on field 
data and data available in published sources. In cases where there are insufficient published 
data, parameter distributions are recommended that conservatively capture the expected range 
with consideration of the authors judgment, external reviews, and expert elicitations. Data 
derived from field observations, sampling, and laboratory measurements are used to infer the 
volcanic history of Lathrop Wells volcano, including volume calculations for effusive and 
explosive products. Brief descriptions of the data used as input are listed in Table 4-1. Data 
from external sources that are used as direct input are listed in Table 4-2. Data from these 
sources have been justified per the requirements of AP-SIII.9Q, and are considered to be 
qualified for intended use. These justifications are documented in Appendix A. Qualification 
status of the input data is indicated in the DIRS database. 
Table 4-1. Data Used as Inputs for Calculations in This Scientific Analysis Report 
Data Used Application of Data 
Data Sources (Data 
Tracking Number) 
Location in This 
Report 
Dike length distribution for Calculation of maximum LA0009FP831811.001 Section 6.3.1.3 
intersection with the magnitudes of dike-induced [DIRS 164712] 
repository earthquakes 
45 chemical analyses of Calculation of mean chemical LA000000000099.002 Section 6.3.2.1 
products from Lathrop composition of Lathrop Wells [DIRS 147725] 
Wells volcano products 
66 137Cs analyses for Calculation of erosion rate for LA0308CH831811.002 Section 6.3.4.2.3 
Fortymile Wash alluvial ash redistribution analyses in a [DIRS 164853] 
fan in Amargosa Valley YMR drainage alluvial fan 
Tephra thickness data for Calculation of the eruption LA0305DK831811.001 Section C4 
Lathrop Wells volumes of YMR volcanoes [DIRS 164026] 

Table 4-2. External Source Data Used as Inputs for Calculations in This Scientific Analysis Report 
Data Sources 
Data Used Application of Data 
(Reference 
[DIRS Number]) 
Location in This 
Report 
Conduit diameter Calculation of conduit diameter 
distribution 
Doubik and Hill (1999 
[DIRS 115338], pp. 5961); 
Keating and 
Valentine (1998 
[DIRS 111236], p. 41) 
Section 6.3.1.1 
88 analyses for the Calculation of percent Symonds et al. (1994 Section 6.3.2.3, 6.3.3.2 
composition of gases concentration of volcanic gases [DIRS 101029], 
Tables 3-5) 
Equation relating water Calculation of saturation Jaupart and Tait (1990 Section 6.3.2.4 
saturation to pressure in pressures, exsolution depths, [DIRS 118292], p. 219) 
basaltic magmas and volume fraction of gas in 
magma as a function of 
pressure 
Equation to estimate Calculation of temperatures of Sisson and Grove (1993 Section 6.3.2.4 
multiple phase-saturation magmas forming potential YMR [DIRS 122564], p. 178) 
(liquidus) temperatures in volcanoes 
magma 
Method for calculating Calculation of viscosities of Shaw (1972 Section 6.3.2.4 
magma viscosity as a magmas forming potential YMR [DIRS 126270], pp. 873function 
of composition volcanoes 878) 
Equation and H2O data to Calculation of magma density Lange and Carmichael Section 6.3.2.4 
calculate density as for potential YMR volcanoes (1990 [DIRS 147767] 
function of composition, Table 3); Ochs and 
pressure and temperature Lange (1999 
[DIRS 144330], 
pp. 1314-1315, Eq. 2) 
Theoretical equations and 
results describing the 
ascent of basaltic 
magmas 
Equation for velocity of magma 
below exsolution depths, 
relationship between magma-
gas mixture density and water 
mass fraction, and plots of 
Wilson and Head (1981 
[DIRS 101034], 
pp. 2974, 2983, 
Eqs. 16-18; Figure 7) 
Section 6.3.3.1, 
Equations 6-3 and 6-6, 
and Figures 6-4 and 
6-5 
eruption velocity as a function of 
initial water content of magmas 
Dimensions of NE Little Calculation of eruption volume Stamatakos et al (1997 Section 6.3.3.4 
Cone for YMR volcanoes [DIRS 138819], pp. 322, 
328) 
Duration for the formation Calculation of duration range for Wood (1980 Section 6.3.3.4 
of an entire volcano the formation of a volcano [DIRS 116536], p. 402, 
Figure 10) 
Duration of explosive Calculation of the duration Jarzemba (1997 Section 6.3.3.4 
eruptive phases at Cerro range for explosive eruptive [DIRS 100460], p. 136) 
Negro, Hekla, Tolbachik, phases 
Parcutin, and Heimaey 
volcanoes 
Estimated bulk density of Recommendations for treatment Blong (1984 Section 6.3.3.6.3 
pyroclastic fallout deposits of bulk deposit density in [DIRS 144263], p. 208); 
consequence analyses Sparks et al. (1997 
[DIRS 144352], p. 366) 

4.2 CRITERIA 
This scientific analysis report provides technical basis for parameters that will be used by the 
License Application (LA) related to the effects of a volcanic eruption through the YMR. The 
report provides discussion and summaries of uncertainties associated with inputs to the analysis 
and outputs from the analysis. The information and data in this report are based largely on 
literature values and simple calculations as described in Section 6. Other information that 
indirectly relates to assessment of a potential igneous disruption of the repository and 
post-eruption processes, such as descriptions of the Lathrop Wells volcano and redistribution of 
ash, is based on field studies and supporting laboratory analyses. The following text identifies 
information in this report that addresses the Yucca Mountain Review Plan, Final Report 
(NRC 2003 [DIRS 163274]) acceptance criteria and/or review methods related to descriptions of 
site characterization work, volcanic disruption of waste packages, airborne transport of 
radionuclides, and redistribution of radionuclides in soil. 
The general requirements to be satisfied by TSPA are listed in 10 CFR 63.114 [DIRS 156605] 
(Requirements for Performance Assessment). Technical requirements to be satisfied by TSPA 
are identified in the Yucca Mountain Projects Requirements Document (Canori and Leitner 2003 
[DIRS 166275]). The acceptance criteria that will be used by the NRC to determine whether the 
technical requirements have been met are identified in the YMRP (NRC 2003 [DIRS 163274]). 
The pertinent requirements and YMRP acceptance criteria addressed by this scientific analysis 
report are listed in Table 4-3, and described in greater detail in Appendix B. 
Table 4-3. Criteria Applicable to This Analysis Report 
Requirement 
Numbera Requirement Titlea 10 CFR 63 Link YMRP Acceptance Criteriab 
PRD-002/T-004 Content of Application 10 CFR 63.21(b)(5) 1.5.3, criteria 1 & 2 
PRD-002/T-015 Requirements for 
Performance Assessment 
10 CFR 63.114 
(a)-(c) and (e)-(g) 2.2.1.3.10.3, criteria 1 to 3 
PRD-002/T-004 Content of Application 10 CFR 63.21(c)(1), 
(9), (15), and (19) 2.2.1.3.11.3, criteria 1 to 3 
PRD-002/T-004 Content of Application 10 CFR 63.21(c)(1), 
(9), (15), and (19) 2.2.1.3.13.3, criteria 1 to 3 
a 
bFrom Canori and Leitner (2003 [DIRS 166275]) 
From Yucca Mountain Review Plan, Final Report (NRC 2003 [DIRS 163274]) 
4.3 CODES, STANDARDS, AND REGULATIONS 
No specific formally established codes, standards, or regulations have been identified as applying 
to this analysis and modeling activity. 

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5. ASSUMPTIONS 
Analyses of eruptive processes are primarily based on the assumption that a plausible future 
volcanic eruption would be of the same character as Quaternary basaltic eruptions in the YMR. 
Another overall assumption is that the event probabilities established in the scientific analysis 
report under current revision Characterize Framework for Igneous Activity at Yucca Mountain, 
Nevada (BSC 2004 [DIRS 169989]), pertain to the potential formation of a new volcano that 
would be accompanied by one or more dikes in the subsurface and some combination of scoria 
cone, spatter cones, ash and lapilli fall, and lava flows on the surface. Eruptive styles and 
magmatic composition recorded at the Lathrop Wells volcano, the most recent in the YMR, are 
emphasized. The following assumptions fall into two types: assumptions that establish general 
equivalency of data (such as gas compositions), and assumptions that support a reasonable 
technical approach to issue resolution. Assumptions specific to each component of this report 
are described in the main text of Section 6 and summarized below with corresponding section 
numbers. 
1. Assumption: The most likely future eruptive event will have a magmatic chemical 
composition that is adequately represented by the mean composition of products of the 
Lathrop Wells volcano. This assumption is discussed in Section 6.3.2.1. In addition, 
eruptive processes associated with a potential future eruption at Yucca Mountain will 
be similar to those recorded in the deposits of the Lathrop Wells volcano. 
Rationale: The Lathrop Wells volcano has geochemical, petrologic, and 
volcanological characteristics that are consistent with other Quaternary volcanoes of 
the YMR and provides the most detailed information on magma chemistry and 
eruptive processes because of its relatively young age and better preservation of 
deposits. 
Need for confirmation: Confirmation is not required because additional data should 
negligibly alter the mean composition values 
2. Assumption: The most likely future eruptive event will exhibit eruptive styles that are 
adequately represented by nearby Quaternary basaltic volcanic cones and, specifically, 
by the Lathrop Wells volcano. This assumption is discussed in Section 1 and forms 
the technical basis for the study of physical volcanology of Lathrop Wells volcano 
presented in Appendix C. 
Rationale: Nearby Quaternary-age volcanoes are the best analog for future eruptive 
styles in the YMR because they are representative of the same persistent eruption 
style, tectonic setting, magma type, and erupted volume. Also, the Lathrop Wells 
volcano, at about 80,000 years old, is the youngest eruptive cone in the YMR and has 
the best-preserved geologic record of its eruptive processes. 
Need for confirmation: Confirmation is not needed because this assumption is based 
on the best available approach. 

3. Assumption: Pressure in dikes and conduits during eruption is equal to lithostatic 
pressure. This assumption is discussed in Section 6.3.3.2. 
Rationale: Actual pressure is a complex function of the velocity, density, and 
composition of the magma as it rises, and of the strength of wall rocks. Because a 
general model for these effects (including the uncertainty associated with wall rock 
properties at depth) does not exist, lithostatic pressure is used as a first-order 
approximation. In addition, significant deviations from lithostatic pressure might 
result in partial failure of the dike or conduit walls such that the size of these features 
might adjust to maintain a fluid pressure that is near to lithostatic pressure. 
Need for confirmation: Confirmation is not needed because this assumption is based 
on the best available approach. 
4. Assumption: Rising magma, composed of melt liquid and volatile gases and not 
undergoing fragmentation, can be considered homogeneous and characterized by 
equilibrium between melt and exsolved volatiles. This assumption is discussed in 
Section 6.3.3.2. 
Rationale: Actual ascent velocities of melt and bubbles are different (Wilson and 
Head, 1981 [DIRS 101034]). However, basaltic lava-fountains and violent 
Strombolian eruptions typically generate very small bubbles (0.1-1 mm diameter) 
whose rise velocity through the melt (10-7-10-5 m/s) is orders of magnitude less than 
the ascent velocity of the mixture (10-1-102 m/s; Mastin and Ghiorso 2000 
[DIRS 170144], p. 4). In such cases, the homogeneous assumption is appropriate. 
During normal Strombolian activity, on the other hand, magma-ascent rates are low 
(<~.01 m/s for unvesiculated magma) and large bubbles (>1 cm) can grow by gas 
diffusion and coalescence (Mastin and Ghiorso 2000 [DIRS 170144], p. 4). 
Need for confirmation: Confirmation is not needed because this assumption is based 
on the best available approach, as discussed in Section 6.3.3.2. 

6. SCIENTIFIC ANALYSIS 
6.1 INTRODUCTION 
6.1.1 Scientific Approach and Technical Methods 
This analysis report is a compilation of values from literature sources and from field and 
laboratory studies of properties of magmatic/volcanic materials and processes. Magma 
properties (e.g., water content, viscosity) and characteristics of buoyant rise (e.g., velocity, 
volatile exsolution) that best reflect the basaltic magma characteristics of the YMR are taken 
from the literature, whereas the basaltic composition that might define the potential future 
volcanic event is derived from multiple chemical analyses from the nearby Lathrop Wells 
volcano. Because of its relative youth, exposure, composition, and position in the sequence of 
basaltic eruptive events in the YMR, the Quaternary Lathrop Wells volcano is an appropriate 
example of the type of eruptive event that could disrupt the proposed repository at Yucca 
Mountain. Eruptive processes are derived from observations and literature on eruptions of 
similar compositional type and from the eruptive sequences deduced from investigation of tephra 
deposited at the Lathrop Wells volcano. The character of redistribution of ash from a potential 
volcanic eruption at Yucca Mountain is derived from geomorphological principles applied to the 
YMR and laboratory analyses of sediment and ash samples from drainage systems surrounding 
and leading away from the Lathrop Wells volcano. Recommended values or distributions of 
values for key parameters, the methods for determining the values (e.g., literature research, field 
studies, or assumptions), intended uses and uncertainties associated with the parameters, are 
provided throughout Section 6.3. These are also summarized in Section 7.1. 
6.1.2 Units of Measurement 
Measurement units employed in this analysis follow System Internationale standards except 
where English units are also used to help convey the scales of distance or volume. 
6.1.3 Definition of Terms 
6.1.3.1 Shallow Intrusive Features 
DikeA tabular, subplanar, magma-filled crack that cuts across local geologic contacts such as 
bedding planes. Length and width (or thickness) describe the size of a dike, although minor 
variations in width and strike direction can be expected along the length of any one dike. 
Dike swarmA group of one or more dikes resulting from the same magmatic event. The 
distance between two dikes is defined as dike spacing. 
ConduitA cylindrical or subcylindrical, roughly vertically oriented, feature through which 
magma flows upward to a volcanic vent. The size of a conduit is described by its diameter. 
6.1.3.2 Eruption Mechanisms 
PyroclasticAny eruption involving explosions and ejection of fragmented magma. Such 
eruptions might be driven by exsolution and expansion of magmatic volatiles (as in Strombolian 

and violent Strombolian eruptions described below) or by explosive interaction between rising 
magma and groundwater or surface waters (hydrovolcanic eruptions, described below). 
Individual fragments produced by pyroclastic eruptions are termed pyroclasts (also simply as 
clasts in this report), and accumulations of such fragments are termed pyroclastic deposits. 
StrombolianEruptions typified by short (seconds to tens of seconds) bursts of gas and fluidal 
magma clots or fragments from a volcanic vent. Strombolian eruptions are driven by rise of 
large bubbles through a magma column and bursting of those bubbles when they reach the top of 
the column. Pyroclasts produced in these bursts are relatively coarse grained and follow ballistic 
paths to accumulate around the vent. Because of their relatively short residence time in the air, 
larger clasts do not cool very much before deposition and may weld to other clasts to form 
welded horizons (also referred to as agglutinate). 
Violent StrombolianEruptions typified by sustained (tens of minutes to days) jets of gas and 
magma clots and fragments. Coarse clasts might follow ballistic paths, but most clasts are more 
finely fragmented (to lapilli and smaller sizes, see below) and are carried to heights of several 
hundred meters to a few kilometers as the eruptive jet becomes buoyant. Clasts tend to be cool 
and brittle upon deposition and fall out of the buoyant plume (eruption column) as it is 
transported by atmospheric winds. 
EffusiveEruptions that produce lava flows by the eruption of unfragmented magma. Note that 
eruption of lavas can occur simultaneously with Strombolian or violent Strombolian eruptions. 
HydrovolcanicExplosive eruption driven by the interaction of rising magma with groundwater 
or surface waters. Eruption products tend to be relatively fine-grained and to be relatively rich in 
wall rock (lithic) fragments. 
6.1.3.3 Eruptive Deposits and Features 
Cone (or scoria cone or cinder cone)A thick accumulation of pyroclastic deposits immediately 
surrounding a vent, usually forming a hill with the shape of an inverted cone that is truncated at 
the top by a crater. The slope of an un-eroded scoria cone is close to the angle of repose of the 
deposits that make up the cone (typically 30 to 35 degrees). 
Lava (or lava flow)Cooled flows of unfragmented magma. At Quaternary basaltic centers of 
the YMR, lavas are typically a few meters to about 30 m thick, have levees along the sides and 
terminal ends of individual flows, and have brecciated tops and bottoms with massive, solid 
interiors. They typically extend up to about 1 km from their source vents (either main craters or 
flank vents on the cones). 
Welded scoria (agglutinate)Indurated deposits of mainly lapilli and bombs (see below) that 
were sufficiently hot and plastic that they stuck together upon deposition. As accumulation rate 
and clast temperature increase during an eruption, degree of welding may increase up to an 
extreme case where clasts completely coalesce with each other and subsequently flow as a lava 
flow. 

Tephra fall deposit (fallout deposit, tephra sheet, tephra blanket)Well-sorted deposit of 
pyroclasts that blankets the terrain, gradually thinning with increasing distance from the source 
vent. 
Pyroclastic surge depositModerately sorted deposit of pyroclasts (typically ash to lapilli in 
size, see below) with evidence of deposition from a laterally-flowing density current (e.g., ripple 
marks, dune forms). 
6.1.3.4 Pyroclast Characteristics 
Bombs and Blocks (larger than 64 mm)A volcanic bomb is a pyroclast larger than 
64 millimeters (mm) in diameter that was ejected while viscous [partly or completely fluid] 
and shaped while in flight (Jackson 1997 [DIRS 109119], p. 75). Bombs are ballistically 
ejected from the crater and typically land around the vent, eventually accumulating to form a 
scoria cone. Depending upon the gas content, magma composition, and viscosity, basaltic 
bombs form a variety of shapes from spindles to cowpies that were deformed on impact with 
the ground surface. Bombs range in size from 64 mm to as much as several meters. Most are 
finely crystalline, with the quench-crystal, diktytaxitic textures (finely crystalline phases 
separated by open space and/or glass) found in most scoria of all clast sizes. Similarly, a 
volcanic block is a pyroclast larger than 64 mm in diameter but angular in shape, having been 
ejected in a solid state. Blocks also can contribute to formation of a scoria cone. 
Lapilli (2-64 mm) and ash (< 2 mm)Ash and lapilli are separated for the purpose of grain size 
analysis and characterization, but have the same variety of particle types: 
 
Sideromelane dropletsClear brown basaltic glass is usually found as a product of 
energetic lava fountains where exsolving gases are released to form a spray of droplets 
and bombs ranging in size from only a few micrometers (m) to decimeters. Many 
sideromelane pyroclasts are highly vesicular with low bulk densities. These are 
common in Hawaiian eruptions, but are also components in Strombolian eruptions; the 
main difference is the Strombolian sideromelane clasts may have been more viscous 
when ejected as reflected in the pyroclast shapes. Pyroclasts are smooth-skinned, light 
brown, and have vesicularities ranging from 20 to 70 percent (Heiken and Wohletz 1985 
[DIRS 106122], pp. 6, 34-41). Variations in pyroclast colors depend upon the absence 
or presence of phenocrysts and/or finely crystalline phases. There are gradations 
between sideromelane and tachylite (finely crystalline) pyroclasts and some grains can 
exhibit both textures. 
 
Tachylite pyroclastsFinely crystalline, diktytaxitic textures are characteristic of most 
scoria bombs and ash from Strombolian eruptions. The quench crystal textures 
correlate with a slight increase in cooling times, perhaps caused by the clogging of the 
vent during slumping of talus into the crater or by decreased eruption rates (Heiken 1978 
[DIRS 162817], Table 5). 
In the field, tachylite bombs, scoria, and ash appear black (or red if oxidized). In 
transmitted light, a thin section of scoria also appears more or less opaque. In polished 
thin sections and when viewed with a scanning electron microscope at high enough 

magnification, tachylite pyroclasts have well-developed pyroxene and plagioclase laths 
on the order of a few micrometers to a few tens of micrometers wide, which are 
surrounded by dendritic growths of 0.2 to 2 m wide pyroxene and Fe-Ti oxides. There 
are traces of glass between the dendritic phases. 
 
Glassy tachylite pyroclastsTephra from the Lathrop Wells volcano contain an 
unusual pyroclast type in which the vesicles are lined with glass, but the bulk of the 
grain has a diktytaxitic texture. These glass linings show deformation by growth of 
quench crystals beneath the linings. 
 
PhenocrystsMost tephra from Strombolian eruptions contain phenocrysts, either whole 
or broken, that were separated during the fragmentation processes in the vent; some have 
thin glass coatings. 
 
Lithic clastsOf special importance to interpreting subsurface processes during 
explosive eruptions are lithic clasts derived from magma flow in the dike or conduit 
formation due to the interaction between rising magma and wall rocks. Information can 
be derived concerning energies related to fragmentation and magma/ground water 
interactions if the stratigraphy of the rock sequence underlying the volcano is known. 
Lithic clasts vary widely in size and shape, ranging from large angular blocks to 
individual sand grains. 
6.1.3.5 Grain Size Limits and Terms for Pyroclastic Rocks 
In addition to grain size of individual pyroclasts, grain size distribution for a pyroclastic deposit 
is commonly expressed in terms of the median clast diameter (Md) and the graphic standard 
deviation (or sorting) parameter sf, as described below (see Heiken and Wohletz 1985 
[DIRS 106122], pp. 5-6, 18). 
well sorted: sf < 1f 
moderately sorted: sf = 1f to 2f 
poorly sorted: sf > 2f 
where: sf=(f84 -f16)/2. f84 is the 84th percentile grain size and f16 is the 
16th percentile grain size expressed in f units. Phi (f) scale is a 
logarithmic transformation of the ratio of a grain diameter (in mm) 
to a standard grain diameter of 1 mm: f = - log2d, where d is the 
particle diameter in mm. 
6.2 FEATURES, EVENTS, AND PROCESSES 
The development of a comprehensive list of FEPs potentially relevant to post-closure 
performance of the Yucca Mountain repository is an ongoing, iterative process based on 
site-specific information, design, and regulations. Table 6-1 provides a list of igneous-related 
FEPs (DTN: MO0407SEPFEPLA.000 [DIRS 170760]) that are included in the TSPA-License 

Application (TSPA-LA) through the use of the results of the calculations described in this 
document. Details of the inclusion or exclusion of disruptive events FEPs are discussed in 
Features, Events, and Processes: Disruptive Events (BSC, 2004 [DIRS 170017] Sections 
6.2.1.7; 6.2.2.2; 6.2.2.3; 6.2.2.6; 6.2.2.7; 6.2.2.8). 
For the igneous eruptive scenario, the TSPA-LA assumes that a hypothetical dike propagates 
upward, intersects the repository, provides a source for magma to enter the repository drifts, and 
magma and ash, potentially with entrained waste, are released to the surface via an eruptive 
conduit. The FEPs listed in Table 6-1 are part of the conceptual basis for such a scenario. 
However, this report does not provide a direct basis for the inclusion in TSPA-LA of the FEPs 
listed in Table 6-1, with the exception of parameters developed to address ash redistribution. 
This report provides supporting analyses to help constrain the potential consequences of the 
listed FEPs. As such, a partial treatment of the included FEPs is provided herein, and the results 
of this analysis report and listed FEPs are considered to be implicitly included in the TSPA-LA. 
It has been determined that the Technical Work Plan: Igneous Activity Assessment for Disruptive 
Events (BSC 2004 [DIRS 171403], Table 5) does not reflect the current FEPs applicable to this 
analysis report. The current FEPs that are applicable to this report are listed in Table 6-1. 
Table 6-1. Disruptive Events Included FEPs for This Scientific Analysis Report 
FEP Number FEP Name Relevant Section(s) 
1.2.03.03.0A Seismicity associated with igneous activity 6.3.1.3 
1.2.04.03.0A Igneous intrusion into repository 6.3.1.1; 6.3.1.2; 6.3.2.1; 6.3.2.3; 
6.2.3.4; 6.3.3.1; 6.3.3.2 
1.2.04.04.0A Igneous intrusion interacts with EBS components 6.3.2.1; 6.3.2.2; 6.3.2.3; 6.3.2.4; 
6.3.3.1; 6.3.3.2; 6.3.3.3; 6.3.3.5 
1.2.04.06.0A Eruptive conduit to surface intersects repository 6.3.1.1; 6.3.1.2; 6.3.2.1; 6.3.2.2; 
6.3.2.3; 6.3.2.4; 6.3.3.1; 6.3.3.4 
1.2.04.07.0A Ashfall 6.3.3.4; 6.3.3.6 
1.2.04.07.0C Ash redistribution via soil and sediment transport 6.3.4 
Source: DTN: MO0407SEPFEPLA.000 [DIRS 170760] 
EBS = engineered barrier system 
6.3 ERUPTIVE PROCESSES ANALYSIS 
There are several characteristics of igneous activity that need to be constrained in order to predict 
potential consequences of a volcanic event were one to occur at Yucca Mountain. These are: 
 
Geometry of shallow intrusive features such as dikes and conduits 
 
Maximum magnitudes of dike-induced earthquakes 
 
Properties (e.g., composition, density, viscosity, temperature) of magmas that might 
interact with repository structures and materials 
 
Dynamic processes associated with magma ascent at shallow depths and subsequent 
eruption 

 
Duration of igneous processes and volumes of igneous material involved in those 
processes 
 
Emplacement and characteristics of eruptive products 
 
Potential redistribution of eruptive products by post-eruption surficial processes. 
This report provides information on all of these characteristics and processes based upon a 
combination of theory and data from volcanic features in the YMR that are analogous to a 
potential volcanic event at Yucca Mountain during the next 10,000 years. In some cases, 
information is used from volcanoes outside the YMR if they provide insight and are 
appropriately analogous to a potential Yucca Mountain event. 
Particular emphasis is given to the Lathrop Wells volcano. This volcano is located about 20 km 
south of the proposed Yucca Mountain repository site. It is the youngest volcano in the region 
(~80,000 years; Heizler et al. 1999 [DIRS 107255]) and, therefore, its deposits have been least 
modified by surficial processes and preserve the best record of eruptive processes. In addition, 
quarry operations have produced excellent exposures of the main cone, allowing combined 
observations of both distant and proximal deposits. Specific aspects of the Lathrop Wells 
volcano are described in sections below, and detailed field descriptions of deposits and inferred 
eruptive processes at this volcano are provided in Appendix C. It is inferred that a volcano that 
might form at Yucca Mountain in the next few tens of thousands of years will exhibit similar 
eruptive processes to those recorded in the deposits at Lathrop Wells volcano. 
6.3.1 Characteristics of Eruptive Conduits, Dike Widths, Dike Swarms, and 
Dike-Induced Earthquakes 
6.3.1.1 Eruptive Conduits and Dike Widths 
Most observed basaltic eruptions begin as fissure eruptions, discharging magma where a dike 
intersects the Earths surface, and they rapidly become focused into roughly cylindrical conduit 
eruptions. Some eruptions, such as Parcutin in Mexico (Luhr and Simkin 1993 [DIRS 144310], 
p. 62), originated from single-point sources, although the vent was located on a long fissure that 
opened just before eruption began. The fissure is likely the surface expression of the tip of an 
ascending dike that fed the eruptions. Because of the effect of the conduit diameter and the 
depth (to which a conduit extends before merging into a simple feeder dike) on the number of 
waste packages disrupted by a potential eruption at Yucca Mountain, it is important to constrain 
both these variables. 
The best data for these parameters would come from a study of basaltic volcanic necks exposed 
by erosion where direct measurements could be made of conduit diameter and variation with 
depth. However, such data are lacking. Although many volcanic necks have been mapped as 
part of regional studies, they were not measured in detail, at least for the range of compositions 
and eruptive volumes of interest to the YMP. Another source of information is abundance of 
wall-rock xenoliths in analog volcanoes. Both sources are used below. However, first some of 
the processes of conduit formation and enlargement are considered. 

The transition from magma flow in a subplanar dike to flow in a cylindrical plug has been 
inferred at many field locations (e.g., Delaney and Pollard 1978 [DIRS 162800], p. 1212). From 
a continuum mechanics view, a planar dike is the preferred form for propagation of magma 
through brittle and elastic host rock, whereas a cylindrical conduit is the preferred form for 
magma flow and delivery to the surface (Delaney and Pollard 1981 [DIRS 162801], p. 1). 
Several processes have been put forward to facilitate this transition, including: 
 
Magma viscosity variations induced by solidification of magma at dike margins (Wylie 
et al. 1999 [DIRS 162861], p. 438) 
 
Brecciation and erosion of dike wall rocks, local enlargement, e.g., the Shiprock NE 
dike (Delaney and Pollard 1978 [DIRS 162800], p. 1212); 
 
Progressive melting of the host rocks, enhancing localized flow 
(Quareni et al. 2001 [DIRS 162830], p. 218) (a slightly different permutation of the 
brecciation mechanism of Delaney and Pollard (1978 [DIRS 162800], p. 1212)). 
Once a bud or zone of widening and flow focusing along a dike has initiated, the evolving 
conduit may continue to widen. Several hypothetical processes, similar to those for the initial 
dike enlargement, have been described to explain this process: 
 
Erosion from shear stress of flowing magma (below fragmentation level) (Dobran 2001 
[DIRS 162802], p. 481) 
 
Thermoelastic stressing of wall rock (McBirney 1959 [DIRS 162826], p. 443; Valentine 
and Groves 1996 [DIRS 107052], p. 85) 
 
Erosion from particle collision (above fragmentation level) (Valentine and Groves 1996 
[DIRS 107052], p. 85; Dobran 2001 [DIRS 162802], p. 481) 
 
Conduit wall collapse due to variations in magmatic pressure as a result of conduit 
processes (variations in magma pressure, shock/rarefaction waves) (Dobran 2001 
[DIRS 162802], pp. 480-484) 
 
Hydromagmatic processes: interaction of magma with groundwater or saturated 
sediments (McBirney 1959 [DIRS 162826], pp. 443-445; Valentine and Groves 1996 
[DIRS 107052], p. 85) 
 
Conduit wall collapse due to offshoot dikes (Valentine and Groves 1996 [DIRS 107052], 
p. 85) 
 
Pore pressure buildup (Delaney 1982 [DIRS 162799], p. 7753; Valentine and 
Groves 1996 [DIRS 107052], p. 85; McBirney 1959 [DIRS 162826], p. 443). 
 
Melt back of wall rocks that have lower melting temperature than the temperature of the 
erupting basaltic magma. 

As a result of these processes, the final width of a conduit could be larger near the end of the 
eruption. Also, the entire cross-sectional area of a conduit may be actively transferring magma 
to the vent, or, at any given time, only a small fraction of its cross-sectional area may be active 
(e.g., due to variations in flow velocity or viscosity as a function of composition and 
temperature) to produce localized flow (subsection or annulus) (Hallett 1992 [DIRS 162813], 
pp. 21-22; Detournay et al. 2003 [DIRS 169660], p. 65). 
Doubik and Hill (1999 [DIRS 115338], pp. 60-61) proposed that the Lathrop Wells conduit may 
have been as wide as 50 m at depths equivalent to repository depth during the last stages of 
eruption. This method for calculating conduit diameter is based on estimates of eruption volume, 
xenolith content of the pyroclastic deposits, and source depths of the xenoliths. 
Doubik and Hills (1999 [DIRS 115338], p. 59) 50 m estimate of conduit diameter for Lathrop 
Wells volcano is based upon the assumption that xenoliths at Lathrop Wells volcano were 
derived only from a 550 m thick Tertiary ignimbrite section. Thick Miocene volcanic units 
beneath the Lathrop Wells volcano are very similar, making it difficult to identify relative 
proportions of those units represented by xenoliths there (and thus any potential conduit diameter 
variations with depth). Given the limitations on specific data to test the assumptions made by 
Doubik and Hill (1999 [DIRS 115338], p. 59), their estimate of a 50 m conduit diameter for the 
Lathrop Wells volcano is suggested as a mode or most likely value for conduit diameter at depth 
for potential eruptions at Yucca Mountain. The maximum value for the conduit diameter in the 
distribution to be used for TSPA is 150 m, which corresponds to the diameter of the Grants 
Ridge conduit/plug in New Mexico (Keating and Valentine 1998 [DIRS 111236], p. 41; 
WoldeGabriel et al. 1999 [DIRS 110071], p. 392). The large size of the Grants Ridge plug 
reflects that it erupted a volume on the order of a few km3 of alkali basalt and, therefore, is 
expected to be a conservative upper bound for conduit diameter at Yucca Mountain (compared, 
for example, to the Lathrop Wells volcano with its approximate total volume of 0.086 km3; see 
Appendix C). The minimum conduit diameter value for a TSPA realization should be the same 
as the dike width selected for that realization. The distribution should be triangular to reflect the 
few data that exist for conduit diameter measurement, but will capture the range of conduit 
diameters for a potential volcanic event at Yucca Mountain. 
Crowe et al. (1983 [DIRS 100972], p. 266) measured basaltic dikes intruded into tuff at eroded 
volcanic centers of the YMR, and observed dike widths ranging from 0.3 m to 4 m, with an 
average of 1 m. The basalt intrusions at Paiute Ridge on the eastern border of the Nevada Test 
Site contain dikes that range in width from 1.2 to 9 m, with several in the 2- to 6-m range 
(CRWMS M&O 1998 [DIRS 123201], pp. 5-31, 5-33). The typical dike for the YMR, with 
dimensions assigned by the probabilistic volcanic hazard assessment (PVHA) experts, was 1 m 
(CRWMS M&O 1996 [DIRS 100116], Appendix E). Finally, Delaney and Gartner (1997 
[DIRS 145370], p. 1177) measured 287 dikes in a mafic dike emplacement at the San Rafael 
Swell, Utah, with the median dike thickness of 1.1 m, minimum of 0.1 m and maximum of 
95
6.5 m. Given the observations from these various field studies, a range of dike widths has been 
chosen for use in the analyses of a potential basaltic intrusion at Yucca Mountain. The range is 
described by a log-normal distribution with a minimum of 0.5 m, a mean of 1.5 m, and a 
th percentile of 4.5 m. This distribution is consistent with this small data set: the minimum and 
mean reflect the larger observed widths (1-2 m), and the 95th percentile ensures that the few dike 
widths observed that exceed 4.5 m are represented. 

It is uncertain whether the intersection of a dike with a repository drift would result in the 
development of a volcanic conduit that is localized and/or elongated along the drift. The issue is 
difficult to assess because there is no information from analogous systems in which a basaltic 
dike intersected a long drift-like void, nor is there a theoretical treatment of the scenario in the 
literature. Dike/Drift Interactions (BSC 2004 [DIRS 170028]) uses numerical modeling to show 
that when rising magma intersects an open drift, there will be a short period of time (on the order 
of several minutes) during which magma flows into the drift (potentially explosively), such that 
the upward-propagating magma front moves more slowly directly above the drift than above 
adjacent pillars. However, the time scale for drift pressurization or filling is only a few minutes, 
a very short period of time compared to the expected duration of a volcanic event (1 day to 
15 years; Section 6.3.3.4), and it is not clear that such short-duration processes would have much 
of an effect on conduit formation. 
Some volcanic conduits, now eroded and exposed at the surface as necks or plugs, are elongated 
along their host dikes. This might represent an incomplete transition from a dike-fed fissure 
eruption to a fully developed, roughly circular conduit (rather than the evolution of an originally 
circular conduit to an elongated one). However, the elongation of a conduit along its host dike, 
which commonly resides in a self-generated vertical fracture, is not completely analogous to the 
case of a dike intersecting a repository drift. The host fracture provides a zone of weakness with 
substantial vertical extent over which magma-flow patterns, focusing of magma, and conduit 
enlargement can develop, whereas a drift on the order of 5 m in diameter would provide limited 
time for development of erosive flow. 
Because of the uncertainties and lack of published information on conduit localization and/or 
elongation, there is no basis for providing a statistical weighting for the location of conduits that 
might form within the repository footprint. It is recommended that the location of a potential 
conduit be treated as a random process within the repository footprint. It is assumed that the 
range of values for circular conduit diameter encompasses the length of potential conduit 
elongation. In this manner, conduit elongation is implicitly treated because the circular cross 
section of a conduit allows interaction with additional drifts besides the set of drifts that are 
initially intersected. 
6.3.1.2 Dike Swarms 
Volcanoes in the YMR are fed by one main dike along which a central cone and other vents may 
form, but subsidiary dikes are also present. For example, the Lathrop Wells volcano may be 
underlain by three dikes (inferred from Perry et al. 1998 [DIRS 144335], Figure 2.10): 
 
The dike that fed the main cone and small spatter vents in a chain to the north and south 
of the cone 
 
A dike that fed spatter and scoria mounds in a parallel chain just to the east of the main 
dike 

 
Possibly a dike that may have fed scoria vents near the northern edge of the volcano, 
although it could be an extension of 2 above (note that an alternative interpretation of 
these mounds is that they are cone material that was rafted by lava flows, in which case 
they would not be underlain by dikes). 
In addition, there are likely to be small dikes that radiate outward from the main cones feeder 
conduit that are not exposed, even in the growing quarry excavation. The Paiute Ridge intrusive 
complex, approximately 55 km NE of Yucca Mountain, which appears to have fed at least one 
volcanic vent (evidenced by the presence of lava-flow remnants and a plug-like body), may have 
as many as 10 dikes, in addition to sill-like bodies (as inferred from examination of Perry 
et al. 1998 [DIRS 144335], Figures 5.15 and 5.16). To account for the likelihood of dike 
swarms, rather than single dikes, during formation of a new volcano, a log-normal distribution is 
recommended for the number of dikes that has a minimum value of 1, a mode of 3 (reflecting our 
assumption that the most likely new volcano will be similar to the Lathrop Wells volcano), and a 
95th percentile of 6. This distribution ensures that a number of dikes greater than or equal to 
10 dikes (treating Paiute Ridge as a large event) will be represented in a number of realizations. 
In addition to the number of possible dikes, the spacing between dikes is another important 
variable. Conceptually, it is evident that the minimum dike spacing occurs when a dike first 
splits to form a new dike, thus the minimum dike spacing is taken to be zero. Based upon field 
observation and map measurement (Krier 2003 [DIRS 165893], pp. 20-21), the estimated dike 
spacing at Lathrop Wells volcano is about 320 m between the two inferred NW-trending dikes 
that fed the cone and the linear set of scoria mounds (vents) immediately east of the cone. 
Spacing is about 700 m between the mounds and an inferred third dike related to scoria mounds 
on the eastern lava flows. For dikes greater than 1 km long at Paiute Ridge, mean dike spacing is 
about 995 m with a maximum of 1,440 m and minimum of 250 m (Byers and Barnes 1967 
[DIRS 101859]; Perry et al. 1998 [DIRS 144335], Figure 5-15; Krier 2003 [DIRS 165893], 
pp. 16-18). For the 3.7-Ma-old Crater Flat basalts, dike spacing is approximately 385 m (Perry 
et al. 1998 [DIRS 144335], Appendix 2-M1; Krier 2003 [DIRS 165893], pp. 22-23). Based on 
this limited, diverse data set, the recommended dike spacing for the YMR can be described by a 
random uniform distribution ranging from 0 to 1500 m. 
6.3.1.3 Dike-Induced Earthquakes 
Worldwide, geodetic measurements, co-intrusive seismicity, and field observations indicate a 
propagating dike incrementally forms small normal faults, fissures, tensile cracks, and graben at 
the surface above the dike. The magma-induced surface faults with co-intrusive displacements 
of several meters, can form aseismically or be accompanied by shallow, low-magnitude 
earthquake swarms (Hackett et al. 1996 [DIRS 169781], p. 147, 158). The volcanic earthquake 
swarms can include high frequency earthquakes that can generate ground motions similar to 
those generated by tectonic induced earthquakes. The volcanic earthquake swarms typically 
occur ahead of the propagating dike tip and are thought to result from slip along suitably oriented 
existing fractures that lie within an ambient differential stress region. If the ambient state of 
stress is such that existing faults are near failure, then the stress perturbation due to dike intrusion 
can induce failure along these faults (Rubin, 1995 [DIRS 164118], p. 321; Rubin and Gillard 
1998 [DIRS 169786], p. 10,017 and 10,026; Rubin et al. 1998 [DIRS 169787], p. 10,011). 
Dike-induced rupturing of fractures and faults near the dike tip, the subject of this discussion, 

form in the shallow crust at depths less than 4  5 km, where differential stress and rigidity are 
lower than at depth (Smith et al. 1996 [DIRS 101020], p. 6,284). Hence, rupture areas and the 
maximum magnitudes of strain release associated with dike intrusion are small, in comparison 
with regional faults that extend to the brittle-ductile transition. 
Numerical and scaled empirical experiments on dike intrusion provide information on the 
relationships between dike geometry, stress and strain distribution, and surface deformation 
(Mastin and Pollard 1988 [DIRS 169783], p. 13,228 and Figure 12; Rubin 1992 [DIRS 169784], 
Figure 6). Dike intrusion produces a broad zone of uplift that results from magma-induced 
compressional stress alongside the dike, with a narrow zone of subsidence that forms above the 
dike and results from tensile stress near the dike tip. Normal faults and fissures form where the 
tensile zone interacts with the earths surface. Fissures form in two symmetrical zones above the 
dike, and form progressively inward with dilation of the dike. Most fissures are oriented parallel 
to the dike plane. As dilation continues, dip-slip movement occurs on the fissures, producing 
normal faults and a central graben. The down-dip extent of faults is small, and they extend only 
slightly deeper than the dike top. Depth to the dike top can be estimated from the graben widths 
(Mastin and Pollard 1988 [DIRS 169783], p. 13,228). 
Maximum magnitudes of dike-induced earthquakes can be estimated for the YMR using an 
approach following Smith et al. (1996 [DIRS 101020], p. 6,284). In the absence of observed 
volcanic seismicity (as in the YMR), the geometry of surface deformation features such as 
surface lengths of normal faults and fissures, and graben widths can be used to estimate fault 
dimensions. Empirical relationships between fault dimensions and magnitude can then be used 
to estimate maximum magnitudes of potential dike-induced earthquakes. There are no 
dike-induced surface features in the YMR, so the dike-length distribution estimated by the 
PVHA experts is used as a proxy for maximum surface lengths of dike-induced normal faults 
and fissures. To estimate the maximum magnitudes of dike-induced earthquakes for the YMR, 
surface-fault length is set equal to the aggregate dike-length distribution derived from the PVHA 
which has 5th percentile, mean, and 95th percentile values of 0.6, 4.0, and 10.1 km, respectively 
(DTN: LA0009FP831811.001 [DIRS 164712]). The surface lengths (SRL) of 0.6, 4.0, and 
10.1 km yield maximum moment magnitudes of 4.8, 5.8, and 6.2, respectively, for the YMR 
using M = 5.08 + 1.16*log10 (SRL); where M is moment magnitude (Wells and Coppersmith 
1994 [DIRS 107201], Figure 9). 
The estimated maximum magnitudes of dike-induced earthquakes for the YMR are compared to 
maximum magnitude ranges: 
 
Estimated for normal faults, fissures, and graben widths in volcanic rift zones worldwide 
and in the eastern Snake River Plain (Smith et al. 1996 [DIRS 101020], Tables 1 and 2) 
 
Estimated for fault width using a volcanic crust 4 km thick (referred to as depth to the 
level of neutral buoyancy shown in Smith et al. (1996 [DIRS 101020], Table 2) 
 
Calculated for instrumentally observed earthquakes at active volcanic rift zones (Smith 
et al. 1996 [DIRS 101020], Figure 5). 

The maximum magnitudes estimated for the YMR are consistent with maximum-magnitude 
estimates derived from surface lengths in volcanic rift zones worldwide and the eastern Snake 
River Plain. They exceed estimates based on observed seismicity at active volcanic rift zones 
and fault widths in volcanic rift zones worldwide, the eastern Snake River Plain, and a 4-km 
volcanic crust (Figure 6-1). Magnitudes of dike-induced earthquakes that are calculated using 
tectonic-fault dimensions will be maximum magnitudes, for the following reasons (Smith et al. 
(1996 [DIRS 101020], p. 6,284-6,285): 
 
The crustal rigidity of the shallow, fractured crust in active volcanic areas is probably 
lower than the rigidity of typical midcrustal regions where most tectonic fault ruptures 
nucleate 
 
Commonly high b values (> 1.0) are associated with volcanic seismicity, indicating the 
effective differential stress in the shallow crust of active volcanic regions is lower than 
for typical midcrustal regions (b is the slope of the Gutenberg-Richter 
magnitude-frequency relationship log N = a  bM; where M is magnitude; N is the 
number of earthquakes with magnitudes greater than M occurring in a given time period; 
a and b are constants that describe the linear relationship, a is the intercept) 
 
Rupture along dike-induced normal faults and fissures occurs incrementally rather than 
as a sudden catastrophic release of strain, where only the latter gives rise to energy 
release that is proportional to the dimensions of the entire fault rupture. 
For example, surface faulting with well over 1-m displacement was observed to accompany a 
fissure eruption near Krafla caldera in Iceland, but the associated earthquakes did not exceed 
magnitude 2.5 (Brandsdottir and Einarsson 1979 [DIRS 155852], p. 209). 
Smith et al. (1996 [DIRS 101020], p. 6,287-6,288) selected a maximum magnitude for 
dike-induced earthquakes in the eastern Snake River Plain to be consistent with the maximum 
magnitudes derived from fault width and rupture area. They reasoned that the maximum 
magnitude estimates derived from fault width and rupture area measured in the eastern Snake 
River Plain were internally consistent, and they were consistent with observed magnitudes 
during dike injection in worldwide volcanic rift zones. Following this approach, the maximum 
magnitudes of 4.8, 5.8, and 6.2 are reasonable estimates for potential dike-induced earthquakes 
in the YMR. These values represent maximum magnitudes derived from the dike length 
distribution recommended by the PVHA experts. In the YMR, the state of stress is sufficiently 
close to failure (Stock et al. 1985 [DIRS 101027], p. 8,701-8,702) that dike intrusion could 
induce slip on pre-existing faults, generating earthquakes of larger magnitude than the maximum 
magnitudes of observed seismicity associated with active volcanic rift zones (represented as the 
mean and one standard deviation for M 3.8  0.8 in Figure 6-1). 
Not all dike-intrusions produce a maximum-magnitude earthquake, nor will all dikes intersect 
the repository. The PVHA calculated the mean annual frequency of intersection of the 
repository by a volcanic event as 1.7 x 10-8 per year (BSC 2004 [DIRS 169989] Table 22). A 
maximum magnitude, dike-induced earthquake can be associated with the volcanic event that 
intersects the repository. Therefore, the recurrence interval of maximum-magnitude, 
dike-induced earthquakes at the repository is given by the frequency of dike intersection of the 
repository. 

Source: YMR dike surface length (this report); other data (Smith et al. 1996 [DIRS 101020] Tables 1 and 2, Figure 5) 
ESRP = Eastern Snake River Plain 
NOTE: Bars indicate upper and lower values of the mean plus and minus the standard deviation, respectively and 
solid circles indicate single calculated values. YMR values are discussed in text. Other maximum 
magnitude (M) values shown are: M 5.7, 6.0, 6.3, and 6.4 for surface lengths of faults and fissures in 
volcanic rift zones worldwide; M 5.6  0.7 for surface lengths of faults and fissures in eastern Snake River 
Plain volcanic rift zones; M 3.4, 4.1, 4.3, 4.5, 4.7, and 5.2 for fault widths derived from graben widths in 
volcanic rift zones worldwide; M 3.8  0.9 for fault widths derived from graben widths in eastern Snake River 
Plain volcanic rift zones; M 5.4 for a fault width equivalent to a volcanic crust 4-km thick; and M 3.8  0.8 for 
the range of instrumentally observed seismicity at active volcanic rift zones. 
Figure 6-1. Plot of Calculated and Observed Maximum Magnitudes for Dike-Induced Earthquakes 
6.3.2 Characteristics of Igneous Material 
6.3.2.1 Magma Chemistry 
Magma-chemistry data are used to determine parameters for important variables such as magma 
viscosity, temperature, and density. Two approaches are possible for predicting the chemistry of 
future magmas. The first is to calculate a volume-weighted mean composition based on analysis 
of basaltic rocks from the YMR, which is a method that would capture the existing magma 
chemistry record. A second approach is to use the most recent eruption at Lathrop Wells 
volcano as the one that most likely represents the composition of future eruptions. The second 
approach was selected because it emphasizes the composition that produced more violent 
explosive eruptions compared to other YMR volcanoes (as inferred from Perry et al. 1998 
[DIRS 144335], Chapter 2). However, the volatile content and the mass flow rate are more 
direct determinants of eruptive violence than non-volatile magma chemistry alone. The second 

approach is more conservative because it represents a greater potential dispersal of radionuclides 
(see Section 5, Assumption 1). 
The major element variation for Lathrop Wells is based on 45 chemical analyses 
(DTN: LA000000000099.002 [DIRS 147725]). Table 6-2 lists statistical parameters associated 
with the 12 most abundant oxides from these analyses. 
6.3.2.2 Water Content of Primary Basaltic Magma 
Eruptive styles in the YMR ranged from violent Strombolian on one end of the spectrum to 
quiescent aa lava on the other (Perry et al. 1998 [DIRS 144335], Chapter 2). Eruption style 
was primarily controlled by volatile content (which is dominated by water) and the rate at which 
volatiles were exsolved from the magma. The inferred eruptive styles indicate a large range in 
volatile contents and, hence, water content of YMR magmas. In addition, variations in energy 
are suggested at individual volcanic centers such as those of the Quaternary Crater Flat field and 
Lathrop Wells volcanoes. 
Amphibole, possibly of magmatic origin, is found as a rare and sparse phase in some Quaternary 
Crater Flat basalts. Knutson and Green (1975 [DIRS 106299], Figure 1, p. 126), performing 
experiments on material similar in composition to YMR basalts, observed that magmatic 
amphibole was stabilized at water contents of between 2 and 5 wt%. Baker and Eggler (1983 
[DIRS 122601], p. 387) showed that at 2 Kbar pressure, water content in excess of 4.5 wt% is 
required to stabilize amphibole in high-alumina basalt similar to YMR basalts. However, water 
content substantially greater than 5 wt% is not considered likely because this high water content 
is most commonly associated with more chemically evolved magmatic compositions 
(e.g., rhyolite) than those observed in young volcanoes near the YMR. Also, Sisson and Grove 
(1993 [DIRS 122564], p. 167) note that low-Mg basalts with high alumina content cannot erupt 
as liquids with water content in excess of 4 wt% because they will exsolve gas and rapidly 
crystallize to form phenocryst-rich magmas as they approach the surface. Based on this, it is 
argued that 4 wt% is an upper bound on initial dissolved water content. At the lower end of the 
range, aa lava may form from relatively low-volatile-content eruptions. 
Even if a particular concentration of volatiles could be tied to a particular eruptive style, the 
YMR post-Miocene (i.e., 5 Ma) record is sparse; therefore, it is difficult to rigorously define a 
probability distribution function for primary magma water content for use in TSPA. The 
following distribution is recommended: 
No magmatic water has a zero probability of occurrence. This statement reflects 
our knowledge that very low volatile contents are very rare. The probability 
should increase linearly from 0 to 1 percent. The probability should be uniform 
from 1 to 3 percent, reflecting that this is the most likely range of water contents. 
The probability should decrease linearly between 3 and 4 wt%, so that it is zero at 
4 wt%, representing the expectation that at about 4 wt%, basaltic magmas will 
crystallize before reaching the surface to erupt. 

Table 6-2. Mean Lathrop Wells Lava Chemistry with Associated Statistics 
SiO2 TiO2 Al2O3 
Mean 48.50 Mean 1.93 Mean 16.74 
Standard Error 0.09 Standard Error 0.01 Standard Error 0.03 
Median 48.57 Median 1.93 Median 16.75 
Mode 48.55 Mode 1.97 Mode 16.87 
Standard 0.58 Standard 0.06 Standard 0.22 
Deviation Deviation Deviation 
Sample Variance 0.34 Sample Variance 0.00 Sample Variance 0.05 
Count 45.00 Count 45.00 Count 45.00 
Fe2O3Ta Fe2O3 
b FeOb 
Mean 11.63 Mean 1.74 Mean 8.90 
Standard Error 0.03 Standard Error 0.00 Standard Error 0.02 
Median 11.58 Median 1.74 Median 8.86 
Mode 11.56 Mode 1.73 Mode 8.84 
Standard 0.22 Standard 0.03 Standard 0.17 
Deviation Deviation Deviation 
Sample Variance 0.05 Sample Variance 0.00 Sample Variance 0.03 
Count 45.00 Count 45.00 Count 45.00 
MnO MgO CaO 
Mean 0.17 Mean 5.83 Mean 8.60 
Standard Error 0.00 Standard Error 0.02 Standard Error 0.03 
Median 0.17 Median 5.83 Median 8.55 
Mode 0.17 Mode 5.88 Mode 8.41 
Standard 0.00 Standard 0.11 Standard 0.22 
Deviation Deviation Deviation 
Sample Variance 0.00 Sample Variance 0.01 Sample Variance 0.05 
Count 45.00 Count 45.00 Count 45.00 
Na2O K2O P2O5 
Mean 3.53 Mean 1.84 Mean 1.22 
Standard Error 0.01 Standard Error 0.01 Standard Error 0.00 
Median 3.55 Median 1.84 Median 1.22 
Mode 3.59 Mode 1.84 Mode 1.21 
Standard 0.09 Standard 0.04 Standard 0.03 
Deviation Deviation Deviation 
Sample Variance 0.01 Sample Variance 0.00 Sample Variance 0.00 
Count 45.00 Count 45.00 Count 45.00 
Source: DTN: LA000000000099.002 [DIRS 147725] 
NOTE: All values except count are in wt%. 
a 
Total iron is reported as Fe2O3T. 
b Fe2O3 and FeO were recalculated assuming a 0.15 mole fraction of ferric iron (Fe2O3). 
The following sample analyses are from Perry and Straub (1996 [DIRS 106490], Appendix A; DTN: 
LA000000000099.002 [DIRS 147725]) was used to develop the statistics in this table: LW11FVP, LW12FVP, 
LW74FVP, LW45FVP, LW72FVP, LW73FVP, LW100FVP, LW120FVP, LW121FVP, LW30FVP, LW31FVP, 
LW32FVP, LW63FVP, LW64FVP, LW65FVP, LW66FVP, LW67FVP, LW110FVP, LW115FVP, LW20FVP, 
LW21FVP, LW22FVP, LW23FVP, LW06FVP, LW07FVP, LW40FVP, LW41FVP, LW44FVP, LW55FVP, 
LW56FVP, LW19FVP, LW25FVP, LW26FVP, LW27FVP, LW28FVP, LW29FVP, LW04FVPA, LW54FVP, 
LW57FVP, LW58FVP, LW05FVPA, LW59FVP, LW60FVP, LW61FVP, LW62FVP. 

Direct measurements of water in mafic (low silica) magmas or magmatic products from a range 
of tectonic settings indirectly support the recommended parameter values and cover the range of 
values that can be reasonably expected for future basaltic igneous activity. Garcia 
et al. (1989 [DIRS 122542], Table 1, p. 10527), Byers et al. (1985 [DIRS 122532], Figure 4, 
p. 1891), and Muenow et al. (1979 [DIRS 125093], Table 1, p. 74) found total water contents in 
Hawaiian tholeiites and transitional alkalic basalts that range from near 0 to nearly 1 percent. 
These melts probably represent higher degrees of partial melting than YMR basalts, so their low 
water contents are expected. On the other hand, Gaetani et al. (1993 [DIRS 144274], 
pp. 332-334) and Sisson and Grove (1993 [DIRS 144351], p. 163) present experimental evidence 
that high-alumina basalt and basaltic andesite magmas commonly contain up to several wt% 
water. Sisson and Layne (1993 [DIRS 122549], Table 1, p. 622) measured water contents in 
glass inclusions from arc basalts and basaltic andesites that range from 1 to 6 percent. True 
magmatic values could be somewhat lower because of concentration of water in the inclusions, 
which is caused by partial crystallization of the melt after entrapment. Water contents of 0.2 to 
2 percent have been reported for back arc basin lavas and 1.2 to 3 percent for island arc tholeiites 
and boninites (Danyushevsky et al. 1993 [DIRS 149303], Tables 1 and 4, pp. 349 and 358). 
6.3.2.3 Mole Percent of Constituents in Volcanic Gas 
A survey of data compilations from the literature, including volcanoes from convergent, 
divergent, and hot-spot tectonic settings, must suffice to constrain the relative proportions of 
major gas constituents in YMR basalts owing to the absence of current activity in the YMR from 
which gases could be directly sampled. Three types of data exist in the literature: 
 
Measurements of emitted volcanic gases 
 
Measurements of gases trapped in volcanic glass or melt inclusions 
 
Experiments on gas solubilities in silicate melts. 
The first type of data is more directly relevant to eruptive scenarios at Yucca Mountain because 
the gases released from an igneous event will include corrosive species. Also, gases will 
fractionate between the magma and the gas phase during exsolution. Consequently, gas 
composition data for glasses may not directly represent their relative abundances in the gas phase 
after exsolution. 
Measured concentrations of volcanic-gas constituents were taken from a compilation by 
Symonds et al. (1994 [DIRS 101029], Tables 3-5), and only the data for mafic centers were 
included in the present analysis. Data in Table 6-3 include hawaiite from Mount Etna; tholeiitic 
basalt from Momotombo, Poas, Kilauea, Ardoukoba, and Erta Ale; nephelenite from 
Nyiragongo; and alkali basalt from Surtsey. Statistics listed in Table 6-3 were calculated by first 
computing the mean for each of the above-mentioned volcanic centers from the data in Symonds 
et al. (1994 [DIRS 101029], Tables 3-5) and then using these individual means to generate the 
overall statistics. 

Table 6-3. Mole Percent Concentration of Volcanic Gases and Associated Uncertainty Estimates 
H2O H2 CO2 CO SO2 
Mean 73.16 1.17 14.28 0.57 9.45 
Square Root of the Sum of the Squares 17.97 0.89 16.03 0.59 8.90 
Standard Deviation 19.81 0.67 15.32 0.75 8.95 
S2 HCl HF H2S fO2 * 
Mean 0.41 0.87 0.17 0.74 -10.63 
Square Root of the Sum of the Squares 0.63 0.21 0.04 1.04 1.92 
Standard Deviation 0.40 1.12 0.08 0.69 1.80 
Source: Eighty-eight analyses in Symonds et al. (1994 [DIRS 101029], Tables 3-5) 
NOTE: * fO2 is listed as log bars. 
This is a closed data set, indicating that each parameter (other than fO2) must vary between 0 and 
100 percent. Clearly, a species such as H2O will rarely be present at levels less than 50 percent 
and probably has some mean or median value of geologic significance. If data from sufficient 
eruptions and individual volcanoes were gathered, a normal distribution of values seems likely. 
As for the minor species, which are also corrosive, the cited uncertainties are quite large relative 
to mean values. Thus, it seems likely that adequate conservatism will be accommodated by a 
normal, or even a uniform, distribution. 
6.3.2.4 Magmatic Temperatures, Viscosities, and Densities 
Many direct measurements of magmatic temperatures have been made for erupting lavas. 
However, this is only possible when water contents are low enough, or rates of magmatic 
outgassing are slow enough, to permit direct measurement. Thus, although direct measurements 
are available for the low end of the spectrum of water content, experiments must be relied on to 
constrain magmatic temperatures for magmas with elevated water content. 
YMR basaltic lavas are generally aphyric to sparsely porphyritic (Perry and Straub 1996 
[DIRS 106490], p. 6), which indicates that they erupted at near-liquidus or superliquidus 
temperatures. The liquidus for dry basaltic magmas increases with increasing pressure. Wet 
liquidi, however, have negative slopes, so that water-bearing magmas may exist at a temperature 
less than that of the dry liquidus. Jaupart and Tait (1990 [DIRS 118292], p. 219) present a 
simple expression for the solubility of water in basaltic magma 
n = 6.8  10-8P0.7 (Eq. 6-1) 
where n is the mass fraction of water and P is the pressure in Pascals. As magmas decompress, 
not only will they tend to exsolve more fluid, they will also tend to crystallize. Magma is 
saturated with respect to water when the pressure is such that n equals the initial water content. 
Table 6-4 shows saturation pressures, calculated from Equation 6-1, for initial water contents of 
0.5, 1.0, 2.0, 3.0, and 4.0 wt% (wt% = 100 times the mass fraction). At lower pressures, water 
vapor would begin to exsolve and form bubbles (see also Section 6.3.3.2 below). 

Table 6-4. Calculated Saturation Pressures, Liquidus Temperatures, Viscosities, and Densities as a 
Function of Water Content for Lathrop Wells Magmas 
Water Content 
(wt%) 
Saturation Pressure 
(Pa) 
Liquidus 
Temperature (C) 
Viscosity 
(log poise) 
Density 
(kg/m3) 
0 1 x 105 1169 2.678 2663 
0.5 9.0 x 106 1153 2.572 2633 
1 2.4 x 107 1137 2.472 2605 
2 6.5 x 107 1106 2.284 2556 
3 1.2 x 108 1076 2.112 2512 
4 1.7 x 108 1046 1.957 2474 
NOTE: Derived using mean Lathrop Wells compositions from Table 6-2. 
Using saturation pressures derived from Table 6-4, the following expression of Sisson and Grove 
(1993 [DIRS 122564], p. 178) can be used to estimate multiple phase-saturation (liquidus) 
temperatures in the magmas: 
T(C) = 969 - (33.1  H2O) + 0.0052 ( Pb - 1) + 742.7  Al# 
-138  NaK# + 125.3  Mg# (Eq. 6-2) 
where 
H2O is the wt% of water 
Pb is pressure in bars (note that elsewhere in this document pressure is in Pascals) 
Al# is the ratio of mass fractions of Al2O3/(Al2O3 + SiO2) 
NaK# is the ratio of mass fractions of (Na2O + K2O)/(Na2O + K2O + CaO) 
Mg# is molar Mg/(Mg + 2Fe2O3T) 
It should be noted that Al# , NaK#, and Mg# do not vary as a function of water content in Lathrop 
Wells magmas as these parameters simply express relative proportions. 
Liquidus temperatures for Lathrop Wells magmas with different hypothetical water contents 
were calculated as follows: First, the mean Lathrop Wells composition (from Table 6-2) was 
normalized to 100 percent (anhydrous). Then, major element oxides were renormalized to sum 
to 99.5, 99.0, 98.0, 97.0, and 96.0 wt%. To these values, 0.5, 1.0, 2.0, 3.0, and 4.0 wt% H2O 
were added, respectively, so that the sum of the renormalized major element oxide content and 
water content sum to 100 wt% in each case. With these new hypothetical compositions, and the 
saturation pressure calculated as described above, Equation 6-2 was used to compute the liquidus 
temperatures shown in Table 6-4. The same hypothetical compositions and calculated 
temperatures were used to calculate bubble- and crystal-free viscosity using the method of Shaw 
(1972 [DIRS 126270], pp. 873, 878). 
Density can also be calculated as a function of composition (including water content), pressure, 
and temperature using the formulation and data of Lange and Carmichael (1990 [DIRS 147767], 
Table 3) with additional data for H2O (Ochs and Lange 1999 [DIRS 144330], pp. 1315). 
Equation 2 from Ochs and Lange (1999 [DIRS 144330], p. 1315) produces the molar volume of 
the silicate liquid, which only requires a simple conversion to density. The density conversion 
can be done as follows. Assume that 100 g of magma are present. In doing the calculation, one 
converts the weight of each oxide (equivalent to the wt%) to the number of moles of each 

constituent. These terms can be summed to give a total number of moles. The density is then 
equal to the inverse of the product of molar volume (cm3/mole) and number of moles per 100 g 
of liquid. This result, in g/cm3, can then be converted to kg/m3 as shown in Table 6-4. 
A review of relevant experimental data reveals that these values are reasonable. The liquidus 
temperature for a mildly alkalic basalt similar in composition to the mean Lathrop Wells lava 
composition is between 1,174 and 1,188C (Mahood and Baker 1986 [DIRS 104663], Tables 1 
and 2). The Mahood and Baker (1986 [DIRS 104663]) temperature calculations are close to 
temperatures reported by Knutson and Green (1975 [DIRS 106299], Figure 1) for a hawaiite that 
is also similar in composition to Lathrop Wells basalt. Yoder and Tilley (1962 [DIRS 122589], 
Figure 28) published results on the water-saturated liquidus for a high-alumina basalt. At 
1.75 
 108 Pa water pressure, the liquidus was more than 100C cooler than the 105 Pa liquidus 
temperature. Thus, our calculated parameter values are consistent with a well-established body 
of experimental data. 
6.3.3 
Eruptive Processes 
Quaternary basalts of the YMR display textural and depositional facies that indicate a range of 
eruptive processes. Explosive processes, in which fragments (clasts), or clots, of melt were 
erupted in a stream of gas, are evidenced by the presence of scoria cones and remnants of ash 
fallout blankets. Effusive processes, in which magma fragmentation did not occur in the feeding 
system, are recorded by the presence of lava flows, although it is also common in basaltic 
eruptions to produce lava flows by the coalescence and remobilization of explosively erupted 
clasts. Within these two broad categories of eruptive facies (explosive and effusive, facies refers 
to the general appearance and characteristics of a rock unit), there are further distinctions. 
Explosively erupted deposits, for example, may display a range of facies depending on the local 
rate of accumulation and on the temperature of clasts when they are deposited. Very high 
accumulation rates of hot (still molten) clasts result in coalescence and formation of lava flows. 
Somewhat lower accumulation rates and temperatures may result in welded spatter, in which 
relicts of individual clast shapes may still be observed to varying degrees. Still lower 
accumulation rates and temperatures (such that the clasts are still plastic upon deposition) result 
in partly welded spatter, in which clast shapes are obvious but the deposit is resistant to erosion. 
Low accumulation rates of very hot clasts result in individual spatter clasts that flatten upon 
deposition but solidify before subsequent clasts are deposited on top and, therefore, do not weld. 
Nonindurated deposits of brittle cinders (or scoria) result from deposition of already cooled 
clasts. All of these explosive facies are present to some degree in the Yucca Mountain basalts. 
Effusive lava flows in the YMR are mainly of the aa type, indicating relatively high effusion 
rates (greater than ca 1.5-3  104 kg/s; Rowland and Walker 1990 [DIRS 115463], p. 626), 
although the limited extent of the flows suggests relatively short eruption duration. 
The Lathrop Wells volcano is a good example of a range of eruptive processes recorded by a 
single volcano (Appendix C). The surface of the main cone, which is about 140 m high and has 
a volume of 0.018 km3, is composed mainly of loose scoria with a relatively high vesicularity. 
The cone is surrounded, particularly to the south, west, and north, by a fallout (tephra) blanket up 
to ca 3 m thick (within 1 km of the cone) composed of the same loose scoria. Remnants of this 
fallout deposit are exposed northward up to 2 km from the crater; about 14 km north of the 
crater, its reworked equivalent is exposed in trenches excavated across the Solitario Canyon fault 

(Perry et al. 1998 [DIRS 144335], pp. 4.24-4.30). Estimated volume of the tephra blanket is 
0.039 km3. These features all suggest a relatively high-energy eruption with an ash column that 
rose kilometers into the air so that clasts were cool when they fell to the ground and finer ash 
was dispersed widely by winds (termed a violent Strombolian eruption by many 
volcanologists). Other parts of the Lathrop Wells volcano were emplaced by quite different 
mechanisms. For example, mounds of coarse, partially welded spatter indicate a local, relatively 
low-energy Strombolian eruption. Recent quarry exposures reveal welded scoria, typical of a 
Strombolian eruption, in the main cone, raising the possibility that only the late stages of the 
cone-forming eruptions were violent Strombolian. A localized area to the west of the cone 
exposes pyroclastic surge deposits that probably record a small, directed blast driven by 
explosive interaction between magma and groundwater (hydrovolcanism). Thick, stubby aa 
flows suggest short-duration, high-mass-flux effusive eruption as mentioned above. The lavas 
have a volume of 0.029 km3. The Lathrop Wells volcano and its deposits, totaling 0.086 km3 in 
volume, are discussed in detail in Appendix C. Other volcanoes of the YMR (e.g., Sleeping 
Butte, Red Cone, and Black Cone) are less well preserved, but they exhibit a similar range in 
eruptive styles at individual centers. This observation means that it is reasonable to assume a 
range of eruption mechanisms and, therefore, multiple exposure pathways for volcanic disruption 
of a repository. 
The solubilities of volatiles such as H2O and CO2 in basaltic magmas are proportional to pressure 
(Jaupart and Tait 1990 [DIRS 118292], p. 219). At depth (for example, in a magma chamber), 
magmas will have relatively high volatile contents. As they ascend through progressively lower 
lithostatic pressure, they will become oversaturated and bubbles will nucleate. Continued rise 
results in increasing numbers and sizes of bubbles (caused by combined exsolution of volatiles 
and decompression and coalescence growth of the bubbles), these two processes increase the 
specific volume of the magma, and as a consequence, its velocity also increases gradually 
(according to conservation of mass). Explosive eruption occurs when, at shallow depths, the 
magma reaches a foamy state, and with further decompression, it fragments, switching from 
being a melt with dispersed bubbles to a gas with dispersed fragments or clots of melt. At and 
above this fragmentation depth, the gas-melt mixture accelerates rapidly until it leaves the 
volcanic vent at speeds of tens to a few hundreds of meters per second. A further complication 
in this sequence of events is the possibility of loss of volatiles through the walls of the conduit or 
dike as magma ascends. This action can reduce the effective volatile content for the eruption. 
The dynamics of magma ascent, and particularly the fragmentation process, are currently a topic 
of intense research in the volcanological community. Most recent advances in this area focus on 
silicic rather than basaltic magmas. The reasons for this are twofold. First, silicic magmas are 
responsible for the most explosive eruptions and present the most severe hazard to populations; 
understanding their dynamics is key in mitigating these hazards. Second, silicic magmas have 
viscosities several orders of magnitude higher than basaltic magmas. This condition greatly 
reduces the effects of bubbles rising more rapidly than their host melts and coalescing with each 
other. Thus, theoretical modeling is made more tractable by having to consider only nucleation, 
decompression growth, and growth by diffusion of exsolving volatiles into bubbles. In other 
words, the dynamics are closely approximated by a homogeneous flow approach, in which the 
gas and melt move at about the same velocity everywhere and are in thermal equilibrium. 
However, the rise of basaltic magmas with their lower viscosities is complicated by the potential 
for rapid rise and coalescence of bubbles (Vergniolle and Jaupart 1986 [DIRS 115585], 

pp. 12,842-12,846). Extreme results of this process are represented by classic Strombolian 
bursts, which are basically large bubbles rising through and bursting at the top of a magma 
column, producing eruptions of mostly gas with small amounts of melt (fragments of bubble 
walls) thrown out ballistically. Another example is the Hawaiian fire fountain eruptions, which 
have been observed to erupt molten pyroclasts with H2O vapor content much higher than the 
H2O solubility at depth. A general theory for the rise of basaltic magmas, accounting fully for 
the important two-phase flow effects, does not exist. Instead, the treatment below simplifies the 
problem by assuming homogeneous flow. 
6.3.3.1 Magma Ascent Rate below Volatile Exsolution 
Wilson and Head (1981 [DIRS 101034]) developed a theory for the ascent of basaltic magmas 
along dikes and cylindrical conduits using the homogeneous flow simplification (Section 5 
Assumption 4). At depth, where magma is under sufficient pressure that all volatiles are 
dissolved, the buoyancy-driven ascent velocity, uf, is (Wilson and Head 1981 [DIRS 101034], 
p. 2,974): 
.
A. .. 64r g 3 (.-. ) K. ... 
1/ 2 
- 1.
uf= c cmm 
(Eq. 6-3) 
22
4K. r 
...
... 
1 + 
A . ...
m 
where 
A = 64 (circular conduit) or 24 (dike) 
. is magma viscosity 
K = 0.01 
.m is the melt density (no bubbles) 
.c 
is the wall rock density 
r is the conduit radius or dike half width 
gc is gravitational acceleration 
Note that the flow described in Equation 6-3 can occur only when .c> .m. 
6.3.3.2 Volatile Exsolution and Fragmentation 
As magmas rise, volatiles may begin to exsolve. The solubility of water (n), the major volatile 
species in basalt, is approximated by Equation 6-1 (Jaupart and Tait 1990 [DIRS 118292], 
p. 219). The depth at which exsolution of water vapor begins to occur is the depth at which the 
magma becomes saturated with respect to its original water content, which, assuming lithostatic 
pressure (P = .cgcd, where d is depth; see Section 5, Assumption 3), can be derived as: 
 
- 10/7
( n / 10 8.6 8 ) (Eq. 6-4) 
i
d =
exs 
. g
cc 
where 
dexs is exsolution depth in meters (m) 

ni is the initial dissolved mass fraction of water at the magmas depth of origin, 
.c 
is the average density of the crust above dexs in kg/m3 
gc is gravitational acceleration (m/s2) 
This relation is plotted in Figure 6-2. The mass fraction of water exsolved from a basaltic 
magma, nexs, at a given depth is 
n
exs = ni - n when d < dexs (Eq. 6-5a) 
n
exs = 0 when d > dexs. (Eq. 6-5b) 
The density of the mixture of silicate melt and water vapor bubbles (.mix) can be calculated from 
(Wilson and Head 1981 [DIRS 101034], p. 2983) 
1 n(1 - n) 
(Eq. 6-6)
.
= 
exs + exs 
mix .g .m 
The density of the gas phase (.g) can be calculated using the ideal gas law: 
P
.= (Eq. 6-7) 
g 
RT
where R is the gas constant for water (in this report, a value of 461 J/kg-K is used) and T is 
temperature. If it is assumed that the pressure in a conduit or dike is determined by the 
lithostatic pressure, .g 
can be computed as a function of depth d: 
.=.cgcd 
g 
RT (Eq. 6-8) 
Equations 6-1 and 6-4 to 6-8 can be used to calculate the mixture density for any initial volatile 
content at any depth, which may be useful for estimating the interactions between the mixture 
and the repository. The mixture density can also be expressed in terms of gas volume fraction, f, 
as 
.
mix =f.g + (1 -f). (Eq. 6-9) 
m
Re-arranging, the gas volume fraction is here derived as: 
f= 
.mix -.m (Eq. 6-10) 
.-.
gm

DTN: N/A (plot of equation 6-4). 
NOTE: The calculations assume that pressure in the magma column is lithostatic and that bubble nucleation kinetics 
can be ignored. The average (shallow) crustal density (.c) is taken to be 2,000 kg/m3, as an example. dexs is 
depth at which exsolution begins; ni is dissolved water (H20) content up to 0.05. 
Figure 6-2. Plot of the Depth at Which Volatile Exsolution Begins in a Lathrop Wells Basalt for Initial 
Dissolved Water Content 

DTN: N/A (plot of equation 6-10). 
NOTE: Calculations assume p c = 2,000 kg/m3, pm = 3,000 kg/m3, T = 1,300 K, and R = 461 J kg/K. The dashed 
line defines a critical gas volume fraction (.) of 0.75, which, in this report, is assumed to be the threshold for 
fragmentation of the magma. Plot is derived by solving Equations 6-1 and 6-5 as functions of depth (d) for a 
given value of ni, Equations 6-8 and 6-6, and finally Equation 6-10 for each value of ni = 0.01, 0.02, 0.03, 
0.04, and 0.05. 
Figure 6-3. Plot of the Variation of Gas Volume Fraction with Depth for a Lathrop Wells Basalt, 
Assuming Pressure in the Magma is Lithostatic and for Initial Dissolved Water Content 

Figure 6-3 shows the depth at which fragmentation occurs in rising basaltic magma, assuming 
that: 
 
The flow is steady and homogeneous, the system is closed (no gas loss into country 
rock), and bubble nucleation and growth kinetics can be ignored (see Section 5, 
Assumption 4). 
 
The vertical pressure profile in the dike/conduit below the fragmentation depth is very 
close to the lithostatic pressure profile (see Section 5, Assumption 3). 
 
A gas volume fraction at which fragmentation commences can be established. 
The limitations of the first assumption have already been discussed. The second assumption is 
very good at depths where fis small, but it becomes less accurate toward the fragmentation 
depth, and it is probably very inaccurate above the fragmentation depth. However, the second 
assumption is a good estimate of the average fragmentation depth for a variety of different 
scenarios. The third assumption is currently a subject of intense research. The commonly 
assumed critical fragmentation value of f = 0.75 (Mader 1998 [DIRS 144419], p. 55) is adopted 
as a reasonable estimate in Figure 6-3, given how little is understood about this process with 
regard to basaltic magmas. Recent studies have demonstrated, however, that fragmentation can 
take place in a range of 0.60 < f< 0.95 (Mader 1998 [DIRS 144419], p. 56). With all these 
assumptions, Figure 6-3 illustrates that estimated fragmentation depths for initial volatile 
contents between 0 and 4 wt% range from about 0 to 900 m. 
6.3.3.3 Velocity as a Function of Depth above Exsolution Depth 
Descriptions of the magma velocity, conduit/dike dimensions, and magma pressure as functions 
of depth (d) require, even with the homogeneous-flow approximation and a steady-state 
assumption, solution of three coupled equations (Wilson and Head 1981 [DIRS 101034], 
Eqs. 16-18, p. 2974). Two of these equations are ordinary differential equations. The detailed 
solution of these equations for a range of parameters appropriate to volcanism in the YMR is 
beyond the scope of this report. However, Wilson and Head (1981 [DIRS 101034], p. 2983) do 
provide some plots that relate eruption velocity, uerupt, (where the magma-gas mixture exits the 
vent) to initial dissolved water content (ni) of the magma, assuming that the pressure in the 
conduit/dike is equal to lithostatic pressure. Their solutions, shown with the solid curves in 
Figures 6-4 and 6-5, are for values of ni up to approximately 0.02 for both dike (fissure) and 
circular conduit geometries. As discussed in Section 6.3.2.2, it is possible that ni values for 
basalts of the YMR have been as high as 0.03 to 0.04, and the possibility of values as high as 
0.05 is allowed in these plots. Thus, Figures 6-4 and 6-5 show the extrapolated values (dashed 
parts of the curves) for velocity at these higher initial water contents. Note that these are only 
graphical extrapolations, not actual solutions to the governing equations. However, given the 
various simplifications that are made in arriving at the Wilson and Head (1981 [DIRS 101034], 
p. 2983) results, these extrapolations are reasonable approximations. 
The velocity of magma ascending from some depth to the vent probably can be estimated with 
sufficient accuracy for modeling by simplifying such that velocity increases linearly from 
0.01uerupt at dexs to 0.1uerupt at the fragmentation depth, thence increasing linearly to uerupt at the 
vent (uerupt obtained from Figures 6-4 and 6-5). Using such an approach will account for the 

greater accelerations that are thought to occur above the fragmentation depth and the more 
gradual acceleration below it. In addition, this approach guarantees consistency in the 
calculations of velocity at various depths (as opposed to random sampling from distributions at 
different depths). 
Source: Wilson and Head (1981 [DIRS 101034]); plot of equations from reference and extrapolations. 
NOTE: Solid curves show values for the variation of eruption velocity (uerupt) with initial dissolved water content (ni) 
calculated by Wilson and Head (1981 [DIRS 101034], p. 2983). Dashed lines are graphical extrapolations to 
include the range of initial volatile contents of concern for Yucca Mountain. The Wilson and Head 
calculations assume homogeneous flow and lithostatic pressure in the rising magma column. 
Figure 6-4. Plot of the Variation of Eruption Velocity with Initial Dissolved Water Content for Various 
Mass Discharge Rates Along a Fissure 

Source: Wilson and Head (1981 [DIRS 101034]); plot of equations 17 to 18 from reference and extrapolations. 
NOTE: Solid curves show values for the variation of eruption velocity (uerupt) with initial dissolved water content (ni) 
calculated by Wilson and Head (1981 [DIRS 101034], p. 2983). Dashed lines are graphical extrapolations to 
include the range of initial volatile contents of concern for Yucca Mountain. The Wilson and Head 
calculations are based on the assumption of homogeneous flow and lithostatic pressure in the rising magma 
column. 
Figure 6-5. Plot of the Variation of Eruption Velocity with Initial Dissolved Water Content for Various 
Mass Discharge Rates from a Circular Conduit 
6.3.3.4 Eruption Volume and Duration 
For the purposes of predicting how much radioactive waste might be erupted and subsequently 
dispersed over significant distances, were a volcano to form at Yucca Mountain, it is important 
to provide constraints on volumes of fallout tephra. The literature on analog cones and their 
tephra volumes is limited, but fallout tephra volumes are generally about two times their cone 
volumes, based upon data that includes Tolbachik 1 (ratio 1.3), Tolbachik 2 (ratio 1.0), Sunset 
Crater (ratio 1.6-3.2), Heimaey (ratio 0.8), Serra Gorda (ratio 1.4), Cerro Negro (ratio 1.7, even 
based upon eruptions from 1850-1995), and Parcutin (ratio 4-5.9, which is by far the greatest) 
(NRC 1999 [DIRS 151592], Table 3). The average of these ratios is 1.9. At Lathrop Wells 
volcano, based on current data, tephra fall volume is about 0.04 km3 and the cone is 0.018 km3 
(see Appendix C, Table C-18), for a ratio of 2.2. To account for uncertainties in this ratio, and to 
define a maximum potential ash volume for the YMR, it is recommended to double the expected 
tephra/cone ratio to four to capture the probable potential future ash eruption volumes. Doubling 
the Lathrop Wells tephra volume of 0.04 km3 yields the recommended maximum volume of 
approximately 0.08 km3 of potential tephra. 

The minimum potential volume is accounted for using a similar ratio for NE Little Cone (the 
smallest volcanic cone in the YMR), whose dimensions are provided by Stamatakos et al. (1997 
[DIRS 138819], p. 322, 328). The cone diameter is 230 m and the height is 40 m, which 
accounts for 15 m of the exposed volcanic material and 25 m buried by younger alluvium 
(interpreted from ground magnetic survey data). Assuming a 50 percent erosion of the cone 
height similar to that used by Issue Resolution Status Report Key Technical Issue: Igneous 
Activity (NRC 1999 [DIRS 151592], Section 4.2.5.3.1, Table 3) for SW Little Cone, the total 
height of NE Little cone would have been 80 m (2 x 40 m). Using the equation for a cone 
(V=1/3*pr2h; where r is the radius of 115 m and h is the cone height of 80 m), the resulting 
volume for NE Little Cone is approximately 0.001 km3 (or about 1.1 x 106 m3). Four times this 
volume, 0.004 km3, is chosen as a minimum volume of tephra for a potential future eruption. 
The estimated NE Little Cone tephra volume of 0.004 km3 compares with Lathrop Wells volcano 
tephra volume of 0.04 km3. Therefore, the recommended range of distribution of potential 
tephra volumes for the YMR is 0.004 to 0.08 km3. 
The population of young cinder cones in the YMR is small and does not constrain the probability 
of one particular volume relative to another volume. We conclude that the probability of any 
volume is equal to the probability of any other volume within the given range. In summary, the 
ash (or tephra fall) volume should be treated as a log-uniform distribution with a minimum of 
0.004 km3 and maximum of 0.08 km3. Figure 6-6 shows the range of expected ash volumes for 
use in TSPA-LA and compares it to the previous range for TSPA-Site Recommendation 
(TSPA-SR), which was .002 to 0.44 km3 (CRWMS M&O 2000 [DIRS 151560], p. 32). The 
previous larger volume was based on the voluminous Sunset Crater, Arizona, eruption, which 
overestimates potential ash volumes in the YMR (Sections 6.3.3 and 6.3.3.6). 
The range of ash volume selected for the TSPA-LA represents a more geologically sound 
estimate than that used for the TSPA-SR for the YMR based on the neighboring population of 
Quaternary volcanoes. 
In addition to constraining volumes of volcanic eruptions, for the purposes of predicting the 
effects of an igneous event on the repository it is important to constrain the duration of various 
processes. There are three durations of interest here: 
 
Duration of the entire volcanic event. This includes all processes ranging from 
explosive eruptions to emplacement of lava flows and may include some periods of 
inactivity at the surface. Based upon data compiled by Wood (1980 [DIRS 116536], p. 
402), scoria-cone forming eruptions range from 1 day to 15 years in duration, with a 
median value of 30 days. Wood (1980 [DIRS 116536], p. 402) also states that about 93 
percent of such events last less than one year. For purposes of TSPA, this report 
recommends a log-normal probability for the range from 1 day to 15 years with a 
median of 30 days. This range is based upon observations of historical scoria cone 
volcanoes and accounts for the expected volume of a potential Yucca Mountain volcano 
(i.e., a volume similar to that of the Lathrop Wells volcano, 0.0862 km3; see 
Appendix C). 

 
The duration of cone-building eruptions. This pertains only to the accumulation of 
pyroclastic materials around the vent to form a cone, and does not include other 
processes such as lava flows. Cone-building requires explosive eruption mechanisms, 
some of which might be relatively mild Strombolian bursts and others of which might be 
violent Strombolian. Based upon observations of rates of cone growth as a function of 
time at a limited number of historical eruptions (Figure 6-7), a cone the size of Lathrop 
Wells volcano (140 m high, 0.018 km3 volume) might have formed over a period 
between about 2 and 21 days. This period might not include times during which lavas 
are erupting with no attendant pyroclastic eruptions (lavas can form with no explosive 
activity, or concurrently with explosive activity). In other words, for a volcanic event 
the scale of Lathrop Wells that lasted, for example, for one year, the twenty or so days of 
cone-building might have been spread out over several months. Note that the duration 
of cone-building processes does not come into play for TSPA, while the duration of 
individual violent Strombolian eruption phases does (see below). 
 
The duration of explosive, violent Strombolian eruptive phases. This is of direct 
importance to TSPA because, combined with the mass discharge rate or eruptive power, 
it determines the total mass of erupted material that can be dispersed downwind and 
therefore affect radionuclide dose to a reasonably maximally exposed individual 
(RMEI). Data on durations of historically observed violent Strombolian eruptive phases 
range from about 0.5 hours to as high as 75 days (taking the anti-log of time in Table 
6-5). Data on volume of material ejected during these eruptive phases (determined by 
multiplying mass discharge rated by duration) indicate that there is insufficient 
information to establish whether there is a strong correlation between duration and total 
volume. There is also insufficient data to determine whether a specific probability 
distribution can describe the range of eruptive phase duration. Therefore, this report 
recommends a log-uniform distribution ranging from 0.5 hours to 75 days for individual 
violent Strombolian eruptive phase distribution. 
An approach for creating a realization for duration, power, and volume of a violent Strombolian 
eruptive phase, for use in PA, would follow the procedure below. 
 
Determine a total volcano volume by sampling from a distribution of volumes that 
captures the volumes of Quaternary Crater Flat volcanoes. An alternative would be to 
just use the volume of the Lathrop Wells volcano since it is the preferred analog to a 
potential future Yucca Mountain volcano. 
 
Determine a volcanic event duration by sampling the distribution recommended above 
(1 day to 15 years, with a median of 30 days). 
 
Determine an eruptive power (or mass discharge rate) for an individual violent 
Strombolian phase by sampling from a probability distribution based upon analog data. 
 
Determine the duration for violent Strombolian phase by sampling the log-uniform 
distribution (0.5 hours to 75 days). Ensure that this duration does not exceed the 
duration of the entire volcanic event (second bullet above). 

 
Calculate the total violent Strombolian volume erupted by multiplying mass discharge 
rate (derived from power) by duration. Ensure that this volume is within the range of 
0.004-0.08 km3 that encompasses tephra fall deposits in the YMR, and that this volume 
does not exceed the total volume of the volcano (first bullet above). 
This procedure maintains consistency in durations and volumes of different aspects of a volcanic 
event, and will err on the conservative side because it allows for the possibility of a violent 
Strombolian phase lasting the full duration of the event, as well as producing the full volume of 
the event. 
Source: CRWMS M&O (2000 [DIRS 151560], p. 32); this report. 
NOTE: This log-uniform plot of ash volume shows the range for TSPA-LA (this report) relative to the larger range for 
the SR. 
Figure 6-6. Potential Volume of Erupted Ash for a Yucca Mountain Region Basaltic Volcano 

Source: Wood (1980 [DIRS 116536], p. 402). 
NOTE: The Lathrop Wells volcano height is approximately 140 m. 
Figure 6-7. Changes in Cone Height During an Eruption Based on Observed Strombolian Activity 

Table 6-5. Explosive Eruptive Events, Duration, Power, and Estimated Mass Discharge Rates Used to 
Develop Probability Distributions for Eruptive Plume Dispersal Calculations 
Event 
Log (t) 
(t in s) a 
Log (Po) 
(Po in W) a 
Mass Discharge Rate 
(kg/s) b 
Cerro Negro, 1992 4.8 12.0 7.4 x 105 
Hekla, 1970 3.9 12.8 4.7 x 106 
Tolbachik, 1975 6.1 11.7 3.7 x 105 
Parcutin, 1944 I 5.6 11.1 9.3 x 104 
Parcutin, 1944 II 6.8 11.5 2.3 x 105 
Parcutin, 1946 6.8 9.0 7.4 x 102 
Hekla, 1947 3.3 13.8 4.7 x 107 
Heimaey, 1973 6.4 9.9 5.9 x 103 
a
bJarzemba (1997 [DIRS 100460], p. 136). 
Mass discharge rates based on T = 1,350 K and magma heat capacity cp = 1,000 J K-1 kg-1 (Best 1982
[DIRS 147740], p. 301). Mass discharge rate = Po(cpT)-1. 
6.3.3.5 Entrainment of Wall Rock and Repository Materials in Ascending Magma 
There are no natural analogs or appropriate experimental data representing the interception of 
engineered systems with or without the equivalent of waste fuel, by extrusive magma. A variety 
of processes affect the entrainment of waste by rising magma and its subsequent dispersal. Some 
of these processes are volcanological in nature, and some are related to the nature of the 
engineered system. Each process is associated with its own uncertainties. 
Engineered barrier systemEngineered barrier system processes that may influence the amount 
of waste entrained involve those that govern the fraction of waste that escapes from packages, 
and those governing the final grain-size distribution of that waste. Regarding waste escape, the 
integrity of waste canisters within an erupting mixture is largely unknown. DOE performance 
assessments have all assumed that the waste package fails upon contact with basaltic magma 
(Reamer 1999 [DIRS 119693], p. 82). 
Waste FormPressurized-water reactor fuels are composed of uranium oxide, processed by 
superheated steam into a fine powder whose crystallites are ~0.2 m in size, with a specific 
surface area of about 2 m2 g-1 (Dehaudt 2001 [DIRS 164019], p. 61). The powder is shaped in a 
uniaxial press, densified by sintering, and ground along its perimeter to ~6 mm diameter. 
Following sintering, the UO2 grain size averages 9 m (Dehaudt 2001 [DIRS 164019], p. 63). 
The fuel pellets are inserted into rods of zirconium alloy clad, about 1 cm in outside diameter 
(Dehaudt 2001 [DIRS 164019], p. 60), with a small gap between the pellets and the clad to 
accommodate the escape of fission gases and slight volume change of the pellets. During power 
production, thermal fractures break the pellet up into several pieces and the clad becomes more 
brittle (Dehaudt 2001 [DIRS 164019], Section 5.2.5). At high burnup (>30 GWd/tM), the fuel 
and clad cement together (Piron 2001 [DIRS 162396], p. 41). 
During volcanic disruption, the fuel pellets could be disaggregated by both physical and 
chemical processes, including: 
 
Volatilization and re-condensation of volatile radionuclides 
 
Dissolution of spent-fuel oxides into magmatic melt 

 
Mechanical disaggregation by impact, abrasion, or shock waves 
 
Oxidation of the clad and UO2 waste-form pellets, causing disintegration of both. 
Among these, the latter two processes are most likely to affect dose. Some waste may enter the 
biosphere by volatilization of fission products containing Cl, I, or Cs. Analysis report, 
Radionuclide Screening (BSC 2004 [DIRS 160059], p. 39), shows that the only volatile 
radioisotope to have any significant dosage effect in the eruptive igneous scenario is 137Cs. Due 
to its short half-life (30 years), its effect is minimal in the post-closure stage of the repository. 
These volatile radionuclides are therefore neglected. Dissolution of spent-fuel oxides into 
magmatic melt has apparently not been studied and insufficient data are available for quantifying 
the outcome. Since this process could reduce the quantity of waste reaching atmospheric 
dispersion, it is more conservative to identify the waste as particulate and available for 
atmospheric dispersal with tephra (BSC 2004 [DIRS 170026], Section 5.2.4). 
Mechanical disaggregation of waste pellets could occur by abrasion, impact, or shock waves. 
The final grain size of the waste resulting from these processes would vary depending on the 
energy and duration of those processes, the number of times waste pellets are subjected to them, 
and the strength of the waste (which depends on alteration). No known work examines the size 
reduction that could result from conditions related to volcanic extrusion. Fragmentation of 
waste-form pellets by crushing and grinding (BSC 2004 [DIRS 170026], Appendix H), and by 
penetration of high-energy devices into shipping casks (Sandoval et al. 1983 [DIRS 156313]), 
suggest possible fragment-size distributions, though the fragmentation mechanisms in these tests 
may bear little resemblance to those in natural eruptions. Studies of xenolith size in eruptive 
deposits and their relation to host-rock size distributions may also provide useful constraints, but 
have yet to be undertaken. 
Oxidation of waste pellets is common and well-studied, though most such studies have been 
conducted at temperatures well below magmatic (BSC 2004 [DIRS 169987], Section 6.2.2.2). In 
warm (T=~100-400 C), humid environments, oxidation of spent fuel in the presence of air 
occurs rapidly; in dry air it takes place more slowly, and in humid environments without air very 
slowly or not at all (BSC 2004 [DIRS 169987], Section 6.2.2.2). At T>500 C, however, waste 
can be oxidized by pure steam (BSC 2004 [DIRS 169987], Section 6.2.2.2) to form thin coatings 
on pre-existing UO2 grains or, under moisture-saturated conditions, dehydrated schoepite crystals 
tens to hundreds of microns in length (BSC 2004 [DIRS 169987], Section 6.2.2.2). Oxidation of 
grain surfaces partially disaggregates the waste and increases specific surface area, making it 
more easily soluble in water (BSC 2004 [DIRS 169987], Section 6.2.2.2). During a volcanic 
eruption, oxidation of waste pellets could occur below the ground surface in the presence of 
magmatic gas, or above the ground surface following ejection, though in the latter case oxidation 
would slow dramatically as the ambient gas cools and dries out. Codell (2003 [DIRS 165503], 
Section IIB and IIE) indicates that time scales for magma/waste and atmospheric transport are 
too short to support significant oxidation of waste. The rate of oxidation at magmatic 
temperature and the effect of oxidation on disaggregation and final grain size are not known in 
any quantitative way. 
Volcanic ProcessesUncertainties are inherent in the following volcanic processes: 
 
Interaction between a rising dike and perturbed stress field around repository drifts 

 
Interaction between rising, vesiculating magma and partially open drifts (e.g., would 
magma flow like lava for long distances down the drifts, would it pile up quickly to 
block the drift and, therefore, allow magma to continue rising, or would it explode down 
the drift as a pyroclastic mixture) 
 
Depth to which conduits might extend (i.e., if a wide conduit is formed but extends only 
200 m below the surface, then it will not have as large a disruptive effect on the 
repository). 
Wall-rock xenoliths are incorporated into rising magma by mechanical disruption of dike walls 
and during conduit growth, but they do not provide a perfect analog for engineered materials that 
could be disrupted by magma flooding a repository drift. There are a few data available on the 
interaction of magma with undisturbed country rock and subsequent eruption of the lithic debris 
for the range of eruptive styles that can be reasonably expected at Yucca Mountain. For 
example, Valentine and Groves (1996 [DIRS 107052], pp. 79-84) report data on the quantity of 
wall rock debris erupted from various depths during Strombolian, Hawaiian, effusive, and 
hydrovolcanic activity at two volcanoes. Hydrovolcanic eruptions reported by Valentine and 
Groves contained between 0.32 and 0.91 volume fraction of wall rock debris, with most of that 
originating in the uppermost about 510 m of the dike/conduit feeder systems. Strombolian, 
Hawaiian, and effusive eruptions ejected much lower volumes of wall rock debris, commonly 
resulting in total volume fractions of 10-3 to 10-5. Doubik and Hill (1999 [DIRS 115338], p. 60) 
state that the Lathrop Wells volcano has a relatively high average lithic volume fraction of 
9  10-3 for xenoliths greater than 1 mm, based on image analysis of unspecified locations. It is 
possible that all the locations studied by Doubik and Hill were located in a quarry that exposes 
proximal cone deposits. Clarification of this issue has required analysis of more exposures at 
Lathrop Wells and is discussed in Appendix C2.2, where it is shown that Doubik and Hill may 
have overestimated the lithic content for Lathrop Wells. Addressing this issue may be important 
because Doubik and Hill (1999 [DIRS 115338], p. 61) cite similarity of lithic content as a 
justification for using the relatively large and violent Tolbachik eruptions as analogs for the 
Lathrop Wells volcano (and, hence, potential eruptions at Yucca Mountain). 
6.3.3.6 Characteristics of Strombolian and Violent Strombolian Deposits 
6.3.3.6.1 Bulk Grain Size 
As described in Section 6.3.3, explosive eruptive styles of Quaternary volcanoes in the YMR 
include both Strombolian and violent Strombolian. Strombolian eruptions are characterized by 
short-duration bursts that throw relatively coarse fragments of melt out of the vent on ballistic 
trajectories. Most of the fragments (clasts) are deposited immediately around the vent, with only 
a very small fraction of finer particles rising higher and being dispersed by wind to form minor 
fallout sheets. 
Violent Strombolian eruptions, on the other hand, are characterized by vertical eruption of a 
high-speed jet of a gas-clast mixture and fragments or clasts tend to be finer grained. Table 6-6 
also shows bulk eruptive clast-size distributions for three historic violent Strombolian eruptions 
(Tolbachik and Cerro Negro, 1971 and 1968; Maleyev and Vande-Kirkov 1983 [DIRS 144325], 
pp. 61-62; Rose et al. 1973 [DIRS 116087], p. 342). Mean clast diameters for these eruptions 

range from 0.19 to 0.37 mm, and standard deviations range from 1.5 to 2.5 f units (defined in 
Section 6.1.3.4). These values can be compared to those from a more typical Strombolian 
eruption (Etna Northeast crater). 
Table 6-6. Estimated Bulk Clast Size Distribution Parameters for Three Violent Strombolian Eruptions 
(Tolbachik and Cerro Negro 1971 and 1968) and One Strombolian Eruption (Etna 1971) 
Violent Strombolian Eruptions 
Strombolian 
Eruption 
Combined Great 
Tolbachik N. 
Breakthrougha 
Cerro Negro 1971 
(Overall)b 
Cerro Negro 1968 
(Overall)b 
Bulk Etna 
Northeast Craterc 
Median (mm) 0.3 0.24 0.15 95 
Graphic Mean (mm) 0.37 0.23 0.19 110 
Graphic Standard 
Deviation (sf) 2.5 1.5 1.83 3.48 
a
Sources: 
b 
Derived from data presented in Maleyev and Vande-Kirkov (1983 [DIRS 144325], pp. 61-62). 
Rose et al. (1973 [DIRS 116087], p. 342). 
c 
Estimated from McGetchin et al. (1974 [DIRS 115469], p. 3264, Figure 9). 
The mean bulk particle size for modeling an energetic violent Strombolian eruption for the 
Yucca Mountain area should be sampled from a log-triangular distribution with a minimum of 
0.01 mm, mode of 0.1 mm, and a maximum of 1.0 mm, to cover 2 orders of magnitude of sizes. 
For comparison, Jarzemba (1997 [DIRS 100460], p. 137) gives a log-triangular distribution with 
a minimum of 0.1 mm, a median of 1 mm, and a maximum of 100 mm. Although this upper 
range accounts for the larger lapilli sizes and smaller blocks and bombs, these particles would 
fall ballistically on or near the cone and would not contribute much or any mass to the downwind 
tephra deposit. Therefore, the upper limit of 1.0 mm for the suggested distribution gives some 
additional conservatism to calculations in Atmospheric Dispersal and Deposition of Tephra from 
Potential Volcanic Eruption at Yucca Mountain, Nevada (BSC 2004 [DIRS 170026]) and TSPA. 
Given a mean clast size, the standard deviation of the particle size is needed to provide 
Atmospheric Dispersal and Deposition of Tephra from Potential Volcanic Eruption at Yucca 
Mountain, Nevada (BSC 2004 [DIRS 170026]) with sufficient information on the particle size 
distribution. Table 6-6 provides information on the graphic standard deviation sf (defined in 
Section 6.1.3.4). It is recommended that, for a given mean particle diameter, sf be sampled from 
a uniform distribution between sf = 1 and sf = 3. 
6.3.3.6.2 Clast Characteristics 
The clasts produced by Strombolian and violent Strombolian eruptions can be quite different in 
character. Strombolian eruptions produce a much higher proportion of coarse clasts, with the 
mean diameter commonly being greater than 10 cm (Table 6-6). Common Strombolian clast 
types include ribbon, spindle, and cowpie bombs. Ribbon and spindle bombs take their shape as 
they are stretched and torn or as they spin through the air on their dominantly ballistic paths; 
these shapes indicate the hot, fluid state of the clasts during flight. Cowpie bombs are very hot 
and fluid when they hit the ground. All these clasts are hot during flight and deposition because 
of their large size (low surface-area-to-volume ratio minimizes heat loss) and low eruption height 

(they have less time to cool before hitting the ground). These large clasts may have vesicle 
(bubble) volume fractions up to about 70 percent. Smaller clasts, in the mm to cm range, tend to 
be sub-equant vesicular scoria clasts, and they can have a range of vesicularities (for example, 
the Cinder Cone eruption at Lassen Volcanic National Park, California, produced scoria with 
vesicularities of 20 to 70 percent; Heiken and Wohletz 1985 [DIRS 106122], p. 34). Finer 
ash-sized clasts tend to be less vesicular, and can range from irregular to fluidal to blocky in 
shape. 
Violent Strombolian eruptions carry clasts much higher in the air, providing more cooling time; 
the clasts also cool more quickly because they have a much higher degree of fragmentation. 
A much larger proportion of the clasts is in the mm to cm size range compared to Strombolian 
eruptions, and most of these clasts have irregular shapes and relatively high vesicularities. 
In violent Strombolian eruptions, the long-range, downwind transport and fallout of clasts 
becomes an important issue for YMP TSPA calculations. Transport and deposition of clasts 
depend on their settling velocity in air, which in turn depends on their bulk density (the melt 
density corrected for the porosity, or vesicularity, of the clasts) and shape. Calculations of clast 
dispersal commonly use a shape factor, F = (b + c)/2a, where a, b, and c are the lengths of the 
longest, medium, and shortest axes of the clasts. Clasts produced by these types of eruptions can 
have a range of shapes. Jarzemba (1997 [DIRS 100460], p. 139) used a value of F = 0.5 as a 
shape factor that is likely to be representative of common clast shapes, and in the absence of 
further data, we recommend this value for TSPA calculations for YMP. 
Density of erupted particles varies with particle size because larger particles tend to have a 
higher fraction of vesicles (bubble voids) than small particles. Detailed data are lacking, but it is 
recommended that the particle density be varied as follows: 
 
For particle diameters less than or equal to 0.01 mm, the particle density is 0.8 of the 
magma density (which is taken to have an average density value of 2,600 kg/m3 for a 
Lathrop Wells-type magma). This value is based on a fine-particles void fraction of 0.2 
due to vesicles. 
 
For particle diameters greater than or equal to 10 mm, the particle density is 0.4 of the 
magma density. This value is based on a void fraction of 0.6 due to vesicles. 
 
Between 0.01 mm and 10 mm, the density should increase linearly with the logarithm of 
the diameter. This accounts for increasing vesicularity with increasing clast size. 
6.3.3.6.3 Density of Fallout Deposits 
Bulk in situ density of fallout deposits typically ranges from 300 to 1,500 kg/m3 
(Sparks et al. 1997 [DIRS 144352], p. 366), but is rarely directly measured, particularly for 
basaltic deposits such as are most likely in the YMR. Blong (1984 [DIRS 144263], p. 208) has 
measured a range of fallout deposits that have a density of approximately 1,000 kg/m3. There are 
two reasonable ways of treating deposit density in TSPA calculations: 1) simply use 
1,000 kg/m3 or 2) use a sample from a normal distribution of deposit densities ranging from 
300 to 1,500 kg/m3 with a mean of 1,000 kg/m3. 

6.3.4 Redistribution of Basaltic Tephra in the YMR 
If a volcano were to intersect the repository, it would most likely result in ash contaminated with 
radioactive waste being dispersed in a direction determined by the prevailing wind during a 
future eruption. The resulting tephra sheet would blanket the terrain, being thickest (perhaps a 
few meters) immediately surrounding a cone and gradually thinning and becoming finer-grained 
towards its distal margins. After deposition of the tephra sheet (ash and waste particles) would 
be available for redistribution by normal sedimentary processes that include erosion and 
deposition by water and wind. This section of the report discusses the field studies and results of 
analyses that support the ash redistribution conceptual model developed in Atmospheric 
Dispersal and Deposition of Tephra from a Potential Volcanic Eruption at Yucca Mountain, 
Nevada (BSC 2004 [DIRS 170026], Section 6.6, Appendix I). The ash redistribution conceptual 
model captures the effects of sedimentary processes leading to redistribution of contaminated ash 
at the location of the RMEI (defined at a location 18 km south of the proposed Yucca Mountain 
repository; Figure 6-8). Two bounding conditions are considered in the conceptual model: 
 
Outcome 1 corresponds to the modeling cases where the sampled wind directions are 
toward the RMEI, resulting in ash deposition at the RMEI location. 
 
Outcome 2 corresponds to the modeling cases where tephra is not deposited directly at 
the RMEI but deposited (consistent with prevailing winds) within the Fortymile Wash 
Basin, which then becomes the source for potential downstream redistribution towards 
the RMEI location. 
For Outcome 1 or cases where the tephra deposition is in the direction of the RMEI location 
(Figure 6-8), the deposit is most likely to be thin and consist of ash-sized particles. The deposit 
would initially blanket both distributary channels (a network of stream channels) and 
interchannel divide surfaces (surfaces between the stream channels, which are several tens of 
centimeters to a maximum of about 1 m above the channel bottoms). These geomorphic features 
are characteristic of alluvial fans that develop in semi-arid and arid climates. Tephra deposited 
on interchannel divide surfaces may be subject to the following processes: 
 
Redistribution by wind 
 
in situ dilution by eolian sand and silt 
 
Mechanical and chemical infiltration into the underlying soil profile. 
Flood events could also dilute and transport material that was originally deposited on 
interchannel divide surfaces into runoff channels. For tephra deposited directly onto distributary 
channel bottoms, the above processes are relevant as well as the additional dilution and 
redistribution of tephra by occasional flash floods. 
For Outcome 2 or cases where the tephra is not deposited in the direction of the RMEI location, 
but is deposited in areas upstream from that location, redistribution of tephra to the RMEI area 
will be dominated by fluvial transport down Fortymile Wash (Figure 6-8). With time, the 
concentration of ash and waste will be reduced as sediment is transported to the RMEI location 
from upstream sources. Initially, this process will result in upstream-derived sediments being 

For illustration purposes only. 
NOTES: The green-colored areas are distributary channels and equal 18% of the total fan area (Planimetered data 
from 1:100,000 topographic map). The tan areas are interchannel divides and equal 82% of the total fan 
area (Planimetered data from 1:100,000 topographic map). 
Figure 6-8. Fortymile Wash Watershed 

mixed in with or deposited on the surface of the primary tephra deposit. Eventually, the primary 
tephra deposit will be locally incised to its base, exposing underlying sediments, and, ultimately, 
the primary deposit may be completely incised across the entire width of the wash so that no 
primary deposit remains. At that time, though, it is likely that tephra will continue to be 
transported into the wash from the flanks and hill slopes immediately adjacent to the wash (e.g., 
Yucca Mountain itself). 
The processes of sediment transport in a setting such as Fortymile Wash are complex and 
sporadic and are very difficult to model. For example, introduction of hill-slope material directly 
into the wash might occur during relatively localized, intense thunderstorms, but these are not 
likely to result in transport far downstream in the wash. Major flood events (e.g., 100-year 
storms) can mobilize hill-slope material into the wash and additionally transport material 
downwash many kilometers. The effects, both during individual storm events and integrated 
over long times and many events, will be dominated by: 
 
Dilution of tephra by arrival of upstream-sourced sediments 
 
Dilution of tephra by material washed from the wash flanks directly into the wash 
 
Mixing with pre-existing sediments along the bed of the wash. 
Results of two studies that quantify some aspects of tephra redistribution are described below 
and discussed in the following sections of this report: 
 
Ash dilution studies, conducted around the Lathrop Wells volcano, demonstrate dilution 
of ash with other sediments as it is transported downstream in a wash. This is most 
pertinent for tephra deposited directly onto distributary channel bottoms associated with 
Outcome 2. 
 
137Cs studies, which constrain the rates of in situ surficial processes in the past 
approximate 50 years based on fallout from atmospheric nuclear weapons testing. This 
provides information that is most applicable to tephra deposited on interchannel divide 
surfaces associated with Outcome 1. 
6.3.4.1 The Ash Dilution Study at Lathrop Wells Volcano 
The ash dilution study focused on the Lathrop Wells volcano tephra sheet as an analog for ash 
that could potentially cover the eastern flank of Yucca Mountain in some future basaltic 
eruption. The part of the tephra sheet used for this study encompasses roughly 500 m2 of a 
tuff-bedrock hillslope (~10 percent slope) to the northwest of the Lathrop Wells volcano and is 
approximately 100 m horizontally from top of the hillslope to the bottom (Figure 6-9). Small 
drainage channels have been excavated by debris-flows into this sheet, and two larger drainage 
systems transport ash and sediment away from the hillslope. One drainage transports material 
around the west side of the cone and southward, ultimately into the Amargosa Valley. The other 
drainage heads near the top of tephra sheet exposure and transports material around the eastern 
side of the cone. Eventually, each of these channels joins much larger channels carrying non-ash 
components. Farther south in the Amargosa Valley, these parallel channels run marginal to the 
edge of the Fortymile Wash alluvial fan and terminate in nearly the same location in the valley. 
All sample locations within this setting for the ash-dilution study and cesium study are shown in 
Figure 6-10. 

NOTES: For illustration purposes only. Photo source: EG&G Mission, August 28, 1994, Photo frame 140, Elevation 
32,000 ft. 
The Lathrop Wells basaltic cone is shown in the center of the photo with a tephra sheet draping the hill to 
the north. Two sets of samples were collected: one off the tephra and the drainage system that goes east 
around the cone; the second set follows the drainage channel that lies west of the cone. The Amargosa 
Valley is south of the photo. 
Figure 6-9. Aerial Photo Showing Lathrop Wells Drainage System 

Source: Harrington (2003) [DIRS 164775]. 
NOTE: Lathrop Wells volcano is indicated with a star symbol. Yucca Mountain is the N-S linear mountain in the 
north-central part of the map. 
Figure 6-10. Sample Locations for Ash Dilution and Cesium Studies 

Sediment samples were collected from the drainage located on the western edge of the tephra 
sheet. In the upper part of the channel, sample spacing was 100 m. In the lower reach, below the 
junction with the larger, non-ash-bearing channel, sample spacing was 600 m. On the eastern 
side of the Lathrop Wells volcano ash sheet, sample spacing was 150 m from the very head of 
the ash sheet, down a debris-flow channel, and into a channel that runs marginally to the tephra 
sheet exposure. This channel drains northeast around the edge of the lava flows to the eastern 
side of the cone. Sample spacing below this point was 600 m. This channel network is joined by 
a much larger channel that drains extensive areas from the northeast for several kilometers 
(Figure 6-9). This channel delivers large quantities of tuffaceous sand and gravel into the 
sampled drainage. Downstream from the juncture, the channel drains south into the Amargosa 
Valley along the western edge of the Fortymile Wash fan. 
The Lathrop Wells volcano ash-dilution study results from the two drainages are listed in 
Table 6-7. Five samples covering a distance of 1,900 m were collected from the western 
drainage through three confluences with larger channels; the latter channels drain progressively 
larger areas that do not contain Lathrop Wells volcano tephra at the surface. The results plotted 
in Figure 6-11 show that after only 1 km of transport, significant dilution to about 50 wt% ash by 
addition of other tuffaceous sediments has occurred. Dilution occurs by the addition of 
tuffaceous sediments from adjoining drainages and by incorporation of a large eolian sand load. 
Continued transport, with the addition of clasts of welded tuff and eolian grains, acts to wear 
down the scoria clasts to smaller particle sizes. This decreased particle size during transport 
shows two major trends down-channel. High on the tephra sheets, the particle size is dominated 
by the 2 to 4 cm granule sizes with few sand size grains present in the sample. Once beyond the 
tephra sheet, however, the sand sizes less than 2 mm become the dominant component due to the 
incorporation of eolian sands blowing in from the Big Dune area and through grain-to-grain 
diminution of larger clast sizes. With continued transport southward into the Amargosa Valley, 
these two processes remain important, leading to the final nature of the deposit that reaches the 
location of the RMEI. 
Table 6-7. Ash Weight Percentages in Samples of Drainage Channels near Lathrop Wells Volcano 
Sample 
Number 
Basaltic Ash 
(wt%) 
Approximate Distance 
from Head of Channel 
(m) 
Lathrop Wells Volcano, West Side 
LWASH1-07/11/02-1 98.7 0 
LWASH1-07/11/02-3 92.3 100 
LWASH1-07/11/02-5 35.0 200 
LWASH1-07/12/02-3 50.8 900 
LWASH1-07/12/02-5 39.6 1,900 
Lathrop Wells Volcano, East Side 
LWASH2-08/1/02-1 54.9 0 
LWASH2-08/1/02-3 59.4 300 
LWASH2-08/1/02-6 10.1 1,400 
LWASH2-08/1/02-8 0.8 2,200 
Source: DTN: LA0405CH831811.001 [DIRS 169998]. 

Source: DTN: LA0405CH831811.001 [DIRS 169998]. 
Figure 6-11. Ash Dilution Percentages in Drainage Along the West Side of Lathrop Wells Volcano 
The second set of drainages sampled at Lathrop Wells volcano traverse the north and east side of 
the scoria cone and lava flows. There are three confluences with larger streams along this 
sampling transect. Four samples were collected over 2.2 km (Table 6-7 and Figure 6-12). The 
sample from the top of the tephra sheet, at the head of a debris-flow channel, shows the effects of 
eolian sand deposition and yields about a 50/50 mixture of ash and sand. After transport off the 
tephra sheet and into a marginal channel at the base of the slope, the ash content in the sample is 
still about 60 wt% (sample LWASH2-08/1/02-3) because the location is adjacent to the tephra 
sheet. Below the point where the channel joins the first drainage bringing tuffaceous material 
from the north, the ash content is reduced by dilution to 10 wt% (sample LWASH2-08/1/02-6). 
After an additional 1.8 km, the channel intersects another larger wash that delivers tuffaceous 
sediments from northeast of the volcano (Figure 6-9). Down-gradient from where the sediments 
from the two channels merge, the basaltic ash present is barely measurable (0.8 wt% ash, sample 
LWASH2-08/1/02-8). The near-complete reduction in volume of ash per volume of sediment 
occurs within a distance of less than 3 km. 

Source: DTN: LA0405CH831811.001 [DIRS 169998]. 
Figure 6-12. Ash Dilution Percentages in Drainage Along the East Side of Lathrop Wells Volcano 
The dilution studies documented at the Lathrop Well volcano demonstrate that significant 
reduction of volume of basaltic ash per volume of sediment occurs over short distances during 
transport due to the continuous addition of other tuffaceous material to the drainage systems. 
However, it is not feasible to develop a simple scaling factor for the ash-dilution rate to apply to 
the much larger drainage area of Fortymile Wash because of the complexities due to differences 
in the basin area, bedrock types, gradients, vegetation, elevation, and precipitation. For the 
Lathrop Wells volcano area, however, the ratio of the drainage basin that includes the extensive 
areas northeast of the volcano to the area down-gradient from the tephra sheet exposure is about 
6:1, meaning that the size of drainage area that supplies non-ash sediment is six times larger than 
that which supplies ash from the tephra sheet. For the Fortymile Wash drainage, the basin area 
above the repository site is approximately 8 times larger than the area down-gradient from the 
repository site. If a future volcanic eruption through Yucca Mountain deposited contaminated 
ash within or across this basin area, rapid and aggressive mixing and dilution of basaltic ash with 
siliceous tuffaceous sediments will occur during the transport toward the RMEI location. 
6.3.4.2 137Cs Studies 
6.3.4.2.1 137Cs Study of the Fortymile Wash Alluvial Fan 
Radioactive 137Cs was distributed worldwide as a result of atmospheric nuclear weapons tests 
beginning around 1950 (Ely et al. 1992 [DIRS 164076], p. 196). As cesium accumulated on 
ground surfaces, it was incorporated into any sediments subsequently formed by transport and 
deposition. Therefore, 137Cs can serve as a time-marker for sediments formed during the last 
50 years. As such, the measurement of the concentration of 137Cs with depth in the soil can be 

used to examine erosion and deposition rates over this short time period. Uncertainty enters 
when relating processes and rates acting over a short time period (~50 years) to 
erosion/deposition over much longer periods (> 1 ky). However, careful examination of where 
and how modern erosion and deposition are occurring can help elucidate what is likely to occur 
sometime in the future. 
In earlier 137Cs landscape-component studies (Chappell 1999 [DIRS 163891], p. 138), the 
investigated sites were either along transects or on plots of about a dozen square kilometers. The 
current study examines the movement of sediment through the drainage systems for an area that 
encompasses several hundred square kilometers, including the Yucca Mountain site and 
Fortymile Wash alluvial fan (the fan alone encompasses 100 km2). Because of the uncertainties 
in applying this technique to this large area, the purpose is to note trends or similarities for sites 
of erosion or deposition. 
137Cs attaches preferentially to silt- and clay-size particles in normal sedimentary profiles, but 
also to dune sand as, for example, in the sands of Big Dune (Amargosa Valley), and to sand 
grains in small coppice dunes that traverse surfaces of alluvial fans. The cesium analyses 
discussed below show some of the highest cesium values from these dune materials, which 
possess almost no fine-grained material. 
In the study area, most alluvial surfaces contain a prominent vesicular A-horizon composed of 
silt with minor amounts of clay, often directly beneath a desert pavement. Because desert 
pavements develop over thousands of years, they are characteristic of very stable surfaces. Part 
of this study (the reference sample suite) was designed to verify that 137Cs does not infiltrate 
rapidly into the deeper sediments so that depth profiles among sites could be compared 
confidently. The remainder of the study examines the cesium quantities in the material, vertical 
cesium profile, and particle-size composition of the upper 6 to 10 cm of sediments to help 
determine erosion/deposition rates on the Fortymile Wash alluvial fan surfaces. 
6.3.4.2.2 Reference Sites for 137Cs Study 
Previous studies using 137Cs in North America (Wallbrink et al. 1994 [DIRS 164092], p. 95) did 
not find a single value that could be used as a calculated background value for every study. 
Thus, a study was performed to determine the nature of cesium distribution around Yucca 
Mountain, and reference samples were used to compute the Yucca Mountain background value. 
Samples were collected at four locations along Fortymile Wash and within Crater Flat 
(Figure 6-10). For each sample location, alluvial surfaces were selected based on characteristics 
associated with their long-term stability, including the presence of a well-developed desert 
pavement overlying a well -developed, 4 to 6 cm thick, vesicular A-horizon (at least 
pre-Holocene time or 10,000+ yrs). Two sample locations, about 3 km apart, were located on a 
high, river-cut terrace in Fortymile Wash, and two sampling sites were located in central Crater 
Flat, about 2 km west of Yucca Mountain. Sample pits were hand-dug to approximately 0.5 to 
0.75 m depth. At each location, three samples were collected from a 0-3, 3 -6, and 6-9 cm depth. 
Commonly, a caliche layer within the alluvium was visible in the bottom of the pit but was not 
sampled. Carbonate in the soil at this depth indicates the age of the overlying soil as Pleistocene 
(10,000+ years) (Gile et al. 1981 [DIRS 144518], pp. 67-68). In addition, the lower alluvium 

commonly contained thin, subvertical carbonate stringers, which usually take more than 1,000 
years to develop in soils (Machette 1985 [DIRS 104660], pp. 5-11). 
6.3.4.2.3 Results and Interpretation of Reference Samples 
The analytical results show that most of the 137Cs is present within the upper 3 cm of the 
A-horizon in these stable environments (Figure 6-13a). Hence, there is little evidence in the 
Yucca Mountain area of any significant cesium infiltration (below 6 cm) into the deeper 
sediments during the last 50 years. 
If cesium infiltration were a significant process over the past 50 years, these stable surfaces 
would exhibit the greatest depths of cesium infiltration, because no surficial processes have 
modified these stable surfaces for times much longer than 50 years. However, the uppermost 
soil layer (vesicular-A), composed mostly of eolian-derived silt, should also act to retain the 
137Cs in the near-surface. 
Depth profiles for 137Cs show similar trends among the suite of reference samples. A typical 
profile has a maximum value of about 0.325 picocuries per gram (pCi/g) (range 0.251 to 
0.421 pCi/g) in the upper 3 cm of soil, a lower average value of about 0.050 pCi/g in the 3 to 
6 cm layer, and effectively an absence of 137Cs in the 6 to 9 cm depth layer. This trend is shown 
schematically in Figure 6-13b. The reference samples retain almost their entire inventory of 
137Cs very near the surface because the 137Cs attaches to fine-grained material in the upper part of 
the soil profile soon after deposition, and remains immobile. Hence, the reference profiles 
suggest minimal infiltration of 137Cs in the profile. This typical depth profile for the reference 
suite can be a useful tool for comparison with other samples (Figure 6-13a). The whole profile at 
each sample location is used in the comparison process. 
6.3.4.2.4 Sampling of the Fortymile Wash Alluvial Fan 
Fifty-one sediment samples for the 137Cs analysis were taken along three latitudinal transects 
across the Fortymile Wash alluvial fan (located in the area where Fortymile Wash crosses 
Highway 95, and to the south; Figure 6-10). Fifteen samples were collected from south of 
Lathrop Wells volcano to near the toe of the fan, as well as from Big Dune and the geomorphic 
surface on which it sits. Samples are representative of the Fortymile Wash channel, tributary 
drainage channels, overbank deposits, interchannel divide areas, coppice dunes near channels, 
and large sand-covered tracts around Big Dune. Analytical results from these laboratory 
measurements are listed in Table 6-8 and archived with DTN: LA0308CH831811.002 
[DIRS 164853]. 

(a) Typical 137Cs Reference Sample Profile with Depth in Soil 
(b) Example of 137Cs Profiles Showing Effects of Erosion 
Source: DTN: LA0308CH831811.002 [DIRS 164853]. 
NOTE: The black line is typical reference sample Cs-137 profile with depth in sediment on the Fortymile Wash fan. 
The red line represents the Cs-137 profile from which 1 cm of material has been eroded. The blue line 
represents the Cs-137 profile from which ~ 1 to 1.25 cm has been eroded. The three curves are similar 
except that the tops of the red and blue curves have been truncated and do not have the upper part that is 
present on the black curve. 
Figure 6-13. 137Cs Sample Profiles 

Table 6-8. Interpretation of 137Cs Profile Values for Samples from the Fortymile Wash Alluvial Fan 
Sample # 
Layer 
Depth 
137Cs(pCi/g) in 
Layer Topographic Position 
Interpretation of 137Cs 
Profile Values 
Cs-071702-A1 
Cs-071702-A2 
0-3 cm 
3-6 cm 
0.259 +/- 0.045 
0.054 +/- 0.016 
In old channel-overbank About 0.5 cm removed by wind 
erosion 
Cs-071702-B1 0-3 cm 0.146 +/-0.030 Channel Sediments well mixed before 
Cs-071702-B2 3-6 cm 0.125 +/- 0.023 deposition 
Cs-071702-C1 0-3 cm 0.209 +/- 0.036 Interchannel divide About 1 cm of eolian removal 
Cs-071702-C2 3-6 cm 0.049 +/- 0.012 
Cs-071702-D1 0-6 cm 0.276 +/- 0.049 Flood channel-overbank Old deposit, slightly stripped (,0.25 
cm) 
Cs-071702-E1 0-3 cm 0.159 +/- 0.030 Interchannel divide About 1.5  2 cm of material 
removed 
Cs-071702-E2 3-6 cm 0.049 +/- 0.015 
Cs-071702-F1 0-6 cm 0.306 +/- 0.053 Coppice dune Wind deposition site, although 
temporary 
Cs-071702-G1 0-3 cm 0.118 +/- 0.025 Interchannel divide Appears to have lost more than 2 
Cs-071702-G2 3-6 cm 0.000 +/- 0.010 cm 
Cs-071802-H1 0-3 cm 0.191 +/- 0.035 Interchannel divide Appears to have lost 2 cm 
Cs-071802-H2 3-6 cm 0.006 +/- 0.013 
Cs-071802-I1 
Cs-071802-I2 
0-3 cm 
3-6 cm 
0.374 +/- 0.065 
0.015 +/- 0.014 
Interchannel divide 
Pebbly pavement 
Stable site, with no removal 
Cs-071802-J1 0-3 cm 0.099 +/- 0.022 In active channel Mixing of sediments during 
Cs-071802-J2 3-6 cm 0.056 +/- 0.025 bottom transport in channel 
Cs-071802-K1 
Cs-071802-K2 
0-3 cm 
3-6 cm 
0.325 +/- 0.055 
0.015 +/- 0.008 
Interchannel divide with 
gravel surface 
Stable site, if material removed 
only 2 cm 
Cs-071802-L1 0-6 cm 0.322 +/- 0.057 Coppice dune Stable sand deposit 
Cs-071802-M1 0-3 cm 0.031+/- 0.017 Main channel Material in channel moved fairly 
recently 
Cs-071802-N1 0-3 cm 0.198 +/- 0.037 Flood surface with Typical overbank deposits 
Cs-071802-N2 3-6 cm 0.020 +/- 0.012 overbank deposits 
Cs-071802-N3 6-9 cm -0.012 +/- 0.013 
Cs-071802-O1 0-6 cm 0.111 +/- 0.022 Coppice dune Sand has been moving across 
surface 
Cs-071802-P1 0-3 cm 0.231 +/- 0.013 Interchannel divide At least 1 cm of removal by wind 
Cs-071802-P2 3-6 cm 0.040 0.0.013 
Cs-071802-Q1 0-3 cm 0.204 +/- 0.037 Interchannel divide with At least 2 cm of removal by wind 
Cs-071802-Q2 3-6 cm 0.001 +/- 0.012 eolian winnowing/lag 
Cs-071802-R1 0-3 cm 0.227 +/- 0.042 Interchannel divide with At least 1 cm removal by wind 
Cs-071802-R2 3-6 cm 0.010 +/- 0.012 pebbly lag/eolian 
removal 
Cs-071802-S1 0-3 cm 0.251 +/-0.0.043 Old fan with poorly Stable fan surface, ~0.5 cm 
Cs-071802-S2 3-6 cm 0.034 +/- 0.010 developed pavement removed 
Cs-071802-T1 0-6 cm 0.014 +/- 0.022 Coppice dune Active dune with sand held 
temporarily 

Table 6-8. Interpretation of 137Cs Profile Values for Samples from the Fortymile Wash Alluvial Fan 
(Continued) 
Sample # 
Layer 
Depth 
137Cs (pCi/g) in 
Layer Topographic Position 
Interpretation of 137Cs 
Profile Values 
Cs-071802-V1 0-3 cm 0.322 +/- 0.056 Interchannel divide with Stable surface, almost no 
Cs-071802-V2 3-6 cm 0.002 +/- 0.011 well developed infiltration of cesium 
pavement 
Cs-071802-W1 
Cs-071802-W2 
0-3 cm 
3-6 cm 
0.097 +/- 0.026 
0.038 +/- 0.014 
On active fan surface 
with flood deposits/ 
overbank 
Active surface with recent 
flood/overbank deposition 
Cs-071802-X1 3-6 cm 0.200 +/- 0.035 Old fan surface divide; About 11.5 cm of removal by 
Cs-071802-X2 3-6 cm 0.028 +/- 0.012 pebble lag indicates eolian processes 
eolian 
Cs-071802-Y1 0-3 cm 0.088 +/- 0.020 Active fan surface, but Sediment mixed 
Cs-071802-Y2 3-6 cm 0.045 +/- 0.014 seldom flooded 
Cs-071802-Z1 0-3 cm 0.240 +/- 0.043 Surface with a silt cap Surface has been stable except for 
Cs-071802-Z2 3-6 cm 0.078 +/- 0.016 indicating ponding in the 1 cm of removal 
past 
Cs-071802-AA1 
Cs-071802-AA2 
0-3 cm 
3-6 cm 
0.275 +/- 0.047 
0.016 +/- 0.011 
Interchannel divide area 
with pebble lag/eolian 
removal 
Surface has 1 cm of removal 
Cs-071802-BB1 
Cs-071802-BB2 
0-2 cm 
2-5 cm 
0.255 +/- 0.045 
0.066 +/- 0.015 
Interchannel divide with 
eolian activity; produced 
a pebble lag 
Surface has eolian removal of at 
least 1 cm 
Source: DTN: LA0308CH831811.002 [DIRS 164853]. 
6.3.4.2.5 137Cs Results and Interpretation of Data 
Overbank deposits on the interchannel divide areas indicative of periodic flooding are 
uncommon and restricted to narrow strips along the channel banks. The overbank and channel 
deposit samples have similar 137Cs signatures (the 3 to 6 cm layers and the 6 to 9 cm layers have 
nearly the same values in the 0.100-0.200 pCi/g range), indicating that the material from each 
environ was mixed during transport and deposited as a homogeneous sediment. The absence of 
many overbank deposits along the channel margins today indicates that flows sufficient to form 
extensive overbank flooding down Fortymile Wash and its distributary channels have not 
occurred in more than 50 years. Therefore, the channels currently transport most of their 
sediment load across the fan until it reaches the toe of the fan, where deposition occurs on the 
broad flats to the south or into the channel of the Amargosa River. 
Sample locations whose 137Cs profiles most resemble the reference-sample (stable surface) 
profiles are located on interchannel divide areas between distributary channels. These profiles 
are similar to the reference profiles that have low 137Cs values (in the range of 0.02 to 0.08 pCi/g) 
in the 3 to 6 cm layers. However, the surface layers (1-3 cm depth) typically have values much 
less than the reference samples from equivalent depths (range from 0.251 to 0.421 pCi/g). The 
data indicate that many of these interchannel divide areas have had part of the upper layer 
removed. Interchannel divide areas have the least likelihood of having been submerged during 
floods over the last fifty years. Thus, the loss of material from these otherwise stable surfaces 
appears to be due to eolian processes. Erosion of an interchannel divide area with little evidence 
of recent water movement is most easily explained by eolian removal. Evidence for wind 

erosion as the predominant process on the interchannel divide areas includes the lack of new or 
developing stream channels and the presence of modern coppice dunes near channels on 
interchannel divides. The presence of nearby Big Dune and other eolian deposits provides strong 
support for eolian erosion and transport. 
The amount of material removed from the interchannel divide areas was estimated by comparing 
the 137Cs value of the upper 3 cm layer to that of the reference value and calculating the thickness 
of the layer that would have to be removed to obtain the lower value. Applying this method 
across the interchannel divide sample locations indicates 1 to 2 cm of material has been removed 
from the interchannel divide surfaces in the last 50 years. This results in erosion rates that range 
from 0.02 to 0.04 cm/yr. These rates are similar to erosion rates of: 
 
0.019 cm/yr predicted to occur on farmland in Amargosa Valley (obtained from BSC 
2004 [DIRS 169459], Section 6.4.2 by converting 0.19 kg/m2-yr using ash bulk density 
of 1 g/cm3; DTN: LA0407DK831811.001). 
 
0.02 cm/yr estimated by the U.S. Department of Agriculture to have occurred on non-
cultivated cropland and pastureland in Nevada (obtained from USDA 2000 
[DIRS 160548], Table 11 and calculated using 1 ton/acre-yr x 907 kg/ton x 2.47 x 
10-4 acre/m x 0.001 m3/kg [bulk density] x 100 cm/m = 0.02 cm/yr). 
Thus, it is recommended that erosion rates from 0.02 to 0.04 cm/yr with a uniform distribution 
be used for interchannel divide surfaces in the YMR. 
6.3.4.3 Storms and Climate Change in the YMR 
Storms at Yucca Mountain can be classed into two types of rainstorms: the local, infrequent, 
high-intensity storms (summer monsoonal thunderstorm) and the larger, lower-intensity regional 
storms, which cover very broad areas on scales larger than entire drainage basins (Coe et al. 
[DIRS 104691], p. 15). Typically, regional storms have longer durations with periods of heavy 
rains during part or most of the storms. These storms occur more commonly during winter, 
although they can occur at any time of the year. 
It is the intense, localized thunderstorm that would be the likely initiator of movement of the 
scoria and ash particles from the ridge top drainage heads into the parallel channels. 
Undercutting of slopes of scoria and ash could cause sloughing of masses of tephra and result in 
addition of disaggregated scoria and ash to the drainage systems. In most localized 
thunderstorms, water rapidly infiltrates into the underlying soil and does not carry its bedload 
long distances. At Yucca Mountain, these storms seldom feed abundant material into Fortymile 
Wash (Coe et al. 1997 [DIRS 104691], pp. 24-26). To get abundant material into the wash and 
to transport it a long distance requires the much broader, longer-period regional rainstorms. 
The flood of 1969 (probably the most severe in recent times) had an estimated peak flow in 
Fortymile Wash of about 20,000 ft3/s (Squires and Young 1984 [DIRS 102783], p. 12). During 
this flood, water flowed through the length of the wash, across the alluvial fan, into the 
Amargosa River, and ultimately into Death Valley, where a shallow lake was impounded over an 
area of 80 mi2 (207 km2) (Hunt 1975 [DIRS 159900], p. 15). It is these long-duration regional 

storm systems that rain on entire drainage basins, flush the hillslopes, and move large quantities 
of materials into the wash. If movement of erupted ash began in the upper watershed of 
Fortymile Wash, mixing of materials would occur along the entire length of transport. 
6.4 POTENTIAL ERUPTION SCENARIO AT THE YUCCA MOUNTAIN 
REPOSITORY 
A future basaltic magma intrusion into the subsurface of Yucca Mountain followed by a surface 
eruption of scoria, lava, and ash would have relatively predictable physical volcanological and 
sedimentological consequences. Based on the properties of basaltic magma and the eruption and 
sediment transport processes discussed in Sections 6.1 through 6.3, one scenario of a surface 
eruption is compiled below. This scenario is proposed as a guide to a possible sequence of 
eruption phenomena at the surface and is not proposed as a conservative event sequence. The 
physical effects of a magmatic dike approaching and intruding the repository drifts filled with 
waste packages are discussed in Dike/Drift Interactions (BSC 2004 [DIRS 170028]). The 
calculation of the number of waste packages encountered by the magma intruding a repository is 
presented in Number of Waste Packages Hit by Igneous Intrusion (BSC 2004 [DIRS 170001]). 
Finally, models for eruption, ash fall distribution, and redistribution of ash from the point of 
deposition by erosive processes are included in Atmospheric Dispersal and Deposition of Tephra 
from a Potential Volcanic Eruption at Yucca Mountain, Nevada (BSC 2004 [DIRS 170026]). 
A. A system of about three fissures, trending approximately N-S, probably a few 
hundreds of meters long, opens up as the dike tip(s) intersect the surface of the 
mountain. Initially the fissures release mainly magmatic gases and some rock 
fragments, but over a period of minutes to hours lapilli- to bomb-sized clots of magma 
begin to be ejected. The magma will be between approximately 1000C to 1100C in 
temperature, of hawaiitic composition, and will have a volatile content dominated by 
H2O that reaches up to about 4 percent by mass. 
B. As eruption proceeds, lapilli and bombs accumulate along the fissure(s) and eruption 
becomes increasingly focused towards one or a few vents. Eventually one of these 
vents becomes the dominant point of eruption, and accumulation of material around 
that vent begins to form a main cone. As the cone grows it buries more and more of 
the original fissure system, but may retain some manifestation of the fissure(s) either 
by having an elongated shape or by having satellite vents that continue to erupt at a 
slower rate at other points along the fissure(s). During initial cone growth, eruptions 
are dominated by Strombolian mechanisms that produce mainly coarse lapilli- and 
bomb-sized material that is erupted a few tens of meters to a few hundreds of meters 
into the air and is distributed around the vent according to ballistic paths. Much of the 
material is still very hot when it lands on the cone slopes, resulting in various degrees 
of welding or agglutination of clasts. Partly because of the welding, cone slopes 
might be oversteepened (steeper than angle of repose) as they accumulate, resulting 
in periodic collapses or avalanches of material into the vent. This material may then 
be re-erupted during subsequent explosions. Only brief periods of higher eruption 
columns might occur during this phase. 

C. As the eruption continues, a more violent eruptive phase begins. During this phase 
the main vent produces sustained jets of relatively finely fragmented (ash to small 
bomb sizes) material, ejected from the ground at velocities of several tens of meters 
per second to perhaps as high as about 300 m/s. The eruptive jet mixes with 
atmospheric air, heats it, and the resulting mixture become buoyant with respect to the 
atmosphere and rises many hundreds of meters to several kilometers into the air. 
Atmospheric winds push the plume and its outward-spreading top in a downwind 
direction. Clasts fall out of this plume after having a long enough residence time in 
the air to cool and become solid, and they accumulate as loose (non-welded) deposits 
that are well sorted and that blanket the terrain. Cone growth continues as the coarser 
clasts accumulate close to the vent after falling directly from the margins of the rising 
jet (but not following simple ballistic paths). Because the new cone-building deposits 
have no welding-induced cohesion, avalanching back into the vent and down the outer 
cone slopes is almost continuous. Variations in gas content, magma supply rate, and 
vent-choking due to avalanches result in pulsing of the eruptive jet or plume. 
Individual pulses (or violent Strombolian eruptive phases) may last between about 
half an hour to many days. Each of these eruptive phases produces a distinct layer of 
tephra on the cone slopes (where it might later be eradicated by avalanching) and in 
the surrounding tephra sheet. 
D. At any time during the above processes, there might be brief periods of explosive 
magma-groundwater interaction (as indicated by deposits at Lathrop Wells volcano). 
These events might eject up to several 100,000s of cubic meters of material that is 
relatively lithic-enriched compared to other eruption products. The events might 
produce thin fallout units or localized pyroclastic surge deposits. Accompanying 
explosions might destroy part of the growing cone, but this is rapidly healed by 
subsequent Strombolian or violent Strombolian events. Although hydrovolcanism is 
included as part of this scenario, it was discounted as a significant phenomenon by the 
PVHA since the depth to the saturated zone is ~600 m and there is negligible perched 
water present within the unsaturated zone at Yucca Mountain. 
E. Lava flows may emanate at any time (concurrently with explosive eruptions or 
separately) from the main vent, satellite vents, or from the base of the main cone. 
Some of these flows might carry, or raft, coherent pieces of the cone along the flow 
tops. If these rafted pieces contain welded/agglutinated beds that were produced 
during Strombolian eruptive phases, they might retain their original bedding structure 
as they are carried along the top of a flow. 
F. Cone growth might occur only during a portion (~2-21 days, subtracting out pauses in 
explosive activity) of the eruptive history of the volcano, which will likely be on the 
order of one month but could be as long as about 15 years. The total erupted volume 
will have been about 0.1 km3. This volume will be dominated by the fallout tephra 
(from violent Strombolian phases), followed by lavas and finally by the main cone in 
a volume ratio of about 5:3:2, respectively. During this time a main conduit of an 
average of about 50 m diameter, reaching down a few hundred meters below the 
surface, will have formed by a combination of mechanical erosion and melting. The 
hypothetical new volcano would form a cone between 100-200 m high, a lava field 

between 5-10 km2 in area and a few tens of meters thick, and a tephra blanket that 
extends many kilometers in the direction of the prevailing wind. After eruption of 
magma ceases, volcanic gases will continue to leak from vents for many years as the 
subsurface magmas continue to cool and degas. Cooling of the surface lavas and cone 
may continue for many decades even after the degassing ends. 
G. The tephra deposit forms a blanket that drapes the surrounding terrain with loose, 
unconsolidated material. Within a few km of the volcano, where the tephra may be 
about 10 cm or more in thickness, any pre-eruption vegetation will likely be either 
buried or completely stripped of its foliage so that it dies. In this area, vegetation will 
provide no protection against rapid fluvial and/or eolian remobilization of the tephra. 
At greater distances, vegetation might be relatively intact with only a thin (mm to cm) 
ash layer on the ground. In addition, compared to the pre-eruptive ground surface, 
which would be capped by desert pavement of coarse fragments, the tephra deposit 
would have no such protection from erosive forces. Therefore it is to be expected that 
radioactively-contaminated tephra from a hypothetical eruption at Yucca Mountain 
would be relatively quickly remobilized. On sloping surfaces, there might be rapid 
erosion during rain events, washing ash into drainages such as Fortymile Wash. 
During especially heavy rains, it is likely that ash could be transported far down these 
washes by a variety of mechanisms ranging from densely-particle-laden debris flows 
to hyperconcentrated, ash-rich flows. As this downstream transport occurs there will 
be progressive dilution of the ash due to introduction of other materials into the flows. 
Such mechanisms might transport contaminated ash to the RMEI that is hypothesized 
for TSPA dose calculations, even if the original volcanic event did not deposit tephra 
directly onto this individual. Transport processes include a combination of eolian and 
slope and hydraulic mechanisms. 
6.5 UNCERTAINTIES (INPUT) 
6.5.1 Input Data and Uncertainty 
This subsection summarizes input data and uncertainties for the analyses that are detailed in this 
scientific analysis report. Column 5 in Table 6-9 lists epistemic uncertainty, which refers to 
the uncertainty that could be reduced by further knowledge, for example, by further sampling 
and analysis. The uncertainties associated with these inputs are discussed in the following 
subsections. 
6.5.1.1 Dike Length Distribution 
The degree of uncertainty associated with dike length distribution reflects the input from the 
expert elicitation for the PVHA (CRWMS M&O 1996 [DIRS 100116]). The statistical 
distribution for dike length encompasses the range of uncertainty in the available data for dike 
length in the YMR. Additional data on dike length from future aeromagnetic surveys are 
anticipated to be within the range of dike lengths considered by the PVHA experts. 

Table 6-9. List of Input Data and Uncertainty Type 
Input Name Input Description Input Source Value or Distribution 
Type of 
Uncertainty 
Dike length 
distribution 
Distribution of dike lengths 
using expert elicitation in 
the PVHA (CRWMS M&O 
1996 [DIRS 100116] 
Appendix E; Figure 4). 
DTN: 
LA0009FP831811.001 
[DIRS 164712] 
0.6 km for 5th percentile; 
4.0 km for mean; 10.1 
km for 95th percentile 
Epistemic 
45 chemical 
analyses of 
products from 
Lathrop Wells 
volcano 
Mean major-element 
chemical composition 
(and related statistics) of 
Lathrop Wells lava. 
DTN: 
LA000000000099.002 
[DIRS 147725] 
Means (see Table 6-2 
for complete statistics) 
SiO2-48.50% 
TiO2-1.93% 
Al2O3-16.74% 
Epistemic 
Fe2O3T-11.63% 
[Fe2O3 1.74%] 
[FeO 8.90%] 
MnO-0.17% 
MgO-5.83% 
CaO-8.60% 
Na2O-3.53% 
K2O-1.84% 
P2O3-1.22% 
137Cs analyses 
for Fortymile 
Wash alluvial 
fan 
66 analytical 
concentrations of 137Cs in 
samples from locations on 
a major YMR drainage 
alluvial fan. 
DTN: 
LA0308CH831811.002 
[DIRS 164853] 
137Cs analyses range 
from 0.002 to 0.322 
pCi/gram 
Epistemic 
Tephra Thicknesses of explosive DTN: Tephra thicknesses at Epistemic 
thicknesses, tephra deposits at LA0305DK831811.001 various map points 
Lathrop Wells 
volcano 
different map locations in 
vicinity of Lathrop Wells 
[DIRS 164026] range from 1 to 304 cm 
volcano. 
6.5.1.2 Forty-five Chemical Analyses of Products from the Lathrop Wells Volcano 
There is a low degree of uncertainty associated with the mean chemical composition of Lathrop 
Wells volcano lava; the uncertainty is quantitatively provided in the statistical information in 
Table 6-2. These data are used to estimate physical properties of a future magma (of similar 
composition) as it ascends through the crust, intercepts and interacts with the repository, and 
erupts onto the surface. The statistics provided in Table 6-2 for the major element chemical 
composition data reflect the natural variations expected among multiple samples of the same lava 
flow, as well as the variations expected for multiple samples from different lava flows from the 
same monogenetic volcanic event. There is a very low degree of uncertainty associated with any 
one major oxide determination because of the tight clustering of values (reflected in their 
standard error and standard deviation) among 45 rock samples and the use of modern analytical 
methods of chemical analysis. Additional analyses would only serve to decrease the standard 
deviations of any one mean. 

6.5.1.3 137Cs Analyses for the Fortymile Wash Alluvial Fan 
There is a low degree of uncertainty associated with the 137Cs analyses of individual samples 
collected from locations on the alluvial fan; quantitative information is provided in terms of +/- 
standard deviation for each analysis in Table 6-6. Analysis is performed by calibrated gamma 
spectroscopy in a certified analytical laboratory performing under strict QA requirements. 
6.5.1.4 Tephra Thicknesses for the Lathrop Wells Volcano 
There is a moderate degree of uncertainty associated with the determinations of tephra section 
thicknesses that are presented in Appendix C. These data are used to estimate the volume of ash 
and lapilli ejected during the more violent phases of the eruptionand the evolution of eruption 
typefor development of the volcanic history. Most recent excavations of tephra sections were 
limited to using a shovel, whereas excavations during several past field seasons were often done 
using a motorized back-hoe. Most of the latter excavations were localized around the base of the 
cone and, therefore, provide constraints on the thicker accumulations of ash. The most recent 
excavations could not always expose the base of the tephra when the thickness of tephra was 
greater than about 1 m, due to its unconsolidated nature. Geologic evidence suggests that the 
tephra was buried and protected by eolian sands and silts soon after deposition, but some 
erosional stripping of the tops of sections is expected to have occurred. Therefore, the tephra 
thicknesses represent minimum values in nearly all cases. 

INTENTIONALLY LEFT BLANK 

7. CONCLUSIONS 
This scientific analysis report provides technical bases for parameter values that will be used for 
the TSPA-LA related to the effects of a volcanic eruption through the Yucca Mountain 
repository. Uncertainties in the output parameters are described in the text as appropriate and 
summarized in Table 7-1. The information and data in this report, which is direct input to the 
TSPA, are based largely on literature values and simple calculations as described in Section 6 
and discussed in Data Qualification Report: Data Related to Characterization of Eruptive 
Processes for Use on the Yucca Mountain Project (CRWMS M&O 2000 [DIRS 156980], p. 17). 
Other information that indirectly relates to assessment of a potential igneous disruption of the 
repository and post-eruption processes, such as descriptions of the Lathrop Wells volcano and 
redistribution of ash, is based on field studies and supporting laboratory analyses. 
7.1 SUMMARY OF SCIENTIFIC ANALYSIS 
The Technical Product Output (Table 7-1) of this scientific analysis report provides distributions 
for parameters to be used by the YMP LA to describe the physical properties of basaltic magmas, 
volcanoes, eruptive processes, and volcanic products related to a volcanic eruption through the 
Yucca Mountain repository. Specific output parameters and uncertainties are described in the 
text and summarized in Section 7.2. Other processes are qualitatively described that relate to the 
progression of eruptive processes, based on both literature-derived data from observations of 
volcanic eruptions worldwide and on data from Lathrop Wells volcano, Nevada (Appendix C). 
Lathrop Wells volcano is a relevant source of information because it is the youngest volcanic 
event (~80,000 years) near Yucca Mountain and, along with other young basaltic cinder cones 
and flows in the area, forms the basis for the potential disruptive volcanic event for the 
repository. Processes that affect the post-eruptive redistribution of volcanic ash are also 
described in Section 6.3 from observations of ash transport and mixing with other tuffaceous 
sediments within the areas of Lathrop Wells volcano, Fortymile Wash, and Fortymile Wash 
alluvial fan. Therefore, processes that encompass volcanic eruption, cone construction, ash-
plume dispersal and deposition, and ash redistribution are depicted in this report. Other related 
reports cover topics that precede or follow in time the potential eruption scenario, such as model 
development and results for dike propagation in the shallow crust and the effects of a magmatic 
dike intercepting a repository drift at atmospheric pressure Dike/Drift Interactions (BSC 2004 
[DIRS 170028]). The number of waste packages involved in a magmatic intrusion into a 
repository drift filled with waste packages is discussed in Number of Waste Packages Hit by 
Igneous Intrusions(BSC 2004 [DIRS 170001). Specific results from modeling and analysis of 
potential ash-plume eruption, dispersal, and deposition from violent Strombolian eruption of 
basaltic magma are described in Atmospheric Dispersal and Deposition of Tephra from a 
Potential Volcanic Eruption at Yucca Mountain, Nevada (BSC 2004 [DIRS 170026]). A 
conceptual model and an alternative mathematical model for ash redistribution are also 
developed in Atmospheric Dispersal and Deposition of Tephra from a Potential Volcanic 
Eruption at Yucca Mountain, Nevada (BSC 2004 [DIRS 170026], Section 6.6, Appendix I). 

Table 7-1. Technical Product Output for This Scientific Analysis Report 
Parameter Recommended Values Uncertainties 
Restrictions on 
Subsequent Use 
Conduit diameter Triangular distribution, minimum 
diameter equal to dike width, mode 
diameter equal to 50 m, and 
maximum value of 150 m. 
Uncertainties in this parameter 
are related mainly to a limited 
amount of published data on 
conduit diameters for volcanoes 
of similar volume, composition, 
and eruptive mechanisms as 
those in the YMR. 
There are no 
restrictions on 
subsequent use of 
this range of 
conduit diameters. 
Dike width (or 
thickness) 
Log-normal distribution, minimum of 
0.5 m, mean of 1.5 m, and 95th 
percentile value of 4.5 m. 
Because this distribution 
incorporates measured basaltic 
dike width values in the YMR, 
there is little uncertainty 
There are no 
restrictions on the 
subsequent use of 
this range of dike 
associated with it. widths. 
Number of dikes 
associated with 
formation of a new 
volcano 
Log-normal distribution with a 
minimum of 1, mode of 3, and 95th 
percentile of 6. 
Because this distribution 
incorporates observations of 
basaltic centers in the YMR, 
there is little uncertainty 
associated with it. 
There are no 
restrictions on the 
subsequent use of 
this range of 
values for the 
number of dikes in 
a dike swarm. 
Dike spacing Random uniform distribution with 
minimum of 0 m and maximum of 
1500 m. 
This distribution captures most 
potential uncertainty by 
exceeding the range of dike 
There are no 
restrictions on the 
use of this range 
spacing in the YMR. of values for dike 
spacing. 
Maximum 
magnitudes of 
dike-induced 
earthquakes 
Maximum moment magnitudes are 
4.8, 5.8, and 6.2. Maximum 
magnitudes were calculated for dike 
length; for details see Figure 6-1. 
The maximum moment 
magnitudes for YMR based on 
dike length (for the mean, 5th , 
and 95th percentile values) 
exceed maximum magnitudes 
instrumentally observed for 
earthquakes associated with 
active volcanic rift zones 
worldwide. 
There are no 
restrictions on the 
use of these 
values for 
maximum 
magnitudes of 
dike-induced 
earthquakes. 
Magma chemistry Mean Lathrop Wells composition, 
Table 6-2. 
Uncertainty in this composition 
(given as standard deviation and 
sample variance) is given directly 
in Table 6-2 of this report and is 
There are no 
restrictions on the 
subsequent use of 
this mean magma 
related simply to the variation in 
compositions directly measured 
on Lathrop Wells volcanic 
composition. 
products. 
Water content of 
magmas 
Uniform distribution between 1 and 3 
wt%, zero probability of 0 wt% 
increasing linearly to 1 wt%, zero 
probability of 4 wt% with linear 
distribution between 3 and 4 wt%. 
This distribution captures all 
potential uncertainty in the water 
content of magmas, as it is 
bounded by a value of zero at 
the low end, and by maximum 
water content (above which 
magmas crystallize and therefore 
could not erupt) at the high end. 
There are no 
restrictions on the 
subsequent use of 
this distribution. 

Table 7-1. Technical Product Output for This Scientific Analysis Report (Continued) 
Parameter Recommended Values Uncertainties 
Restrictions on 
Subsequent Use 
Gas composition Table 6-3 of this report, which is 
derived from a suite of active 
A measure of the uncertainty 
associated with the 
There are no 
restrictions on the 
volcanoes. recommended gas composition 
is provided directly in Table 6-3 
of this report as the standard 
deviation; the uncertainty reflects 
the range of volcanic data from 
which the values are derived. 
subsequent use of 
this gas 
composition. 
Magmatic 
temperatures, 
viscosities, and 
densities 
Calculated from theoretical relations 
(Table 6-4). For water content 
ranging from 4 to 0%, liquidus 
temperature ranges from 1,046 to 
1,169 C, viscosity ranges from 1.957 
to 2.678 (log poise units), density 
ranges from 2,474 to 2,663 kg/m3 . 
Uncertainties associated with 
these values are expected to be 
small because the mathematical 
relationships use to calculate the 
values are closely tied to 
experimental data. 
There are no 
restrictions on the 
subsequent use of 
these values. 
Magma ascent 
rate below 
vesiculation depth 
Equation 6-3: 
. 
. 
. 
. 
. 
. 
. 
. 
-.. 
. 
. 
.. 
. 
. - += 1)(641 
4 
2/1 
22 
3 
. 
... 
. 
. 
A 
Kgr 
rK 
A u mmc 
m 
f 
Uncertainties associated with this 
equation would relate to 
processes and material 
properties not accounted for in 
Subsequent use of 
this equation 
should explicitly 
state the sources 
the equation. For example, if 
there is a pressure driving force 
in addition to buoyancy between 
the magma and surrounding 
of uncertainty and 
the assumptions 
made in the 
theory. 
rocks or if the rheology of the 
magma is non-Newtonian. 
Volatile exsolution 
depths 
Figure 6-1: range from about 9 km to 
zero depth for water contents 
between 0 and 0.04 weight fraction (0 
and 4 wt%). 
Uncertainties in Figure 6-1 are 
related to the assumptions made 
in the theoretical approach: 
steady and homogeneous flow, 
and lithostatic pressure within the 
dike or conduit. The 
Subsequent use of 
Figure 6-1 should 
explicitly state the 
assumptions made 
in the theory and 
should not violate 
uncertainties could be large. the theory. 
Fragmentation 
depths 
Figure 6-4: range from 0 to 900 m 
(approximately) for water contents 
between 0 and 4 wt%. 
Uncertainties in fragmentation 
depth are related to a lack of 
understanding of the 
mechanisms of fragmentation, 
which has been observed to 
occur at gas volume fractions 
ranging from 0.60 to 0.95. 
Subsequent use of 
these 
fragmentation 
depths should 
explicitly state that 
they are based on 
an assumption of 
fragmentation at a 
gas volume 
fraction of 0.75. 
Velocity as a 
function of depth 
Eruption velocity uerupt is estimated 
from Figures 6-3 and 6-4. Velocity 
Uncertainty in the value of uerupt 
is related both to the validity of 
Subsequent use of 
these velocity 
then decreases linearly downward to assumptions made in developing profiles should 
0.1uerupt at the fragmentation depth. the theory that produces the explicitly state the 
Below fragmentation depth, the curves in Figures 6-3 and 6-4 simplifications that 
velocity continues to decrease (steady, homogeneous flow, with are made to derive 
linearly to 0.01uerupt at the depth lithostatic pressure in the rising them. 
where water exsolution begins. magma column), and to the 
limitations of graphical 
extrapolation of the actual 
calculated curves. Uncertainty in 
the velocity versus depth 
functions are associated with the 

Table 7-1. Technical Product Output for This Scientific Analysis Report (Continued) 
Parameter Recommended Values Uncertainties 
Restrictions on 
Subsequent Use 
simple linear nature of the 
recommended functions, 
whereas in reality, the functions 
would be nonlinear due to poorly 
understood processes of magma 
ascent. 
Eruption duration 
for formation of an 
entire volcano 
For formation of an entire volcano, a 
log-normal distribution with a 
minimum of 1 day, a median of 30 
days, and a maximum of 15 years. 
The distributions recommended 
for eruption duration include 
uncertainty associated with 
observations of historical scoria 
cone volcanoes around the 
There are no 
restrictions on the 
subsequent use of 
these distributions. 
world. 
Duration of a A log-uniform probability ranging from Uncertainty associated with this There are no 
single explosive 0.5 hours to 75 days parameter is from the limited restrictions on the 
phase constituting number of observed, relevant subsequent use of 
a violent explosive eruptions. this distribution. 
Strombolian 
eruptive phase 
Tephra fall or ash 
volume 
Log-uniform distribution between 
0.004 km3 and 0.08 km3 . 
This distribution captures most of 
the potential uncertainty 
associated with ash volume, 
based upon the estimated 
eruption volumes of Quaternary 
volcanoes in the YMR. 
There are no 
restrictions on the 
subsequent use of 
this distribution. 
Mean particle size 
erupted during 
violent 
Strombolian 
phases 
Log-triangular distribution with a 
minimum of 0.01 mm, a mode of 0.1 
mm, and a maximum of 1.0 mm. 
Uncertainties associated with this 
parameter are due mainly to the 
rarity of data in the published 
literature that pertain to the bulk 
erupted particle size from violent 
Strombolian eruptions. The 
recommended distribution 
There are no 
restrictions on the 
subsequent use of 
this distribution. 
incorporates the range of values 
that have been estimated. 
Standard deviation Uniform distribution between sf = 1 Uncertainties associated with this There are no 
of particle size 
distribution for a 
given mean 
and sf = 3. parameter are due mainly to the 
rarity of data in the published 
literature that pertain to the bulk 
erupted particle size from violent 
Strombolian eruptions. The 
recommended distribution 
restrictions on the 
subsequent use of 
this distribution. 
incorporates the range of values 
that have been estimated. 
Clast Shape factor of 0.5. Uncertainty in this parameter is There are no 
characteristics related to an absence of data in restrictions on the 
the published literature. subsequent use of 
this value. 
Density of erupted 
particles 
For particle diameters less than or 
equal to 0.01 mm, density is 0.8 of 
the magma density. For particles 
Uncertainty in this parameter is 
related to the wide range of 
vesicularities of clasts that can 
There are no 
restrictions on 
subsequent use of 
greater than 10 mm, density is 0.4 of 
the magma density. For particles 
between 0.01 and 10 mm, density 
should decrease linearly with 
be erupted during a single 
volcanic event. 
the recommended 
values. 
increasing diameter. 

Table 7-1. Technical Product Output for This Scientific Analysis Report (Continued) 
Parameter Recommended Values Uncertainties 
Restrictions on 
Subsequent Use 
Tephra deposit 
density or ash 
settled density 
There are two possible ways of 
treating deposit density calculations: 
(1) simply use 1,000 kg/m3 or (2) a 
sample from a normal distribution of 
deposit densities ranging from 300 to 
1,500 kg/m3, with a mean of 1,000 
kg/m3 . 
Uncertainties associated with this 
parameter are due to a lack of 
published data. 
There are no 
restrictions on 
subsequent use of 
the recommended 
values. 
Erosion/ 
aggradation 
estimate 
Erosion rates for interchannel divide 
surfaces are uniformly distributed 
from 0.02 to 0.04 cm/yr. 
Erosion rates were obtained from 
analysis of data in the Forytmile 
Wash drainage, and are 
consistent with soil loss (erosion) 
rates in other relevant areas. 
There are no 
restrictions on 
subsequent use of 
the recommended 
values. 
Output DTN: LA0407DK831811.001. 
The following specific parameter distributions are suggested for the eruptive processes described 
in this report. 
 
Conduit diameterLog-normal distribution, minimum diameter equal to dike width, 
mode diameter equal to 50 m, maximum value 150 m. Uncertainties in this parameter 
are related mainly to a limited amount of published data on conduit diameters for 
volcanoes of similar volume, composition, and eruptive mechanisms as those in the 
YMR. There are no restrictions on subsequent use of this range of conduit diameters. 
 
Dike widthLog-normal distribution, minimum of 0.5 m, mean of 1.5 m, 95th percentile 
value of 4.5 m. There is little uncertainty associated with this distribution because it 
incorporates measured basaltic dike width values in the YMR. There are no restrictions 
on the subsequent use of this range of dike widths. 
 
Number of dikes associated with formation of a new volcanoLog-normal distribution 
with minimum of 1, mode of 3, and a 95th percentile of 6. There is little uncertainty 
associated with this distribution, because it incorporates observations of basaltic centers 
in the YMR. There are no restrictions on the subsequent use of this range of values for 
the number of dikes in a dike swarm. 
 
Dike spacingUniform distribution with a range from 0 to 1500 m. Uncertainty in this 
range is related to lack of dike sets in the Yucca Mountain area in which to make 
measurements. There are no restrictions on the use of this range of dike spacings. 
 
Maximum moment magnitudes of dike-induced earthquakesMaximum moment 
magnitudes are 4.8, 5.8, and 6.2. Uncertainties associated with this parameter are due to 
the lack of observed volcanic seismicity in the YMR. The maximum magnitudes are 
calculated using rupture dimensions of normal fault surface lengths equivalent to dike 
lengths (5th, mean, and 95th percentiles, respectively). This approach results in estimated 
maximum magnitudes that exceed instrumentally observed magnitudes of seismicity 
associated with dike-intrusion at active volcanic rift zones worldwide. There are no 
restrictions on the subsequent use of these values. 

 
Magma chemistryMean Lathrop Wells composition (Table 6-2). Uncertainty in this 
composition (given as standard deviation and sample variance) is provided in Table 6-2 
and is related to the variation in compositions directly measured on Lathrop Wells 
volcanic products. There are no restrictions on the subsequent use of this mean magma 
composition. 
 
Water content of magmasUniform distribution between 1 and 3 wt%, zero probability 
of 0 wt% increasing linearly to 1 wt%, zero probability of 4 wt% with linear distribution 
between 3 and 4 wt%. This distribution captures all potential uncertainty in the water 
content of magmas as it is bounded by a value of zero at the low end and by a maximum 
water content (above which magmas crystallize and, therefore, could not erupt) at the 
high end. There are no restrictions on the subsequent use of this distribution. 
 
Gas compositionDerived from a suite of active volcanoes (Table 6-3). A measure of 
the uncertainty associated with the recommended gas composition is provided in 
Table 6-3 as the standard deviation; the uncertainty reflects the range of volcanic data 
from which the values are derived. There are no restrictions on the subsequent use of 
this gas composition. 
 
Magma temperature, viscosity, and densityCalculated from theoretical relations 
(Table 6-4). Liquidus temperature ranges from 1,046 to 1,169C, viscosity ranges from 
1.957 to 2.678 (log poise units), and density ranges from 2,474 to 2,663 kg/m3. 
Uncertainties associated with these values are expected to be small because the 
mathematical relationships used to calculate the values are closely tied to experimental 
data. There are no restrictions on the subsequent use of these values. 
 
Magma ascent rate below vesiculation depthEquation 6-3. Uncertainties associated 
with this equation relate to processes and material properties not accounted for in the 
equationfor example, if there is a pressure driving force in addition to buoyancy 
between the magma and surrounding rocks or if the rheology of the magma is 
non-Newtonian. Subsequent use of this equation should explicitly state the sources of 
uncertainty and the assumptions made in the theory. 
 
Volatile exsolution depthThe depth ranges from 0 to 9 km depth for water contents 
between 0 and 4 wt%. Uncertainties in Figure 6-2 are related to the assumptions made 
in the theoretical approach: steady and homogeneous flow and lithostatic pressure within 
the dike or conduit. The uncertainties could be large. Subsequent use of Figure 6-2 
should explicitly state the assumptions made in the theory and should not violate the 
theory. 
 
Fragmentation depthsThese depths range from 0 to 900 m (approximately) for water 
contents between 0 and 4 wt%. Uncertainties in fragmentation depth are related to a 
lack of understanding of the mechanisms of fragmentation, which has been observed to 
occur at gas volume fractions ranging from 0.60 to 0.95. Subsequent use of these 
fragmentation depths should explicitly state that they are based on an assumption of 
fragmentation at a gas volume fraction of 0.75. 

 
Velocity as a function of depthEruption velocity uerupt is estimated from Figures 6-4 
and 6-5. Velocity then decreases linearly downward to 0.1uerupt at the fragmentation 
depth. Below fragmentation depth, the velocity continues to decrease linearly to 
0.01uerupt at the depth where water exsolution begins. Uncertainty in the value of uerupt is 
related both to the validity of assumptions made in developing the theory that produces 
the curves in Figures 6-4 and 6-5 (steady, homogeneous flow with lithostatic pressure in 
the rising magma column) and to the limitations of graphical extrapolation of the actual 
calculated curves. Uncertainty in the velocity versus depth functions are associated with 
the simple linear nature of the recommended functions, whereas, in reality, the functions 
are likely to be nonlinear due to poorly understood processes of magma ascent. 
Subsequent use of these velocity profiles should explicitly state the simplifications that 
are made to derive them. 
 
Eruption duration for formation of an entire volcanoFor formation of an entire YMR 
basaltic volcano, a log-normal distribution with a minimum of 1 day, a median of 
30 days, and a maximum of 15 years. There are no restrictions on the subsequent use of 
these distributions. 
 
Duration of a single explosive phase constituting a violent Strombolian eruptive phase 
Log-uniform probability ranging from 0.5 hours to 75 days. Uncertainty in this range is 
related to the small number of observed eruptions. The maximum of 75 days 
encompasses the duration of the most energetic phase of Parcutin (73 days). There are 
no restrictions on the subsequent use of this distribution. 
 
Violent Strombolian eruption volumeLog-uniform distribution between 0.004 km3 and 
0.08 km3. Based on the estimated volumes of Quaternary basaltic volcanoes in the 
YMR, this range captures most of the uncertainty associated with potential ash volume 
from a basaltic eruption at the repository. There are no restrictions on the subsequent 
use of this distribution. 
 
Mean particle size erupted during violent Strombolian phasesLog-triangular 
distribution with a minimum of 0.01 mm, a mode of 0.1 mm, and a maximum of 
1.0 mm. Uncertainties associated with this parameter are due mainly to the rarity of data 
in the published literature that pertain to the bulk erupted particle size from violent 
Strombolian eruptions. The recommended distribution incorporates the range of values 
that have been estimated in published studies as referenced and recent work on Lathrop 
Wells volcano tephra sheet (this report). There are no restrictions on the subsequent use 
of this distribution. 
 
Standard deviation of particle size distribution for a given meanUniform distribution 
between sf = 1 and sf = 3. Uncertainties associated with this parameter are due mainly 
to the rarity of data in the published literature that pertain to the bulk erupted particle 
size from violent Strombolian eruptions. The recommended distribution incorporates 
the range of values that have been estimated. There are no restrictions on the subsequent 
use of this distribution. 

 
Clast characteristicsShape factor of 0.5. Uncertainty in this parameter is related to an 
absence of data in the published literature. There are no restrictions on the subsequent 
use of this value. 
 
Density of erupted particlesFor particle diameters less than or equal to 0.01 mm, 
density is 0.8 of the magma density (this accounts for an estimated 0.2 volume fraction 
of microvesicles). For particles greater than 10 mm, density is 0.4 of the magma density 
(this accounts for 0.6 volume fraction of vesicles). For particles between 0.01 and 
10 mm, density should increase linearly with the logarithm of the diameter. Uncertainty 
in this parameter is related to the wide range of vesicularities of clasts that can be 
erupted during a single volcanic event. There are no restrictions on subsequent use of 
the recommended values. 
 
There are two ways of treating deposit density in TSPA-LA calculations1) Use 
1,000 kg/m3 or 2) a sample from a normal distribution of deposit densities ranging from 
300 to 1,500 kg/m3, with a mean of 1,000 kg/m3. Uncertainties associated with this 
parameter are due to a lack of published data. There are no restrictions on subsequent 
use of the recommended values. 
 
Erosion/aggradation estimateUniform distribution from 0.02 to 0.04 cm/yr for 
interchannel divide surfaces on the Fortymile Wash alluvial fan. Uncertainties 
associated with this parameter are based on laboratory analytical uncertainty for each 
cesium analysis (Table 6-8); and on evaluation of depth/concentration variation for each 
interchannel divide sample and interpretation of amount of eroded material. There are 
no restrictions on subsequent use of the recommended values. 
7.2 OUTPUT PARAMETERS AND UNCERTAINTY 
The output parameter distributions and their uncertainties, as summarized in Table 7-1 form the 
Technical Product Output for this scientific analysis report (DTN: LA0407DK831811.001). The 
Volumes of Lathrop Wells Cone, Lava, and Tephra is an intermediate output with 
DTN: LA0305DK831811.002 (see Appendix C, Table C-18). 

8. INPUTS AND REFERENCES 
8.1 DOCUMENTS CITED 
Altman, W.D.; Donnelly, J.P.; and Kennedy, J.E. 1988. Peer Review for High-Level 103597 
Nuclear Waste Repositories: Generic Technical Position. NUREG-1297. 
Washington, D.C.: U.S. Nuclear Regulatory Commission. TIC: 200651. 
Altman, W.D.; Donnelly, J.P.; and Kennedy, J.E. 1988. Qualification of Existing 103750 
Data for High-Level Nuclear Waste Repositories: Generic Technical Position. 
NUREG-1298. Washington, D.C.: U.S. Nuclear Regulatory Commission. 
TIC: 200652. 
Baker, D.R. and Eggler, D.H. 1983. Fractionation Paths of Atka (Aleutians) 122601 
High-Alumina Basalts: Constraints from Phase Relations. Journal of Volcanology 
and Geothermal Research, 18, 387-404. Amsterdam, The Netherlands: Elsevier. 
TIC: 246252. 
Best, M.G. 1982. Igneous and Metamorphic Petrology. New York, New York: 147740 
W.H. Freeman and Company. TIC: 247662. 
Blong, R.J. 1984. Volcanic Hazards, A Sourcebook on the Effects of Eruptions. 144263 
Sydney, Australia: Academic Press. TIC: 247016. 
Brandsdottir, B. and Einarsson, P. 1979. Seismic Activity Associated with the 155852 
September 1977 Deflation of the Krafla Central Volcano in North-Eastern Iceland. 
Journal of Volcanology and Geothermal Research, 6, 197-212. Amsterdam,
The Netherlands: Elsevier. TIC: 250651. 
BSC (Bechtel SAIC Company) 2002. Radionuclide Screening. 160059 
ANL-WIS-MD-000006 REV 01. Las Vegas, Nevada: Bechtel SAIC Company. 
ACC: MOL.20020923.0177. 
BSC 2004. Atmospheric Dispersal and Deposition of Tephra from a Potential 170026 
Volcanic Eruption at Yucca Mountain, Nevada. MDL-MGR-GS-000002, Rev. 01. 
Las Vegas, Nevada: Bechtel SAIC Company. 
BSC 2004. Characterize Framework for Igneous Activity at Yucca Mountain, 169989 
Nevada. ANL-MGR-GS-000001, Rev. 02. Las Vegas, Nevada: Bechtel SAIC 
Company. 
BSC 2004. CSNF Waste Form Degradation: Summary Abstraction. ANL-EBS-169987 
MD-000015, Rev. 02. Las Vegas, Nevada: Bechtel SAIC Company. 

BSC 2004. Development of Earthquake Ground Motion Input for Preclosure Seismic 170027 
Design and Postclosure Performance Assessment of a Geologic Repository at Yucca 
Mountain, NV. MDL-MGR-GS-000003 REV 01. Las Vegas, Nevada: Bechtel 
SAIC Company. 
BSC 2004. Dike/Drift Interactions. MDL-MGR-GS-000005, Rev. 01. Las Vegas, 170028 
Nevada: Bechtel SAIC Company. 
BSC 2004. Features, Events, and Processes: Disruptive Events. ANL-WIS-MD-170017 
000005, Rev. 02. Las Vegas, Nevada: Bechtel SAIC Company. 
BSC 2004. Number of Waste Packages Hit by Igneous Intrusion. ANL-MGR-GS-170001 
000003, Rev. 01. Las Vegas, Nevada: Bechtel SAIC Company. 
BSC 2004. Q-List. 168361 
000-30R-MGR0-00500-000-000 REV 00. Las Vegas, Nevada: Bechtel SAIC 
Company. ACC: ENG.20040721.0007. 
BSC 2004. Soil-Related Input Parameters for the Biosphere Model. ANL-NBS-MD-169459 
000009, Rev. 02. Las Vegas, Nevada: Bechtel SAIC Company. 
BSC 2004. Technical Work Plan for Igneous Activity Assessment for Disruptive 171403 
Events. TWP-WIS-MD-000007 REV 06. Las Vegas, Nevada: Bechtel SAIC 
Company. ACC: DOC.20040820.0001. 
Byers, C.D.; Garcia, M.O.; and Muenow, D.W. 1985. Volatiles in Pillow Rim 122532 
Glasses from Loihi and Kilauea Volcanoes, Hawaii. Geochimica et Cosmochimica 
Acta, 49, 1887-1896. New York, New York: Pergamon Press. TIC: 246241. 
Byers, F.M., Jr. and Barnes, H. 1967. Geologic Map of the Paiute Ridge 101859 
Quadrangle, Nye and Lincoln Counties, Nevada. Map GQ-577. Washington, D.C.: 
U.S. Geological Survey. ACC: HQS.19880517.1104. 
Canori, G.F. and Leitner, M.M. 2003. Project Requirements Document. 166275 
TER-MGR-MD-000001 REV 02. Las Vegas, Nevada: Bechtel SAIC Company. 
ACC: DOC.20031222.0006. 
Chappell, A. 1999. The Limitation of Using {superscript 137}Cs for Estimating 163891 
Soil Redistribution in Semi-Arid Environments. Geomorphology, 29, ([1-2]), 
135-152. [New York, New York]: Elsevier. TIC: 254464. 

Codell, R. 2003. Alternative Igneous Source Term Model for the Yucca Mountain 165503 
Repository. Proceedings of the 10th International High-Level Radioactive Waste 
Management Conference (IHLRWM), March 30-April 2, 2003, Las Vegas, Nevada. 
Pages 405-412. La Grange Park, Illinois: American Nuclear Society. TIC: 54559. 
Coe, J.A.; Glancy, P.A.; and Whitney, J.W. 1997. Volumetric Analysis and 104691 
Hydrologic Characterization of a Modern Debris Flow Near Yucca Mountain, 
Nevada. Geomorphology, 20, (1-2), 11-28. Amsterdam, The Netherlands: Elsevier. 
TIC: 241945. 
Coe, J.A.; Oswald, J.; Vadurro, G.; and Lundstrom, S.C. 1996. Quaternary Faulting 101527 
on the Fatigue Wash Fault. Chapter 4.8 of Seismotectonic Framework and 
Characterization of Faulting at Yucca Mountain, Nevada. Whitney, J.W., ed. 
Milestone 3GSH100M. Denver, Colorado: U.S. Geological Survey. TIC: 237980. 
ACC: MOL.19970129.0041. 
Crowe, B. 1992. Volcanism Field Notebook #6. Scientific Notebook 162823 
TWS-EES-13-LV-11-89-07. ACC: NNA.19920918.0044. 
Crowe, B. 1996. Volcanism Field Notebook EES-13-LV-01-93-05. Scientific 164317 
Notebook EES-13-LV-01-93-05. ACC: MOL.20030721.0266. 
Crowe, B.; Self, S.; Vaniman, D.; Amos, R.; and Perry, F. 1983. Aspects of 100972 
Potential Magmatic Disruption of a High-Level Radioactive Waste Repository in 
Southern Nevada. Journal of Geology, 91, (3), 259-276. Chicago, Illinois: 
University of Chicago Press. TIC: 216959. 
Crowe, B.M.; Wohletz, K.H.; Vaniman, D.T.; Gladney, E.; and Bower, N. 1986. 101532 
Status of Volcanic Hazard Studies for the Nevada Nuclear Waste Storage 
Investigations. LA-9325-MS. Volume II. Los Alamos, New Mexico: Los Alamos 
National Laboratory. ACC: NNA.19890501.0157. 
CRWMS M&O 1996. Probabilistic Volcanic Hazard Analysis for Yucca Mountain, 100116 
Nevada. BA0000000-01717-2200-00082 REV 0. Las Vegas, Nevada: CRWMS 
M&O. ACC: MOL.19971201.0221. 
CRWMS M&O 1998. Physical Processes of Magmatism and Effects on the 123201 
Potential Repository: Synthesis of Technical Work through Fiscal Year 1995. 
Chapter 5 of Synthesis of Volcanism Studies for the Yucca Mountain Site 
Characterization Project. Deliverable 3781MR1. Las Vegas, Nevada: CRWMS 
M&O. ACC: MOL.19990511.0400. 

CRWMS M&O 1999. Final Report on Qualification of Volcanism Isotope, 170965 
Trace-Element, and Halogen Data Using Procedure YAP-SIII.1Q/Rev. 3/ICN 0. 
Las Vegas, Nevada: CRWMS M&O. ACC: MOL.19990406.0471. 
CRWMS M&O 2000. Data Qualification Report: Data Related to Characterization 156980 
of Eruptive Processes for Use on the Yucca Mountain Project. 
TDR-NBS-GS-000016 REV 00. Las Vegas, Nevada: CRWMS M&O. 
ACC: MOL.20000810.0002. 
CRWMS M&O 2000. Igneous Consequence Modeling for the TSPA-SR. 151560 
ANL-WIS-MD-000017 REV 00 ICN 01. Las Vegas, Nevada: CRWMS M&O. 
ACC: MOL.20001204.0022. 
Danyushevsky, L.V.; Falloon, T.J.; Sobolev, A.V.; Crawford, A.J.; Carroll, M.; and 149303 
Price, R.C. 1993. The H2O Content of Basalt Glasses from Southwest Pacific Back-
Arc Basins. Earth and Planetary Science Letters, 117, 347-362. Amsterdam, The 
Netherlands: Elsevier. TIC: 246102. 
Dehaudt, P. 2001. Physical and Chemical State of the Nuclear Spent Fuel After 164019 
Irradiation. Section 5.2 of Synthesis on the Long Term Behavior of the Spent 
Nuclear Fuel. Poinssot, C., ed. CEA-R-5958(E). Volume I. [Paris], France:
Commissariat  lnergie Atomique. TIC: 253976. 
Delaney, P.T. 1982. Rapid Intrusion of Magma into Wet Rock: Groundwater Flow 162799 
due to Pore Pressure Increases. Journal of Geophysical Research, 87, (B9), 
7739-7756. Washington, D.C.: American Geophysical Union. TIC: 254049. 
Delaney, P.T. and Gartner, A.E. 1997. Physical Processes of Shallow Mafic Dike 145370 
Emplacement Near the San Rafael Swell, Utah. Geological Society of America 
Bulletin, 109, (9), 1177-1192. Boulder, Colorado: Geological Society of America. 
TIC: 247421. 
Delaney, P.T. and Pollard, D. 1978. Basaltic Subvolcanic Conduits Near Shiprock, 162800 
New Mexico: Magma Flow, Heat Transport, and Brecciation of Host Rocks. Eos 
Transactions, 59, (12), 1212. Washington, D.C.: American Geophysical Union. 
TIC: 254390. 
Delaney, P.T. and Pollard, D.D. 1981. Deformation of Host Rocks and Flow of 162801 
Magma During Growth of Minette Dikes and Breccia-Bearing Intrusions Near Ship 
Rock, New Mexico. Geological Survey Professional Paper 1202. Washington, 
D.C.: U.S. Geological Survey. TIC: 254050. 

Detournay, E.; Mastin, L.G.; Pearson, J.R.A.; Rubin, A.M.; and Spera, F.J. 2003. 169660 
Final Report of the Igneous Consequences Peer Review Panel, with Appendices. 
Las Vegas, Nevada: Bechtel SAIC Company. ACC: MOL.20031014.0097; 
MOL.20030730.0163. 
Dobran, F. 2001. Conduit Erosion. Volcanic Processes, Mechanisms in Material 162802 
Transport. Pages 480-484. New York, New York: Kluwer Academic/Plenum
Publishers. TIC: 254051. 
Doubik, P. and Hill, B.E. 1999. Magmatic and Hydromagmatic Conduit 115338 
Development During the 1975 Tolbachik Eruption, Kamchatka, with Implications for 
Hazards Assessment at Yucca Mountain, NV. Journal of Volcanology and 
Geothermal Research, 91, 43-64. Amsterdam, The Netherlands: Elsevier. 
TIC: 246029. 
Ely, L.L.; Webb, R.H.; and Enzel, Y. 1992. Accuracy of Post-Bomb 137Cs and 14C 164076 
in Dating Fluvial Deposits. Quaternary Research, 38, 196-204. New York, 
New York: Academic Press. TIC: 254471. 
Fierstein, J. and Nathenson, M. 1992. Another Look at the Calculation of Fallout 162804 
Tephra Volumes. Bulletin of Volcanology, 54, 156167. Berlin, Germany: 
Springer-Verlag. TIC: 254491. 
Fisher, R.V. and Schmincke, H.-U. 1984. Pyroclastic Rocks. New York, New York: 162806 
Springer-Verlag. TIC: 223562. 
Gaetani, G.A.; Grove, T.L.; and Bryan, W.B. 1993. The Influence of Water on the 144274 
Petrogenesis of Subduction-Related Igneous Rocks. Nature, 365, 332-335. London, 
England: Macmillan Journals. TIC: 246792. 
Garcia, M.O.; Muenow, D.W.; Aggrey, K.E.; and ONeil, J.R. 1989. Major 122542 
Element, Volatile, and Stable Isotope Geochemistry of Hawaiian Submarine 
Tholeiitic Glasses. Journal of Geophysical Research, 94, (B8), 10525-10538. 
Washington, D.C.: American Geophysical Union. TIC: 246240. 
Gile, L.H.; Hawley, J.W.; and Grossman, R.B. 1981. Soils and Geomorphology in 144518 
the Basin and Range Area of Southern New MexicoGuidebook to the Desert 
Project. Memoir 39. Socorro, New Mexico: New Mexico Bureau of Mines & 
Mineral Resources. TIC: 228406. 
Hackett, W.R.; Jackson, S.M.; and Smith, R.P. 1996. Paleoseismology of Volcanic 169781 
Environments. Chapter 4 of Paleoseismology. McCalpin, J.P., ed. San Diego, 
California: Academic Press. TIC: 256139. 

Hallett, R.B. 1992. Volcanic Geology of Cerro Chafo. San Juan Basin IV, 162813 
New Mexico Geological Society Forty-Third Annual Field Conference, 
September 30-October 3, 1992. Lucas, S.G.; Kues, B.S.; Williamson, T.E.; and Hunt, 
A.P.; eds. Pages 19-24. [Socorro, New Mexico: New Mexico Geological Society]. 
TIC: 254052. 
Harrington, C. 2003. Ash and Soil Redistribution Studies. Scientific Notebook 164775 
SN-LANL-SCI-285-V1. ACC: MOL.20030411.0312. 
Heiken, G. 1978. Characteristics of Tephra from Cinder Cone, Lassen Volcanic 162817 
National Park, California. Bulletin of Volcanology, 41-2, 119-130. New York, New 
York: Springer-Verlag. TIC: 235508. 
Heiken, G.H. and Wohletz, K. 1985. Volcanic Ash. Berkeley, California: University 106122 
of California Press. TIC: 242991. 
Heizler, M.T.; Perry, F.V.; Crowe, B.M.; Peters, L.; and Appelt, R. 1999. The Age 107255 
of Lathrop Wells Volcanic Center: An 40Ar/ 39Ar Dating Investigation. Journal of 
Geophysical Research, 104, (B1), 767-804. Washington, D.C.: American 
Geophysical Union. TIC: 243399. 
Hieken, G. 2003. Eruptive Processes and Consequences. Scientific Notebook 171289 
SN-LANL-SCI-291-V1. Pages 1-66 ACC: MOL.20031020.0141; 
MOL.20040819.0067. 
Hunt, C.B. 1975. Death Valley, Geology, Ecology, Archaeology. Berkeley, 159900 
California: University of California Press. TIC: 246234. 
Jackson, J.A., ed. 1997. Glossary of Geology. 4th Edition. Alexandria, Virginia: 109119 
American Geological Institute. TIC: 236393. 
Jarzemba, M.S. 1997. Stochastic Radionuclide Distributions After a Basaltic 100460 
Eruption for Performance Assessments of Yucca Mountain. Nuclear Technology,
118, 132-141. [Hinsdale, Illinois]: American Nuclear Society. TIC: 237944. 
Jaupart, C. and Tait, S. 1990. Dynamics of Eruptive Phenomena. Chapter 8 of 118292 
Modern Methods of Igneous Petrology: Understanding Magmatic Processes. 
Nicholls, J. and Russell, J.K., eds. Reviews in Mineralogy Volume 24. 213-238. 
Washington, D.C.: Mineralogical Society of America. TIC: 246394. 

Keating, G.N. and Valentine, G.A. 1998. Proximal Stratigraphy and Syn-Eruptive 111236 
Faulting in Rhyolitic Grants Ridge Tuff, New Mexico, USA. Journal of 
Volcanology and Geothermal Research, 81, 37-49. Amsterdam, The Netherlands: 
Elsevier. TIC: 246096. 
Knutson, J. and Green, T.H. 1975. Experimental Duplication of a High-Pressure 106299 
Megacryst/Cumulate Assemblage in a Near-Saturated Hawaiite. Contributions to 
Mineralogy and Petrology, 52, 121-132. Berlin, Germany: Springer-Verlag. 
TIC: 225057. 
Kotra, J.P.; Lee, M.P.; Eisenberg, N.A.; and DeWispelare, A.R. 1996. Branch 100909 
Technical Position on the Use of Expert Elicitation in the High-Level Radioactive 
Waste Program. NUREG-1563. Washington, D.C.: U.S. Nuclear Regulatory 
Commission. TIC: 226832. 
Krier, D. 2003. Ash Redistribution, Lava Morphology, and Igneous Processes 165893 
Studies (Volume 2). Scientific Notebook 
SN-LANL-SCI-286-V2. ACC: MOL.20031021.0192. 
Krier, D. and Harrington, C.D. 2003. Ash Redistribution, Lava Morphology, and 164023 
Igneous Processes Studies. Scientific Notebook 
SN-LANL-SCI-286-V1. ACC: MOL.20030701.0109. 
Lange, R.L. and Carmichael, I.S.E. 1990. Thermodynamic Properties of Silicate 147767 
Liquids with Emphasis on Density, Thermal Expansion and Compressibility. 
Chapter 2 of Modern Methods of Igneous Petrology: Understanding Magmatic 
Processes. Nicholls, J. and Russell, J.K., eds. Reviews in Mineralogy Volume 24. 
25-64. Washington, D.C.: Mineralogical Society of America. TIC: 246394. 
Luhr, J.F. and Simkin, T., eds. 1993. Paricutin, The Volcano Born in a Mexican 144310 
Cornfield. Phoenix, Arizona: Geoscience Press. TIC: 247017. 
Machette, M.N. 1985. Calcic Soils of the Southwestern United States. Soils and 104660 
Quaternary Geology of the Southwestern United States. Weide, D.L. and Faber, 
M.L., eds. Special Paper 203. Pages 1-21. Boulder, Colorado: Geological Society 
of America. TIC: 239387. 
Mader, H.M. 1998. Conduit Flow and Fragmentation. The Physics of Explosive 144419 
Volcanic Eruptions. Gilbert, J.S. and Sparks, R.S.J., eds. Geological Society Special 
Publication No. 145. Pages 51-71. London, United Kingdom: Blackwell Scientific 
Publications. TIC: 247115. 

Mahood, G.A. and Baker, D.R. 1986. Experimental Constraints on Depths of 104663 
Fractionation of Mildly Alkalic Basalts and Associated Felsic Rocks: Pantelleria, 
Strait of Sicily. Contributions to Mineralogy and Petrology, 93, 251-264. 
New York, New York: Springer-Verlag. TIC: 225072. 
Maleyev, Ye.F. and Vande-Kirkov, Yu.V. [1983]. Features of Pyroclastics of the 144325 
Northern Breakthrough of the Great Tolbachik Fissure Eruption and the Origin of Its 
Pale-Grey Ash. The Great Tolbachik Fissure Eruption, Geological and Geophysical 
Data 1975-1976. Fedotov, S.A. and Markhinin, Ye.K., eds. Pages 5771. 
New York, New York: Cambridge University Press. TIC: 247236. 
Mastin, L.G. and Ghiorso, M.S. 2000. A Numerical Program for Steady-State Flow 170144 
of Magma-Gas Mixtures Through Vertical Eruptive Conduits. Open-File Report 
00-209. Vancouver, Washington: U.S. Geological Survey. ACC: 
MOL.20040629.0228. 
Mastin, L.G. and Pollard, D.D. 1988. Surface Deformation and Shallow Dike 169783 
Intrusion Processes at Inyo Craters, Long Valley, California. Journal of 
Geophysical Research, 93, (B11), 13,221-13,235. Washington, D.C.: American 
Geophysical Union. TIC: 256132. 
McBirney, A.R. 1959. Factors Governing Emplacement of Volcanic Necks. 162826 
American Journal of Science, 257, (1), 431448. New Haven, Connecticut: Yale 
University, Sterling Tower. TIC: 254240. 
McGetchin, T.R.; Settle, M.; and Chouet, B.A. 1974. Cinder Cone Growth Modeled 115469 
after Northeast Crater, Mount Etna, Sicily. Journal of Geophysical Research, 79, 
(23), 3257-3272. Washington, D.C.: American Geophysical Union. TIC: 246027. 
Muenow, D.W.; Graham, D.G.; Liu, N.W.K.; and Delaney, J.R. 1979. The 125093 
Abundance of Volatiles in Hawaiian Tholeiitic Submarine Basalts. Earth and 
Planetary Science Letters, 42, 71-76. Amsterdam, The Netherlands: Elsevier. 
TIC: 246833. 
NRC (U.S. Nuclear Regulatory Commission) 1999. Issue Resolution Status Report 151592 
Key Technical Issue: Igneous Activity. Rev. 2. Washington, D.C.: U.S. Nuclear 
Regulatory Commission. Accessed September 18, 2000. TIC: 247987. 
http://www.nrc.gov/NMSS/DWM/ia-rev2.htm
NRC 2003. Yucca Mountain Review Plan, Final Report. NUREG-1804, Rev. 2. 163274 
Washington, D.C.: U.S. Nuclear Regulatory Commission, Office of Nuclear Material 
Safety and Safeguards. TIC: 254568. 

Ochs, F.A., III and Lange, R.A. 1999. The Density of Hydrous Magmatic Liquids. 144330 
Science, 283, 1314-1317. Washington, D.C.: American Association for the 
Advancement of Science. TIC: 246839. 
Perry, F.V. and Straub. K.T. 1996. Geochemistry of the Lathrop Wells Volcanic 106490 
Center. LA-13113-MS. Los Alamos, New Mexico: Los Alamos National 
Laboratory. ACC: MOL.19961015.0079. 
Perry, F.V.; Crowe, B.M.; Valentine, G.A.; and Bowker, L.M., eds. 1998. Volcanism 144335 
Studies: Final Report for the Yucca Mountain Project. LA-13478. Los Alamos, 
New Mexico: Los Alamos National Laboratory. TIC: 247225. 
Piron, J.P. 2001. Presentation of the Key Scientific Issues for the Spent Nuclear 162396 
Fuel Evolution in a Closed System. Section 5.1 of Synthesis on the Long Term 
Behavior of the Spent Nuclear Fuel. Poinssot, C., ed. CEA-R-5958(E). Volume I. 
[Paris], France: Commissariat  lnergie Atomique. TIC: 253976. 
Pyle, D.M. 1989. The Thickness, Volume and Grainsize of Tephra Fall Deposits. 123891 
Bulletin of Volcanology, 51, (1), 1-15. [Berlin, Germany]: Springer-Verlag. 
TIC: 237451. 
Quareni, F.; Ventura, G.; and Mulargia, F. 2001. Numerical Modelling of the 162830 
Transition from Fissure- to Central-Type Activity on Volcanoes: A Case Study from
Salina Island, Italy. Physics of the Earth and Planetary Interiors, 124, ([3-4]), 
213-221. New York, New York: Elsevier. TIC: 254053. 
Ramelli, A.R.; Oswald, J.A.; Vadurro, G.; Menges, C.M.; and Paces, J.B. 1996. 101106 
Quaternary Faulting on the Solitario Canyon Fault. Chapter 4.7 of Seismotectonic 
Framework and Characterization of Faulting at Yucca Mountain, Nevada. Whitney, 
J.W., ed. Milestone 3GSH100M. Denver, Colorado: U.S. Geological Survey. 
TIC: 237980. ACC: MOL.19970129.0041. 
Reamer, C.W. 1999. Issue Resolution Status Report (Key Technical Issue: Igneous 119693 
Activity, Revision 2). Letter from C.W. Reamer (NRC) to Dr. S. Brocoum
(DOE/YMSCO), July 16, 1999, with enclosure. ACC: MOL.19990810.0639. 
Reamer, C.W. 2001. U.S. Nuclear Regulatory Commission/U.S. Department of 159894 
Energy Technical Exchange and Management Meeting on Igneous Activity 
(September 5, 2001). Letter from C.W. Reamer (NRC) to S. Brocoum
(DOE/YMSCO), September 12, 2001, with enclosure. ACC: MOL.20011114.0008. 

Rose, W.I., Jr.; Bonis, S.; Stoiber, R.E.; Keller, M.; and Bickford, T. 1973. Studies 116087 
of Volcanic Ash from Two Recent Central American Eruptions. Bulletin 
Volcanologique, XXXVII-3, 338-364. New York, New York: Springer-Verlag. 
TIC: 246073. 
Rowland, S.K. and Walker, G.P.L. 1990. Pahoehoe and AA in Hawaii: Volumetric 115463 
Flow Rate Controls the Lava Structure. Bulletin of Volcanology, 52, 615-628. 
New York, New York: Springer-Verlag. TIC: 246030. 
Rubin, A.M. 1992. Dike-Induced Faulting and Graben Subsidence in Volcanic Rift 169784 
Zones. Journal of Geophysical Research, 97, (B2), 1839-1858. Washington, D.C.: 
American Geophysical Union. TIC: 256133. 
Rubin, A.M. 1995. Propagation of Magma-Filled Cracks. Annual Review of Earth 164118 
and Planetary Sciences, 23, 287-336. Palo Alto, California: Annual Reviews. 
TIC: 254554. 
Rubin, A.M. and Gillard, D. 1998. Dike-Induced Earthquakes: Theoretical 169786 
Considerations. Journal of Geophysical Research, 103, (B5), 10,017-10,030. 
[Washington, D.C.]: American Geophysical Union. TIC: 256130. 
Rubin, A.M.; Gillard, D.; and Got, J-L. 1998. A Reinterpretation of Seismicity 169787 
Associated with the January 1983 Dike Intrusion at Kilauea Volcano, Hawaii. 
Journal of Geophysical Research, 103, (B5), 10,003-10,015. Washington, D.C.: 
American Geophysical Union. TIC: 256131. 
Sandoval, R.P.; Weber, J.P.; Levine, H.S.; Romig, A.D.; Johnson, J.D.; Luna, R.E.; 156313 
Newton, G.J.; Wong, B.A.; Marshall, R.W., Jr.; Alvarez, J.L.; and Gelbard, F. 1983. 
An Assessment of the Safety of Spent Fuel Transportation in Urban Environs. 
SAND82-2365. Albuquerque, New Mexico: Sandia National Laboratories. 
ACC: NNA.19870406.0489. 
Shaw, H.R. 1972. Viscosities of Magmatic Silicate Liquids: An Empirical Method 126270 
of Prediction. American Journal of Science, 272, 870-889. New Haven,
Connecticut: Yale University, Kline Geology Laboratory. TIC: 246470. 
Sisson, T.W. and Grove, T.L. 1993. Experimental Investigations of the Role of H2O 144351 
in Calc-Alkaline Differentiation and Subduction Zone Magmatism. Contributions to 
Mineralogy and Petrology, 113, 143-166. New York, New York: Springer-Verlag. 
TIC: 246909. 

Sisson, T.W. and Grove, T.L. 1993. Temperatures and H{subscript 2}O Contents of 122564 
Low-MgO High-Alumina Basalts. Contributions to Mineralogy and Petrology, 113, 
167-184. New York, New York: Springer-Verlag. TIC: 246251. 
Sisson, T.W. and Layne, G.D. 1993. H2O in Basalt and Basaltic Andesite Glass 122549 
Inclusions from Four Subduction-Related Volcanoes. Earth and Planetary Science 
Letters, 117, 619-635. Amsterdam, The Netherlands: Elsevier. TIC: 246239. 
Smith, R.P.; Jackson, S.M.; and Hackett, W.R. 1996. Paleoseismology and Seismic 101020 
Hazards Evaluations in Extensional Volcanic Terrains. Journal of Geophysical 
Research, 101, (B3), 6277-6292. Washington, D.C.: American Geophysical Union. 
TIC: 238265. 
Sparks, R.S.J.; Bursik, M.I.; Carey, S.N.; Gilbert, J.S.; Glaze, L.S.; Sigurdsson, H.; 144352 
and Woods, A.W. 1997. Volcanic Plumes. 574. New York, New York: John Wiley 
& Sons. TIC: 247134. 
Squires, R.R. and Young, R.L. 1984. Flood Potential of Fortymile Wash and Its 102783 
Principal Southwestern Tributaries, Nevada Test Site, Southern Nevada. Water-
Resources Investigations Report 83-4001. Carson City, Nevada: U.S. Geological 
Survey. ACC: HQS.19880517.1933. 
Stamatakos, J.A.; Connor, C.B.; and Martin, R.H. 1997. Quaternary Basin 138819 
Evolution and Basaltic Volcanism of Crater Flat, Nevada, from Detailed Ground 
Magnetic Surveys of the Little Cones. Journal of Geology, 105, 319-330. Chicago, 
Illinois: University of Chicago. TIC: 245108. 
Stock, J.M.; Healy, J.H.; Hickman, S.H.; and Zoback, M.D. 1985. Hydraulic 101027 
Fracturing Stress Measurements at Yucca Mountain, Nevada, and Relationship to the 
Regional Stress Field. Journal of Geophysical Research, 90, (B10), 8691-8706. 
Washington, D.C.: American Geophysical Union. TIC: 219009. 
Symonds, R.B.; Rose, W.I.; Bluth, G.J.S.; and Gerlach, T.M. 1994. Volcanic-Gas 101029 
Studies: Methods, Results, and Applications. Chapter 1 of Volatiles in Magmas. 
Carroll, M.J. and Holloway, J.R., eds. Reviews in Mineralogy Volume 30. 
Washington, D.C.: Mineralogical Society of America. TIC: 238061. 
USDA (U.S. Department of Agriculture) 2000. Summary Report, 1997 National 160548 
Resources Inventory (Revised December 2000). Washington, D.C.: U.S. Department 
of Agriculture. TIC: 253006. 

Valentine, G.A. and Groves, K.R. 1996. Entrainment of Country Rock During 107052 
Basaltic Eruptions of the Lucero Volcanic Field, New Mexico. Journal of Geology, 
104, 71-90. Chicago, Illinois: University of Chicago Press. TIC: 246146. 
Vaniman, D. and Crowe, B. 1981. Geology and Petrology of the Basalts of Crater 101620 
Flat: Applications to Volcanic Risk Assessment for the Nevada Nuclear Waste 
Storage Investigations. LA-8845-MS. Los Alamos, New Mexico: Los Alamos 
Scientific Laboratory. ACC: HQS.19880517.1541. 
Vergniolle, S. and Jaupart, C. 1986. Separated Two-Phase Flow and Basaltic 115585 
Eruptions. Journal of Geophysical Research, 91, (B12), 12,842-12,860. 
Washington, D.C.: American Geophysical Union. TIC: 239308. 
Wallbrink, P.J.; Olley, J.M.; and Murray, A.S. 1994. Measuring Soil Movement 164092 
Using {superscript 137}Cs: Implications of Reference Site Variability. Variability 
in Stream Erosion and Sediment Transport, Proceedings of a Symposium held at 
Canberra, Australia, 12-16 December 1994. Olive, L.J.; Loughran, R.J.; and Kesby, 
J.A., eds. IAHS Publication No. 224. Pages 95-102. Wallingford, Oxfordshire, 
England: International Association of Hydrological Sciences. TIC: 254472. 
Wells, D.L. and Coppersmith, K.J. 1994. New Empirical Relationships Among 107201 
Magnitude, Rupture Length, Rupture Width, Rupture Area, and Surface 
Displacement. Bulletin of the Seismological Society of America, 84, (4), 974-1002. 
El Cerrito, California: Seismological Society of America. TIC: 226273. 
White, J.D.L. 1991. Maar-Diatreme Phreatomagmatism at Hopi Buttes, Navajo 124930 
Nation (Arizona), USA. Bulletin of Volcanology, 53, (4), 239-258. Berlin, 
Germany: Springer-Verlag. TIC: 239072. 
Whitney, J.W.; Simonds, F.W.; Shroba, R.R.; and Murray, M. 1996. Quaternary 107313 
Faulting on the Windy Wash Fault. Chapter 4.9 of Seismotectonic Framework and 
Characterization of Faulting at Yucca Mountain, Nevada. Whitney, J.W., ed. 
Milestone 3GSH100M. Denver, Colorado: U.S. Geological Survey. TIC: 237980. 
ACC: MOL.19970129.0041. 
Wilson, L. and Head, J.W., III 1981. Ascent and Eruption of Basaltic Magma on the 101034 
Earth and Moon. Journal of Geophysical Research, 86, (B4), 2971-3001. 
Washington, D.C.: American Geophysical Union. TIC: 225185. 
Wohletz, K. and Heiken, G. 1992. Volcanology and Geothermal Energy. Berkeley, 105544 
California: University of California Press. TIC: 241603. 

Wohletz, K.H. 1986. Explosive Magma-Water Interactions: Thermodynamics, 140956 
Explosion Mechanisms, and Field Studies. Bulletin of Volcanology, 48, 245-264. 
Berlin, Germany: Springer-Verlag. TIC: 225183. 
WoldeGabriel, G.; Keating, G.N.; and Valentine, G.A. 1999. Effects of Shallow 110071 
Basaltic Intrusion into Pyroclastic Deposits, Grants Ridge, New Mexico, USA. 
Journal of Volcanology and Geothermal Research, 92, ([3]), 389-411. New York, 
New York: Elsevier. TIC: 246037. 
Wood, C.A. 1980. Morphometric Evolution of Cinder Cones. Journal of 116536 
Volcanology and Geothermal Research, 7, 387-413. Amsterdam, The Netherlands: 
Elsevier. TIC: 225565. 
Wylie, J.J.; Helfrich, K.R.; Dade, B.; Lister, J.R.; and Salzig, J.F. 1999. Flow 162861 
Localization in Fissure Eruptions. Bulletin of Volcanology, 60, (8), 432440. 
New York, New York: Springer-Verlag. TIC: 254054. 
Yoder, H.S., Jr. and Tilley, C.E. 1962. Origin of Basalt Magmas: An Experimental 122589 
Study of Natural and Synthetic Rock Systems. Journal of Petrology, 3, (3), 342532. 
London, England: Oxford University Press. TIC: 247024. 
8.2 CODES, STANDARDS, REGULATIONS, AND PROCEDURES 
10 CFR 63. Energy: Disposal of High-Level Radioactive Wastes in a Geologic 156605 
Repository at Yucca Mountain, Nevada. Readily available. 
AP-2.22Q, Rev. 1 ICN 0, Classification Criteria and Maintenance of the Monitored 164786 
Geologic Repository Q-List 
AP-SIII.2Q, Rev. 1 ICN 2, Qualification of Unqualified Software 169197 
AP-SIII.9Q, Rev. 1 ICN 7, Scientific Analyses 169151 
LP-SI.11Q-BSC, Rev. 0 ICN 0, Software Management 168412 
8.3 SOURCE DATA, LISTED BY DATA TRACKING NUMBER 
LA000000000099.002. Major Element, Trace Element, Isotopic, and Mineral 147725 
Chemistry Data from Lathrop Wells. Submittal date: 08/02/1995. 
LA0009FP831811.001. Compilation and Summaries of Data Supporting 164712 
Computation of Volcanic Event Intersection Frequencies. Submittal 
date: 09/01/2000. 
LA0302GH831811.002. Grain Size of Tephra from Tephra Deposits Around the 162864 

Lathrop Wells Volcano, Nevada. Submittal date: 02/19/2003. 
LA0302GH831811.003. Lithic Clasts Measured at Lathrop Wells Cone, Nevada. 162865 
Submittal date: 02/25/2003. 
LA0302GH831811.004. Grain Counts-Types of Pyroclasts from Tephra Deposits 162866 
Around the Lathrop Wells Volcano, Nevada. Submittal date: 02/25/2003. 
LA0305DK831811.001. Locations and Thicknesses of Tephra (Ashfall) from 164026 
Lathrop Wells Cone, Nevada. Submittal date: 05/09/2003. 
LA0306GH831811.001. SEM Photos-Types of Pyroclasts from Tephra Deposits 171286 
Around the Lathrop Wells Volcano, Nevada. Submittal date: 06/16/2003. 
LA0308CH831811.002. Interpretation of 137-Cesium Profile Values for Samples 164853 
from the Fortymile Wash Alluvial Fan. Submittal date: 08/20/2003. 
LA0405CH831811.001. Basaltic Ash Weight Percentages of Drainage Channel 169998 
Samples Near Lathrop Wells Cone. Submittal date: 04/05/2004. 
MO0407SEPFEPLA.000. LA FEP List. Submittal date: 07/20/2004. 170760 
8.4 OUTPUT DATA, LISTED BY DATA TRACKING NUMBER 
LA0305DK831811.002. Volumes of the Lathrop Wells Cone, Lava, and Tehphra, 
Characterize Eruptive Processes at Yucca Mountain Nevada, Submittal date 
05/14/2003. 
LA0407DK831811.001. Technical Product Output for ANL-MGR-GS-000002, 
Rev. 02. 

APPENDIX A 
QUALIFICATION OF INPUT DATA 


APPENDIX A 
QUALIFICATION OF INPUT DATA 
External sources have provided unqualified data that have been used as direct input to this 
document. The inputs from these sources are qualified for intended use within the document 
using the criteria found in AP-SIII.9Q, Scientific Analyses. These criteria represent a subset of 
the methods and attributes required for qualification of data per AP-SIII.2Q, Qualification of 
Unqualified Data. The following information is provided for each source: The full reference 
citation, a description of the data that were used from the source, and the extent to which the data 
demonstrate the properties of interest. In addition one or more of the following criteria is also 
addressed: 
 
Reliability of data source 
 
Qualifications of personnel or organizations generating the data 
 
Prior uses of the data 
 
Availability of corroborating data. 
The criteria described above meet the requirements of AP-SIII.10Q and are provided as 
justification that the data that have been used from these sources are considered to be qualified 
for intended use. 
A1. DOUBIK AND HILL 1999 
ReferenceDoubik, P. and Hill, B.E. 1999. "Magmatic and Hydromagmatic Conduit 
Development During the 1975 Tolbachik Eruption, Kamchatka, with Implications for Hazards 
Assessment at Yucca Mountain, NV." Journal of Volcanology and Geothermal Research, 91, 
43-64. Amsterdam, The Netherlands: Elsevier. TIC: 246029. [DIRS 115338] 
Description of UseDoubik and Hill (1999, p. 60) estimate a conduit diameter of a 50 m for the 
Lathrop Wells Cone. This estimate is used as a mode or most likely value for conduit diameter 
at depth for potential eruptions at Yucca Mountain. 
Extent to which the Data Demonstrate the Properties of InterestAs discussed in Section 5 
of this document, the Lathrop Wills volcano represents the most recent volcanism in the YMR, 
and is used as an analogue for eruptive style and magmatic composition. Studies of this volcano 
have been underway by the DOE's Yucca Mountain Project, as well as by the Center for Nuclear 
Waste Regulatory Analysis at the Southwest Research Institute that provides technical support 
for the NRC's Yucca Mountain programs. This reference publishes some of the work that was 
conducted by Southwest Research Institute for the NRC. The paper provides an estimate of 
conduit diameter that is combined with other data and observations to determine the distribution 
of this parameter that is used in other analyses of eruptive events. 
Qualifications of Personnel or Organizations Generating the Data and Prior Use of the 
DataSouthwest Research Institute provides technical support for the NRC's Yucca Mountain 
programs, thus the Institute can be considered to have the necessary credentials to provide 
qualified data. The referenced data has been acquired by Southwest Research Institute under 
contract to the NRC. The data (conduit diameter of 50 m) and this specific reference (Doubik 

and Hill) are referred to by the NRC in Issue Resolution Status Report (Key Technical Issue: 
Igneous Activity, Revision 2) (Reamer 1999 [DIRS 119693]). 
Dr. Doubik received has Ph.D (1998) from the State University of New York at Buffalo for his 
research in the Study of the eruptive products from three volcanoes in Kamchatka with insights 
into shallow magma evolution and dynamics. 
Dr. Hill received his Masters and Doctoral degrees in Volcanology from Oregon State 
University. He has over 20 years experience in helping government and industry use complex 
scientific information to make important decisions. At Southwest Research Institute, he has led 
multidisciplinary teams in developing long-term risk assessments for volcanic hazards at nuclear 
facilities. 
A2. BLONG 1984 
ReferenceBlong, R.J. 1984 [DIRS 144263]. Volcanic Hazards, A Sourcebook on the Effects of 
Eruptions. Sydney, Australia: Academic Press. TIC: 247016. 
Description of UseQuaternary basalts of the YMR display textural and depositional facies that 
indicate a range of eruptive processes. Explosive processes, in which fragments (closets), or 
clots, of melt were erupted in a stream of gas, are evidenced by the presence of scoria cones and 
remnants of ash fallout blankets. The Blong 1984 reference is used as one of the sources of input 
for bulk in situ density of fallout deposits, setting a typical value 0f 1000 kg/m3. 
Extent to which the Data Demonstrate the Properties of InterestThe calculations that are 
run to provide a feed to the TSPA require input values for the density of tephra deposits or 
settled ash. The values that are used from Sparks et al. (1997 [DIRS 144352]) are recommended 
as one of two reasonable ways of treating these deposit densities, by providing a range of values. 
The range of values is compared with data from Sparks, et al., 1997, which sets typical ranges 
from 300 to 1,500 kg/m3. 
Qualifications of Personnel and Organizations Generating the DataEmeritus Professor 
Russell Blong retired as Director of Risk Frontiers* in July 2003 after more than 30 years on the 
staff at Macquarie University. 
Dr. Blong holds Masters degrees in Geography (Auckland) and Engineering Science and a Ph.D. 
in Geomorphology (Sydney). He has researched a wide range of natural hazards and their 
consequences including volcanic, earthquake, flood, and landslide hazards and their 
consequences in Australia, the South Pacific, and Asia. His other interests include building 
damage assessments, loss modeling, and integrated risk rating. He has published ten books and 
more than 200 research papers. He is the past-president of the International Society for the 
Prevention and Mitigation of Natural Hazards (the Natural Hazards Society). One of his books 
on volcanic hazards is considered to be a sourcebook on volcanic risk. It is probably the most 
complete reference on volcanic hazards-including the effects on people, infrastructure, and 
economic activity. 
*Risk Frontiers (formerly the Natural Hazards Research Centre) is regarded as a world leader in 
quantitative natural hazards risk assessment and risk management. Risk Frontiers, based at 

Sydney's Macquarie University, is a not-for-profit research organization sponsored by the 
Australian insurance community. For ten years, it has provided insurers with sophisticated 
research-based solutions. Other applications include emergency management, land use planning 
and floodplain management. As well as Australia, these tools are currently being used in 
Europe, North America, and Asia. 
A3. JARZEMBA 1997 
ReferenceJarzemba, M.S. 1997. "Stochastic Radionuclide Distributions After a Basaltic 
Eruption for Performance Assessments of Yucca Mountain." Nuclear Technology, 118, 
132-141. [Hinsdale, Illinois]: American Nuclear Society. TIC: 237944. [DIRS: 100460] 
Description of UseSection 6.3.3.4 discusses the potential eruption volume and duration. 
Jarzemba (1997 [DIRS 100460], p. 136) is the source for the log time values from eight different 
analogue volcanic eruptions from around the world. These values are presented in Table 605. 
Extent to which the Data Demonstrate the Properties of InterestSec. 6.3.3.4 develops 
parameters that will be used to develop probability distributions for Eruptive Plume Dispersal 
calculations. The necessary inputs include the duration and power of explosive, eruptive events, 
as well as the mass discharge rates. The Jarzemba (1997) reference provides values for duration 
and power from various volcanic eruptions around the world and is consistent with similar 
calculations being run for the NRC. 
Qualifications of Personnel or Organizations Generating the Data and Prior Use of the 
DataSouthwest Research Institute provides technical support for the NRC's Yucca Mountain 
programs, thus the Institute can be considered to have the necessary credentials to provide 
qualified data. Studies have been underway by the DOE's Yucca Mountain Project, as well as by 
the Center for Nuclear Waste Regulatory Analysis at the Southwest Research Institute, which 
provides technical support for the NRC's Yucca Mountain programs. This reference publishes 
some of the work that was conducted by Southwest Research Institute for the NRC. The 
referenced data have been acquired by Southwest Research Institute under contract to NRC. 
While the specific data (log time of the eruption duration) has not been specifically quoted by the 
NRC, this specific reference (Jarzemba 1997) is referred to by the NRC in Issue Resolution 
Status Report (Key Technical Issue: Igneous Activity, Revision 2) (Reamer 1999 
[DIRS 119693]). 
Dr. Jarzemba earned his Ph.D. in 1993 in Nuclear Engineering and an undergraduate degree in 
Engineering Physics from Ohio State University. Dr. Jarzemba has over 15 years of research 
and professional experience. At the time of publication, Dr. Jarzemba was a research scientist 
with Southwest Research Institute. Dr. Jarzemba is the author and co-author of numerous books 
and publications. 
A4. KEATING AND VALENTINE 1998 
ReferenceKeating, G.N. and Valentine, G.A. 1998. "Proximal Stratigraphy and Syn-Eruptive 
Faulting in Rhyolitic Grants Ridge Tuff, New Mexico, USA." Journal of Volcanology and 
Geothermal Research, 81, 37-49. Amsterdam, The Netherlands: Elsevier. TIC: 246096. 
[DIRS 111236] 

Description of UseKeating and Valentine (1998) is the source of the value of 150 m, which is 
the diameter of Grants Ridge conduit/plug in New Mexico. This value is used to set the 
maximum value in the conduit diameter distribution. 
Extent to which the Data Demonstrate the Properties of InterestAs discussed in Section 5 
of this analysis report, the Lathrop Wills volcano represents the most recent volcanism in the 
YMR, and is used as an analogue for eruptive style and magmatic composition. The conduit for 
Lathrop Wells is estimated at 50 m. In order to provide a distribution of conduit diameters for 
the use in subsequent analyses, data from a larger eruptive analogue was needed. The large size 
of the Grants Ridge plug reflects an eruptive volume on the order of a few km3 of alkali basalt 
and, therefore, is expected to be a conservative upper bound for conduit diameter at Yucca 
Mountain. Note that the basalt plug represents a later phase conduit in a basalt rhyolite 
sequence. 
Qualifications of Personnel and Organizations Generating the DataDr. Gordon Keating is a 
postdoctoral research associate with the Environmental Geology and Risk Analysis Group at the 
Los Alamos National Laboratory. Dr. Keating received a Ph.D in Geology from the University 
of New Mexico, an M.S. in Geology from Michigan Technological University (1991), and a 
B.A. in Geology from Carleton College (1988). He is building on a background in physical 
volcanology, hydrogeology, and numerical modeling of heat and fluid flow to address aspects of 
Geographic Information Systems and spatial decision support for mitigating natural hazards. 
Dr. Valentine is Team Leader for Magmatic and Planetary Dynamics, Geoanalysis Group, Los 
Alamos National Laboratory. He is the Principal Investigator for Physical Processes of 
Magmatism and Effects on the Potential Repository (Yucca Mountain Project). His fields of 
research include numerical simulation of flow in porous media, explosive volcanic eruptions, and 
magma chamber dynamics. His field studies are related to volcanic hazards assessment, 
large-volume pyroclastic eruptions, fossil hydrothermal systems, intrusion mechanisms, and 
dynamics. Dr. Valentine received his Ph.D. in Geological Sciences (1988) from the University 
of California, Santa Barbara and a B.S. in Geological Engineering and Geology (1984) from the 
New Mexico Institute of Mining and Technology. 
A5. SISSON AND GROVE 1993 
ReferenceSisson, T.W. and Grove, T.L. 1993. "Experimental Investigations of the Role of 
H2O in Calc-Alkaline Differentiation and Subduction Zone Magmatism." Contributions to 
Mineralogy and Petrology, 113, 143-166. New York, New York: Springer-Verlag. 
TIC: 246909. [DIRS 144351] 
Description of UseSection 6.3.2.4 of this analysis report presents an approach to determining 
the temperatures of magmas with elevated water content. Sisson and Grove (1993) is a source of 
an equation that represents their experimental work, which expresses the relationship between 
temperature and the weight percentage of water, pressure, and composition of magmas. This 
analysis uses this expression to determine the liquidus temperatures for Lathrop Wells magmas 
with different hypothetical water contents. 

Extent to which the Data Demonstrate the Properties of InterestDirect measurements of 
physical properties of erupting magma are difficult to sample, especially in those magmas with 
elevated water content. Thus, although direct measurements are available for the low end of the 
spectrum of water content, experiments must be relied upon to constrain magmatic temperatures 
for magmas with water contents equivalent to the higher end of the potential range being 
evaluated in the YMR. The experimental results that are presented in the Sisson and Grove 
article provide a mathematical representation of temperature, and water content in magmas that 
are similar in composition to those seen at Lathrop Well volcano and other volcanism in the 
YMR. 
Qualifications of Personnel and Organizations Generating the DataDr. Sisson earned his 
Ph.D. in Geology from the Massachusetts Institute of Technology and has over 25 years of 
professional and research experience. His current research includes the use of a high-temperature, 
high-pressure experimental laboratory to determine: 
 The depths at which magmas are stored before eruptions 
 
How volatile concentrations influence eruption styles 
 
How magma ascent rates control the growth of gas bubbles that power explosive 
eruptions 
 
How magmas form by melting of diverse source-rocks. 
Experimental and petrologic research led to his election in 2000 as a Fellow of the Mineralogical 
Society of America. In addition, he leads the Undersea Hazards of Hawaiian Volcanoes task, a 
collaborative effort between the U.S. Geological Survey and the Japan Marine Science and 
Technology Center to use deep-diving submersibles and remotely operated vehicles to 
understand the growth, deformation, and collapse of Earth's largest ocean island volcanoes. As 
task leader, he coordinates research efforts between United States and Japanese participants and 
guides research activities. Other research has been to study deep marine volcanic rocks that 
erupted early in the growth of Kilauea Volcano. Results bear on the melting processes that 
initiated growth of Kilauea, Earth's most active volcano, and on the stability of volcano flanks. 
Dr. Grove holds a Ph.D in Geology from Harvard University. He has over thirty years of 
professional and research experience. Dr. Grove's research focus is on the processes that have 
led to the chemical differentiation of the crust and mantle of the Earth and on the processes of 
formation and evolution of the interiors of other planets, including the moon, Mars, and 
meteorite parent bodies. The development of new experimental techniques has allowed 
examination of the role of H2O in magmatic processes. The results of the experiments are used 
with thermodynamic and kinetic theory to develop models of physical conditions and chemical 
exchange processes. 

A6. SPARKS, BURSIK, CAREY, GILBERT, GLAZE, SIGURDSSON, AND 
WOODS 1997 
ReferenceSparks, R.S.J.; Bursik, M.I.; Carey, S.N.; Gilbert, J.S.; Glaze, L.S.; Sigurdsson, H.; 
and Woods, A.W. 1997. Volcanic Plumes. 574. New York, New York: John Wiley & Sons. 
TIC: 247134. [DIRS 144352] 
Description of UseQuaternary basalts of the YMR display textural and depositional facies that 
indicate a range of eruptive processes. Explosive processes, in which fragments (closets), or 
clots, of melt were erupted in a stream of gas, are evidenced by the presence of scoria cones and 
remnants of ash fallout blankets. The Sparks et al. (1997) reference is used as one of the sources 
of input for bulk in situ density of fallout deposits, setting typical ranges from 300 to 
1,500 kg/m3. 
Extent to which the Data Demonstrate the Properties of InterestThe calculations that are 
run to provide a feed to the TSPA require input values for the density of tephra deposits or 
settled ash. The values that are used from Sparks et al. (1997, are recommended as one of two 
reasonable ways of treating these deposit densities, by providing a range of values. The range of 
values is compared with data from Blong (1984 [DIRS ]144263]) that provide an approximation 
of 1000 kg/m3. 
Qualifications of Personnel or Organizations Generating the Data and Prior Use of the 
DataWhile the data (bulk in situ density of fallout deposits) has not been specifically quoted by 
the NRC, this specific reference (Sparks et al. 1997) is referred to by the NRC in Issue 
Resolution Status Report (Key Technical Issue: Igneous Activity, Revision 2) (Reamer 1999 
[DIRS 119693]). 
Dr. Sparks is currently Research Professor and Director of the Centre for Environmental and 
Geophysical Flows at the University of Bristol, U.K. His research interests are in volcano 
dynamics, igneous petrology, and application of fluid mechanics to understanding flow processes 
in the earth and the environment. Dr. Sparks authored and co-authored numerous books and 
articles on volcanology. 
Dr. Bursik holds a Ph.D. in Geology, from the California Institute of Technology (1989). The 
title of his dissertation was Volcanotectonic Evolution of the Mono Basin, Eastern California. 
Dr. Bursiks current position is Professor, Department of Geology, State University of New York 
at Buffalo. His research is mostly in the area of geological fluid mechanics and surface 
processes. He is also interested in erosion in semi-arid regions, landform change related to 
wildfires, growth of deltas, the hydraulics of the Niagara River, and the coupling between 
faulting and volcanism. His field areas include San Francisco Volcanic Field, Arizona; 
Mammoth Mountain-Mono Craters, California; Kamchatka, Russia, and Colima and 
Popocatepetl volcanoes, Mexico. 
Dr. Carey holds a Ph.D in Geological Oceanography from University of Rhode Island (1983). 
He has over 29 years of research and professional experience. His current position is Professor 
of Oceanography at the Graduate School of Oceanography, University of Rhode Island. Dr. 
Carey's current research interests can be subdivided into three main areas, all of which are related 

to the study of explosive volcanism at convergent plate boundaries. The three areas include 
computer simulation of explosive eruption processes (tephra fallout and eruption column 
dynamics); the petrology and physical properties of magmas involved in explosive volcanism, 
and; the origin and characteristics of marine volcaniclastic sediments adjacent to island arcs and 
continental margins. Dr. Carey is also currently working on research projects in Indonesia 
(Krakatau volcano), Iceland, and the West Indies (Kick'em Jenny) volcano) where he uses 
sub-bottom geophysical surveys with CHIRP and bubble pulser systems together with gravity 
and SCUBA coring and ROVs to investigate the nature of volcaniclastic deposits on the seafloor. 
Dr. Gilbert is a Senior Lecturer at the University of Lancaster, United Kingdom. Her main 
research interests include physical and chemical effects of volcanic ash on vegetation and soil; 
subglacial volcanism processes, products, and hazards; volcanic facies as indicators of climate 
change; and volcanic pollutant dispersal in the atmosphere. Dr. Gilbert has extensive fieldwork 
skills, as well as expertise in laboratory based volcanology experiments and analytical 
geochemistry and has authored and co-authored numerous peer-reviewed journal articles. 
The other authors of this volume, Drs. L.S. Glaze, H. Sigurdsson, and A.W. Woods, each 
represent many years of experience in geoscience academics and research, including specific 
expertise in geophysics, geochemistry, oceanography. 
A7. SYMONDS, ROSE, BLUTH, AND GERLACH 1994 
Symonds, R.B.; Rose, W.I.; Bluth, G.J.S.; and Gerlach, T.M. 1994. "Volcanic-Gas Studies: 
Methods, Results, and Applications." Chapter 1 of Volatiles in Magmas. Carroll, M.J. and 
Holloway, J.R., eds. Reviews in Mineralogy Volume 30. Washington, D.C.: Mineralogical 
Society of America. TIC: 238061. [DIRS 101029] 
Description of UseThis reference provides data tables containing gas concentrations from 
various convergent-plate (Table 3), divergent-plate (Table 4), and hot-spot (Table 5) volcanoes. 
The tables are a compilation of the study results performed by the authors and other 
volcanologists. The values of the gas concentrations (total of 88 sample analyses) listed in the 
tables have been used in the analysis report to arrive at the mean value, square root of the sum of 
the squares and the standard deviation of the tabulated concentrations (Table 7 of the analysis 
report). As such, the gas analyses results listed in the reference are a direct input to the statistical 
measurements obtained in Section 6.3.2.3. 
Extent to which the Data Demonstrate the Properties of InterestThe referenced gas 
concentrations from Symonds et al 1994 [DIRS 101029], provide a range of gas compositions 
from a variety of volcanic centers from around the world. For the purpose of including hawaiite 
from Mount Etna; tholeiitic basalt from Momotombo, Poas, Kilauea, Ardoukoba, and Erta Ale; 
nephelenite from Nyiragongo; and alkali basalt from Surtsey. The data from these mafic centers 
are considered to be representative of a range of volcanism that may be analogous to potential 
volcanic activity in the Yucca Mountain region. The use of these data must suffice to constrain 
the relative proportions of major gas constituents in Yucca Mountain region basalts owing to the 
absence of current volcanic activity in the YMR from which gases could be directly sampled. 

Qualifications of Personnel and Organizations Generating the DataDr. Symonds earned his 
Ph.D. and M.S. degrees in Geology from Michigan Technological University. He has over 
20 years of research and professional experience in volcanology, including over ten years 
experience as a research geologist with the United States Geological Survey, Cascade Volcano 
Observatory, Vancouver, Washington. At the time of publication, Dr. Symonds was a research 
scientist with the United States Geological Survey, Cascade Volcano Observatory. Dr. Symonds 
has authored and co-authored numerous peer reviewed professional articles on volcanology. 
Dr. Rose has earned a B.A. and a Ph.D from Dartmouth College, in the field of Earth Sciences. 
With more than 30 years of professional experience and over 150 published papers on volcanic 
studies, Dr. Rose has investigated multi-species and regional gas measurements of volcanic 
emissions, ash/aerosol interactions, aircraft hazards, distal ash fallout patterns, quantitative 
retrievals of ash particles, and detection of ice in volcanic clouds. He developed the first 
methodology to use infrared satellite data for quantitative retrievals of ash particles, size, and 
cloud mass. Dr. Rose received the Bowen Award, presented by the Volcanology, Geochemistry, 
and Petrology Section of the American Geophysical Union in 2002. 
Dr. Bluth holds a Ph.D in Geochemistry from Pennsylvania State University in addition to a B.A. 
in Geology and an M.S. in Geochemistry. Dr. Bluth has more than 15 years of professional 
experience, including the study of high temporal resolution links between degassing and 
subsurface dynamics by merging of volcanic seismic and gas emission data for Montserrat 
Volcano, sponsored by the National Science Foundation (2003present), volcanic hazard studies 
in Guatemala (2001present), focusing on remote sensing evaluation of volcanic activity, 
ground-based gas and thermal measurements and the development algorithms and software 
interface to study volcanic hazards for the Pacific Disaster Center, in Maui, Hawaii. Dr. Bluth 
authored and co-authored numerous professional publications on volcanology and geo sciences. 
Dr. Gerlach earned his B.S. and M.S. in Geology from the University of Wisconsin, with 
emphasis on physics and geophysics. In 1974 he was graduated from the University of Arizona 
with a Ph.D. in Geology. Dr. Gerlach has more than 30 years of professional experience, 
including fourteen years as a member of the Volcano Emissions Project, which is headquartered 
at the Cascades Volcano Observatory. he position requires international leadership through 
scientific contributions on the geochemistry of volcanic gas emissions, their application in 
assessing volcano hazards, their relationship to magmatic and hydrothermal processes, and their 
impact on the atmosphere, climate change, ecosystems, and human health. Dr. Gerlach authored 
and co-authored numerous professional publications on volcanology and geo sciences. 
A8. WILSON AND HEAD 1981 
Wilson, L. and Head, J.W., III. 1981. Ascent and Eruption of Basaltic Magma on the Earth and 
Moon. Journal of Geophysical Research, 86, (B4), 2971-3001. Washington, D.C.: American 
Geophysical Union. TIC: 225185. [DIRS 101034] 
Description of UseThis reference provides equations and resulting plots used to estimate the: 
 
Ascent velocity of magma at depth were magma is under sufficient pressure where all 
volatiles are dissolved (Section 6.3.3.1) 

 
Density of the mixture of silicate melt and water vapor bubbles (Section 6.3.3.2) 
 
Velocity of the magma and magma pressure as a function of depth (Section 6.3.3.3). 
The report contains a discussion of the development of the equations, as well as associated 
limitations and assumptions. The report was co-authored by Dr. Lionel Wilson, Lunar and 
Planetary Unit, Department of Environmental Sciences, University of Lancaster, Lancaster, LA1 
4YQ, United Kingdom; and Dr. James W. Head III, Department of Geological Sciences, Brown 
University, Providence, Rhode Island 02912. 
Extent to which the Data Demonstrate the Properties of InterestAs discussed in 
Assumption 4, rising magma, composed of melt liquid and volatile gases, can be considered 
homogeneous and characterized by equilibrium between melt and exsolved volatiles, even 
though actual ascent velocities of melt and bubbles (exsolved volatiles) are different. Since a 
general theory for multi-phase ascent of basaltic magmas that encompasses the potential range of 
magmas in the YMR is not yet available, Wilson and Head, 1981, provides a mathematical 
approach to estimating ascent velocity for magma with varying range of initial water content 
(0 to 2+%). Utilizing this approach, this analysis extends those curves to include potential 
magmas containing up to 5% initial dissolved water content. 
Qualifications of Personnel or Organizations Generating the DataDr. Lionel Wilson and 
Dr. James William Head, III, are internationally recognized scientists in the fields of volcanology 
and earth and planetary science. Both of them have authored and co-authored numerous books 
and professional papers related to their fields of expertise. 
Dr. Wilson is Professor Emeritus of Earth and Planetary Sciences, Department of Environmental 
Science, Lancaster University, U.K. Dr. Wilson has worked at Lancaster University from 1970 
through 1997, and continues to occupy a one-quarter position, his main responsibility being to 
lead the Planetary Science Research Group. He is also the co-editor of the Journal of 
Volcanology and Geothermal Research. In addition to his position at Lancaster University, 
Dr. Wilson holds positions at Brown University (Planetary Geosciences Group) and the Hawaii 
Institute of Geophysics and Planetology. He is on the Science Advisory Board for the 
Geophysics Department of the University of Alaska. He was elected (2004) as one of 
41 distinguished scientists as a Fellow of the American Geophysical Union, the largest 
professional body for Geophysicists and earth-scientists in the world. 
Dr. Head is a Louis and Elizabeth Scherck Distinguished Professor, Department of Geological 
Sciences, at Brown University, Providence, Rhode Island. He received his B.S. from 
Washington and Lee University (1964) and his Ph.D from Brown University (1969). From 
19681972, Dr. Head worked for NASA and participated in the Apollo Lunar Exploration 
Program activities of landing site selection, astronaut field and science training, surface geologic 
traverse planning, mission operations, and data analysis. Over the past 25 years, he has served 
on numerous national and international committees concerned with the various aspects of earth 
and planetary science and space research. 

A9. STAMATAKOS, CONNOR, AND MARTIN 
ReferenceStamatakos, J.A.; Connor, C.B.; and Martin, R.H. 1997. "Quaternary Basin 
Evolution and Basaltic Volcanism of Crater Flat, Nevada, from Detailed Ground Magnetic 
Surveys of the Little Cones." Journal of Geology, 105, 319-330. Chicago, Illinois: University of 
Chicago. TIC: 245108. [DIRS 138819] 
Description of UseStamatakos et al. (1997, pp. 322 and 328) estimate the dimensions and the 
amount of alluvium accumulation for the Little Cones. This estimate is used to determine the 
amount of the eruptive volume of the NE Little Cone, which is used to estimate the potential 
minimum eruption volume in the YMR. 
Extent to which the Data Demonstrate the Properties of InterestSection 6.3.3.4 of this 
document discusses the potential distribution of the volume of material form eruptive volcanic 
cones in the YMR. The Little Cones at Crater Flats represent some of the most recent 
volcanism, and, because of their size, are used as an analogue for eruptive volume at the 
minimum end of the distribution. Studies of this volcanic complex have been underway by the 
DOE's Yucca Mountain Project, as well as by the Center for Nuclear Waste Regulatory Analysis 
at the Southwest Research Institute. The Center provides technical support for the NRC's Yucca 
Mountain programs and this reference publishes some of the work that was conducted under that 
program. The paper provides an estimate of the original dimensions and the amount of alluvium 
accumulation (25 m) of Little Cones that is combined with other data and observations to 
determine the distribution of this parameter that is used in other analyses of eruptive events. 
Qualifications of Organizations Generating the Data and Prior Use of the Reference 
Southwest Research Institute provides technical support for the NRC's Yucca Mountain 
programs, thus the Institute can be considered to have the necessary credentials to provide 
qualified data. Studies have been underway by the DOE's Yucca Mountain Project, as well as by 
the Center for Nuclear Waste Regulatory Analysis at the Southwest Research Institute, which 
provides technical support for the NRC's Yucca Mountain programs. This reference publishes 
some of the work that was conducted by Southwest Research Institute for the NRC. The 
referenced data have been acquired by Southwest Research Institute under an NRC contract. 
While the specific data (25 m of alluvium accumulation, 230-m diameter and 15-m height of 
Little Cone) has not been specifically quoted by the NRC, this specific reference (Stamatakos et 
al. 1997) is referred to by the NRC in Issue Resolution Status Report (Key Technical Issue: 
Igneous Activity, Revision 2) (Reamer 1999 [DIRS 119693]). 
A10. LANGE AND CARMICHAEL 1990 
ReferencesLange, R.L. and Carmichael, I.S.E. 1990. "Thermodynamic Properties of Silicate 
Liquids with Emphasis on Density, Thermal Expansion and Compressibility." Chapter 2 of 
Modern Methods of Igneous Petrology: Understanding Magmatic Processes. Nicholls, J. and 
Russell, J.K., eds. Reviews in Mineralogy Volume 24. 25-64. Washington, D.C.: Mineralogical 
Society of America. TIC: 246394. [DIRS 147767] 

Ochs, F.A., III and Lange, R.A. 1999. "The Density of Hydrous Magmatic Liquids." Science, 
283, 1314-1317. Washington, D.C.: American Association for the Advancement of Science. 
TIC: 246639. [DIRS: 144330] 
Description of UseSection 6.2.3.4 of this analysis report discusses the methods used to 
calculate estimated temperatures, viscosities, and densities of magmas with varying water 
contents. The two references listed above provided a method for calculation of magma density 
as a function of composition (including water content), pressure, and temperature. The approach 
used the formulation and data of Lange and Carmichael (1990, Table 3) with additional data for 
H2O (Ochs and Lange 1999, pp. 1315). Equation 2 from Ochs and Lange (1999, p. 1315) 
produces the molar volume of the silicate liquid, which then requires a simple conversion to 
density. 
Extent to which the Data Demonstrate the Properties of InterestThe two references 
discussed above provide a theoretical and mathematical approach to calculating densities of 
magmas. This analytical method represents the state of the art in understanding the relationship 
of chemical composition and other physical properties of basaltic magmas. The density 
calculations were based on the mean chemical composition of extruded materials from the 
Lathrop Wills cone, utilizing calculated temperatures and pressures that were also derived and 
discussed in Section 6.2.3.4. The calculations were run for a range of water contents from 0 to 
4 wt%. 
Qualifications of Personnel and Organizations Generating the DataDr. Lange holds a Ph.D. 
fin Geology from the University of California, Berkeley, and has over 15 years of professional 
and research experience. She currently holds the position of Associate Professor at the 
Department of Geological Sciences at the University of Michigan-Ann Arbor. Professor Langes 
research involves field studies of volcanic rocks in Mexico, Wyoming, and California, as well as 
experimental studies on magmatic liquids at high temperatures and pressures. Current topics of 
study by Professor Lange and her research group include the: 
 
Origin of continental crust and its internal stratification; measurements of 
thermodynamic properties of magmatic liquids 
 
Entropy and volume of solution of H2O in silicate melts 
 
Phase equilibria of hydrous basalts in the lower crust 
 
Argon age-dating chronology 
 
Geographic Information Systems methods applied to quantifying eruption rates at 
continental arcs 
 
Acoustic interferometry applied to silicate melts at high temperatures and pressures. 
Dr. Ian Carmichael earned his Ph.D. in Geology at Imperial College of Science, University of 
London, and has over 50 years of professional and research experience in the field of igneous 
petrology. He is currently Professor at the Department of Earth and Planetary Science, 

University of California, Berkeley, where he has been associated since 1964. He is 
internationally recognized as one of the leading experts in the field of igneous petrology and his 
textbooks are used widely within the field. Dr. Carmichael has authored and co-authored over 
150 peer-reviewed journal articles and books. 
Mr. Ochs completed his M.A. in Geology in 1996 at the University of Michigan-Ann Arbor, 
where he was a graduate student studying with Dr. Lange. 
Reliability of Data SourceLange and Carmichael (1990) appear as Chapter 2 of Modern 
Methods of Igneous Petrology: Understanding Magmatic Processes, which is the 24th volume of 
a collection of journal articles and monographs published in conjunction with a series of short 
courses sponsored by the Mineralogical Society of America. Referred to as the Reviews in 
Mineralogy Series, Volume 24 represents the seventeenth year of published material 
accompanying courses in the subjects of mineralogy, petrology, crystallography, and 
geochemistry. The courses are conducted in conjunction with annual meetings of professional 
organizations such as the Geological Society of America and the American Geophysical Union. 
The editors of the volume, in addition to their own reviews and feedback to authors, also manage 
the peer review process. 
The findings of the Ochs and Lange research, undertaken at University of Michigan-Ann Arbor, 
were reported in Science, which is published by the American Association for the Advancement 
of Science. Science is a weekly journal that publishes significant original scientific research, 
plus reviews and analyses of current research and science policy. All articles published in 
Science are peer reviewed and are expected to present important new research results of broad 
significance and must meet stringent guidelines published by the editors. The American 
Association for the Advancement of Science is an international non-profit organization dedicated 
to advancing science around the world by serving as an educator, leader, spokesperson and 
professional association. In addition to organizing membership activities, AAAS publishes the 
journal Science, as well as many scientific newsletters, books, and reports, and spearheads 
programs that raise the bar of understanding for science worldwide. Founded in 1848, American 
Association for the Advancement of Science serves some 262 affiliated societies and academies 
of science, serving 10 million individuals. Science has the largest paid circulation of any 
peer-reviewed general science journal in the world. 
A11. SHAW 1972 
ReferenceShaw, H.R. 1972. "Viscosities of Magmatic Silicate Liquids: An Empirical Method 
of Prediction." American Journal of Science, 272, 870-889. New Haven, Connecticut: Yale 
University, Kline Geology Laboratory. TIC: 246470 [DIRS 126270] 
Description of UseSection 6.2.3.4 of this analysis report discusses the methods used to 
calculate estimated temperatures, viscosities, and densities of magmas of similar chemical 
compositions, with varying water contents. In addition to the other physical properties, the 
hypothetical compositions and calculated temperatures were used to calculate bubble- and 
crystal-free viscosity using an approach described in the Shaw reference. 

Extent to which the Data Demonstrate the Properties of InterestDirect measurements of 
physical properties of erupting magma are difficult to sample, especially in those magmas with 
water content at the higher end of the range projected for magmas in the YMR. Thus, 
experiments and calculated values must be relied upon to constrain the physical properties for 
magmas being evaluated in this analysis report. The method outlined by Shaw provides an 
approach for calculating viscosity of multi-component anhydrous silicate liquids using four 
partial molar coefficients of silica. 
Reliability of Data Source Shaw, a staff member of the U.S. Geological Survey at the time of 
this 1972 publication, presented his method for calculating viscosity of silicate magmas in the 
American Journal of Science. Founded in 1818, the American Journal of Science is the oldest 
scientific journal in the United States that has been published continuously. The Journal is 
devoted to geology and related sciences and publishes articles from around the world presenting 
results of major research from all earth sciences. All articles are subject to peer review prior to 
publication. Readers are primarily earth scientists in academia and government institutions from 
around the world. 
A12. JAUPART AND TAIT 1990 
ReferenceJaupart, C. and Tait, S. 1990. "Dynamics of Eruptive Phenomena." Chapter 8 of 
Modern Methods of Igneous Petrology: Understanding Magmatic Processes. Nicholls, J. and 
Russell, J.K., eds. Reviews in Mineralogy Volume 24. 213-238. Washington, D.C.: 
Mineralogical Society of America. TIC: 246394. [DIRS 118292] 
Description of UseThis analysis report uses the Jaupart and Tait (1990) reference as a source 
for an equation that represents the solubility of water in basaltic magmas, as related to pressure. 
The saturation pressures that are derived from this equation are then used as part of the analysis 
that provides an estimate of multi-phase saturation. 
Extent to which the Data Demonstrate the Properties of InterestSection 6.2.3.4 of this 
analysis report discusses the methods used to calculate estimated temperatures, viscosities, and 
densities of magmas with varying water contents. To complete the calculations of these physical 
properties, values for saturation pressure were required for varying weight percent of water. The 
Jaupart and Tait (1990) reference provides simplified expressions of the solubility of gases in 
silicate melts, including water in basalt. They state that the simplified equations relating water 
solubility to pressure only are sufficient for use in systems of low concentrations of water. The 
expression is judged to be sufficient for the use in this report, which is calculating saturated 
pressures for water contents from 1 to 4 wt%. 
Reliability of Data SourceThe Jaupart and Tait (1990) reference appears as Chapter 8 of 
Modern Methods of Igneous Petrology: Understanding Magmatic Processes, which is the 24th 
volume of a collection of journal articles and monographs published in conjunction with a series 
of short courses sponsored by the Mineralogical Society of America. Referred to as the Reviews 
in Mineralogy Series, Volume 24 represents the seventeenth year of published material 
accompanying courses in the subjects of mineralogy, petrology, crystallography, and 
geochemistry. The courses are conducted in conjunction with annual meetings of professional 
organizations such as the Geological Society of America and the American Geophysical Union. 

The editors of the volume, in addition to their own reviews and feedback to authors, also manage 
the peer review process of all materials that are published in these volumes. These volumes are 
considered by the scientific community to represent the current state of knowledge in the various 
disciplines. 
A13. WOOD 1980 
ReferenceWood, C.A. 1980. "Morphometric Evolution of Cinder Cones." Journal of 
Volcanology and Geothermal Research, 7, 387-413. Amsterdam, The Netherlands: Elsevier. 
TIC: 225565. [DIRS: 116536] 
Description of UseThe data compiled and published in Wood 1980 were used in formulating 
the values used for eruption duration for explosive eruptions that form scoria cones. The range 
reported by Wood gives a duration of 1 day to 15 years, with a median value of 50 days. The 
data presented in the Wood article are also used to estimate the duration of the cone-forming 
eruption at Lathrop Wells, which has volcanological characteristics that are consistent with other 
Quaternary volcanoes of the YMR. 
Extent to which the Data Demonstrate the Properties of InterestThe Wood (1980) reference 
provides data on the duration of eruption as related to volcanic cone height and estimated cone 
volume for twelve cones from around the world that have formed through explosive eruption. 
Based on these observations of rates of cone growth as a function of time, a cone the size of that 
at the Lathrop Wells volcano (140-m high, 0.018-km3 volume) might have formed over a period 
between about 2 and 21 days. 
Qualifications of Personnel and Organizations Generating the DataDr. Wood (University of 
North Dakota.) is a volcanologist with 25 years of experience using remote sensing and other 
techniques to study volcanoes. His Ph.D is in Planetary Science (Brown University, 1979). In 
addition to having published 180 professional papers and abstracts on volcanoes and other 
geologic topics he is a member of the NASA EOS Interdisciplinary Team on Volcanology and a 
volcano Principle Investigator on the SIR-C Shuttle radar mission. His current position is 
Professor and Chair at Department of Space Studies, University of North Dakota, Grand Forks. 

APPENDIX B 
ADDRESSING YMRP ACCEPTANCE CRITERIA 


APPENDIX B 
ADDRESSING YMRP ACCEPTANCE CRITERIA 
The following information describes how this analysis addresses the acceptance criteria in the 
Yucca Mountain Review Plan, Final Report (NRC 2003 [DIRS 163274], Sections 1.5.3, 
2.2.1.3.10.3, 2.2.1.3.11.3, and 2.2.1.3.13.3). Only those acceptance criteria that are applicable to 
this report (see Section 4.2) are discussed. In most cases, the applicable acceptance criteria are 
not addressed solely by this report; rather, the acceptance criteria are fully addressed when this 
report is considered in conjunction with other analysis and model reports that describe igneous 
FEPs. Where a subcriterion includes several components, only some of those components may 
be addressed. 
B1. DESCRIPTION OF SITE CHARACTERIZATION WORK CRITERIA 
YMRP Section 1.5.3, Acceptance Criteria: 
Acceptance Criterion 1: The General Information section of the License Application 
contains an adequate description of Site Characterization activities. 
1. An adequate overview is provided of the site characterization activities related to 
geology; hydrology; geochemistry; geotechnical properties and conditions of the host 
rock; climatology, meteorology, and other environmental sciences; and the reference 
biosphere. 
Field studies and analyses were conducted in the Yucca Mountain region to 
characterize the geology and volcanic activity. Results of field studies, available data 
in literature sources, external reviews, and expert elicitation were used to develop 
parameter values and distributions that can be used to model processes of the shallow 
subsurface and surface volcanic activity relevant to a repository at Yucca Mountain. 
Characteristics of eruptive conduits, dike widths, dike swarms, and dike-induced 
earthquakes are described in Section 6.3.1.1 and 6.3.1.2. Characteristics of igneous 
material (magma chemistry and magma physical properties) are described in 
Section 6.3.2. Eruptive processes, including magma ascent rate, volatile exsolution 
and fragmentation, velocity as a function of depth above exsolution depth, eruption 
volume and duration, entrainment of wall rock and repository materials in ascending 
magma, and characteristics of Strombolian and violent Strombolian eruption deposits, 
are described in Section 6.3.3. Studies of the redistribution of basaltic tephra in the 
Yucca Mountain region are described in Section 6.3.4. Uncertainties are described in 
Section 6.3.5. 
Acceptance Criterion 2: The General Information section of the license application 
contains an adequate description of site characterization results 
1. A sufficient understanding is provided of current features and processes present in the 
Yucca Mountain region. 
This report provides basic descriptive information about the volcanic eruptive 
products and processes that resulted in the surface deposition of the scoria 

cone, lava flows, and tephra fall associated with the Lathrop Wells volcano 
(Section 6.3; Appendix C). The Lathrop Wells volcano is the youngest 
volcanic expression known in the YMR and is considered to exemplify the 
type of eruptive phenomena that would occur during a future eruption of 
basaltic magma in the region. The Lathrop Wells volcano is the southernmost 
surface expression of the Crater Flat Volcanic Zone, which, in large part, 
defines the probabilistic volcanic hazard for the repository (Characterize 
Framework for Igneous Activity at Yucca Mountain, Nevada, BSC 2003 
[DIRS 169989], Section 6.4.1.5). The eruptive volumes of scoria (cone), lava, 
and tephra are used to develop parameter values and distributions for use in the 
model report Atmospheric Dispersal and Deposition of Tephra from a 
Potential Volcanic Eruption at Yucca Mountain, Nevada (BSC 2004 
[DIRS 170026]). The eruptive processes at Lathrop Wells volcano, as inferred 
from analysis of lithologies preserved in the cone and tephra sheet, help define 
the processes of mass ejection from the volcanic vent for both proximal 
(ballistic) and distal (ash cloud) distances. Further, this report defines 
properties of magma that directly influence the interaction of a magma-filled 
dike(s) with a subsurface repository that are direct inputs to TSPA. Section 
6.3.4 provides the basis for conceptual models of ash and sediment 
redistribution from the Yucca Mountain site to depositional sites along 
Fortymile Wash and the Fortymile Wash alluvial fan located in the Amargosa 
Valley developed in Atmospheric Dispersal and Deposition of Tephra from a 
Potential Volcanic Eruption at Yucca Mountain, Nevada (BSC 2004 
[DIRS 170026]). 
2. Adequate information is provided for evolution of future events and processes likely to 
be present in the Yucca Mountain region that could affect repository safety. 
This report provides basic descriptive information about the volcanic eruptive 
processes that are characteristic of the YMR, as exemplified by features 
observed at Lathrop Wells volcano (Section 6; Appendix C). Parameter values 
are developed for use in models of igneous processes or as inputs to TSPA-LA 
models that support the analysis of the direct-release and indirect-release 
volcanic scenarios. The report identifies information that has been collected 
from the YMR, as well as information developed from studies at analog sites 
or developed from the review of published literature. The report also provides 
the technical basis for the use of the Lathrop Wells volcanic center as the most 
appropriate analog for a future volcanic eruption through the repository at 
Yucca Mountain. 

B2. DESCRIPTION OF VOLCANIC DISRUPTION OF WASTE PACKAGES 
CRITERIA 
YMRP Section 2.2.1.3.10.3, Acceptance Criteria: 
Acceptance Criterion 1: System description and model integration are adequate 
1. 
Total system performance assessment adequately incorporates important design 
features, physical phenomena, and couplings, and uses consistent and appropriate 
assumptions throughout the volcanic disruption of the waste package abstraction 
process. 
This report provides basic descriptive information about the volcanic eruptive 
processes that are characteristic of the YMR, as exemplified by features 
observed at Lathrop Wells volcano (Section 6.3; Appendix C). Parameter 
values are developed for use in models of igneous processes or as inputs to 
TSPA-LA models that support the analysis of the direct-release and 
indirect-release volcanic scenarios. This report describes the basis for the 
parameters used in such models (e.g., Dike/Drift Interactions (BSC 2004 
[DIRS 170028]). 
2. 
Models used to assess volcanic disruption of waste packages are consistent with 
physical processes generally interpreted from igneous features in the Yucca Mountain 
region and/or observed at active igneous systems. 
This report provides basic descriptive information about the volcanic eruptive 
processes that are characteristic of the YMR, as exemplified by features 
observed at Lathrop Wells volcano (Section 6.3; Appendix C). Parameter 
values are developed for use in models of igneous processes or as inputs to 
TSPA-LA models that support the analysis of the direct-release and indirect-
release volcanic scenarios. Characteristics of eruptive conduits, dike widths, 
dike swarms, and dike-induced earthquakes are described in Section 6.3.1. 
Chemical characteristics of igneous material are described in Section 6.3.2. 
The processes associated with volcanic eruptions are described in 
Section 6.3.3, and processes that might entrain radioactive waste in eruption 
products are described in Section 6.3.3.5. Finally, ash plumes and associated 
deposits are described in Section 6.3.4. The report describes the basis for the 
parameters used in the volcanic scenarios and traces the outputs forward into 
analyses that use these parameters. The report identifies information that has 
been collected from the YMR, as well as information developed from studies at 
analog sites or developed from the review of published literature. The report 
also provides the technical basis for the use of the Lathrop Wells volcanic 
center as the most appropriate analog for a future volcanic eruption through the 
repository at Yucca Mountain. A potential eruption scenario at the Yucca 
Mountain repository is described in Section 6.4. 

3. 
Models account for changes in igneous processes that may occur from interactions 
with engineered repository systems. 
Not applicable. This report does not address changes in igneous processes that 
might occur as a result of interactions with engineered repository systems. 
Possible changes have been analyzed and documented in Dike/Drift 
Interactions (BSC 2004 [DIRS 170028]). The technical basis for the waste 
particle size used by Atmospheric Dispersal and Deposition of Tephra from a 
Potential Volcanic Eruption at Yucca Mountain, Nevada (BSC 2004 
[DIRS 170026]) is provided Section 6.3.3.5. 
4. 
Guidance in NUREG-1297 and NUREG-1298 (Altman et al. 1988 [DIRS 103597]; 
1988 [DIRS 103750]) or other acceptable approaches is followed. 
External sources have been used as direct input to this document. The inputs from 
these sources are qualified for intended use within the document using the criteria 
found in AP-SIII.9Q, Scientific Analyses. These criteria represent a subset of the 
methods and attributes required for qualification of data per AP-SIII.2Q, Qualification 
of Unqualified Data. These methods and attributes are based on those that are 
presented in NUREG 1298, which are meant to provide the level of confidence in the 
data  commensurate with their intended use. 
The data contained in DTN: LA000000000099.002 [DIRS 147725], Major Element, 
Trace Element, Isotopic, and Mineral Chemistry Data from Lathrop Wells, were 
qualified in the data qualification report Final Report on Qualification of Volcanism 
Isotope, Trace-element, and Halogen Data Using Procedure YAP-SIII.1Q/REV 3/ICN 
0 {Qualification of Unqualified Data} (CRWMS M&O 1999 [DIRS 170965]). 
Data that were acquired during earlier studies sponsored by the DOE's Nevada Nuclear 
Waste Storage Investigation, prior to the establishment of a 10 CFR 60, Subpart G 
compliant quality assurance program, were used as direct input. These data have been 
qualified within this report in accordance with AP-SIII.2Q, Qualification of 
Unqualified Data. 
The requirements, methods and, attributes for qualification of unqualified data, as 
outlined in the two procedures discussed above, are based on the guidance that is 
presented in NUREG 1298. 
Acceptance Criterion 2: Data are sufficient for model justification 
1. Parameter values used in the license application to evaluate volcanic disruption of 
waste packages are sufficient and adequately justified. Adequate description of how 
the data were used, interpreted, and appropriately synthesized into the parameters is 
provided. 
Section 6.3 provides basic descriptive information about the volcanic eruptive 
processes that are characteristic of the Yucca Mountain region. The report 
describes the synthesis of the information and basis for parameter values that 

are used to model igneous processes and inputs to TSPA-LA models that 
support the analysis of the direct-release and indirect-release volcanic 
scenarios. The report also traces the parameter outputs forward into analyses 
and models that use these parameters. A potential eruption scenario at the 
Yucca Mountain repository is described in Section 6.4. 
2. 
Data used to model processes affecting volcanic disruption of waste packages are 
derived from appropriate techniques. These techniques may include site-specific field 
measurements, natural analog investigations, and laboratory experiments. 
The report identifies information that has been collected from site-specific field 
measurements in the Yucca Mountain region as well as information that has 
been developed from studies at analog sites or developed from the review of 
published literature. Data have also been obtained from samples collected and 
analyzed by procedures governed by a strict quality assurance program. Data, 
parameters, and other inputs are described in Section 4.1. A potential eruption 
scenario at the Yucca Mountain repository is described in Section 6.6. Data 
uncertainties for inputs to, and outputs from, this analysis and limitations on 
use of outputs are described in detail in Sections 6.5 and 7.2. The report also 
provides the technical basis for the Lathrop Wells volcanic center being the 
most appropriate analog for a future volcanic eruption through the repository at 
Yucca Mountain. 
3. 
Sufficient data are available to integrate features, events, and processes relevant to the 
volcanic disruption of waste packages into process-level models, including 
determination of appropriate interrelationships and parameter correlations. 
The report identifies information that has been collected from the Yucca 
Mountain region as well as information that has been developed from studies at 
analog sites or developed from the review of published literature. FEPs 
relevant to this analysis are discussed in Section 6.2. These FEPs have guided 
the approach to field observation and collection/analysis of appropriate 
samples and sample parameters. Sufficient data are collected to help integrate 
the relevant FEPs into process-level models (Section 4.1). The report describes 
the relevant eruptive processes and describes the development of parameters 
based on the integration of those FEPs. Characteristics of igneous material are 
described in Section 6.3.2. Relationships between various magma 
characteristics and their effects on an eruption are described in Section 6.3.3. 
Processes related to entrainment of waste in an ascending magma are described 
in Section 6.3.3.5, and ash plumes and their deposits are discussed in 
Section 6.3.3.6. The physical volcanology of the Lathrop Wells volcano and 
its suitability as an analog for a future eruption through the repository are 
discussed in Section 6.4. A potential eruption scenario at the Yucca Mountain 
repository is described in Section 6.4. Process-level models that use the 
parameters developed from these processes are described in other reports (e.g., 
Dike/Drift Interactions (BSC 2004 [DIRS 170028]). Output parameters from 
this analysis and associated uncertainties are described in Section 7.2. 

Interrelationships and correlations between parameters are described in 
Section 6. 
4. Where sufficient data do not exist, the definition of parameter values and associated 
uncertainty is based on appropriate use of expert elicitation, conducted in accordance 
with NUREG-1563 (Kotra et al. 1996 [DIRS 100909]). If other approaches are used, 
the U.S. Department of Energy adequately justifies their use. 
The dike length distribution developed by expert elicitation for the PVHA was 
used as input to the calculation in Section 6.3.1.3. 
Acceptance Criterion 3: Data uncertainty is characterized and propagated through the 
model abstraction 
1. 
Models use parameter values, assumed ranges, probability distributions, and bounding 
assumptions that are technically defensible, and reasonably account for uncertainties 
and variabilities, and do not result in an under-representation of the risk estimate. 
The report identifies information that has been collected from the Yucca 
Mountain region as well as information that has been developed from studies at 
analog sites or developed from the review of published literature. Data 
uncertainties for inputs to, and outputs from, this analysis and limitations on 
use of outputs are described in detail in Sections 6.5 and 7.2. The report also 
traces the parameter outputs forward into analyses that use these parameters. 
However, the report does not discuss the specific uses of the parameters in the 
downstream models, nor does the report discuss potential effects of parameter 
variations on the representation of risk. 
2. 
Parameter uncertainty accounts quantitatively for the uncertainty in parameter values 
observed in situ data and the available literature (i.e., data precision) and the 
uncertainty in abstracting parameter values to process-level models (i.e., data 
accuracy). 
Data uncertainties for inputs to, and outputs from, this analysis and limitations 
on use of outputs are described in detail in Sections 6.5 and 7.2, and are 
discussed individually with each derived parameter. The report also traces the 
parameter outputs forward into analyses that use these parameters. However, 
the report does not discuss how the parameters are used in the downstream 
models, nor does this report describe methods used to abstract parameter 
values into the downstream, process-level models. 
3. 
Where sufficient data do not exist, the definition of parameter values and associated 
uncertainty is based on appropriate use of expert elicitation, conducted in accordance 
with NUREG-1563 (Kotra et al. 1996 [DIRS 100909]). If other approaches are used, 
the U.S. Department of Energy adequately justifies their use. 
The dike length distribution developed by expert elicitation for the PVHA was 
used as input to the calculation in Section 6.3.1.3. 

Acceptance Criterion 4: Model uncertainty is characterized and propagated through the 
model abstraction 
Not applicable. The analysis documented in this report does not produce abstractions of 
the volcanic disruption of waste packages. 
Acceptance Criterion 5: Model abstraction output is supported by objective comparisons. 
Not applicable. The analysis documented in this report does not produce model 
abstractions of the volcanic disruption of waste packages. 
B3. DESCRIPTION OF AIRBORNE TRANSPORT OF RADIONUCLIDES CRITERIA 
YMRP Section 2.2.1.3.11.3, Acceptance Criteria 
Acceptance Criterion 1: System description and model integration are adequate 
1. 
Total system performance assessment adequately incorporates important design 
features, physical phenomena, and couplings and uses consistent and appropriate 
assumptions throughout the airborne transport of radionuclides abstraction process. 
This analysis report develops parameter values and distributions that directly or 
indirectly influence the airborne transport of radionuclide particles via surface 
volcanic eruption of basaltic magma after intersection with the 
waste-packages-filled drifts. This report provides the technical basis for the 
parameters, assumptions, and conceptual models used in modeling the airborne 
transport of radionuclides in Atmospheric Dispersal and Deposition of Tephra 
from a Potential Volcanic Eruption at Yucca Mountain, Nevada (BSC 2004 
[DIRS 170026]). 
2. 
Models used to assess airborne transport of radionuclides are consistent with physical 
processes generally interpreted from igneous features in the Yucca Mountain region 
and/or observed at active igneous systems. 
Physical processes of eruption and emplacement of basaltic particulate matter 
are described in this report. Parameters that define many aspects of the 
processes and resulting deposits are developed for use in downstream models 
used to assess the airborne transport of radionuclides. The report provides 
basic descriptive information about the volcanic eruptive processes that are 
characteristic of the Yucca Mountain region, as exemplified by features 
observed at Lathrop Wells volcano. Characteristics of eruptive conduits, dike 
widths, and dike swarms are described in Section 6.3.1. Chemical 
characteristics of igneous material are described in Section 6.3.2. The 
processes associated with volcanic eruptions are described in Section 6.3.3, and 
processes that could entrain radioactive waste in eruption products are 
described in Section 6.3.3.5. Finally, ash plumes and associated deposits are 
described in Section 6.3.3.6. The report carefully identifies information that 
has been collected from the Yucca Mountain region as well as information 

developed from studies at analog sites or developed from the review of 
published literature. A potential eruption scenario at the Yucca Mountain 
repository is described in Section 6.4. The report also provides the technical 
basis for the use of the Lathrop Wells volcanic center as the most appropriate 
analog for a future volcanic eruption through the repository at Yucca Mountain 
(Appendix C). 
3. 
Models account for changes in igneous processes that may occur from interactions 
with engineered repository systems. 
This report discusses ash particle sizes as measured from the tephra deposit 
from the Lathrop Wells volcano (Appendix C) and from several historical 
eruptions (Section 6.3.3.6.1). Section 6.3.3.5 describes processes that could 
entrain radioactive waste in eruption products after interaction with the 
engineered repository. The range in ash particle sizes provides the input for 
incorporating waste particles within the eruption column that is described and 
modeled in Atmospheric Dispersal and Deposition of Tephra from a Potential 
Volcanic Eruption at Yucca Mountain, Nevada (BSC 2004 [DIRS 170026]). 
Physical properties of eruptions that may lead to variations in the eruptive 
dispersal and deposition of ash and waste particles are addressed in this report, 
including magma velocity above the vesiculation depth, variable volatile 
content of magma and its effects on velocity of magma ascent, conduit 
diameter, and a range of possible mass discharge rates that affect ash column 
characteristics. Interactions of a dike of ascending magma with engineered 
repository design features, including drifts, waste packages, and waste form are 
discussed in Dike/Drift Interaction (BSC 2004 [DIRS 170028]). 
4. 
Guidance in NUREG-1297 and NUREG-1298 (Altman et al. 1988 [DIRS 103597]; 
1988 [DIRS 103750]) or in other acceptable approaches for peer review and data 
qualifications is followed. 
Data used to develop parameter values and distributions for output from this 
report were qualified for intended use (Section 4). 
Acceptance Criterion 2: Data are sufficient for model justification 
1. Parameter values used in the license application to evaluate airborne transport of 
radionuclides are sufficient and adequately justified. Adequate description of how the 
data were used, interpreted, and appropriately synthesized into the parameters is 
provided. 
This report provides basic descriptive information about the volcanic eruptive 
processes that are characteristic of the Yucca Mountain region. This report 
provides the technical basis for the parameters used in modeling the airborne 
transport of radionuclides in Atmospheric Dispersal and Deposition of Tephra 
from a Potential Volcanic Eruption at Yucca Mountain (BSC 2004 
[DIRS 170026]). A potential eruption scenario at the Yucca Mountain 

repository that might result in airborne transport of radionuclides is described 
in Section 6.4. The report also traces the parameter outputs forward into 
analyses that use these parameters. 
2. 
Data used to model processes affecting airborne transport of radionuclides are derived 
from appropriate techniques. These techniques may include site-specific field 
measurements, natural analog investigations, and laboratory experiments. 
The report identifies information that has been collected from site-specific field 
measurements in the Yucca Mountain region as well as information that has 
been developed from the studies at analog sites or developed from the review 
of published literature (Section 6.8). A potential eruption scenario at the 
Yucca Mountain repository is described in Section 6.5. Data uncertainties for 
inputs to, and outputs from, this analysis and limitations on use of outputs are 
described in detail in Sections 6.5 and 7.2. The report also provides the 
technical basis for the Lathrop Wells volcanic center being the most 
appropriate analog for a future volcanic eruption through the repository at 
Yucca Mountain. 
3. 
Sufficient data are available to integrate features, events, and processes relevant to the 
airborne transport of radionuclides into process-level models, including determination 
of appropriate interrelationships and parameter correlations. 
The report identifies information that has been collected from site-specific field 
measurements in the Yucca Mountain region as well as information that has 
been developed from studies at analog sites or developed from the review of 
published literature (Sections 4.1 and 6). FEPs relevant to this analysis are 
discussed in Section 6.2. The report describes the relevant eruptive processes 
and describes the development of parameters based on the integration of those 
processes. Characteristics of igneous material are described in Section 6.3.2. 
Relationships between various magma characteristics and their effects on an 
eruption are described in Section 6.3.3. Processes related to entrainment of 
waste in an ascending magma are described in Section 6.3.3.5, and ash plumes 
and their deposits are discussed in Section 6.3.3.6. The physical volcanology 
of the Lathrop Wells volcano and its suitability as an analog for a future 
eruption through the repository are discussed in Appendix C. A potential 
eruption scenario at the Yucca Mountain repository is described in Section 6.4. 
Process-level models that use the parameters developed from these processes 
are described in other reports (e.g., Dike/Drift Interactions (BSC 2004 
[DIRS 170028]). Interrelationships and correlations between parameters are 
described in Section 6. 
4. 
Not applicable. Where sufficient data do not exist, the definition of parameter values 
and associated uncertainty is based on the appropriate use of expert elicitation, 
conducted in accordance with NUREG-1563 (Kotra et al. 1996 [DIRS 100909]). If 
other approaches are used, the U.S. Department of Energy adequately justifies their 

use. Expert elicitation was not used to develop parameter values pertinent to airborne 
transport of radionuclides described in this report. 
Acceptance Criterion 3: Data uncertainty is characterized and propagated through the 
model abstraction 
1. 
Models use parameter values, assumed ranges, probability distributions, and bounding 
assumptions that are technically defensible, and reasonably account for uncertainties 
and variabilities, and do not result in an under-representation of the risk estimate. 
The report identifies information that has been collected from the Yucca 
Mountain region as well as information that has been developed from studies at 
analog sites or developed from the review of published literature. Data 
uncertainties for inputs to, and outputs from, this analysis and limitations on 
use of outputs are described in detail in Sections 6.5 and 7.2. The report also 
traces the parameter outputs forward into analyses that use these parameters. 
However, the report does not discuss the specific uses of the parameters in the 
downstream models, nor does the report discuss potential effects of parameter 
variations on the representation of risk. 
2. 
Parameter uncertainty accounts quantitatively for the uncertainty in parameter values 
derived from site data and the available literature (i.e., data precision) and the 
uncertainty introduced by model abstraction (i.e., data accuracy). 
Data uncertainties for inputs to, and outputs from, this analysis and limitations 
on use of outputs are described in detail in Sections 6.5 and 7.2. The report 
also traces the parameter outputs forward into analyses that use these 
parameters. However, the report does not discuss how the parameters are used 
in the downstream models, nor does this report discuss methods used to 
abstract parameter values into the downstream, process-level models. 
3. 
Where sufficient data do not exist, the definition of parameter values and associated 
uncertainty is based on the appropriate use of expert elicitation, conducted in 
accordance with NUREG-1563 (Kotra et al. 1996 [DIRS 100909]). If other 
approaches are used, the U.S. Department of Energy adequately justifies their use. 
Expert elicitation was not used to develop parameter values pertinent to 
airborne transport of radionuclides described in this report. 
Acceptance Criterion 4: Model uncertainty is characterized and propagated through the 
model abstraction 
Not applicable. The analysis documented in this report does not assess model 
uncertainty for abstractions of the airborne transport of radionuclides. 

Acceptance Criterion 5: Model abstraction output is supported by objective comparisons. 
Not applicable. The analysis documented in this report does not produce model 
abstractions of the airborne transport of radionuclides. 
B4. DESCRIPTION OF REDISTRIBUTION OF RADIONUCLIDES IN SOIL 
CRITERIA 
YMRP Section 2.2.1.3.13.3, Acceptance Criteria 
Acceptance Criterion 1: System description and model integration are adequate 
1. Total system performance assessment adequately incorporates important features, 
physical phenomena, and couplings between different models, and uses consistent and 
appropriate assumptions throughout the abstraction of redistribution of radionuclides 
in the soil abstraction process. 
Section 6.3.4 of the report describes the processes that could redistribute ash 
and waste particles from an eruption through a repository at Yucca Mountain. 
A study of ash dilution at the Lathrop Wells volcano is described in 
Section 6.3.4.1, and the results and interpretation are presented in 
Section 6.3.4.1. The results of a study of 137Cs concentrations in surficial 
material are presented in Section 6.3.4.2. Tephra thicknesses for the Lathrop 
Wells volcano are described in Appendix Section C3. 137Cs analysis results for 
the Fortymile Wash alluvial fan are described in Section 6.3.4.2.4, and the 
basaltic ash content of surficial materials around the Lathrop Wells volcano is 
described in Section 6.3.4.1. However, the analyses described in the report do 
not address the redistribution of radionuclides in the soil abstraction process. 
Model implementation is described in Atmospheric Dispersal and Deposition 
of Tephra from a Potential Volcanic Eruption at Yucca Mountain, Nevada 
(BSC 2004 [DIRS 170026]). 
2. The total system performance assessment model abstraction identifies and describes 
aspects of redistribution of radionuclides in soil that are important to repository 
performance, including the technical bases for these descriptions. For example, the 
abstraction should include modeling of the deposition of contaminated material in the 
soil and determination of the depth distribution of the deposited radionuclides. 
Section 6.3.4 of the report describes the processes that could redistribute ash 
and waste particles from an eruption through a repository at Yucca Mountain. 
A study of ash dilution at the Lathrop Wells volcano is described in 
Section 6.3.4.1, and the results and interpretation are presented in 
Section 6.3.4.1. The results of a study of 137Cs concentrations in surficial 
material are presented in Section 6.3.4.2. Tephra thicknesses for the Lathrop 
Wells volcano are described in Appendix Section C3. 137Cs analysis results for 
the Fortymile Wash alluvial fan are described in Section 6.3.4.2, and the 
basaltic ash content of surficial materials around the Lathrop Wells volcano is 
described in Section 6.3.4. The model abstraction used to assess the 

redistribution of radionuclides from secondary transport processes is discussed 
in Atmospheric Dispersal and Deposition of Tephra from a Potential Volcanic 
Eruption at Yucca Mountain, Nevada (BSC 2004 [DIRS 170026]). 
3. 
Relevant site features, events, and processes have been appropriately modeled in the 
abstraction of redistribution of radionuclides from surface processes, and sufficient 
technical bases are provided. 
Section 6.3.4 of the report provides the basis for the model abstractions used to 
assess the redistribution of radionuclides from secondary transport processes 
discussed in Atmospheric Dispersal and Deposition of Tephra from a Potential 
Volcanic Eruption at Yucca Mountain, Nevada (BSC 2004 [DIRS 170026]). 
4. 
Guidance in NUREG-1297 and NUREG-1298 (Altman et al. 1988 [DIRS 103597]; 
1988 [DIRS 103750]) or other acceptable approaches for peer reviews is followed. 
Data used to develop parameter values and distributions for output from this 
report were qualified for intended use (Section 4). 
Acceptance Criterion 2: Data are sufficient for model justification 
1. 
Behavioral, hydrological, and geochemical values used in the license application are 
adequately justified (e.g., irrigation and precipitation rates, erosion rates, radionuclide 
solubility values, etc.). Adequate descriptions of how the data were used, interpreted, 
and appropriately synthesized into the parameters are provided. 
Section 6.3.4 of the report describes the processes that could redistribute ash 
and waste particles from an eruption through a repository at Yucca Mountain. 
A study of ash dilution at the Lathrop Wells volcano is described in 
Section 6.3.4.1, and the results and interpretation are presented in 
Section 6.3.4.1. The results of a study of 137Cs concentrations in surficial 
material are presented in Section 6.3.4.2. Tephra thicknesses for the Lathrop 
Wells volcano are described in Appendix Section C3. 137Cs analysis results for 
the Fortymile Wash alluvial fan are described in Section 6.3.4.2.4, and the 
basaltic ash content of surficial materials around the Lathrop Wells volcano is 
described in Section 6.3.4.1. Consideration of behavioral, hydrological, and 
geochemical processes referred to in the criteria (e.g., irrigation rates, plow 
depth, etc.) is discussed in biosphere analysis or model reports. 
2. 
Sufficient data (e.g., field, laboratory, and natural analog data) are available to 
adequately define relevant parameters and conceptual models necessary for developing 
the abstraction of redistribution of radionuclides in soil in the total system 
performance assessment. 
Section 6.3.4 of the report provides the basis for the conceptual model(s) used 
to assess the redistribution of radionuclides discussed in Atmospheric Dispersal 
and Deposition of Tephra from a Potential Volcanic Eruption at Yucca 
Mountain, Nevada (BSC 2004 [DIRS 170026]). 

Acceptance Criterion 3: Data uncertainty is characterized and propagated through the 
model abstraction 
1. 
Models use parameter values, assumed ranges, probability distributions, and bounding 
assumptions that are technically defensible, reasonably account for uncertainties and 
variabilities, do not result in an under-representation of the risk estimate, and are 
consistent with the characteristics of the reasonably maximally exposed individual. 
Item 1, for Acceptance Criterion 1, describes the information provided in this 
report that is relevant to the analysis of ash deposition and redistribution from 
an eruption at a Yucca Mountain repository. The report does not address the 
representation of the risk estimate, nor does it address the characteristics of the 
reasonably maximally exposed individual in 10 CFR 6 Part 63. 
2. 
The technical bases for the parameter values and ranges in the total system 
performance assessment abstraction are consistent with data from the Yucca Mountain 
region [e.g., Amargosa Valley survey (Cannon Center for Survey Research 1997)], 
studies of surface processes in the Fortymile Wash drainage basin, applicable 
laboratory testing, natural analogs, or other valid sources of data. For example, soil 
types, crop types, plow depths, and irrigation rates should be consistent with current 
farming practices, and data on the airborne particulate concentration should be based 
on the resuspension of appropriate material in a climate and level of disturbance 
similar to that which is expected to be found at the location of the reasonably 
maximally exposed individual during the compliance time period. 
Item 1, for Acceptance Criterion 1, describes the information provided in this 
report that is relevant to the analysis of ash deposition and redistribution from 
an eruption at a Yucca Mountain repository. Studies specific to the Fortymile 
Wash drainage are described in Sections 6.3.4, and 6.3.4.1. Effects of storms 
and climate changes on natural soil redistribution processes are described in 
Section 6.3.4.4. The report does not address biosphere topics of crop types, 
plow depths, irrigation rates, current farming practices, or airborne particulate 
concentrations. 
3. 
Uncertainty is adequately represented in parameters for conceptual models, process 
models, and alternative conceptual models considered in developing the total system 
performance assessment abstraction of redistribution of radionuclides in soil, either 
through sensitivity analyses, conservative limits, or bounding values supported by 
data, as necessary. Correlations between input values are appropriately established in 
the total system performance assessment. 
Item 1, for Acceptance Criterion 1, describes the information provided in this 
report that is relevant to the analysis of ash deposition and redistribution from 
an eruption at a Yucca Mountain repository. Uncertainties associated with 
tephra thicknesses for the Lathrop Wells volcano are described in 
Section 6.5.1.5. Uncertainties associated with 137Cs analyses for the Fortymile 
Wash alluvial fan are described in Section 6.5.1.3. Alternative conceptual 

models and parameters correlations are discussed in Atmospheric Dispersal 
and Deposition of Tephra from a Potential Volcanic Eruption at Yucca 
Mountain, Nevada (BSC 2004 [DIRS 170026]). 
4. 
Parameters or models that most influence repository performance based on the 
performance measure and time period of compliance, specified in 10 CFR Part 63, are 
identified. 
Not applicable. Discussion of the sensitivity of repository performance to 
specific TSPA-LA models or parameters is beyond the scope of this report and 
is not discussed. 
5. 
Where sufficient data do not exist, the definition of parameter values and conceptual 
models on appropriate uses of other sources, such as expert elicitation, are conducted 
in accordance with appropriate guidance, such as NUREG-1563 (Kotra et al. 1996 
[DIRS 100909]). 
Not applicable. Expert elicitation was not used to develop parameter values 
pertinent to redistribution of radionuclides in soil described in this report. 
Acceptance Criterion 4: Model uncertainty is characterized and propagated through the 
model abstraction 
Not applicable. The analysis report does not contain models. 
Acceptance Criterion 5: Model abstraction output is supported by objective comparisons 
Not applicable. The analysis report does not contain models. 
B5. KEY TECHNICAL ISSUES, IGNEOUS ACTIVITY 
KTI IA 2.17 is an agreement between NRC and DOE for which DOE agreed to evaluate the risk 
effects of the redistribution of tephra (ash) contaminated with radionuclides due to eolian and 
fluvial remobilization off slopes, rates of transport in Fortymile Wash, and rates of deposition or 
removal at proposed critical group locations (Reamer 2001 [DIRS 159894], Attachment 1, p. 1). 
Information to address KTI IA 2.17 is supported by field studies and analyses discussed in 
Section 6.3.4. 

APPENDIX C 
PHYSICAL VOLCANOLOGY OF THE LATHROP WELLS VOLCANO 


APPENDIX C 
PHYSICAL VOLCANOLOGY OF THE LATHROP WELLS VOLCANO 
C1. AGE AND GENERAL FEATURES 
The Lathrop Wells volcano lava flows have an eruption age of approximately 77.3  6.0 ka, 
based on seventeen 40Ar/39Ar ages on the stratigraphically oldest lava flow (Heizler et al. 1999 
[DIRS 107255], p. 799). In this report, an age of approximately 80,000 years is used. The most 
probable interpretation for the Lathrop Wells eruptive center is that of a complex monogenetic 
volcanic center producing a cone, lava flows, and tephra deposit erupted within a span of a few 
months or years, but the center also exhibits some features that support other interpretations of 
age and eruptive history (Perry et al. 1998 [DIRS 144335], pp. 2-107 - 2-113). 
C2. SCORIA CONE 
The Lathrop Wells scoria cone (Figure C-1) is approximately 140 m high and oval, with its long 
axis oriented NNW-SSE. The cone measures 875 m by 525 m at its base and is capped by a 
similarly elongate, 190-m by 145-m crater that is about 20 m deep. The outer slopes of the cone 
range from 28 to 32 and consist of mostly loose scoria lapilli. The cone shape has been 
somewhat modified by erosion and is rapidly changing because of active quarrying along the 
south margins. The cinder cone has an approximate volume of 0.018 km3. Quarrying is 
revealing the three-dimensional structure of the cone, currently exposing approximately 
one-quarter of the cones interior. Figure C-2 is a digital elevation model portraying the relief of 
the cone and surrounding area as if illuminated from the northwest. It shows the locations of 
samples used for this study, most of which are discussed specifically in the following 
subsections. 
NOTE: For illustration purposes only. 
Figure C-1. Lathrop Wells Scoria Cone and Adjacent Lava Flows (Capped by Beige, Eolian Sand) 
Viewed from the North 

NOTES: For illustration purposes only 
The Lathrop Wells volcano occupies the lower center of the map. The dots show locations of samples; the 
numbers correspond to the sample numbers given in this report (preceded with DK-LW-). Grid is NAD 
1927 UTM, Zone 11 North, in meters. Contour interval is 20 feet. 
Figure C-2. Topographic Map and Tephra Sample Locations for Lathrop Wells Volcano Area 

Most cone deposits exposed in the quarry dip concentrically outward from the cone center with 
primary depositional slopes of 30 to 32. Primary dips gradually decrease to about 20 near the 
top of the cone. The stratigraphically lowest deposits exposed in the quarry are irregular masses 
of welded scoria and bombs and mostly or partly welded lapilli. Some of these agglutinate 
masses dip inward about 10 toward the presumed location of the vent. The representative 
stratigraphic sections of the cone described below are compiled from exposures within the quarry 
and along bulldozer cuts from the base to the summit. 
Overlying the agglutinate unit, a basal, 2.5-m thick section (elevation ~840 m) in the quarry, 
about 100 m north of the loading facility, consists of the following (Figure C-3): 
NOTES: For illustration purposes only 
Left photo: Exposures of cone interior showing sharp transition from nonwelded, massive or poorly 
bedded, lapilli- and bomb-size ballistic ejecta to overlying moderately bedded avalanche deposits of ash 
and lapilli (> 50 percent ash); most clasts are deposited at angles of repose as ballistic ejecta. Height of 
the lower coarse beds is about 2.5 m. Right photo: Close-up of ejecta (at base of left image), mostly 
broken scoria bombs and lapilli. The scale is 10 cm. 
Figure C-3. Cone Interior Showing Scoria and Close-up of Ejecta 
 
The lowest 0.9 m of exposed units composed of massive, nonwelded, poorly sorted, gray 
to reddish-gray scoria lapilli with approximately 8 to 12 percent bombs and blocks 
(maximum observed was 28 cm by 18 cm). 
 
A 0.3- to 0.6-m thick deposit of poorly sorted lapilli, blocks, and bombs with no ash 
matrix. Ninety-five percent of the deposit consists of blocky, angular scoria with a few 
percent large (> 20 cm) cauliflower and spindle bombs. 

 
A 0.9-m deposit of clast-supported reversely graded lapilli and bombs, with bombs up to 
0.75 m long and thin (2-3 cm) interbeds of lapilli. 
 
At the top, a wedge-shaped avalanche deposit (thickening down-slope from about 0.3 to 
> 1 m) with a slope of 32, near the angle of repose. Reddish-brown lapilli and ash with 
10 to 50 percent ash. This unit extends upward toward the summit. Up-slope, this 
deposit is cut by an irregular small channel with decreasing slope from about 30 to near 
horizontal; the channel is filled with olive-gray scoria. 
Uppermost deposits of the cone are visible along road-cuts near the cone summit. At this 
elevation (~968 m), the deposits slope into the crater at approximately 15 to 20. Exposed are 
about 8 m of crudely bedded, vesicular, scoriaceous lapilli and coarse ash with about 5 percent 
bombs, and 1 to 2 m of coarser, frothy scoria lapilli. These units contain less than about 
0.5 percent lithic clasts comprising angular pieces of bedded tuff and rhyolitic pumice. About 
38 m below these beds (elevation ~925 m) are exposures of a sharp angular unconformity 
between the upper, inward-dipping lapilli beds, and the underlying, outward-sloping avalanche 
deposits (Figure C-4). These exposures were destroyed by quarry operations during Fall 2002. 
NOTES: For illustration purposes only. 
Elevation of the outcrop is approximately 925 m; top of cinder cone is about 968 m elevation. 
Figure C-4. Angular Unconformity Between Outward-Sloping Lapilli-Ash Avalanche Deposits and 
Deposits Sloping Toward the Crater 
C2.1 Upper Hydrovolcanic Beds 
About 6-m below the south summit (elevation 954 m), a fresh bulldozer cut exposes a 40-cm 
thick, well-sorted, finely bedded, cross-bedded ash and coarse ash deposit. Individual beds range 
from 3 mm to 1.5 cm thick and dip conformably 30 to 35 toward the crater. The reddish beds 
are sandwiched between poorly sorted beds of massive, nonwelded, angular, clast-supported, 
scoria lapilli. Upper and lower bed contacts are parallel to the internal bedding, and no scouring 
or excavation of the lower coarse bed is evident (Figure C-5). Rare, rounded, clear quartz sand 
grains are present in a few hand specimens but are volumetrically insignificant (estimated 
< 0.1 vol%). 

Source: Krier and Harrington (2003 [DIRS 164023], pp. 118-120) 
NOTE: Inset photo is centered on the 40 cm thick, finely bedded ash; measuring tape is extended 1 m. The thin, 
white layer is disseminated secondary mineralization, probably carbonate. 
Figure C-5. Hydrovolcanic Beds Near the Top of Lathrop Wells Volcano 
Grain size data for DK-LW-074 (ash and coarse ash beds 4-8 cm above the base of the 
hydrovolcanic beds), DK-LW-075 (20-25 cm above the base of the upper hydrovolcanic beds), 
and DK-LW-076 (coarse lapilli fall above the hydrovolcanic beds) are given in Table C-1. This 
deposit appears to be the result of a brief hydrovolcanic event late in the cone-building history. 
Figure C-6 plots grain size for these deposits; the hydrovolcanic samples stand out as much 
finer-grained and better sorted than the scoria fall that is more typical of the cone. 
Scanning electron microscope analysis of the hydrovolcanic bed constituents reveals equant, 
rounded grains of tachylite with smooth, glassy vesicle wall remnants and less abundant 
sideromelane. Surface alteration of the grains is not abundant, but includes drusy silica and rare 
micrometer-sized, euhedral barite. 

Table C-1. Grain Size Data for Crater Deposits in the Lathrop Wells Volcano 
Sample Number Md. (median) s. (sorting) Md (mm) 
DK-LW-076 -2.97 1.66 7.8 
DK-LW-075 2.47 1.08 0.18 
DK-LW-074 2.94 1.07 0.13 
Source: Calculated from data in Krier and Harrington (2003 [DIRS 164023]) 
Mdf. (median) = median grain size in f. units (defined in Section 6.1.3.5) 
sf. (sorting) = (f84  f16)/2 (defined in Section 6.1.3.5) 
Md (mm) = median grain size in mm 
Source: DTN: LA0302GH831811.002 [DIRS 162864] 
Figure C-6. Grain Size Variations of Hydrovolcanic Beds and Overlying Lapilli Fall Near the Top of 
Lathrop Wells Volcano 
C2.2 Lithic Clasts in the Lathrop Wells Scoria Cone Deposits 
The best estimates for the volume and types of lithic clasts are important to repository risk 
assessment because the same processes that erode dike and conduit wall rock could influence the 
volume of waste reaching the surface (e.g., Crowe et al. 1983 [DIRS 100972], p. 269). 
Larger and more interior quarried exposures provide a better opportunity to measure lithic clast 
abundances within the Lathrop Wells scoria cone than in the past (Crowe et al. 1986 
[DIRS 101532], Figure 13; Appendix F). Table C-2 lists results of counts of 18, 1 m2 areas 

located at several elevations in the cone. The elevations recorded with each measurement 
accurately reflect relative stratigraphic position (lower elevation represents earlier cone history; 
higher elevations represent later cone history). Measurements of lithic clasts were made in 
nonwelded deposits of coarse ash, lapilli, and larger material. They are not indicative of the 
stratigraphically lower, short pulse of hydrovolcanic activity recorded in deposits outside the 
cone (Section C3.3, Figure C-11; Wohletz 1986 [DIRS 140956], p. 258). Counts were made 
with 12X and 10X hand lenses. Each visible lithic clast more than or equal to 1 mm was 
identified and its short and long axis measured. Lithic clast volume fractions F were determined 
using the following equation (Valentine and Groves 1996 [DIRS 107052], p. 80): 
F = (area fraction)3/2 (1.18)3 (Eq. C-1) 
where areas measured are 1 m by 1 m squares on vertical exposures. Measured lithic clast 
abundances range from 0.91 vol% to less than 0.018 vol%. The volume data indicate that 
lithic-clast abundance is greatest within the measured lower stratigraphic levels in the scoria 
cone and decreases one to two orders of magnitude in overlying, younger scoria intervals 
(Figure C-7). The lithic clasts production during eruption was not uniform throughout the cone 
construction period, and the variation suggests less vigorous conduit enlargement with time. 
This observation is tempered with the recognition that much of the scoria (and included lithic 
clasts) within volcanic cones is subject to avalanching, slumping, and redeposition during 
construction (McGetchin et al. 1974 [DIRS 115469], p. 3268). 
Table C-2. Lithic Clast Measurements in the Lathrop Wells Scoria Cone 
Patch Elevation (ft) Volume Fraction 
17 3146 0.000140 
15 3136 0.000200 
12 3119 0.000160 
14 3106 0.000029 
13 3079 0.000083 
18 3074 0.000940 
16 3056 0.000290 
11 2940 0.000039 
7 2926 0.006700 
Mean (7-10) = 
0.004985 
8 2926 0.000940 
9 2926 0.008700 
10 2924 0.003600 
1 2886 0.009100 
Mean (1-6) = 
0.002899 
2 2886 0.005800 
3 2886 0.000075 
4 2886 0.001300 
5 2886 0.001100 
6 2886 0.000018 
Source: DTN: LA0302GH831811.003 [DIRS 162865]. 
NOTE: Lithic clast measurements were done in eighteen 1-m2 areas in 
Lathrop Wells scoria cone outcrops. Elevations reflect relative 
stratigraphic position (early to late cone activity), as explained in the 
text. Multiply the volume fraction by 100 to obtain a percentage. 
ANL-MGR-GS-000002 REV 02 C-7 September 2004 

Source: DTN: LA0302GH831811.003 [DIRS 162865] 
NOTE: Volume fractions of lithic clasts more than 1 mm were measured in the Lathrop Wells scoria cone. Lathrop 
Wells measurements (filled boxes) are shown in actual stratigraphic positions. Measurements from the 
Lucero volcanic field, New Mexico (Valentine and Groves 1996 [DIRS 107052] Table 1), and Hopi Buttes, 
Arizona (White 1991 [DIRS 124930], Figure 3), are plotted at arbitrary elevations for comparison. 
Figure C-7. Volume Fractions of Lithic Clasts 
Figure C-7 is a plot of the Lathrop Wells volcano lithic volume fraction data versus elevation. 
The data are compared with similar data from the Lucero, New Mexico, volcanic field (Valentine 
and Groves 1996 [DIRS 107052], Table 1) and Hopi Buttes, Arizona (White 1991 
[DIRS 124930], Figure 3), for both cone-building and hydrovolcanic deposits. The exposures at 
the Lucero field indicate that the so-called lapilli and block-rich tuff (which can contain up to 
90 vol% lithic clasts) represents hydrovolcanic phases of the eruptions there and contain a mean 
lithic abundance of greater than 50 vol%. By contrast, Lucero vesicular scoria and spatter 
facies, representative of cone-building processes, average (< 0.1 vol%) lithic clasts. In 
comparison, the mean lithic clast abundance at Hopi Buttes, Arizona, perhaps an extreme 
example of well-exposed hydrovolcanic events, is between 50 and 60 vol%. Lathrop Wells 
volcano lithic clast abundances are not unusually high. Within the studied exposures, which 
represent a substantial vertical section through the cone, no lithic clast abundances were 
encountered that are indicative of significant conduit-clearing activity at the cone. As noted by 
Doubik and Hill (1999 [DIRS 115338], p. 60), small basaltic breccia blocks containing angular 
fragments of Tertiary ignimbrite are found on the lower flanks of Lathrop Wells cone. 
Individual blocks range up to 15 cm-diameter and lithics can account for up to 50 vol% or more. 
Their occurrence is limited to the youngest, possibly last, deposits on the cone and immediately 
near the base. The small volume represented by the breccia blocks is insignificant relative to the 
cone volume or the tephra sheet volume, although their occurrence signifies a disruption to 

feeder dike or conduit boundaries along some length of the 550-m thick Tertiary ignimbrite 
section beneath the cone. 
There is a common occurrence of secondary silica and/or carbonate coatings on many lapilli and 
larger grain surfaces that may be the cause of the elevated volume of lithic clasts obtained using 
computer-assisted image analysis (average 0.9 vol%; Doubik and Hill 1999 [DIRS 115338], 
p. 60). Using this approach (digital images and image analysis) will result in a high estimate of 
lithic clasts. Results from Crowe et al. (1986 [DIRS 101532], Appendix F), based on only 
four nonhydrovolcanic samples of the cone, ranged from 0.3 to 2.4 vol% in the less than 
0.707 mm size fraction. 
C3. TEPHRA DISTRIBUTION AND DESCRIPTION 
Much information about eruption processes can be gleaned from the Lathrop Wells volcano 
itself. However, until the cone has been totally dissected by quarrying, an important component 
of studying the sequence of eruption processes is to describe and analyze the tephra (ash-fall) 
deposits beyond the cone flanks. The distribution of Lathrop Wells tephra and changes in grain 
size and pyroclast types are described here in the context of the stratigraphy as exposed in 
representative sections of the tephra fall deposit. 
C3.1 Estimated Tephra Distribution 
The thickness of Lathrop Wells volcano tephra (using the plotted data points) can be seen in 
Figure C-8 (which shows estimated isopach lines using data from LA0305DK831811.001 
[DIRS 164026]). The isopachs (300, 200, 100, 50, 10, and 1 cm) are drawn based on a visual fit 
to the data collected from both hand-dug pits and natural exposures. The tephra thicknesses in 
most locations represent minima because of an unknown amount of erosion of the tops of the 
sections of tephra. Therefore, larger thickness values were emphasized in estimating contours of 
tephra thickness. There is a relative consistency in the distribution of thicknesses that suggests 
that erosion was less than 0.5 m, but this is difficult to quantify with the available data. 
Preservation of the tephra sheet was enhanced due to low topography and apparently rapid post-
eruption covering by eolian sands, but these factors also limit the number of exposures and data 
points. The northern 1 cm isopach is chosen to be near the location of Solitario Canyon fault 
trench T8, where US Geological Survey employees exposed Lathrop Wells volcano ash 
concentrated within deposits in the fault plane (Perry et al. 1998 [DIRS 144335], 
pp. 4-25  4-26). The amount and condition of ash particles suggest they represent ash runoff 
from the surrounding slopes and deposition in the fault plane when it was open during or soon 
after the earthquake that exposed the fault plane (Ramelli et al. 1996 [DIRS 101106], 
pp. 4.7-11  4.7-12). A second notation of scattered basaltic ash on the west side of Busted Butte 
(Volcanism Field Notebook TWS-EES-13-LV-01-93-05 [Crowe 1996 (DIRS 164317), p. 54]) 
suggests that some deposition from the Lathrop Wells volcano ash-column occurred there. 
Without any preserved primary ash deposits to measure, a thickness of one cm of ash was used 
for the original thickness at this locality. 

Source: Krier and Harrington (2003 [DIRS 164023], p. 153) 
NOTE: The triangle marks the volcano summit; the numbers are thicknesses, in cm, in dug pits or natural 
exposures. Isopach lines drawn using data from LA0305DK831811.001 [DIRS 164026]. Coordinate grid 
is NAD 1927 UTM, Zone 11 North, in meters. 
Figure C-8. Isopach Map (Estimated) of Tephra Fall from the Lathrop Wells Volcano 

Observations of preserved tephra further than 1 km west of the cone are limited to isolated, trace 
concentrations in detrital sediments in gullies on the hill slopes. Data on tephra thicknesses to 
the east and south of the cone are extremely limited and the isopachs are conjectural. There are 
no exposures beyond 800 m south of the cone base. The southernmost tephra location is in 
trench SP-7A (due south of the cone), where a 3-cm thick basaltic ash (termed airfall scoria by 
Crowe 1992 [DIRS 162823], p. 90) was located using a backhoe directly beneath the south toe of 
the lava flow (Volcanism Field Notebook TWS-EES-13-LV-11-89-07 [Crowe 1992 
(DIRS 162823), p. 90]). The ash lies directly upon a desert pavement. This thin ash predates the 
lava, but another tephra deposit, exposed 500 m to the N - NE, is greater than 255-cm thick and 
postdates the lava. The known tephra distribution around Lathrop Wells volcano suggests that 
during eruption the lofted basaltic tephra column may have been directed predominantly 
northward with minimal tephra deposition south of the cone. 
C3.2 Proximal Tephra Fall Near the Base of the Lathrop Wells Volcano 
Stratigraphic section at N36 40' 54.8., W116 30' 26,. and elevation 821.7 m (2,696 feet), 
650 m south of the summit of the Lathrop Wells volcano. 
Massive scoria fallout deposits at least 255 cm thick, overlying lava flows from the Lathrop 
Wells volcano, are exposed in a small quarry and they are used here to characterize proximal 
fallout (Table C-3). Measured grain size variations are listed in Table C-4 and plotted in 
Figure C-9, which shows an overall median size decrease up-section. All samples are coarse 
grained and consist of mostly lapilli and coarse ash. The lower 130 cm has at least five reversely 
graded lapilli-ash fall sequences. The upper 125 cm begins with a normally graded lapilli-ash 
fall overlain by 2 to 3 beds of coarse and fine ash grading upward to about 0.5 m of bioturbated 
coarse ash mixed with eolian sand and silt. A 5 cm thick yellowish layer at 78 cm above the 
base contains up to 1 percent silicic pumice lithic clasts; the remainder of the sequence has few 
or no lithic clasts. 
Table C-3. Samples Used to Characterize the Proximal Scoria Fall Section 
Sample Description 
DK-LW-057 Massive, brownish-gray ash and platy, vesicular lapilli fall, from an 11-cm thick bed at 180 cm above 
base of exposure. 
DK-LW-055 Well sorted, medium to dark gray lapilli and coarse ash fall, 170 cm above base, between two 
continuous, thin (< 1 cm) resistant beds of calichified ash. 
DK-LW-054 Well-sorted, reddish-brown lapilli and coarse ash scoria fall, 80 cm above base, and immediately 
above 5-cm wide yellowish color band. Largely equant, vesicular fragments. Individual fall beds 10 
to 80 cm thick. 
Source: Krier and Harrington (2003 [DIRS 164023], pp. 57-59) 

Source: DTN: LA0302GH831811.002 [DIRS 162864]. 
Figure C-9. Grain Size Variations in Scoria Fall Section Close to the Southern Cone Base (boneyard) 
Table C-4. Grain Size Variations in Scoria Fall Section Close to the Southern Base of Lathrop Wells 
Volcano 
Sample Number Mdf (median) sf (sorting) Md (mm) 
DK-LW-057 -0.19 1.31 1.15 
DK-LW-055 -1.11 1.43 2.2 
DK-LW-054 -2.01 1.43 4 
Source: Values calculated from data in DTN: LA0302GH831811.002 [DIRS 162864] 
Mdf. (median) = median grain size in f. units (defined in Section 6.1.3.5) 
sf. (sorting) = (f84  f16)/2 (defined in Section 6.1.3.5) 
Md (mm) = median grain size in mm 
Variations in Pyroclast TypesTable C-5 lists the percent pyroclasts measured in samples from 
this scoria fall section. The measured pyroclast samples are in the 0.5 to 1.0 mm size fractions, 
and abundances are based on 300-grain counts, as measured using a binocular microscope. 

Table C-5. Percent Pyroclasts in Samples in Scoria Fall Section Close to the Southern Cone Base 
Sample Number Tachylite 
Glassy 
Tachylite 
Sidero-
melane 
Quartz + 
Feldspar 
Sand Tuff Clasts 
Feldspar + 
Olivine 
Phenocrysts 
DK-LW-057 17.6 64.3 17.6 0.0 0.0 0.3 
DK-LW-055 29.0 57.0 15.0 0.0 0.0 0.0 
DK-LW-054 8.0 58.6 32.6 0.3 0.3 0.0 
Source: DTN: LA0302GH831811.004 [DIRS 162866] 
NOTE: Estimated Error equals  0.1 percent 
C3.3 Tephra Stratigraphy Beyond the Lathrop Wells Scoria Cone 
Stratigraphic section (hydrovolcanic) at N36 41'42.7,. W116 30'53.5,. and elevation 863.8 m 
(2,834 feet), located 0.7 km NW of the summit of Lathrop Wells volcano. 
Observations were made from several pits excavated along small arroyos and by sweeping clean 
a portion of the outcrop along the east-facing slope of a ridge of Miocene welded tuff. 
A composite section comprises, from the bottom up: Miocene densely welded tuff overlain by 
about 1 m of coarse, angular, tuffaceous colluvium; 60 cm of massive basaltic lapilli and ash; 
four beds, each 10 to 15-cm thick, of reversely graded lapilli and ash; 15 cm of massive lapilli 
and ash; about 100 to 120 cm of slanted, thinly bedded and cross-bedded fine to coarse ash; and 
an overlying massive lapilli and ash bed greater than 1-m thick. In all, there are about 125 cm of 
flat-lying fallout tephra beneath the slanted, cross-bedded ash (Figure C-10). The cross-bedded 
ash has consistent bedding slopes of 8 to 10 toward the cone and appears stacked like a deck of 
cards against the sloping hill of Miocene welded tuff (Figure C-11). These ash beds have been 
interpreted as hydrovolcanic in origin (pyroclastic surge deposits of Vaniman and Crowe 1981 
[DIRS 101620], pp. 20-21; Wohletz 1986 [DIRS 140956], p. 258). The hydrovolcanic beds are 
exposed over a distance of 58 m, along a trend radial from the vent. Figure C-12 is a photograph 
looking up-section (toward the cinder cone) at the hydrovolcanic deposits. 
Beds within the hydrovolcanic section are grayish-black (N2) to light beige, 1 to 6 mm thick, 
(approximate maximum of 1.3 cm) and consist of medium to coarse ash-sized pyroclasts. Most 
are planar beds, but there are interbedded low-angle cross beds (an example has a wavelength of 
36 cm and amplitude of 1 cm). Cross-beds indicate up-slope current directions away from the 
cone. Near the center of the hydrovolcanic section is a 44 cm long by 10 cm wide, 10 cm deep 
bedding plane sag caused by a block impacting wet and/or soft ash from the direction of the 
cone. 
Within the area flanked by the cinder cone and protruding ridge of Miocene tuff, there is a 
transition southward, over a distance of about 400 m, from thousands of thin beds of a 
hydrovolcanic deposit (e.g., Figure C-12) to hundreds and eventually one or two resistant ash 
beds sandwiched between coarse lapilli beds. Observations in trenches immediately southwest 
of the cone also indicate a southward thinning hydrovolcanic sequence (Volcanism Field 
Notebook TWS-EES-13-LV-01-93-05 (Crowe 1996 [DIRS 164317], pp. 33-37). The field 
relations suggest that the limited deposit resulted from a ground-hugging sector blast directed to 
the northwest. Because the unit slopes about 8 back toward the cone and projects to beneath the 
cone base, the exact relations are covered with alluvium. There are currently no field data 

confirming a concentric tuff ring as proposed by Wohletz (1986 [DIRS 140956], p. 261). In any 
case, the sequence of massive and reversely graded lapilli beds beneath the hydrovolcanic unit 
indicates initial nonhydrovolcanic eruptive phases followed by a brief explosive, hydrovolcanic 
event. 
Source: Krier and Harrington (2003 [DIRS 164023], pp. 22, 53-56) 
NOTE: Composite stratigraphic section from underlying colluvium through a scoria fall sequence, a hydrovolcanic 
sequence, and grading up at the top into scoria fall beds. Figure C-11 shows the field relations for this 
section. 
Figure C-10. Tephra Fall Stratigraphy for Section D 

Source: Krier and Harrington (2003 [DIRS 164023], p. 55) 
NOTE: The diagram shows the tephra sequence located northwest of the Lathrop Wells volcano on an east-facing 
slope of Miocene welded tuff and colluvium. Overlying the colluvium is a sequence of scoria lapilli and ash 
fall beds, which in turn are overlain by a sequence of hydrovolcanic tuffs, which grade upward into more 
massive scoria lapilli fall beds. The hydrovolcanic sequence consists of mostly plane- and dune-bedded 
surge deposits. 
Figure C-11. Schematic Diagram of Hydrovolcanic Tephra Sequence 
For illustration purposes only 
NOTE: View is up-stratigraphic section, toward the cone (from right to left on Figure C-11). Angular cobble at 
upper right is about 25 cm long. 
Figure C-12. Hydrovolcanic Deposits West and near the Base of the Lathrop Wells Volcano 

The samples used to characterize this hydrovolcanic section are described in Table C-6. 
Measured grain size variations are given in Table C-7 and plotted in Figure C-13. The 
hydrovolcanic deposits are much finer grained than the over or under-lying tephra fall deposits. 
As is the case for most dry surge deposits (little condensation of vapor before deposition), no 
accretionary lapilli were observed. 
Table C-6. Composite of Samples Used to Characterize the Hydrovolcanic Sequence and Underlying 
Tephra Fall Sequence (tephra fall samples are in italics) 
Sample Number Description 
DK-LW-053 Exposed hydrovolcanic sequence. Collected from 1.2-cm-thick, light brown, ash/lapilli bed, 
42.3-m above the base of the sequence. 
DK-LW-052 Exposed hydrovolcanic sequence. Collected from 0.8-cm-thick, light brown, ash/lapilli bed, 
42 m-above the base of the sequence. 
DK-LW-050 Well-bedded foreset beds of medium to coarse ash, 110 cm above the base of sequence. Pit 
in southern margin of exposed hydrovolcanic section. 
DK-LW-049 Well-bedded ash; plane beds to small dunes, 45 cm above the base of sequence. Pit in 
southern margin of hydrovolcanic section. 
DK-LW-048 Medium to coarse ash, 10 cm above the base of sequence. Pit in southern margin of exposed 
hydrovolcanic section. 
DK-LW-017 Massive lapilli and ash fall bed. 
DK-LW-016 Reversely graded lapilli and ash fall beds. 
DK-LW-015 Massive lapilli and ash fall ~35-40 cm above DK-LW-051. 
DK-LW-051 Collected 8-10 cm above colluvium and beneath the hydrovolcanic tephra sequence. Massive 
scoria lapilli fallout. 
Source: Krier and Harrington (2003 [DIRS 164023], pp. 22, 53-56) 
NOTE: Samples DK-LW-015 to -017 and DK-LW-051 are fallout beds located between underlying Miocene tuff 
and colluvium and the overlying hydrovolcanic sequence. Samples DK-LW-052 and -053 were collected 
along the 42-m long surface outcrop of the hydrovolcanic sequence. 
Table C-7. Grain Size Variations in Hydrovolcanic Sequence and Underlying Tephra Fall Sequence 
Sample Number Mdf (median) sf.(sorting) Md (mm) 
DK-LW-053 2.5 1.33 0.18 
DK-LW-052 1.77 0.81 0.29 
DK-LW-050 1.60 1.51 0.33 
DK-LW-049 1 1.42 0.5 
DK-LW-048 1.25 1.34 0.42 
DK-LW-051 -0.6 1.25 1.5 
DK-LW-017 -1.44 1.49 2.8 
DK-LW-016 -1.44 1.18 2.8 
DK-LW-015 -1.11 1.14 2.2 
Source: Values calculated from data in DTN: LA0302GH831811.002 [DIRS 162864] 
NOTE: Tephra fall samples are in italics 
Mdf. (median) = median grain size in f. units (defined in Section 6.1.3.5) 
sf. (sorting) = (f84  f16)/2 (defined in Section 6.1.3.5) 
Md (mm) = median grain size in mm 
ANL-MGR-GS-000002 REV 02 C-16 September 2004 

Source: DTN: LA0302GH831811.002 [DIRS 162864]. 
NOTE: For comparison, DK-LW-051, DK-LW-015, DK-LW-016, and DK-LW-017 scoria fall beds underlying the 
hydrovolcanic sequence are plotted. 
Figure C-13. Grain Size Variations in Ash-Rich Hydrovolcanic Sequence 
Variations in Pyroclast TypesTable C-8 lists the percent pyroclasts measured in samples in 
the hydrovolcanic sequence. The pyroclast sizes are in the 0.5 to 1.0 mm size fractions of the 
samples, and abundances are based on 300-grain counts, as measured using a binocular 
microscope. Figures C-14 through C-19 are scanning electron micrographs of different samples. 
Table C-8. Percent Pyroclasts in Samples in Hydrovolcanic Sequence 
Sample 
Number Tachylite 
Glassy 
Tachylite 
Sidero-
melane 
Quartz & 
Feldspar 
Sand 
Tuff Clasts 
(lithic) 
Feldspar 
and Olivine 
Phenocrysts 
DK-LW-048 9.3 71.6 18.6 0.3 0.0 0.0 
DK-LW-049 34.6 48.0 13.6 0.6 0.0 3.0 
DK-LW-050 43.6 42.0 10.6 2.6 1.0 0.0 
DK-LW-052 1.6 73.0 24.3 0.0 0.3 0.6 
DK-LW-053 9.6 68.6 19.3 1.3 0.3 0.6 
DK-LW-051 57.0 26.0 10.3 0.0 5.3 1.2 
Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: Estimated Error =  0.2 percent 

Source: DTN: LA0306GH831811.001 [DIRS 171286]. 
NOTE: The sample is mostly glassy tachylite pyroclasts (vesicular, with thick vesicle walls). The more vesicular, 
thin-walled pyroclasts are sideromelane (basaltic glass). Most of the glassy tachylite pyroclasts have been 
rounded. Scale: width of image is about 1.4 mm. 
Figure C-14. Scanning Electron Micrograph of the 0.125- to 0.250-mm Fraction of Sample DK-LW-048 
Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: The sample is mostly tachylite (poorly vesicular, rough grain surfaces) and glassy tachylite pyroclasts 
(vesicular, with thick vesicle walls). The more vesicular, thin-walled pyroclasts are sideromelane (basaltic 
glass). Most of the glassy tachylite pyroclasts have been rounded. Scale: width of image is about 
1.4 mm. 
Figure C-15. Scanning Electron Micrograph of the 0.125- to 0.250-mm Fraction of Sample DK-LW-049 

Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: The sample shows an increase in tachylite scoria (poorly-vesicular, rough grain surfaces). Nearly all 
particle types show some degree of rounding. Scale: width of image is about 1.4 mm. 
Figure C-16. Scanning Electron Micrograph of the 0.125- to 0.250-mm Fraction of Sample DK-LW-050 
Source: DTN: LA0302GH831811.004 [DIRS 162866] 
NOTE: In this sample, nearly all pyroclasts are tachylite or glassy tachylite, with little rounding. Scale: width of 
image is about 1.4 mm. 
Figure C-17. Scanning Electron Micrograph of the 0.125- to 0.250-mm Fraction of Sample DK-LW-051 

Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: The sample is mostly glassy tachylite pyroclasts. Nearly all particle types show some degree of rounding. 
Scale: width of image is about 1.4 mm. 
Figure C-18. Scanning Electron Micrograph of the 0.125- to 0.250-mm Fraction of Sample DK-LW-052 
Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: The sample is mostly glassy tachylite pyroclasts, with a substantial fraction of sideromelane pyroclasts. 
Nearly all particle types show some degree of rounding. Scale: width of image is about 1.4 mm. 
Figure C-19. Scanning Electron Micrograph of the 0.125- to 0.250-mm Fraction of Sample DK-LW-053 

Stratigraphic Section at N36 41'36.1,.W116 31'02.4,. and elevation 839.7 m (2,755 feet), 
located 620 m NW of the summit of the Lathrop Wells volcano. 
This 1.1 m thick tephra section consists of mostly coarse ash and lapilli fall beds that were 
deposited directly upon older colluvium. From the base of the section, 0 to 14 cm, there are 
several 3 to 7 cm thick beds of reversely graded lapilli and ash (sample DK-LW-040), which 
grade into 16 cm of massive lapilli fallout with maximum scoria size of 3 by 2 cm (sample 
DK-LW-041). From 31 to 41 cm, there are three resistant ash beds, each 2 to 3 cm thick (sample 
DK-LW-042 is a thin lapilli interbed). The three intercalated, resistant beds may be distal 
equivalents of the hydrovolcanic facies exposed NW of the cone (Section C3.3). From 41 cm to 
the top of the section, there is a massive lapilli and coarse ash fallout bed (samples DK-LW-044 
and -043). The basal colluvium consists of angular, poorly sorted sand, pebbles, and cobbles of 
welded tuff with a bimodal grain-size distribution. Grain size variations for samples from this 
section are shown in Table C-9 and Figure C-20. Sample DK-LW-042 is finer grained than the 
fall samples (DK-LW-041, 043, 044), similar to the hydrovolcanic sequence described earlier. 
Table C-9. Grain Size Variations in the Colluvium and Tephra Fall Section 
Sample Number Mdf (median) sf (sorting) Md (mm) 
DK-LW-044 -1.05 1.29 2.1 
DK-LW-043 -1.17 1.31 2.2 
DK-LW-042 0.25 1.49 0.85 
DK-LW-041 -1.39 1.36 2.6 
DK-LW-039 
(colluvium 2.13 2.91 0.23 
matrix) 
Source: Values calculated from data in DTN: LA0302GH831811.002 
[DIRS 162864]. 
Mdf. (median) = median grain size in f units (defined in Section 6.1.3.5) 
sf. (sorting) = (f84  f16)/2 (defined in Section 6.1.3.5) 
Md (mm) = median grain size in mm 

Source: DTN: LA0302GH831811.002 [DIRS 162864]. 
Figure C-20. Grain Size Variations in Colluvium and Tephra Fall Section 
Pyroclast TypesSample DK-LW-041 is from 22-cm above the base in massive lapilli and ash 
fallout; DK-LW-042 is from 38 cm above the base and between two thin (hydrovolcanic?), 
resistant ash beds; DK-LW-044 is 60 cm above the base and representative of the 40- to 80-cm 
zone; and sample DK-LW-043 is from 100 cm above the base and representative of the upper 
30 cm of massive fallout. Table C-10 lists the percent pyroclasts measured in samples from this 
tephra section. The pyroclast sizes are in the 0.5 to 1.0 mm size fractions, and abundances are 
based on 300-grain counts, as measured using a binocular microscope. No lithic clasts were 
identified in the grain counts. 
Table C-10. Percent Pyroclasts in Samples in the Colluvium and Tephra Fall Section 
Sample Number Tachylite Glassy Tachylite Sideromelane 
Feldspar + 
Olivine Phenocrysts 
DK-LW-043 61.6 27.3 10.6 0.3 
DK-LW-044 57.0 28.0 14.6 0 
DK-LW-042 34.0 51.6 14.3 0 
DK-LW-041 42.3 44.0 13.6 0 
Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: Estimated Error =  0.3 percent. 

Stratigraphic section at N36 41'39.2,.W116 31'03.1,. and elevation 849.8 m (2,788 feet), 
located 780 m NW of the summit of the Lathrop Wells volcano and on the NW side (lee side, 
relative to the cone) of the small ridge of Miocene welded tuff. 
This tephra section, no base exposed, is visible in a bank of the wash. The bedding is parallel to 
the hill slope of about 9. 
Grain Size VariationsThe section consists of more than 82 cm of bedded coarse ash and 
lapilli, reversely graded at the base and normally graded at the top, overlain by 7 cm of thinly 
bedded ash and lapilli that has been interpreted by Wohletz (1986 [DIRS 140956], p. 262) as 
hydrovolcanic in origin. The samples (Table C-11 and Figure C-21) are from the basal massive 
unit (DK-LW-035 is from 20 cm above the base of exposure; DK-LW-036 is from 70 cm above 
the base). Both samples appear to be tephra fall beds, on the basis of field description and grain 
size analyses. 
Table C-11. Grain Size Variations in Tephra Section Overlying Ridge of Miocene Welded Tuff 
Sample Number Mdf (median) sf (sorting) Md (mm) 
DK-LW-036 -1.32 1.04 2.5 
DK-LW-035 -0.48 1.21 1.4 
Source: Values calculated from data in DTN: LA0302GH831811.002 [DIRS 162864] 
Mdf. (median) = median grain size in f units (defined in Section 6.1.3.5) 
sf. (sorting) = (f84  f16)/2 (defined in Section 6.1.3.5) 
Md (mm) = median grain size in mm 
Source: DTN: LA0302GH831811.002 [DIRS 162864]. 
Figure C-21. Grain Size Variations in Tephra Section Overlying Ridge of Miocene Welded Tuff

Stratigraphic section at N36 41'53.0, W116 30' 44.2, and elevation 852.2 m (2,796 feet), 
located 850 m NW of the summit of the Lathrop Wells volcano. 
This section of tephra fall (Section F) is 1.15 m thick, overlies tuffaceous colluvium, and is, in 
turn, overlain by reworked silty tephra (Figure C-22). 
Grain size VariationsSamples are arranged from bottom to top of the stratigraphic section. 
DK-LW-021 is from a 3-cm thick bed of lithic-bearing, highly vesicular ash and lapilli about 
10 cm above the colluvium base; DK-LW-020 is from a 5-cm thick ash-lapilli fall; DK-LW-022 
is from a 35 cm thick bed of clast-supported lapilli and ash; DK-LW-023 is from poorly sorted 
lapilli and coarse ash; and DK-LW-024 is from a reversely graded bed of fine ash to lapilli. The 
measured grain size variations are shown in Table C-12 and Figure C-23. 
Table C-12. Grain Size Variations in Tephra Fall for Section F 
Sample Number Mdf (median) sf (sorting) Md (mm) 
DK-LW-024 -1.43 1.04 2.7 
DK-LW-023 -0.92 1.21 1.9 
DK-LW-022 -1.68 1.13 3.2 
DK-LW-020 -1.0 1.0 2.0 
DK-LW-021 0.32 1.02 0.8 
Source: Values calculated from data in DTN: LA0302GH831811.002 [DIRS 162864] 
or from Figure C-23. 
Mdf. (median) = median grain size in f units (defined in Section 6.1.3.5) 
sf. (sorting) = (f84  f16)/2 (defined in Section 6.1.3.5) 
Md (mm) = median grain size in mm 

Source: Krier and Harrington (2003 [DIRS 164023], p. 27). 
Figure C-22. Tephra Fall Stratigraphy for Section F 

Source: DTN: LA0302GH831811.002 [DIRS 162864]. 
Figure C-23. Grain Size Variations in Tephra Fall for Section F 
Variations in Pyroclast TypesPercent of pyroclast types in the 0.5- to 1.0-mm size fractions of 
samples DK-LW-020 to DK-LW-024, based on 300-grain counts, as measured using a binocular 
microscope, are listed in Table C-13. 
Table C-13. Percent Pyroclasts in Samples in Tephra Fall for Section F 
Sample 
Number Tachylite 
Glassy 
Tachylite Sideromelane 
Quartz & 
Feldspar 
Sand 
Carbonate 
Clasts 
(lithic) 
Tuff 
Clasts 
(lithic) 
Feldspar & 
Olivine 
Phenocrysts 
DK-LW-024 56.3 24.3 19.3 0.0 0.0 0.0 0.0 
DK-LW-023 75.0 17.3 7.6 0.0 0.0 0.0 0.0 
DK-LW-022 59.0 27.6 13.0 0.0 0.0 0.0 0.3 
DK-LW-020 77.3 7.3 11.3 1.0 1.0 0.0 2.0 
DK-LW-021 21.6 18.0 52.0 0.3 0.3 7.6 0.0 
Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: Estimated Error =  0.1 percent. 
ANL-MGR-GS-000002 REV 02 C-26 September 2004 

The eruption sequence for this section begins with 10 cm of frothy lapilli fall, superposed by 
lithic-bearing hydrovolcanic(?) ash, dominated by sideromelane pyroclasts, but changes to 
lithic-poor lapilli and ash, which is mostly tachylite and glassy tachylite. Figures C-24 to C-28 
are illustrations of the particle populations (0.125 to 0.5 mm fraction) in scanning electron 
microscope images. 
Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: The sample is dominated by vesicular sideromelane (basaltic glass) pyroclasts. Scale: width of image is 
approximately 1.4 mm. 
Figure C-24. Scanning Electron Micrograph of the 0.125- to 0.250-mm Fraction of Sample DK-LW-021 
Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: In this sample, there is a noticeable increase (from DK-LW-021) in tachylite and glassy tachylite 
pyroclasts. Scale: width of image is about 1.4 mm. 
Figure C-25. Scanning Electron Micrograph of the 0.125- to 0.250-mm Fraction of Sample DK-LW-020 

Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: Most pyroclasts in this sample are tachylite or glassy tachylite. Scale: width of image is approximately 
1.4 mm. 
Figure C-26. Scanning Electron Micrograph of the 0.125- to 0.250-mm Fraction of Sample DK-LW-022 
Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: Most pyroclasts in this sample are tachylite or glassy tachylite. Undisturbed fallout has no edge modification 
of pyroclasts. Scale: width of image is approximately 1.4 mm. 
Figure C-27. Scanning Electron Micrograph of the 0.125- to 0.250-mm Fraction of Sample DK-LW-023 

Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: The sample is mostly vesicular and non-vesicular or poorly vesicular tachylite pyroclasts. There are no lithic 
clasts. Scale: width of image is approximately 1.4 mm. 
Figure C-28. Scanning Electron Micrograph of the 0.125- to 0.250-mm Fraction of Sample DK-LW-024 
Stratigraphic section at N36 42'14.0., W116 30'14.0,. and elevation 861.1 m (2,825 feet), 
located 1.6 km NNW of the summit of the Lathrop Wells volcano. 
In this 70-cm thick stratigraphic section, the tephra overlies eolian sand deposits and consists of 
well-bedded medium to fine-grained ash in the lower 15 cm, grading upward into massive to 
crudely graded lapilli and ash bed. The top of the sequence has been reworked. The basal 3 cm 
is bedded ash with lithic sand grains giving it a salt and pepper appearance. 
Grain size VariationsSamples are arranged from bottom to the top of the stratigraphic section. 
DK-LW-014 is from the basal fallout unit; DK-LW-018 is of a massive lapilli fall; and 
DK-LW-019 is from tephra fall near the top of the stratigraphic section (Figure C-29). The 
measured grain size variations are shown in Table C-14 and Figure C-30. 
Table C-14. Grain Size Variations in Tephra Fall for Section E 
Sample Number Mdf (median) sf (sorting) Md (mm) 
DK-LW-019 -0.85 1.05 1.8 
DK-LW-018 -1.63 1.40 3.1 
DK-LW-014 0.07 1.62 0.95 
Source: Values calculated from data in DTN: LA0302GH831811.002 [DIRS 162864] or 
from Figure C-30. 
Mdf. (median) = median grain size in f units (defined in Section 6.1.3.5) 
sf. (sorting) = (f84  f16)/2 (defined in Section 6.1.3.5) 
Md (mm) = median grain size in mm 

Source: Krier and Harrington (2003 [DIRS 164023], p. 25). 
Figure C-29. Tephra Fall Stratigraphy for Section E, elevation 2820 feet 

Source: DTN: LA0302GH831811.002 [DIRS 162864]. 
Figure C-30. Grain Size Variations in Tephra Fall for Section E 
Variations in Pyroclast TypesPercent pyroclast types in the 0.5- to 1.0-mm size fractions of 
samples DK-LW-014, DK-LW-018, and DK-LW-019, based on 300-grain counts, as measured 
using a binocular microscope, are listed in Table C-15. 
Table C-15. Percent Pyroclasts in Samples in Tephra Fall for Section E 
Sample Glassy Quartz & Tuff Clasts 
Number Tachylite Tachylite Sideromelane Feldspar Sand (lithic) 
DK-LW-019 31.6 52.0 8.0 0.0 8.3 
DK-LW-018 43.6 47.3 7.0 0.6 1.3 
DK-LW-014 23.6 34.0 27.6 1.3 13.3 
Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: Estimated Error =  0.2 percent. 
The most evident changes include the decreasing sideromelane and increasing tachylite and 
glassy tachylite pyroclasts up-section. Below are illustrations of the particle populations 
(0.125 to 0.5 mm fraction) in scanning electron microscope images (Figures C-31 to C-33). 

Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: The smooth-skinned, droplet-like pyroclasts are sideromelane (basaltic glass). The angular, rough-surfaced 
grains are tachylites; those with smooth, glassy vesicle walls are glassy tachylites. The rounded, 
rough-surfaced grains are fine-grained tuff. Scale: width of image is about 1.4 mm. 
Figure C-31. Scanning Electron Micrograph of the 0.125- to 0.250-mm Fraction of Sample DK-LW-014 
Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: Same description for pyroclast types as previous figure. Scale: width of image is about 1.4 mm. 
Figure C-32. Scanning Electron Micrograph of the 0.125- to 0.250-mm Fraction of Sample DK-LW-018 

Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: The difference between this sample and those from lower in the section is the rounding and edge 
modification of many of the particles, implying grain interactions. Scale: width of image is about 1.4 mm. 
Figure C-33. Scanning Electron Micrograph of the 0.125- to 0.250-mm Fraction of Sample DK-LW-019 
Stratigraphic Section at N36 42'44.3., W116 30'55.3,. and elevation 890.0 m (2,915 feet), 
located 2.5 km NNW of the summit crater of the Lathrop Wells volcano. 
This section and other nearby exposures of primary or reworked tephra are located in small 
drainages on the south-facing slopes of the low hills approximately 2.5 km north of the cone 
(Figure C-34). 
Source: Krier and Harrington (2003) [DIRS 164023], p. 10, 13-14. 
Figure C-34. Tephra Fall Stratigraphy for Section B 

Grain Size VariationsThe measured grain size variations for this section are given in 
Table C-16 and Figure C-35. 
Table C-16. Grain Size Variations in Tephra Fall for Section B 
Sample Number Mdf (median) sf (sorting) Md (mm) 
DK-LW-007 0.15 1.75 0.90 
DK-LW-006 0.32 1.19 0.80 
DK-LW-005 0.62 1.25 0.65 
DK-LW-004 -0.38 1.20 1.30 
Source: Values calculated from data in DTN: LA0302GH831811.002 [DIRS 162864] or 
from Figure C-35 
Mdf. (median) = median grain size in f units (defined in Section 6.1.3.5) 
sf. (sorting) = (f84  f16)/2 (defined in Section 6.1.3.5) 
Md (mm) = median grain size in mm
Source: DTN: LA0302GH831811.002 [DIRS 162864].
Figure C-35. Grain Size Variations in Tephra Fall for Section B 

Pyroclast TypesPyroclast types, in vol% and determined with binocular examination of 
300 grains in the 0.5 to 1.0 mm size fractions, are listed in Table C-17. 
Table C-17. Percent Pyroclasts in Samples in Tephra Section B 
Sample 
Number Tachylite 
Glassy 
Tachylite Sideromelane 
Feldspar + Olivine 
Phenocrysts 
Tuff 
Clasts 
DK-LW-007 63.3 26.6 9.6 0.3 0 
DK-LW-006 75.3 15.0 8.6 0.6 0 
DK-LW-005 31.3 21.6 39.0 0.6 7.3 
DK-LW-004 52.3 37.6 10.0 0 0 
Source: DTN: LA0302GH831811.004 [DIRS 162866]. 
NOTE: Estimated Error =  0.3 percent. 
Distal ashfallPrimary tephra deposits from the Lathrop Wells volcano have not been located 
beyond about 2.5 km north of the cone. Reworked basaltic ash has been identified in several 
trenches excavated along 3 faults at distances of 10 km (Windy Wash fault, Whitney et al. 1996 
[DIRS 107313], p. 4.9-12), 12 km (Fatigue Wash fault, Coe et al. 1996 [DIRS 101527], 
pp. 4.8-9, 4.8-12), and 14 km (Solitario Canyon fault) north of the cone (Ramelli et al. 1996 
[DIRS 101106], pp. 4.7-114.7-12). The trenches were previously excavated as part of the YMP 
seismic hazards program. 
Basaltic ash in each occurrence was found as a fissure-filling unit within fault-plane deposits and 
ranged from an ash component in matrix of coarse cobbles (e.g., Windy Wash fault) to a nearly 
pure ash deposit (trench T8, Solitario Canyon fault). The ash within the Solitario Canyon fault 
was correlated to Lathrop Wells volcano tephra by geochemical analysis of trace elements 
(Perry et al. 1998 [DIRS 144335], pp. 4-254-26). The ash particles, along with other volcanic 
and carbonate clasts, fill the bottom 1 m of the narrow fissure and appear to have been 
transported over short distances down-slope to their present position when the fissure was open. 
Another occurrence of ash is found on the west side of Busted Butte, about 11 km E-NE of 
Lathrop Wells volcano. Basaltic ash was noted within drainage sediments in the wash near 
outcrops of Paintbrush Tuff (Volcanism Field Notebook TWS-EES-13-LV-01-93-05 [Crowe 
1996 (DIRS 164317)], p. 54). Only trace amounts were seen under binocular microscope, and 
positive correlation with the Lathrop Wells eruption has not been made. 
These distal occurrences of basaltic tephra, of which at least one is correlated with the Lathrop 
Wells eruption, are used for estimations of ash volume from the Lathrop Wells volcano eruption, 
discussed below. 
At other locations distant from the cone, small amounts of basaltic ash are found scattered on 
ground surfaces, concentrated as part of coarse sand deposits in small gullies, or preserved in 
banks along small drainages. An example of the latter occurrence is found on the south slopes of 
the hills, approximately 1.6 km west-southwest of the cone (Figure C-2). None of these ashes 
are positively correlated with the Lathrop Wells volcano. 

C4. LATHROP WELLS VOLCANOVOLUME ESTIMATIONS 
Locations and thicknesses of Lathrop Wells volcano tephra were used to develop a 
1:72,000 scale isopach map for the area around the cone (Figure C-8). Lines representing equal 
tephra thicknesses (isopachs) were hand-drawn through the tephra thickness data 
(LA0305DK831811.001 [DIRS 164026]) to estimate distribution and volume of the ash from the 
eruption. Two occurrences of distal ash at Solitario Canyon and Busted Butted described in 
Section C3.1 were also included. Isopachs of 300, 200, 100, 50, 10, and 1 cm were drawn. 
Based on this map, the area covered by at least 1 cm of tephra is approximately 182 km2. Two 
limitations of this estimate are 1) data are unavailable for tephra thicknesses less than 1 cm and 
2) the area south of the cone is devoid of data, biasing the distribution largely to the north and 
west of the cone. 
Table C-18 lists values for volumes of the Lathrop Wells tephra, lava, and cone. Tephra volume 
estimates were made by two methods. The first used a planimeter for calculating areas between 
neighboring isopachs and multiplying by the mid-value between them. This method gives a 
tephra volume of 0.039 km3. The second method used the volume equation developed by Pyle 
(1989 [DIRS 123891]), further evaluated by Fierstein and Nathenson (1992 [DIRS 162804], 
p. 160), that accounts for the observation that most tephras thin exponentially away from the 
source: 
Volume = (2T0)/(k2) (Eq. C-2) 
where 
T0 is the thickest tephra (extrapolated, as necessary) 
k is the slope of the line on a lnT versus (area)1/2 plot. 
The Pyle method yields a tephra volume of 0.037 km3, but also accounts for thicknesses beyond 
the 1 cm isopach, whereas the planimeter method did not. Lava flow estimates were also made 
by planimeter; area covered by lava flows is 1.946 km2. A field-derived estimated mean 
thickness of 15 m was used for the flows to obtain lava volume of 0.0292 km3. Cone volume, 
0.018 km3, was calculated using the standard cone formula and a mean radius of 700 m. No 
correction was made for any potential erosion from the top of the cone. The Lathrop Wells 
volcano volumes in Table C-18 are the recommended estimates for use in calculations. 

Table C-18. Volumes of Lathrop Wells Cone, Lava, and Tephra 
Lathrop Wells Cone 
Cone 
(km3) 
Lavas 
(km3) 
Tephra 
(km3) 
Total 
(km3) Comments 
Planimetera 0.018 0.0292 0.039 0.0862 Best estimate of event volume 
Method of Pyle (1989 
[DIRS 123891]) for falloutb   0.037  
Perry et al. 1998 
[DIRS 144335], p. 3-39    0.14 Assumed ash ~5X cone volume 
Source: Output DTN: LA0305DK831811.002. 
a 
Planimeter: Cone volume calculated as V = (1/3)pr2h, where r = 350 m and h = 140 m. Volumes of lavas and 
b 
fallout tephra are from planimeter areas. 
"Method of Pyle": Fallout tephra volume calculated using Pyle (1989 [DIRS 123891]). See also Fierstein and 
Nathenson (1992 [DIRS 162804]). 
C5. EXPLOSIVE ERUPTION MECHANISMS AND SEQUENCE FOR THE LATHROP 
WELLS VOLCANO AND TEPHRA FALL 
Evidence for variations in the eruption phenomena that built the Lathrop Wells volcano can be 
found in the tephra fallout sequence. Representative fallout sections are used here to illustrate 
these variations. The descriptions of these beds are tied to a general model of scoria cone 
formation (Figure C-36) proposed by McGetchin et al. (1974 [DIRS 115469]): 
A. Within a kilometer of the vent, the earliest eruption phase deposited moderately sorted 
coarse ash with up to 52 percent vesicular sideromelane droplets (Figure C-37). These 
are similar in shape and composition to glassy droplets produced in fire (lava) 
fountains. The fire fountaining could have been from a N-S-trending fissure (parallel 
to the long axis of the oval-shaped Lathrop Wells volcano and equivalent to stages 1 
and 2 in Figure C-36). The predominantly glassy droplets imply a largely unimpeded 
spray of melt from a vent or fissure. Some conduit opening is implied from the 
7.6 percent tuff lithic clasts in the ash. Closer to the vent, a greater proportion of 
tachylite and glassy tachylite than sideromelane is present, indicating that some 
quench-crystallization was occurring within the rising magma, possibly due to 
avalanching of scoria and ash back down the incipient crater slopes to intermittently 
block the vent. There are four or five repeating, upward coarsening tephra sequences 
in the lowest 125 cm of the observed section, with no recognized unconformities. This 
can be interpreted either as a continuous pulsing eruption manifest at the surface or 
the result of varying wind directions during this part of the eruption. 

Source: McGetchin et al. (1974 [DIRS 115469], p. 3268). 
NOTES: In stages 1 and 2, nearly all tephra are deposited ballistically (with the exception of finer material carried 
away by the wind). Much of this activity could be characterized as lava fountaining. At the Lathrop Wells 
volcano, this sequence would include hydrovolcanic activity that formed hydrovolcanic beds outside the 
low-rimmed scoria ring. Early activity could have consisted of fountaining along a fissure, accounting for 
the N-S elongation of the cone. 
In stages 3 and 4, cone growth is accompanied by Strombolian activity consisting of bursting gas bubbles 
in ponded lava; blockage of the vent by the slumping of unconsolidated ejecta leads to intermittent 
Strombolian blasts. Occasional interbeds of hydrovolcanic tephra reflect intermittent interaction with 
groundwater. 
Talus is shown in gray. 
Figure C-36. Stages of Scoria Cone Formation 

NOTES: For Illustration purposes only. 
: The sample, located 850 m NW of the summit of the Lathrop Wells volcano, has mostly vesicular 
sideromelane (basaltic glass) pyroclasts with fluidal surface textures. Scale: width of image is 
approximately 617 m. 
Figure C-37. Pyroclasts from Fallout Sequence in the 0.125- to 0.250-mm Fraction of Sample 
DK-LW-021 
B. The tephra sequence immediately northwest of the Lathrop Wells volcano is 
representative of the hydrovolcanic phase of the eruption (Vaniman and Crowe 1981 
[DIRS 101620], p. 21; Wohletz 1986 [DIRS 140956], p. 262). Hydrovolcanic activity 
requires that rising magma come into contact with water in an aquifer(s) or a shallow 
water body at the ground surface (Fisher and Schmincke 1984 [DIRS 162806], 
pp. 231-234; Wohletz and Heiken 1992 [DIRS 105544], pp. 85-134). The resulting 
steam explosion finely fragments the magma and produces large amounts of kinetic 
energy. If the encounter occurs below the ground surface, the host rocks are highly 
fractured and the eruption products contain more lithic clasts. Hydrovolcanic deposits 
consist mostly of ash deposited in density currents (surges), leaving distinctive thin 
planar beds and cross-beds, which are typical of the sequence immediately northwest 
of Lathrop Wells volcano. At Lathrop Wells volcano, median grain size for this tephra 
sequence ranges from 0.15 mm to 0.5 mm (an interbedded fall layer has a mean grain 
size of 1.5 mm) (Figure C-38). Volume fractions of lithic clasts in the fine-grained ash 
deposits range from 0.003 to 0.036 and consist mostly of white tuff and rounded 
quartz and feldspar sand grains. The presence of rounded quartz and feldspar grains 
and tuff xenoliths in the hydrovolcanic deposits suggest the water-magma encounter 
may have occurred in the shallow surficial deposits upon which the cone was built. 
Crowe et al. (1986 [DIRS 101532], p. 38) ascribe the dominant tuff xenolith to the 
Tiva Canyon Tuff, which forms most of the surface outcrops in the area and is also a 
major constituent of the surficial colluvium. Because of the minimum 1-m thickness 
of tephra fall beneath the hydrovolcanic beds, this hydrovolcanic event occurred 
during the early phases of the eruption. 

Source: Plotted values are derived from data in DTN: LA0302GH831811.002 [DIRS 162864] 
NOTE: The hydrovolcanic surge deposits are commonly finer-grained (higher phi number) than the scoria (tephra) 
fall deposits. Phi (f) numbers are defined in Section 6.1.3.5. 
Figure C-38. Median diameter versus sorting of tephra deposits around the Lathrop Wells volcano 
Most basaltic hydrovolcanic pyroclasts in hydrovolcanic deposits are glassy and have 
low vesicularity and blocky shapes (Heiken and Wohletz 1985 [DIRS 106122], p. 13). 
However, in many examples, there is some rounding, perhaps by grain-to-grain 
interactions in surges. Pyroclasts in hydrovolcanic surge deposits of the Lathrop Wells 
volcano are characterized by considerable edge modification (rounding). For 
comparison, Figures C-39 and C-40 are images of pyroclasts from fall and surge 
deposits that have very similar pyroclast types. The rounding of pyroclasts is evident 
in the hydrovolcanic tephra (Figure C-38). The rounding and edge modification of 
tachylitic pyroclasts is even more evident when looking at individual grains 
(Figure C-39). 

(a) (b) 
Source: (a) DTN: LA0302GH831811.004 [DIRS 162866]; (b) For illustration purposes only. 
NOTES: The left panel is from fall deposits 780 m NW of the Lathrop Wells volcano (Sample DK-LW-022, 0.125- to 
0.250-mm fraction). Most pyroclasts are tachylite or glassy tachylite with rough grain surfaces and delicate 
edges. Scale: width of image is about 1.3 mm. This image is part of the image shown in Figure C-26. 
The right panel is from surge deposits 700 m NW of the Lathrop Wells volcano (Sample DK-LW-048, 
0.125- to 0.250-mm fraction). Note the degree of rounding of all pyroclast types. Scale: width of image is 
about 1.4 mm. 
Figure C-39. Scanning Electron Micrographs Showing Differences in Fall Deposits (left) Versus Surge 
Deposits (right) of Hydrovolcanic Tephra 

(a) (b) 
Source: (a) DTN: LA0306GH831811.001 [DIRS 171286]; (b) For illustration purposes only. 
NOTES: The left panel is of pyroclasts from fall deposits 780 m NW of Lathrop Wells volcano (sample DK-LW-024, 
0.125- to 0.250-mm fraction). In the center is a tachylite pyroclast, with typical quench textures, angular 
shape, and sharp edges. The edge of the vesicle wall is visible in the lower left corner of the grain. In 
contrast is the small vesicular sideromelane pyroclast at the bottom of the image. Scale: width of image is 
about 400 m. 
The right panel is of pyroclasts from surge deposits 700 m NW of Lathrop Wells volcano (sample 
DK-LW-049, 0.125- to 0.250-mm fraction). This tachylite pyroclast has been mechanically rounded. 
Scale: width of image is about 300 m. 
Figure C-40. Scanning Electron Micrographs of Individual Grains Showing Differences in Fall Deposits 
(left) Versus Surge Deposits (right) of Individual Grains of Tephra 
C. Later cone-forming activity deposited moderately sorted lapilli with 81 percent to 92 
percent tachylite and glassy tachylite pyroclasts (Figures C-41 and C-42). These are 
similar to ash and lapilli formed during later stages of scoria cone construction 
(Figure C-36, stages 3 and 4). During later stages of cone formation, avalanching of 
scoria and ash down crater slopes blocked the vent. Sporadic blasts carried out a 
mixture of scoria bombs, comminuted fragments of partly crystalline melt (quenched) 
and recycled scoria bombs, lapilli, and ash that slumped into the crater. Lithic clast 
concentrations are low in these tephra fall deposits. 
D. An abrupt transition, exposed within the lower quarry wall, from coarse scoria lapilli 
to fine lapilli and ash, is inferred to mark an increase in eruption energy from 
Strombolian to violent Strombolian. The sudden abundance of lapilli and ash on the 
upper slopes of the cone became oversteepened and continuously avalanched 
downslope to be deposited as debris-flow material along with primary material raining 
down from an eruption column. The lapilli and ash directly overlie the coarser 
non-welded scoria representative of more Strombolian-like eruption (Figure C-3). The 
large volume of lapilli and ash from this eruption phase, making up to an estimated 
two-thirds of the cone, is the main product of the mining operations at the cone. The 
bulk of the ashfall that is mapped beyond the scoria cone is inferred to be related to 
this phase of the eruption. 

Source: Heiken 2003 [DIRS 171289]. 
NOTE: The sample, located 850 m NW of the summit of the Lathrop Wells volcano, has angular, blocky tachylite 
(center) and glassy tachylite (top and bottom), which are characteristic of later stages in Strombolian 
eruptions. Scale: width of image is about 600 m. 
Figure C-41. Pyroclasts from Fallout Sequence in the 0.125- to 0.250-mm Fraction of Sample DK-LW-023 
NOTES: For Illustration purposes only. 
Quench crystals, including laths of pyroxene and plagioclase, surrounded by dendritic growths of pyroxene 
and Fe-Ti oxides are visible on the tachylite pyroclast surface. Scale: width of image is about 100 m. 
Figure C-42. Detailed View of Tachylite Grain Surface 
E. Quarry exposures of the cone suggest cone building continued largely unabated. An 
event toward the end of the eruption deposited nearly a half-meter of inward dipping, 
thin planar ash beds and cross beds, interpreted as hydrovolcanic in origin. Rounded 
quartz grains, although not numerous in the deposit, suggest this event may have 
occurred, once again, at shallow depth in or near the elevation of pre-volcanic surficial 
deposits. Shallow groundwater in alluvium or sand ramp deposits is inferred to have 
reached the near-surface conduit system, providing for a steam explosion. Above 

these fine-grained beds, coarse scoria deposits suggest the abrupt return to the less 
violent eruptive phase that preceded this brief hydrovolcanic event. These scoria 
deposits are the last observed units to be deposited on the cone.