Abstracts for the October 2012 Meeting on Volcanism 

in the American Southwest, Flagstaff, Arizona

Edited By Jacob B. Lowenstern

Open-File Report 2013–1026

U.S. Department of the Interior 

U.S. Geological Survey 
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2013 

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Lowenstern, Jacob B., ed., 2013, Abstracts for the October 2012 meeting on Volcanism in 

the American Southwest, Flagstaff, Arizona: U.S. Geological Survey Open-File Report 

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iii

Contents

Introduction..................................................................................................................................................... iv

List of Organizers ............................................................................................................................................v

List of Attendees..............................................................................................................................................v

List of Abstracts............................................................................................................................................ viii

Abstracts .........................................................................................................................................................1 

Meeting Agenda ............................................................................................................................................36

Conversion Factors

Multiply By To obtain

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

cubic foot per second (cfs) 0.02832 cubic meter per second (m3/s)
iv

Abstracts for the October 2012 Meeting on Volcanism

in the American Southwest, Flagstaff, Arizona

Edited by Jacob B. Lowenstern

Introduction

Though volcanic eruptions are comparatively rare in the American Southwest, the States of 

Arizona, Colorado, New Mexico, Nevada, and Utah host Holocene volcanic eruption deposits 

and are vulnerable to future volcanic activity. Compared with other parts of the western United 

States, comparatively little research has been focused on this area, and eruption probabilities are 

poorly constrained. Monitoring infrastructure consists of a variety of local seismic networks, and 

“backbone” geodetic networks with little integration. Emergency response planning for volcanic 

unrest has received little attention by either Federal or State agencies. 

On October 18–20, 2012, 90 people met at the U.S. Geological Survey campus in 

Flagstaff, Arizona, providing an opportunity for volcanologists, land managers, and emergency 

responders to meet, converse, and begin to plan protocols for any future activity. Geologists 

contributed data on recent findings of eruptive ages, eruption probabilities, and hazards extents 

(plume heights, ash dispersal). Geophysicists discussed evidence for magma intrusions from 

seismic, geodetic, and other geophysical techniques. Network operators publicized their recent 

work and the relevance of their equipment to volcanic regions. Land managers and emergency 

responders shared their experiences with emergency planning for earthquakes.

The meeting was organized out of the recognition that little attention had been paid to 

planning for or mitigation of volcanic hazards in the American Southwest. Moreover, few 

geological meetings have hosted a session specifically devoted to this topic. This volume 

represents one official outcome of the meeting—a collection of abstracts related to talks and 

poster presentations shared during the first two days of the meeting. In addition, this report 

includes the meeting agenda as a record of the proceedings.

One additional intended outcome will be greater discussion and coordination among 

emergency responders, geologists, geophysicists, and land managers regarding geologic hazards 

in the Southwest.
v

Meeting organizers

Jacob B. Lowenstern, U.S. Geological Survey, Menlo Park, California 

Laz Kestay, U.S. Geological Survey, Flagstaff, Arizona 

Nelia Dunbar, New Mexico Bureau of Mines and Geology, Socorro, New Mexico 

Michael Ort, Northern Arizona University, Flagstaff, Arizona 

Greg Valentine, University at Buffalo, Buffalo, New York 

Susan Perry, U.S. Geological Survey, Pasadena, California 

John Bwarie, U.S. Geological Survey, Pasadena, California 

List of Attendees

Alfano, Fabrizio, Arizona State University, Tempe, Arizona 

Allison, Chelsea, Arizona State University, Tempe, Arizona

Aster, Rick, New Mexico Tech, Socorro, New Mexico

Aubele, Jayne, New Mexico Museum of Natural History and Science

Birch, Scott, National Weather Service, Salt Lake City, Utah

Bischoff, Judy, National Park Service, Flagstaff, Arizona

Blackwell, Wendy, New Mexico DHSEM Preparedness Bureau

Bowman, Steve, Utah Geological Survey, Salt Lake City, Utah

Brumbaugh, David, Northern Arizona University, Flagstaff, Arizona

Bwarie, John, USGS Pasadena, California (Science Applications for Risk Reduction)

Chamberlin, Richard, New Mexico Bureau of Geology, Socorro, New Mexico

Champion, Duane, USGS Menlo Park, California

Chung, Diane, National Park Service, Flagstaff, Arizona

Clarke, Amanda, Arizona State University, Tempe, Arizona

Connor, Chuck, University of South Florida, Tampa, Florida

Conway, Michael, Arizona Geological Survey, Tempe, Arizona

Cortes, Joaquin, University at Buffalo, Buffalo, New York

Courtland, Leah, University of South Florida, Tampa, Florida

Cousens, Brian, Carleton University, Ottawa, Canada

Crumpler, Larry, NM Museum of Natural History and Science

Driedger, Carolyn, USGS, Vancouver, Washington

Duffield, Wendell, Retired, Northern Arizona University, Flagstaff, Arizona

Dunbar, Nelia, New Mexico Tech, Socorro, New Mexico
vi

Earle, Paul, USGS National Earthquake Information Center (Denver, Colorado)

Elson, Mark, Desert Archaeology, Inc., Flagstaff, Arizona

Ewert, John, USGS, Vancouver, Washington

Finn, Carol, USGS, Denver, Colorado

Goff, Cathy, Retired, USGS, Losa Alamos, New Mexico

Goff, Fraser, Retired, Los Alamos National Laboratory, New Mexico

Greco, Deanna, National Park Service, Flagstaff, Arizona

Haller, Miguel, Univ. Nac. de Patagonia, Argentina

Hammond, Bill, University of Nevada, Reno

Harburger, Aleeza, University of South Florida, Tampa, Florida

Henry, Chris, Nevada Bureau of Mines and Geology, Reno, Nevada

Hintz, Amanda, Utah Geological Survey, Salt Lake City, Utah

Jackson, Christina, Coconino County Public Health Services District, Flagstaff, Arizona

Johnsen, Racheal, University of Nevada, Las Vegas

Johnson, Peter, University at Buffalo, Buffalo, New York

Judge, Shelley, College of Wooster, Wooster, Ohio

Karlstrom, Leif, Stanford University, Stanford, California

Kestay, Laz, USGS Flagstaff, Arizona

Kopcik, Ron, Arizona Division of Emergency Management, Tucson, Arizona

Koper, Keith, University of Utah, Salt Lake City, Utah

Kuentz, Dave, Miami University, Oxford, Ohio

Lee, Jeff, Coconino County Emergency Management, Flagstaff, Arizona

Lefebvre, Nathalie, University of Otago, Dunedin, New Zealand

Lorenz, Volker, University of Würzburg, Germany

Lowenstern, Jacob, USGS Menlo Park, California

McIntosh, Bill, New Mexico Tech, Socorro, New Mexico

Murray, Tom USGS Anchorage, Alaska

Neal, Tina, USGS Anchorage, Alaska

Norris, Bob, Retired Seismologist, Flagstaff, Arizona

Nushart, Nate, University of South Florida, Tampa, Florida

Ort, Michael, Northern Arizona University, Flagstaff, Arizona

Osiensky, Jeff, National Weather Service, Anchorage, Alaska

Penn, Ruthanne., Coconino County Emergency Management, Flagstaff, Arizona

Perry, Sue, USGS Pasadena, California (Science Applications for Risk Reduction)

Pollock, Meagen, College of Wooster, Wooster, Ohio

Poole, Jason, Federal Aviation Administration, Seattle, Washington
vii

Ramsey, Dave, USGS Vancouver, Washington

Richardson, Jacob, University of South Florida, Tampa, Florida

Riggs, Nancy, Northern Arizona University, Flagstaff, Arizona

Roggensack, Kurt, Arizona State University, Tempe, Arizona

Rowley, Robert L., Coconino County Emergency Management, Flagstaff, Arizona

Self, Steve, Nuclear Regulatory Commission, Alameda, California

Smith, Gene, University Nevada, Las Vegas, Nevada

Stanley, Ellis, Dewberry, Inc., Atlanta, Georgia

Stovall, Wendy, USGS Menlo Park, California

Taylor, Andrew, National Weather Service, Flagstaff, Arizona

Thompson, Katherine, Columbia University, New York, New York

Trammell, Darlene, Arizona Division of Emergency Management, Tucson, Arizona

Trammell, Lou, Arizona Division of Emergency Management, Tucson, Arizona

Turner, Jessica, USGS, National Earthquake Information Center, Denver, Colorado

Valentine, Greg, University at Buffalo, Buffalo, New York

Vaughan, Greg, USGS, Flagstaff, Arizona

Vazquez, Jorge, USGS, Menlo Park, California

Venzke, Ed, Smithsonian Global Volcanism Program, Washington, DC

White, James, University of Otago, Dunedin, New Zealand

Whitefield, Paul, Flagstaff Area National Monuments, Flagstaff, Arizona

Widom, Liz, Miami University of Ohio, Oxford, Ohio

Zimmerer, Matt, New Mexico Tech, Socorro, New Mexico
Volcanism in the American Southwest

Abstracts

Monitoring and Geophysics 

Communications and Mitigation 

Page Authors Institution Title Type

2 Aster et al. New Mexico 

Tech

Earthquakes in the Central Rio Grande Rift 

and the Socorro Magma Body 

P 

4 Brumbaugh NAU Seismic monitoring of the San Francisco 

volcanic field 

P 

16 Hammond U. Nevada 

Reno 

Potential contributions of geodesy to 

monitoring volcanic unrest in the southwest 

United States 

O 

22 Koper et al. U. Utah Capabilities of University of Utah 

Seismograph Stations for monitoring 

seismicity in Utah 

P 

23 Lu et al. USGS InSAR mapping of Holocene volcanoes in 

the western conterminous U.S. – preliminary 

results 

P 

10 Crumpler et 

al.

New Mexico 

Museum of 

Natural 

History and 

Science 

The New Mexico volcano collection and 

resource: Volcanoes of New Mexico website 

developed by the New Mexico Museum of 

Natural History and Science 

P 

11 Driedger USGS Volcano work groups and effective 

communication partnerships for volcanic 

hazards education 

P 

13 Elson and 

Ort 

Desert 

Archaeology, 

Inc. 

Human adaptation to catastrophic events: 

Lessons from the 11th Century CE eruption 

of Sunset Crater volcano 

O 

24 Neal USGS Pondering the consequences of an eruption 

in the American Southwest: Challenges for 

emergency management and scientific 

response 

O 

25 Osiensky 

and Birch 

NOAA/NWS Volcanic ash plumes and impact to aviation 

in the western United States 

O 

26 Ramsey and 

Driedger 

USGS Spatial database of Holocene and Latest 

Pleistocene volcanic vents in the western 

conterminous U.S. 

29 Thompson Columbia U. The view from Social Science: How people 

will think and behave during an extended 

crisis with large uncertainties. 

O 
Geology 

32 Venzke Smithsonian Data compiled by the Smithsonian about 

volcanoes in the southwestern United States 

P 

1 Alfano et al. Arizona State 

Univ. 

Characterization of the 1000 AD Sunset 

Crater eruption and its pyroclastic products 

P 

3 Bleacher et 

al.

NASA 

Goddard 

Surface textures and relationships indicative 

of endogenous growth at the McCartys and 

Carrizozo flow fields, New Mexico 

P 

5 Chamberlin 

et al. 

New Mexico 

Tech

Ignimbrite calderas and a large radiating 

mafic dike swarm of Oligocene age, Rio 

Grande Rift, New Mexico: Possible 

implications to restless calderas 

P 

6 Cortés et al. U. Buffalo Intrinsic conditions of magmas in Lunar 

Crater Volcanic Field, Nevada 

P 

7 Courtland et 

al.

University 

South Florida 

Into the cone: a ground penetrating radar 

study of cone-building processes at Cerro 

Negro volcano, Nicaragua 

P 

8 Cousens 

and Henry 

Carleton Univ. Geochemistry and hazard assessment of 

Pliocene-Quaternary volcanism beneath the 

central Sierra Nevada and adjacent Great 

Basin, northern California and western 

Nevada 

P 

9 Crumpler et 

al.

New Mexico 

Museum of 

Natural 

History and 

Science 

Environmental consequences of large 

volume lava flow fields in the southwest: 

Preliminary inferences from mapping the 

McCartys lava flow field, New Mexico 

P 

12 Dunbar and 

McIntosh 

New Mexico 

Tech

Volcanism in New Mexico: Past activity and 

future expectations: Zuni-Bandera volcanic 

field, Valles caldera, Socorro magma body, 

and beyond 

O 

14 Goff UNM Eruption potential and hazard, Valles 

Caldera, New Mexico 

O 

15 Haller and

 Frumento

Univ. Nacional 

de la Patagonia 

Estimating remobilization rate of ash 

deposited during the Puyehue (Southern 

Andes) eruption in 2011 

P 

17 Henry and 

Cousens 

NV Bureau of 

Mines and 

Geology 

Young volcanism of the Lake Tahoe–Reno–

Fallon area, California and Nevada: The 

geologic record 

P 

18 Johnson et 

al.

U. Buffalo Tephra dispersal and deposition from the 

Marcath eruption, Lunar Crater volcanic 

field, Nevada 

P 
19 Karlstrom 

et al. 

Stanford Univ. Focusing of melt by magma chambers in 

time and space: Theory and application to 

Mount Mazama, Crater Lake, Oregon 

P 

20 Keszthelyi USGS Modeling mafic lava flows with an eye to 

emergency response 

O 

21 Kiyosugi et 

al.

U. South 

Florida 

Relationship between dike and volcanic 

conduit distribution in a highly eroded 

monogenetic volcanic field: San Rafael, 

Utah

P 

27 Roggensack 

and Moore 

ASU Experimental determination of H2O and CO2

solubility in basalt and basaltic andesite 

P 

28 Self NRC Scenario for an eruption in the San 

Francisco Peaks or similar volcanic field: 

Effects on northern Arizona and beyond 

O 

30 Valentine 

and Ort 

U. Buffalo Basaltic volcanism in the American 

Southwest over the last million years: What 

happens here, how often, and why? 

O 

31 Vazquez et 

al.

USGS Timing of late Pleistocene volcanism at Big 

Pine volcanic field: insights from volcanic 

stratigraphy, cosmogenic 36Cl dating and 

paleomagnetism. 

P 

33 White Otago, NZ Uncertainties regarding explosive maardiatreme eruptions within volcanic fields P 

34 Widom et 

al.

Miami U. 

(OH) 

Petrogenetic processes in the Lunar Crater 

volcanic field, Nevada 

P 

35 Zimmerer 

and 

McIntosh 

New Mexico 

Tech

Postcaldera magmatism at three RioGrande-rifted calderas: Implications for 

assessing volcanic hazards at active caldera 

systems in the USA 

P 
Characterization of the 1000 AD Sunset Crater eruption and its pyroclastic products 

Fabrizio Alfano1, Laura Pioli2, Amanda Clarke1, Michael Ort3, Stephen Self3

1. School of Earth and Space Exploration (Arizona State University, USA); 2. Department of Mineralogy 

(University of Geneva, Switzerland); 3. Department of Environmental Sciences and Geology (North Arizona 

University, USA); 4. CEPSAR (The Open Universty, UK). 

Sunset Crater is a >300 m high scoria cone located ~25 km northeast of Flagstaff, AZ (USA). It is 

the youngest of about 600 scoria cones in the San Francisco Volcanic Field and the only one active in the 

Holocene (1064-1067 A.D.). The eruption produced three lava flows that cover ~8 km2, a scoria blanket 

up to 12 m thick covering an area of about 500 km2, and minor spatter cones and ramparts that marked the 

onset of the eruption (Amos, 1986; Ort et al., 2008). Pre-historical communities living in the area were 

heavily influenced by the eruption (Ort et al., 2008). The tephra sequence, as described in Amos (1986), 

consists of at least eight fall units associated with major explosive phases. The units are generally lithic 

poor, well sorted, non-welded, even at proximal locations, and inversely graded, with an average bulk 

density of about 1.5 x 103 kg/m3, dispersed to the E and W (Amos 1986). Additional fieldwork conducted 

in September 2010 has pointed to more complexity than previously presented. In proximal areas, the 

sequence also includes cm-thick coarse ash layers, and multiple layering within the main units. These 

complexities may explain bilobate dispersal patterns exhibited by some of the original stratigraphic units 

(Amos, 1986). Their volume was estimated using the Weibull fitting method (Bonadonna and Costa 

2011) and varies between 0.02 and 0.08 km3 DRE, with the maximum value estimated for the Unit 3 

deposit (0.08 km3 DRE) and the total cumulative volume is estimated to be 0.3 km3 DRE. This value is 

close to the volume calculated based on the total deposit isopach map from Ort et al (2008) (0.4 km3

DRE). The associated column heights calculated using the Carey and Sparks (1986) method, based on the 

maximum clast distribution of Amos (1986), are between 7 km (Unit 2) and 25 km (Unit 3). These values 

have a high degree of uncertainty due to a paucity of data preventing good constraints on isopleths maps. 

Scoria clasts are porphyritic with the main phenocryst assemblage consisting of plagioclase, olivine and 

rare clinopyroxene crystals with longest axis to up to 0.5 mm, and variable groundmass crystallinity 

(plagioclase, olivine and Fe oxides), ranging from glassy to almost completely crystalline. They show 

only minor compositional variations along the sequence. The variability can be relevant both within and 

among clasts, but the largest percentages of glassy scoria are associated with the largest fallout units. 

Scoria vesicles are rounded to elongated with diameters up to 1 mm, and often show non-homogeneous 

distribution suggesting post-fragmentation expansion and coalescence. Olocrystalline clasts also display a 

diffuse vesicularity characterized by small vesicles (hundreds to tens of microns) with shapes controlled 

by the surrounding crystals. Large xenocrysts of pyroxene characterized by rounded morphologies and 

reaction rims are frequently observed. 

References

Amos, R.C., 1986, Sunset Crater, Arizona-evidence for a large magnitude strombolian eruption: M.S. thesis, Arizona State 

University, Tempe, 165 p. 

Bonadonna C, Costa A (2012) Estimating the volume of tephra deposits: a new simple strategy, Geology, doi: 10.1130/G32769.1 

Carey, S. N. and R. S. J. Sparks (1986). Quantitative models of the fallout and dispersal of tephra from volcanic eruption 

columns. Bulletin of Volcanology 48: 109-125. 

Ort, M. H., M. D. Elson, K. C. Anderson, W. A. Duffield, J. A. Hooten, D. E. Champion and G. Waring (2008). Effects of scoriacone eruptions upon nearby human communities. Geological Society of America Bulletin 120(3-4): 476-486. 
Earthquakes	in	the	Central	Rio	Grande	Rift and	the	Socorro	Magma	Body

Richard	Aster,	Susan	Bilek,	Jana	Stankova,	Emily	Morton

Department	of	Earth	and	Environmental	Science

New	Mexico	Institute	of	Mining	and	Technology

Socorro,	NM	87801

The Socorro	Seismic	Anomaly	(SSA),	occupies	just	2%	(~	5,000	km2

)	of	the area	of	New	Mexico	but is	

responsible	for	20-40%	of	magnitude	≥	2.0	events in	the	60-year	instrumental	record.	This relatively	high	

rate	of seismicity	is	due	to	the	presence	of	an	inflating	(~2	mm/year maximal	surface	uplift),	

predominantly thin,	mid-crustal	magma	body	(the	Socorro	Magma	Body;	SMB)	with an	upper	surface at	

~19	km	depth.		The	SMB	bears	similarities	to	other	interpreted	magmatic	seismic	“bright	spots”,	such	as	

one	noted	from	COCORP	studies	near	Death	Valley	as	well	as	others	in	the	Basin	and	Range	province.		

Reflected phases	of	microearthquake	seismograms	recorded	above	the	SSA and	COCORP	active	seismic	

studies were	initially	used	to	define	the	depth	and	the	extent	of	this	feature.	More	recently,	InSAR	

studies	confirmed	and	refined	the	boundaries	of	the	associated	uplift.	 Over	the	last	few	decades	many	

hundreds	of magnitude	≥	2.0	earthquakes	have	been	recorded	in	the	SSA.	The	largest	events	in	the	

historical record	occurred in	1906	as	part	of	a	protracted	(multi-year)	swarm,	and	have	been	estimated	

to	about	magnitude	5.8.		Typically,	notable earthquake events in	the	SSA	occur	as	a	part	of	a	seismic	

swarm lasting	few	days	to	a	few	weeks.		Only	about	1-3	events	from	such	sequences	are	typically	felt	

and	reach	magnitude	≥	2.0.		As	expected	in	a	rifting	environment,	most	of	these	events	represent

movement	along	normal	faults,	sometimes	with	a	strike-slip	component. Recent	volcanism	in	the	region	

(e.g.,	the	Carrizozo	Lava	Flows)	as	young	as	~5,000	years	indicates	the	possibility	of	basaltic	volcanism

associated	with	this	feature,	and	the	extraordinary	flatness	of	the	upper	SMB	surface	is consistent	with	

such	a	low	viscosity composition.		An	alternative	possibility	is	that	the	SMB	is an	active, primarily	sill-like

mafic	intrusion	that	will	ultimately	solidify	in	the	mid-crust	without	erupting.	The	long-standing	

seismicity	above	the	SMB,	including	events	as	shallow	as	~2	km,	suggests	that	amagmatic	migration	of	

hydrothermal	fluids	and	uplift	accommodation	can	be	expected	to	generate	earthquakes	above	such	

features,	which	may	make	it	difficult	to	definitively	track	the	ascent	of	smaller	volumes	of	magma	from

depth	in	an	eruptive	scenario. We	present	a	summary	of	present	knowledge	of	the	SMB	and	its	

seismicity	and	uplift	in	a	volcanological	context.
SURFACE TEXTURES AND RELATIONSHIPS INDICATIVE OF ENDOGENOUS GROWTH 

AT THE MCCARTYS AND CARRIZOZO FLOW FIELDS, NEW MEXICO 

J. E. BLEACHER1, L. S. CRUMPLER2, W. B. GARRY3, J. R. ZIMBELMAN4, S. SELF5, and J. C. AUBELE2. 1

NASA Goddard Space Flight Center, Planetary Geodynamics Laboratory, Greenbelt, MD, 20771, jacob.e.bleacher@nasa.gov, 2

New Mexico Museum of Natural History & Science, Albuquerque, NM, 3Planetary Science Institute, Tucson, AZ, 4Smithsonian 

Institution, National Air and Space Museum, 5

Dept. of Earth and Environmental Sciences, The Open University, UK

 Introduction: Basaltic lavas are well known to form 

channels or tubes during emplacement. However, the 

importance of sheet flow and inflation within basaltic 

terrains only received recognition over the last 10-20

years. Here we discuss evidence for endogenous 

growth of the McCartys and Carrizozo flow fields, 

NM. We focus on the distal margins of each field 

where the flows progressed over near zero degrees 

slopes, or in the southwest portion of the McCartys 

flow even progressed up hill over slopes < 1 degree. 

 Textures and Relationships: The McCartys lava 

flow field is among the youngest (~3000 yrs) [1] basaltic lava flows in the continental United States whereas 

the Carrizozo is estimated to be ~ 5000 years old [2,3]. 

Both features are located within an arid environment, 

which combined with their age results in a display of

pristine textures and unit relationships. The southwest 

sections of both flows display smooth, flat-topped 

plateaus with irregularly shaped pits and hummocky 

inter-plateau units that form a polygonal surface. 

 Plateaus are typically elongate in map view, up to 20 

m high and display lineations within the glassy crust. 

Lineated surfaces occasionally display small < 1m 

diameter lava coils. Lineations are generally straight 

and parallel each other, somtimes for many 10s to over 

100 meters. The boundaries between plateaus and depressions are also lineated and tilted to angles sometimes approaching vertical. Plateau-parallel cracks, 

sometimes containing squeeze-ups, mark the boundary 

between tilted crust and plateau. Some plateau depressions display level floors with hummocky surfaces, 

while some are bowl shaped with floors covered in 

broken lava slabs. Infrequently, pit floors display the 

upper portion of a tumulus from an older flow. 

 In some places the surface crust has been disrupted 

forming a slabby texture. Slabs are typically on the 

scale of a meter or less across and no less than 7-10 cm 

thick. The slabs preserve the lineated textures of the 

undisturbed plateau crust. 

 Interpretation & Implications: We interpret the 

southwest portions of both flow fields to have experienced lava flow inflation. The lineated texture appears 

to represent the primitive emplacement of a laterally 

extensive sheet flow. Lineations likely form as shear 

zones within the sheet [4], occasionally forming coils

[5]. The parallel nature of lineations suggest single 

active sheets during emplacement. Slabs indicate disruption of the original crust [6]. Unlike platy-ridge 

flows [7], these slabby units are confined to several 

meter diameter patches across the plateaus. As such, 

they did not involve extensive lateral transport. We 

suggest that disruption occurs as the sheet flow stagnates and inflation begins, perhaps cycling through 

minor localized deflation/inflation events, resulting in 

patchy, slabby terrain . Once the crust reached a thickness of 7-10 cm, or 75 to 120 mins of cooling and crust 

formation (inverse Hon et al. [4] cooling equation [8]), 

the surface was generally capable of supporting sheetwide inflation without crust disruption. In places where 

the liquid sheet was thin due to flow around or over 

pre-existing topography, hindered- or non-inflation 

occurs, resulting in the formation of pits. 

 The Carrizozo displays delta-shaped slabby units 

that were breakout points from one sheet lobe to feed 

the next sheet lobe. In this case, lateral transport of 

crust likely contributed to disruption and is the closest 

morphology we see to platy-ridge. Not all outbreaks 

form slabby deltas, but we have begun using measurements of lineation trends to map out the direction of 

flow. Thus, we hope to continue mapping the flow 

emplacement history among lobes. Some breakouts do 

not feed substantially inflated sheets. Often these flows 

form the polygonal, hummocky terrain. 

 We present two interesting implications. First, the 

McCartys flow appears to have up a gentle slope to the 

SW. The mechanism for this process likely involved 

the emplacement of an elongate sheet against the dip of 

the preexisting surface. If inflated, the lobe creates a 

trough against the rising slope. The next breakout fills 

this trough and enables the flow field to generally 

“step” upslope. Second, the development of disrupted

crust creates a rough texture that might be misinterpreted as a’a lava. However, the process described 

above is fundamentally different from the formation of 

an aā flow, or even a platy ridge surface that involves lateral transport of the crust. As such, it might 

be critical to conduct facies-style mapping of lava flow 

textures, particularly in planetary data, if those textures 

are used to constrain emplacement conditions. 

 References: [1] Laughlin et al. (1994) Geology, 22, 135-

138. [2] Anthony E. Y. et al. (1998) New MexicoGeol. Soc. 

Guidebook, 117-122. [3] Dunbar N. W. (1999) New Mexico 

Geology, 21, 25-29. [4] Hon et al., (1994) GSA Bulletin 106, 

351-370. [5] Peck (1966) USGS PP 550-B, 148-151. [6] 

Wentworth & Macdonald, (1953) USGS Bull, 994, 1-98. [7] 

Keszthelyi et al., Platy-ridge, [8] Keszthelyi et al. (2004), 

GGG, 5, 1-32.
Seismic monitoring of the San Francisco volcanic field

David S. Brumbaugh 

Arizona Earthquake Information Center 

The northern Arizona Seismic network was created in 1985 to fill a need for seismic monitoring 

of the earthquake activity in Arizona, particularly for the active belt of seismicity on the 

Colorado Plateau stretching from Utah south to the plateau rim. Contained within the northern 

Arizona seismic belt (NASB) is the largest urban center, Flagstaff and also the San Francisco 

volcanic field classified as active by the U.S.G.S. 

The geoscope program which occupied sites in Arizona 2006-2008 demonstrated the potential 

for a better understanding of Arizona seismicity by more extensive monitoring than had been 

possible in the past. As part of this program when Geoscope moved east of Arizona, A 

consortium of the three state universities in coordination with the Arizona Geological survey 

obtained funding from FEMA for purchase of eight geoscope stations, which when combined 

with the short period northern Arizona network formed a new statewide net now termed the 

Arizona Integrated Seismic Network (AISN). The sixeen station network in combination with 

other national stations at Wupatki, Tucson, Painted Desert and Organ Pipe has resulted in a 

lowering of the threshold for catalogue completeness in the state and therefore allowed an 

increase in detection of small magnitude swarms that could not be previously identified and 

located. 

Earthquakes have occurred throughout historic time in the San Francisco volcanic field (1892-

present). Due to the lack of stations in the volcanic field and around it, only less frequent larger 

events could be identified and located until the advent of AISN. Two permanent AISN stations 

lie within the volcanic field (FLAG and WMZ) while others are near and around it providing 

additional coverage (GCAZ, CCAZ, X16A, X18A, U15A). Data from the national station 

WUAZ is often critical. 

Two swarms of interest within the volcanic field have been located within the last three years by 

the AISN network. The 2009 Halloween swarm occurred over a six hour period on October 31 

and had some characteristics that when compared to swarms related to eruptive activity 

elsewhere suggested a potential volcanogenic source. The events, at mid-crustal depths were 

aligned in a NE-SW trend between FLAG and WUAZ to the west of Sunset Crater. 

The June 2011 swarm just south of Flagstaff occurred near the Anderson Mesa fault and when 

added to previous activity near the fault suggests that it poses a seismic hazard to the Flagstaff 

urban area. This swarm has characteristics not unlike that of other swarms in the state which 

differ from the Halloween swarm. 
Ignimbrite Calderas and a Large Radiating Mafic Dike Swarm of Oligocene Age,

Rio Grande Rift, New Mexico: Possible Implications to Restless Calderas

R. M. Chamberlin1

, W.C. McIntosh1, N.W. Dunbar1 and M. I. Dimeo2: 1New Mexico Bureau of Geology and Mineral 

Resources, New Mexico Tech, Socorro NM, 87801 2 Evolving Gold Corp., Longmont, CO 80501

The Oligocene Socorro-Magdalena magmatic system (SMMS, 7000 km3; Fig.1) of the early Rio Grande rift is 

expressed by three domains: 1) a cluster of 6 large rhyolitic calderas (Socorro-Magdalena caldera cluster, SMCC) at the 

core, 2) a medial apron of basaltic-andesite lavas (1500 km3) with intertonguing ignimbrite sheets, and 3) a large diameter 

(200 km) radial swarm of dominantly basaltic-andesite dikes (Magdalena radial dike swarm, MRDS) broadly focused on 

the SMCC. Closely spaced mafic dikes near Riley (n ~100) strike NNW to NNE, essentially parallel to the Oligocene rift 

axis as defined by domino-style early rift faults in the Lemitar Mountains (Fig.1). Most dikes near Riley exhibit minimal 

contact metamorphism and are interpreted as non-eruptive dikes. Non-eruptive dikes also contain abundant magmatic 

carbonate (from trapped CO2

) that has deuterically replaced sparse olivine and clinopyroxene phenocrysts. Three eruptive 

(feeder) dikes near Riley exhibit 10-20 m wide contact metamorphic aureoles that indicate strong heating of wall rocks 

hundreds of meters below where the dike once 

fed a basaltic volcano. Feeder dikes contain 

relatively fresh olivine basalt, which implies 

they lost CO2 during eruption. Close spacing 

and relative abundance of mafic dikes at Riley 

is attributed to local coincidence of outward 

(northward) magmatic pressures and westward 

extension of the early Rio Grande rift (i.e. 

magmatic σ3 and tectonic σ3 were both eastwest ). 

Four long dikes of the MRDS —at Pie 

Town, Hickman, Jones Camp and Ft. McRae 

(Fig.1)— yield reasonably precise 40Ar/39Ar 

ages (0.4-1.0 % error) analytically equivalent 

to the large volume (1250 km3) La Jencia Tuff 

erupted from the Sawmill Canyon caldera at 

29.1 Ma (0.3% error). Near horizontal flow 

lineations on the chilled margin of the Hickman 

dike (~15 km3) and relatively precise age data 

suggest that it propagated northward during a 

period of high magma pressure shortly before 

caldera-forming eruption of the La Jencia 

Tuff (Fig.2). Our cross sectional model suggests 

that during periods of high magma pressure (precaldera tumescence) large volumes of relatively 

fluid basaltic magma were driven into fractures 

that propagated as much as 100 km outward from 

a lower crustal basaltic sill complex that fueled 

the caldera cluster (Figs. 1& 2). A restless caldera, 

such as Yellowstone, that experiences a noneruptive earthquake swarm propagating several 

tens of km outward, over a few days, and in an odd 

direction relative to regional tectonic extension, 

may be indicative of a large volume magmatic 

system under extreme magmatic pressure (i.e. precaldera tumescence). 

Supporting documents are available at 

http://geoinfo.nmt.edu/staff/chamberlin/mrds/

home.html

CO2

mush-melt

column

pre-La Jencia-Tuff lava

dome 29.09 ± 0.11 Ma

modern 

erosion 

rising flow lineation surface

PRE-CALDERA TUMESCENCE

Rio Grande rift

PROFILE OF LATERALLY PROPAGATING DIKE*

Colorado Plateau

Hickman dike

29.13 ± 0.20 Ma

weighted mean 29.10 ± 0.11 Ma

*dike thickness = 7m

basaltic-sill complex “Hot Plate” Moho

h=v (true scale)

primary melt accumulation zone

Morenci shear zone (Laramide),

reactivated by rifting as Socorro 

accomodation zone (SAZ)

upwelling asthenosphere

80

60

40

20

0 km

brittle 29.09 ± 0.13 Ma

ductile

thin

lithospheric

mantle

thick

lithospheric

mantle

(old and relatively cold)

pre-caldera 

uplift

~300 m

Figure 2.

Ft. McRAE

Ma

24.7

27.7 28.4

29.1 32.5

28.9

MOGOLLON

PLATEAU

JORNADA

BLOCK

Flow

Lineation

Basaltic

Lavas

Oligocene Magmatic System

Caldera Mafic Dikes (Ma)

Bingham

T or C

felsic

core

feeder 

dike

~33

L M

Riley HICKMAN

PIE 

TOWN 

28.0-27.8

29.1

33-24

34 ̊N

107 ̊W

M = Magdalena

LM = Lemitar Mountains

ACOMA

Cox Peak COLORADO

PLATEAU

Mangas

Mtn. SOCORRO

CHUPADERA

MESA

Rosebud

Flats

RESERVE GRABEN

O-Bar-O

Mtn.

Pelona

Mtn.

Luera Pk.

FT. McRAE

basaltic-sill 

RIO

GRANDE

La 

Joya

M early

rifting

SAN AGUSTIN BASIN (rift arm)

ALBUQUERQUE

50 km

SAZ

G

REAT

PLAINS

RIFT

OSCURA BASIN

TULAROSA BASIN

lower crustal

complex

Figure 1.
 Intrinsic conditions of magmas in Lunar Crater Volcanic Field, Nevada.

J.A. Cortés1

, E.I. Smith2, Racheal Johnsen2, E. Widom3, G.A. Valentine1

1 Department of Geology, 411 Cooke Hall, Buffalo, NY 14260, State University of New York, USA.

2 Department of Geoscience, 4505 S. Maryland Parkway, Las Vegas, NV 89154, University of Nevada, Las Vegas, USA.

3 Department of Geology and Environmental Earth Science, 114 Shideler Hall, Oxford, OH 45056, Miami University, USA.

Geochemistry of the products of Quaternary monogenetic volcanoes in the northern part of the Lunar 

Crater volcanic field shows clear differences between spatially close and coeval volcanoes [1]. In this 

contribution we further constrain the intrinsic conditions of such magmas based on geothermobarometry 

performed using the mineral chemistry of phases occurring in the volcanic products. We have informally 

named the studied units OPB (older, phenocryst-bearing unit), PB (plagioclase bearing), YMB (younger, 

megacryst- and phenocryst-bearing unit) and Qml (Marcath volcano) [2]. Mineral phases in all of the 

studied products are olivine, clinopyroxene, plagioclase and a minor amount of groundmass titanomagnetite.. Olivine ranges between Fo88 and Fo60 in PB/OPB and between Fo88 and Fo75 in YMB/Qml. 

A narrow range of diopsidic compositions occur in PB/OPB, while some high-Ca diopside is the 

common composition in YMB/Qml. Plagioclase is mostly bytownite with the occurrence of andesine 

and anorthoclase in PB and anorthite in OPB. Since no melt inclusions or groundmass glass occur in the 

samples, geothermometry was based on olivine-clinopyroxene mineral equilibria [3] while geobarometry 

and oxygen fugacity were based on clinopyroxene mineral chemistry [4,5]. Calculated temperatures for 

PB/OPB are ~1050o

C, between 950 and 1150oC for YMB and ~1000oC for Qml. Calculated pressures 

for PB/OPB are between 9 and 10 kbars, between 5 and 15 kbars for YMB and between 3 and 15 kbars 

for Qml. In terms of intrinsic oxygen fugacity, PB/OPB ranges between ΔQFM+3 and ΔQFM+5, YMB 

ranges between ΔQFM and ΔQFM+3 while Qml ranges between ΔQFM+2 and ΔQFM+4. These results 

constrain the depth of a crystallising event between 12 and 60 km, and suggest clear differences between 

plumbing systems for all the units. Results also suggest similar evolution for the younger units (YMB 

and Qml) but a different history for the older, phenocryst bearing units. This conclusion is strongly 

consistent with our geochemical results [1]. 

[1] Widom et al., (2012) this volume 

[2] Valentine et al., (2011) EOS Fall AGU fall V33C-2657 

[3] Loucks (1996) Contrib. in Min. and Pet. 125: 140-150. 

[4] Nimis (1999) Contrib. in Min. and Pet. 121: 115-125. 

[5] Cortés et al., (2006) JPet 47(7): 1345-1373 
Into the cone: a ground penetrating radar study of cone-buiding processes at

Cerro Negro volcano, Nicaragua 

Leah Courtland, Sarah Kruse, Chuck Connor 

Cinder cones, also called scoria or tephra cones, represent the most common type of volcanism 

on earth. These “toy” volcanoes are comprised of a combination of pyroclastic material and 

lava flows and pose a significant threat to life and property during times of eruptive activity. 

Though cinder cones have long been considered the simplest example of volcanism, models of 

their formation have advanced very little from their original formulation in the 1970s. 

Furthermore, while competing models can account for the geometry of observed deposits in a 

general sense, none address finer scale cone features such as asymmetries in the cone due to 

variable deposition mechanisms, the pervasion of granular flows vs. in-situ deposits, or the 

presence of faulting. In order to gain a better understanding of near vent processes which may 

be used in volcanic modeling and hazard assessment, new data collection techniques must be 

implemented. Ground penetrating radar imaging of tephra can reveal details of deposits at 

depths of approximately 2-20+ meters. Data collected in the September of 2007 and January of 

2010 is here used to investigate the cone building processes of Cerro Negro, an active basaltic 

cinder cone in Northwestern Nicaragua. The data display evidence of cone steepening over 

time, patterns of ballistic and tephra dispersal, granular flows, and faulting within the cone, 

among other features. 

Figure: Ground penetrating radar profile crests crater rim and heads radially outward in the 

direction of maximum plume deposition. Up-cone profile collected with 100 MHz antennas, 

farther down the cone data collected with both 50 and 200 MHz antennas. Deposits from both 

the 1992 and 1995 eruptions are identified. 
Geochemistry and Hazard Assessment of Pliocene-Quaternary Volcanism Beneath 

the central Sierra Nevada and Adjacent Great Basin, northern California and 

Western Nevada 

Brian Cousens, Ottawa-Carleton Geoscience Centre, Department of Earth Sciences, 

Carleton University, Ottawa, ON. K1S5B6, Canada 

Christopher D. Henry, Nevada Bureau of Mines and Geology, University of Nevada, 

Reno., NV. 89557, USA. 

ABSTRACT 

Latest Pliocene to Quaternary, mildly alkaline, primarily mafic volcanic activity 

extends in a swath from the Lake Tahoe region in the eastern Sierra Nevada across the 

western Great Basin to the Battle Mountain area, Nevada. This region overlies a zone of 

high heat flow and lithospheric thinning, termed the Humboldt Lineament, and is a zone 

of potential volcanic hazard. The Lake Tahoe region is a major locus of four-season 

tourism in the central Sierra Nevada (Smith et al., 2004). In 2003 and 2004, a series of 

deep (~30 km) earthquakes occurred beneath the north shore of Lake Tahoe, where the 

progression of earthquake depths and the focal mechanisms are consistent with a 

magmatic dyke intrusive event. Youthful, explosive cinder cones are common in the 

Tahoe area. The area around Fallon, NV., the site of a major naval air station and a 

population of over 6,000 people, hosts two tuff cone and maar complexes that are less 

than 25,000 years old (Fultz et al., 1984). These volcanoes record explosive phases of 

volcanic activity that would have an impact on the nearby population. 

The goal of our petrological and geochemical work is to determine the sources of 

volcanic activity, what processes dominate the magmatic evolution of the lavas, and how 

these processes impact the style of eruptive activity along the Tahoe to Battle Mountain 

swath of volcanic activity. From west to east, the volcanic centers exhibit a dramatic 

gradient in chemical and isotopic composition. Centers situated in or adjacent to the 

Sierra Nevada have incompatible element and isotopic compositions consistent with an 

old, subduction-modified lithospheric mantle source (87Sr/86Sr > 0.7045; δ18O > +6.5%o). 

Mafic volcanic centers east of the Sierra Nevada, in the Carson Sink and in the Buffalo 

Valley region, have an intraplate incompatible element and isotopic signature (87Sr/86Sr < 

0.7045; δ18O < +6.5%o) consistent with an asthenospheric mantle source. Earlier 20–3 

Ma arc volcanism in the Sierra Nevada also tapped the old lithospheric mantle source 

along with the mantle wedge, indicating that the lithospheric mantle source existed well 

prior to the onset of Tertiary arc volcanism. Thus the lithospheric mantle beneath the 

Sierra Nevada has remained a geochemically consistent, fertile, fusible source for at least 

the past 20 Ma. Lithospheric mantle was also an important source for Miocene mafic 

through intermediate volcanic rocks erupted in the Fish Creek, Clan Alpine, Stillwater, 

Desatoya, Lahontan, and other ranges west and south of Battle Mountain, as a result of 

rollback of the Farallon plate beneath North America. Old lithospheric mantle likely still 

exists beneath the Great Basin east of the Sierra Nevada, but lithospheric thinning and/or 

exhaustion of fusible components inhibits its melting such that during the Quaternary 

melting could only occur in the asthenosphere. Young, explosive volcanic activity is 

associated with magmas derived from both types of mantle source. 
ENVIRONMENTAL CONSEQUENCES OF LARGE VOLUME LAVA FLOW FIELDS IN THE 

SOUTHWEST: PRELIMINARY INFERENCES FROM MAPPING THE McCARTYS LAVA FLOW 

FIELD, NEW MEXICO

L.S. CRUMPLER1, J.E. BLEACHER2, S. SELF3, J.R. ZIMBELMAN4, W. B. GARRY5, J. C. AUBELE1, 1

New Mexico Museum of Natural History & Science, 1801 Mountain Rd NW Albuquerque, NM, 87104,USA, larry.crumpler@state.nm.us, (2) Planetary Geodynamics Laboratory, NASA Goddard Space Flight Center, (3) Dept. of Earth and 

Environmental Sciences, The Open University, UK, (4) Smithsonian Institution, National Air and Space Museum, (5) Planetary 

Science Institute, Tucson, AZ 

 Introduction. Conditions necessary for eruption of two 

large, several cubic kilometer basaltic lava flows (each 3 to 6 

km3

) have prevailed in last 5,000 yrs in New Mexico 

(McCartys and Carrizozo). Although lava eruptions of this 

scale are relatively infrequent, a basaltic eruption of a similar 

volume (Laki, [1]) was one of the most globally disruptive 

volcanic events in recorded history due in part to the sulfur 

and halogen aersols and the relatively widespread effects on 

the environment at the time, including global cooling. Because of the potential for profound influence on society, both 

in the Southwest and globally, and because the geologic conditions necessary for a repeated occurrence may still persist, 

the special environmental effects of a repeated event of this 

scale should be assessed. 

This study was initiated in part to document the 

mechanisms and rates of emplacement of the McCartys lava 

flow field through mapping of physical surface units and 

acquisition of high resolution relief data. The findings are 

proving useful on several fronts. They are enabling development a more complete picture of the substantial role of inflation in development of large lava flow fields, provide a more 

detailed picture of the volume, effusion rates, and timing of 

the eruption, and provide a modern proxy for details of flood 

basalt emplacment. These results in turn provide some constraint on likely patterns of sulfur and halogen release and 

aerosol production, and the corresponding environmental 

consequences that may have prevailed at the time of the 

eruption (~3.2 ka before present, [5]).

Volume. The McCartys lava flow field covers approximately 

220 km2 and extends 52 km from south to north, the flows 

reaching a maximum distance of some 40 km from the small 

vent region located in the southern half of the flow. Our current estimates of volume lie between 3 and 6 km3 (the volume of the Laki eruption is 14 km3

). The surface of the lava 

flow preserves glassy crusts, is dominantly pahohoe, and 

evidence for inflation of the surface is prevalent. 

Mapping. A pilot mapping effort was initiated to unravel the 

details of the lava emplacement, focusing on the spatial and 

temporal patterns of sheet lobe emplacement and the evidence of eruption longevity from patterns of inflation. One 

of goals is to understand the net volume and overall timing of 

the released volatiles and pyroclastic materials. Thicknesses 

of disrupted surface slabs, evidence for crustal thicknesses at 

the time of deformation on plateau margins, and mapped 

distribution and timing of subsequent multi-generation flow 

lobes provide estimates of duration of the eruption. We can 

account for approximately two years within the detailed map 

area and later we hope to have an estimate for the duration of 

the entire eruption sequence. 

Volatile effects. As an example of the impact of volatiles 

released during the eruption, consider possible SO2 production. We have yet to measure the S contents of glassy rinds, 

but assuming that the relationship between composition (specifically TiO2/FeO) and S concentrations are similar to those 

in recent tholeiitic eruptions [2], values of 1000 – 1500 ppm 

S are reasonable. Ignoring details of the distribution (magma, 

pyroclastics, and included phenocrsts) in the light of the prelimnary nature of the volume estimates, and using estimates 

of S emissions from [3], the McCartys eruption could have 

yielded 20 to 30 Tg of SO2 within the space of a few years. 

This is equivalent to the largest historic explosive eruptions 

for which SO2 impact on the atmosphere was notable. Given 

our initial estimates of eruption duration, the rates of SO2

release were likely on the order of 1 Tg per month. This is 30 

to 100 times the production of large copper smelters [4]. 

Lessor basaltic eruption could yield disruptive gas release, 

although in quantities that scale with their erupted volume.

References: [1] T. Thordarson, S. Self, Bull. Volcanol. 55 

(1993) 233–263; [2] T. Thordarson, S. Self, J.D. Miller, G. 

Larsen, E.G. Vilmundar- dottir, Volcanic Degassing, Geol 

SocLondon Special Pub, vol. 213, 2003, pp. 103–122.; [3] 

Self et al. 1991. EPSL, 248 (2006) 518–532. [4] Carn eta;, 

2007. GRL, 34, L09801 doi:10.1029/2006GL029020. [5] Dunbar, and Phillips, 1994 New Mexico Geology, v. 16, no. 4, p. 80. 
THE NEW MEXICO VOLCANO COLLECTION AND RESOURCE: VOLCANOES OF NEW MEXICO 

WEBSITE DEVELOPED BY THE NEW MEXICO MUSEUM OF NATURAL HISTORY & SCIENCE

L.S. Crumpler1

, J.C. Aubele1, R. Elsinger1, and M.Celeskey1

1

New Mexico Museum of Natural History and Science (1801 Mountain Rd. NW, Albuquerque, NM, 87104, 

jayne.aubele@state.nm.us)

A Collection of Volcanoes: The New Mexico 

Museum of Natural History and Science is 

developing an updated resource for all geoscientists 

and the public that will provide current information, 

maps, and images for volcanic areas and individual 

volcanoes, within the state of New Mexico. Although 

most Museum collections consist of physical objects 

that can be housed within the walls of a building, 

volcanoes present a problem. Volcanic rock types 

can be collected, but the entire state of New Mexico 

is a “museum” of all of the various types of 

volcanological edifices and eruptive styles, and these 

cannot be physically collected. They can, however, 

be collected as photographic images, maps, and 

detailed information; and this collection will be 

useful to both the general public and the research 

volcanologist. That is the intent of the “Volcanoes of 

New Mexico” website. 

The website opens with a map of the state with all 

volcanic fields and regions of volcanism shown. A 

click on any one of these areas sends the viewer to 

more detailed maps, photographs, and information 

about the area. Layers of information are given so 

that the interested non-scientist can read a basic 

summary, while the research volcanologist can access 

the most recently published research. Compiling and 

updating this information is being done by a team 

consisting of the Museum’s Curator of Volcanology 

(Crumpler), Geoscience Educator (Aubele), Graphic 

artist (Celeskey), and committed volunteers, 

including Museum volunteers and classroom 

teachers. The updated Volcanoes of New Mexico 

website will be linked to the Museum website 

(www.NMnaturalhistory.org) for easy access.

Increasing regional volcano literacy: Geology is 

frequently perceived by the student, teacher, or adult 

non-geologist as “difficult to understand”; however, 

most non-geologists of all ages notice and appreciate 

scenic or exciting landforms such as volcanoes and 

are interested in related phenomena such as 

earthquakes and the development of mineral 

resources. The New Mexico Volcano Collection and 

Resource, as part of the Museum’s website, is an 

opportunity to increase the non-geologist’s 

understanding of New Mexico’s volcanoes and to 

excite the general public about volcanological 

research.

The Museum Advantage: Museums, as informal 

science education centers, have the following 

advantages in volcano-related education for the 

public: (1) graphics/display expertise; (2) flexibility 

in approach and programming; (3) self-directed 

learning opportunities; (4) audience ranging from 

pre-K through Senior Citizen; and (5) accessible, 

visitor-friendly and non-threatening resource site.

The general public is interested in the local and 

regional geology and is fascinated by volcanoes; 

however, most people don’t know how or where to 

obtain this information. Museums and museum 

websites are trusted resources for concise, factual, 

reliable and entertaining presentations of the relevant 

information. By emphasizing the local or regional 

connection, museums allow people to make a 

personal connection to scientific research and new 

discoveries in their own “backyards.” K-12 teachers 

are able to make use of Museum programs, content, 

and the ongoing research that also takes place in 

Museums to provide a “real world” approach to 

science in the classroom.

In addition, museums serve a wide audience, For 

example, the New Mexico Museum of Natural 

History and Science is a statewide institution, part of 

the New Mexico Department of Cultural Affairs. It 

serves a regional population that includes 38% 

Hispanic and 9% Native American, as well as a high 

percentage of rural communities, and therefore 

reaches an audience traditionally underrepresented in 

science. With the increase in web-based information 

and learning, the Museum website is perfectly placed 

to become an important resource for a statewide, 

national, and global population interested in 

volcanoes. 
Volcano Work Groups and Effective Communication Partnerships for Volcanic Hazards Education 

Carolyn L. Driedger driedger@usgs.gov tel: 360-993-8907

USGS—Cascades Volcano Observatory, 1300 SE Cardinal Court, Vancouver, WA, 98683

In Washington and Oregon, public officials, emergency managers, first responders, park staff, and emergency 

educators, and scientists participate in regional volcano hazard work groups that plan responses to volcanic 

activity within their jurisdictions. Work group agencies are trained to exercise the response and recovery plans 

effectively, enabling them to communicate with the public about regional volcano hazards. That communication 

can be most influential when multiple sectors within the community work as a team to deliver consistent and 

complementary messages. Each sector has a specific intention and function: emergency managers and public 

officials require up-to-date and exercised coordination plans and an informed and supportive community; 

educators endeavor to create a more informed younger generation; community and tourism officials plus, park 

interpreters and managers wish to provide up-to-date and meaningful interpretation, and resource 

management; scientists strive to provide accurate information, technically sound interpretations, and useful 

hazards assessments; the media seeks an interesting story. All seek to raise awareness and preparedness. 

The effort shows successes that are measurable in part by surveys of community awareness and 

preparedness. Partnerships provide potential for consistent and efficient dispersal of information that can 

lead to improved awareness, safety policies, heightened protection, and increased appreciation of volcanic 

parks and preserves. Consider these guidelines when initiating a volcano outreach plan in your community: 

• Determine desired outcomes, such as governmental policy improvements and funding support for volcano 

monitoring, mitigation plans by emergency responders, and measureable heightened awareness and personal 

preparedness by officials and populations at risk. 

• With partners, craft consistent and complementary key messages that explain hazards, and the importance 

of intra-community risk mitigation and personal preparedness measures, stressing how these actions will bring 

family and personal safety, peace of mind, and greater appreciation of nearby Cascade volcanoes. 

• Seek partnerships with policy makers, professional information disseminators and vested interest groups

who can be advocates–emergency managers, educators, health practitioners, community and business 

leaders, park interpreters, media, and other groups with interest in general preparedness. Confer less attention 

on the diffuse “general public” and more focus on established social groups that can re-transmit key messages 

with efficiency. 

• Develop outreach products and services in partnership, usable by and for local communities.

• Measure effectiveness. Plan pre- and post-outreach assessments of community knowledge.

• Extend your reach. Use multiple approaches to establish your message. Plan for a long-term yet 

sustainable commitment. Show how cooperation leads to family protection, peace-of-mind, community 

economic benefits, and faster recovery after disaster. 

Communication partnerships can increase the impact and sustainability of volcano hazards and mitigation, 

even when resources are limited.
Volcanism in New Mexico: Past activity and future expectations: Zuni-Bandera Volcanic Field, Valles 

Caldera, Socorro magma body, and beyond.

Nelia W. Dunbar, William C. McIntosh. New Mexico Bureau of Geology and Mineral Resources, New 

Mexico Tech, Socorro, NM, 87801. nelia@nmt.edu; 

mcintosh@nmt.edu

Volcanism has been widespread throughout New Mexico over 

the past ~2 Ma, with two main compositions, basaltic and 

rhyolitic, represented. The basaltic volcanism occurs mainly 

along the Rio Grande rift or the Jemez lineament, and occurs in 

nine distinct fields (Figs 1 and 2). The rhyolitic volcanism is 

focused in the Jemez Mountain volcanic center, which is 

located at the intersection of the Rio Grande rift and the Jemez 

lineament, and features two, large-volume, highly explosive 

eruptions, the deposits of which are widespread throughout 

the state. A compilation of the ages and geographic 

distribution of New Mexico Quaternary volcanism suggests no 

systematic episodicity or variation in geographic location of 

eruptions, but rather a consistent level of temporally and 

geographically distributed activity. In terms of geographic 

distribution, much of the volcanism that has occurred over the 

past ~2 Ma has been 

basaltic, with rhyolitic 

activity occurring only in 

the Jemez Mountain 

Volcanic Field. Based on 

that observation, the next 

recurrence of volcanism in 

New Mexico would be 

most likely to be basaltic, 

although rhyolitic activity 

cannot be ruled out. 

Furthermore, the style of 

volcanism will most likely 

be a small lava flow with 

associated cinder cone. 

This style of anticipated

activity will probably have 

little impact on the local climate, although impact on landscape evolution, particularly through 

disruption of drainage patterns, could be significant. Based on the frequency of eruptions over the past 5 

Ma, there is a 1% chance of a volcanic event in New Mexico in the next 100 years (Limburg, 1990), and the 

most likely location of activity will be associated with the geophysically-defined Socorro magma body. 

This tabular magma body, the top of which is located at 19 km depth in the central part of the state (Fig. 

2), has been recognized for many years through geophysical observations (see Aster et al., this volume). 

More recently, anomalous seismicity, crustal deformation measured at ~2.5 mm/yr and long-term heat 

flow have been recognized associated with this sill-like magma body. Most discussion of this magma 

body in the literature suggests that it is probably basaltic, but the possibility that it contains rhyolitic 

magma cannot be ruled out. 

Figure 1. Map of surface outcrops of <1.7 

Ma volcanism in New Mexico. Numbers 

keyed to Figure 2. Socorro magma body 

in red

Figure 2. Integrated ages of <1.7 Ma volcanism in New Mexico. Red lines indicate basaltic activity, 

blue lines rhyolitic, which occurs only in the Jemez Mountain Volcanic Field.
Human Adaptation to Catastrophic Events: 

Lessons from the 11th Century CE Eruption of Sunset Crater Volcano

Mark D. Elson, Desert Archaeology, Inc. 

Michael H. Ort, Northern Arizona University 

 The Flagstaff area was never an easy place to make a living. Situated in an area early 

Spanish explorers aptly named “Sierra Sin Agua” (the mountains without water), the climate and 

topography of the region are barely sufficient for long-term settlement. Water sources are rare 

and permanently flowing streams almost nonexistent. The climate is harsh and unpredictable, 

with only areas above 1,900 m in elevation receiving sufficient precipitation for corn cultivation. 

The >600 cinder cones in the San Francisco volcanic field covered the ground surface with thick 

layers of black basalt tephra and rendered large areas barren of vegetation and inhospitable to 

settlement. 

Sunset Crater Volcano is located ~20 km north of Flagstaff. New data from the 

archaeological excavation of 40 prehistoric sites in the Sunset Crater area, combined with 

geochemical and dendrochemical analyses, suggest that the volcano erupted for a short period 

(weeks to months) sometime between 1060 and 1090 CE, and most likely around 1085 CE. At the 

time of the eruption, nearby areas were densely populated by small, prehistoric farming groups 

that archaeologists call the Sinagua. Lava and tephra were deposited over an area of 2,300 km2, 

dramatically changing both the physical landscape and the world view of the prehistoric 

inhabitants. 

 Agricultural experiments demonstrate that an area of greater than 400 km2had to be 

abandoned due to the deposition of a scoria cover deeper than 20-30 cm, under which agriculture 

was no longer possible, and roof collapse likely occurred in a much larger area. Given the density 

of pre-eruptive settlement in this area, 1000s of volcano refugees were likely displaced. 

Conversely, these same agricultural experiments agree with earlier research showing that the 

deposition of a 3-8-cm-thick layer of scoria acted as a mulch and increased moisture retention 

enough to support agriculture in areas previously too dry to be farmed. 

Prehistoric populations not only adapted to these conditions, they thrived. The 

archaeological evidence strongly suggests that within a few years following the eruption, many of 

the volcano refugees migrated 15-20 km north of Sunset Crater into the arid lower elevations that 

were now covered by 3-10 cm of tephra. Here they developed new technological methods to 

manage the tephra mulch and ensure agricultural success in an area receiving less than 200 mm of 

yearly precipitation. This previously little inhabited area – now called Wupatki National 

Monument – soon became the site of some of the largest pueblo structures ever built in the 

Flagstaff area. 

The deliberate creation of corn-impressed pieces of lava further suggests that the local 

inhabitants made ritual offerings to the volcano, which likely played a role in their successful 

adaptation. Studies of catastrophic events show that religious mechanisms for coping with a 

natural disaster are highly adaptive, enabling affected individuals and groups to more readily 

accept the event and begin the recovery process. The results of these investigations are used to 

examine human adaptation to catastrophic events in general. Today, more than 900 years after 

Sunset Crater arose on the landscape, the Hopi, who are thought to be the descendents of the 

prehistoric Sinagua, still pass accounts of the eruption from generation to generation as a part of 

traditional clan knowledge, underscoring the significance of this event. 
ERUPTION POTENTIAL AND HAZARD, VALLES CALDERA, NEW MEXICO 

Fraser Goff, Earth and Planetary Sciences Department, University of New Mexico, 

Albuquerque, NM 87131, candf@swcp.com 

The 22-km-diameter Valles caldera (1.25 Ma) is famous as the type locality of 

large resurgent calderas, the host of a classic 260-300 °C liquid-dominated geothermal 

system, the site of a seminal investigation identifying the Jaramillo and Santa Rosa 

paleomagnetic events, and the location of a large 552-368 ka mid-Pleistocene lake. Valles 

formed during eruption of ca. 400 km3 of Tshirege Member, Bandelier Tuff and is the 

only large Quaternary caldera in the southwestern USA. After caldera formation, a short 

period of resurgence and associated rhyolitic volcanism (1.25 to 1.22 Ma) was followed 

by major ring fracture volcanism from 1.22 Ma to 40 ka. About 25 rhyolite domes, flows 

and minor tuffs were erupted from the ring fracture zone. Thus, on a very crude statistical 

basis, the ring fracture has produced about 1 eruption every 50 kyr since caldera 

formation. 

Various geologic, geochemical and geophysical investigations conducted during 

the last 35 years provide additional insight on eruption potential and hazard. 

Hydrothermal activity once occurred throughout most of the caldera, but the present 

geothermal system is centered in the SW sector of the resurgent dome and ring fracture 

zone, nearly coincident with the youngest rhyolitic eruptions. 3

He/4He ratios of the 

hydrothermal fluids range from 4.5 to 6 R/RA indicating a significant contribution of 

primordial helium and a current pathway from the mantle. Seismic investigations show 

that a circular low-velocity zone extends to the mantle beneath the SW caldera. Modeling 

indicates a melt fraction of 10 to 30% at 5 to 15 km depth. In contrast, limited geodetic 

and GPS surveys show that the resurgent dome is static and that the caldera is relatively 

aseismic compared to adjacent fault systems such as the Rio Grande rift. 

Although another caldera-forming eruption of Bandelier Tuff scale is highly 

unlikely, the youngest group of Valles eruptions (East Fork Member) exhibits explosive 

character and may provide an example for future eruptions. This group consists of the El 

Cajete Pyroclastic Beds and Battleship Rock Ignimbrite (55 ka, ≥10 km3

) followed by the 

Banco Bonito Flow (40 ka, ~4 km3

). These units are chemically and mineralogically 

distinct from ring-fracture rhyolites that erupted 460 kyr earlier and may record onset of a 

new magmatic cycle at Valles. Plinian eruptions from the El Cajete event were dispersed 

mostly to the south and east covering much of eastern New Mexico in ash. Due to rugged 

topography, ignimbrites and flows were restricted to the immediate Valles caldera area. 

In summary, a magma chamber resides beneath the southwestern Valles caldera, 

which provides heat and volatiles to an active geothermal system. Although future 

rhyolitic eruptions at Valles are possible, it is presently impossible to predict when these 

will occur. Eruption products and volumes produced by the young East Fork Member 

suggest that rhyolitic plinian eruptions are probable and most likely to effect surrounding 

regions. 
Estimating remobilization rate of ash deposited during the Puyehue 

(Southern Andes) eruption in 2011 

Miguel J. Haller, Universidad Nacional de la Patagonia San Juan Bosco & CONICET (haller@cenpat.edu.ar) 

Oscar A. Frumento, Centro Nacional Patagónico – CONICET (oscar@cenpat.edu.ar) 

Puyehue – Cordón del Caule volcano in Southern Andes erupted explosively in June 2011 

depositing ash over a region of more than 75,000 km2

to the east and southeast of the 

volcano in the Argentine Patagonian meseta. A minimum of 1.36 km3 of uncompacted 

tephra was ejected, which is equivalent to 0.29 km3 of solid rock. The thickness of ash 

ranged from 30 cm in the Andean area to less than 1 mm in the Atlantic coast zone. This 

deposited ash has been frequently remobilized for months by the wind impacting on the 

population, transportation, agriculture, livestock and water resources of the region. 

The research was carried out to determine whether it would be possible to predict the time 

required for the complete remobilization of ash and its related effects. In order to estimate 

the transport of volcanic dust deposited over an extended area of the argentine northern 

Patagonia the coupled dust-RegCM4 regional climate model has been used over an area 

covering southernmost South America. An imposed dust source area was deducted from 

satellite images of the first few days following the eruption. Particle distribution based on 

textural analysis of ash collected in the Meseta Central was further associated to the four 

categories of particles sizes (from 0.1 μm to 20 μm) the coupled dust-REGCM4 usually 

handles. 

Modelling approach based on empirical field observations, considers that one third of the 

fallen ash is fixed by the vegetation or incorporated into the soil by illuviation processes, 

while two thirds are resuspended by the wind. The climate model allowed us to calculate a 

monthly average emission rate (catch and remobilization of particles outside the region) 

700g/m2, equivalent to 52 x 106 tons/month. Based on these calculations it was estimated 

that the remobilization of Puyehue volcano ashes and decreasing of the consequent adverse 

effects would extend for a period of 33 months. Current observations (July 2012) show that 

during strong wind storms volcanic ash reaches the Atlantic coast. 
Potential	Contributions	of	Geodesy	to	Monitoring	Volcanic	Unrest		

in	the	Southwest	United	States

William	C.	Hammond,	Corné	Kreemer,	Geoffrey Blewitt

Volcanism	in	the	American	Southwest,	October	18-20,	2012

Flagstaff,	AZ

Precise and	timely measurement	of	surface	deformation	associated	with	volcanic	or	tectonic	unrest	is a	

highly	valuable component	of	a	coordinated	response	to	precursory activity such	as	seismic	swarms.	

Geodesy,	in	combination	with	other	geophysical	datasets, has	a	role	in	each	stage	of	the	event	

information	life	cycle,	including	detection,	characterization,	integration	and	interpretation	of	data	needed	

to	provide	understanding	and	warning	of	natural	volcanism.		 Geodesy	is	particularly	illuminating when	

surface deformation	indicates	that	a	large	or	even	dominant	fraction	of	the	deformation	is	aseismic,	as	is	

the	case	for	many	intrusive	events.	

The	geologic	record	of	volcanism	in	the	southwest	US	includes many young low-volume eruptions	whose	

geographic	distribution	is	strikingly	similar	to	the	contemporary	zones	of	higher	active	crustal	strain	rate.		

Our	recent	experience	with	seismic	swarms	in	the	western	Great	Basin	also	suggests that	magmatism	is	

an	active	and	possibly	pervasive	component	of tectonic	evolution	the	crust	and	upper	mantle,	and	not	

only	focused	on	existing	large	volcanic	centers.		Examples	of	recent	swarms	in	eastern	California	and	

western	Nevada	include	the	2003	Slide	Mountain, 2008	Mogul/Reno,	2011	Hawthorne, and	2011	

Sierraville episodes for	which	detailed	seismic	and	geodetic	datasets	were	collected.	 In	each	of	these	

cases	it	was	unclear	early	on	how	far	the	events	would	progress.		While	each	had	large numbers	of	

earthquakes, their geodetically	observed	surface	deformation	characteristics varied	substantially,	as	did

the	amount of	verifiable	contribution	from	a	magmatic	source.	 However,	they	were similar in	their

consistency with	the	dextral	transtensional regime	of	western	Great	Basin	and	Walker	Lane	active	

tectonic	deformation,	further	suggesting	that	maps	of	active	crustal strain	rate	provide	important	

information	about	volcanic	hazards.

GPS	networks	that	may	contribute	to	

monitoring	future	volcanic	unrest	include	the	

NSF	EarthScope	Plate	Boundary	Observatory	

and	the	University	of	Nevada's	flexible	

Mobile	Array	of	GPS	for	Nevada	Transtension	

(MAGNET).		We	will	present	results	from	a	

few recent	case	studies	where	MAGNET was	

deployed	in response	to	seismic	swarms.		

These	cases	illustrate	the	utility	of	GPS	

measurements,	their	precision,	scope,	and	

latency.		We	will describe	the	status	of	UNR's	

new	low-latency,	high	rate	data	products	that	

are now available or	on	the	horizon,	and	also	

recent	directions	of	a	nascent	communitywide surge	in	real	time	GPS	data	availability

whose	aim	is	to	provide	easier	access	to	

solutions with	cm	accuracy	with latency	near

1	second.		

Figure (right).	 	A	 geodetic	 strain	 rate	 map	 for	 a	 portion	 of	 the	

southwest	 U.S.	 	 For	 more	 information	 and	 free	 download see

http://geodesy.unr.edu
Young Volcanism of the Lake Tahoe – Reno – Fallon Area, California and Nevada: The 

Geologic Record

Christopher D. Henry, Nevada Bureau of Mines and Geology, University of Nevada, Reno, NV 

89557, USA

Brian Cousens, Ottawa-Carleton Geoscience Centre, Department of Earth Sciences, Carleton 

University, Ottawa, ON. K1S5B6, Canada

ABSTRACT

An approximately west-east belt of young volcanic rocks (mostly ~2.6 to 1 Ma, but at least as 

young as 10,000 years) extends ~150 km from the north end of Lake Tahoe, California, through 

Reno to Fallon, Nevada. Additionally, two groups of deep earthquake swarms in the last ten 

years, one beneath the north end of the lake and another ~50 km to the north-northwest, that are 

interpreted to indicate upward propagating igneous dikes suggest some potential for future 

volcanism (Smith et al., 2004). The belt of young volcanic rocks encompasses several population 

centers, a major transportation corridor, Lake Tahoe, and the Fallon Naval Air Station so 

assessment of potential volcanic hazard is worthwhile.

The young volcanic rocks are mostly basaltic but include a cluster of rhyolite lava domes. 

Volcanic eruptions in the north Tahoe area are as young as 0.9 Ma (Kortemeier et al. 2009), were 

almost all basaltic, and formed numerous cinder cones and lava flows and at least one tuff cone, 

a more explosive type of eruption. These rocks form a semi-continuous belt eastward to Reno 

and Carson City, where several more cinder cones formed at ~1.4 Ma and were accompanied by 

at least three lava flows. Two lavas from one cone flowed ~6 km into what are now suburbs of 

Carson City and across US Highway 50. Another lava flowed about 17 km down a canyon to the 

present I-80 and Truckee River, which it blocked at the time. Four rhyolite lava domes up to 

~600 m in diameter formed during mixed explosive-effusive eruptions at ~1.2 Ma in what are 

now the south suburbs of Reno. An ~50 km wide gap of no known young volcanic rocks 

separates the Tahoe – Reno area rocks from those near Fallon, which are exclusively basaltic. 

The youngest and some of the most explosive activity in the region formed the Soda Lakes 

complex of several, partly overlapping maars individually up to 1.2 km in diameter and 

extending over a 2.5 km long, north-northeast zone northwest of Fallon. The maars cut Lake 

Lahontan sediments so are younger than ~10,000 years, possibly as young as 1,500 years. The 

Upsal Hogback group of overlapping maars, individually up to 1 km in diameter and extending 

over a 5 km long north-northeast zone that approximately aligns with Soda Lakes were 

extensively eroded by Lake Lahontan. They are probably ~25,000 years old based on the 

presence of basaltic tephra interbedded with sediments that are estimated to be that old. The 

north-northeast alignment of volcanic centers suggests control of magma transport through the 

upper crust by faults and fractures related to regional extension. An ~1 Ma cone and flow 

complex sits at the northeastern edge of Fallon. Another group of cinder cones and lava flows as 

young as 1 Ma occurs in an unpopulated area south of Battle Mountain, Nevada about 150 km 

northeast of Soda Lakes and Upsal Hogback.

Most volcanism appears to have ended throughout the eastern California – western Nevada 

region at ~1 Ma. The two maar complexes near Fallon are the only known Holocene or Late 

Pleistocene eruptions. However, they and the propagating dikes shown from seismicity allow the 

possibility of future eruptions. Given the record of activity over the last 2.6 Ma, future eruptions 

are likely to be basaltic. If emplaced into major groundwater basins, they could be highly 

explosive like the young maars. If emplaced into Sierra Nevada bedrock, eruptions probably 

would be less explosive, probably cinder cones accompanied by lava flows. We can offer no 

probability for an eruption but hope that any eruption would be long presaged by seismicity. 
Tephra dispersal and deposition from the Marcath eruption, Lunar 

Crater Volcanic Field, Nevada

Peter Johnson, Greg Valentine, Marcus Bursik 

Department of Geology, 411 Cooke Hall, University at Buffalo, Buffalo, NY 14260 

email: peterjoh@buffalo.edu 

Explosive volcanic eruptions pose well-established hazards to aviation and public health. One 

possible source for explosive eruptions is basaltic monogenetic scoria cones. Although generally 

regarded as a well-understood eruptive style, few data have been collected of tephra deposits 

from prehistoric scoria cone eruptions. This project focused on a 38 ka eruption at Lunar Crater 

Volcanic Field, NV, which produced a tephra fall deposit that can be traced up to 6 km from the 

source vent. A total of 28 sample sites were characterized for depth, maximum grain size, and 

scoria texture. Samples were collected at each site for laboratory determination of deposit 

density and, based on that, mass per area, as well as for granulometric analysis. Field data 

indicate that the deposit contains two beds which were likely produced by two separate phases of 

the eruption. We focused on the topmost bed due to its greater lateral extent, and the consequent 

interpretation that it resulted from a higher plume. Reconstruction of the eruption column based 

on mass per unit area is presently being undertaken to ascertain plume height and wind speed, 

but preliminary results based on grain size suggest an eruption column between 6 and 8 km in 

elevation with a 25 m/s wind blowing to the northeast. Post-eruptive erosion has rendered 

identification of deposit boundaries difficult, resulting in a high degree of uncertainty in eruption 

column height. 
Focusing)of)melt)by)magma)chambers)in)time)and)space:)theory)and)application)to)

Mount)Mazama,)Crater)Lake,)Oregon

Leif)Karlstrom

Stanford

Heather M.N. Wright

USGS

Charles)R.)Bacon

USGS

Even)during)periods)of)constant)melt)flux)into)the)crust,)volcanic)eruptions)

will)be)episodic)in)space)and)time.))The)crustal)magma)transport)processes)

responsible)for)this)unsteadiness)are)not)available)for)direct)observation. However,)

the)distribution)of vents)and)eruptive)products)at)a)given)volcanic)center)provide)

important)clues)to)the)nature)and)time)variation)in)magmatic)plumbing.)Many)

evolved)centers)exhibit)a)wide)region)of)monogenetic)vents)surrounding)a)central)

composite)volcano,)with)episodicity)in)the)timing,)composition,)and)volume)of)

eruptions)as)functions)of)distance)from)the)center.)

Melt)focusing (lensing))by)magma)chambers)is)one)potential)mechanism)for)

generating)spatioOtemporal)patterns)in)central)vents)versus)monogenetic)regional)

volcanism.)Magma)chambers)that)attain)some)overpressure)with)respect)to)the)

lithostatic)stress)gradient)may)affect)the)trajectory)of)rising)melt,)becoming)

effectively “lenses”)for)dikes)rising)from)depth)(Karlstrom)et)al.,)2009).)This)is)a)

mechanism)for)generating)discrete)volcanic)edifices)over)a)larger)source)region.)The)

degree)of)lensing)also)varies)in)time,)due)to a)positive)feedback)between)

overpressure)and)meltOfocusing)efficiency that)creates)a)growing)region)of)melt)

capture)at)depth.)Lensing)experiences)a)sudden)decrease following)centralized)

eruptions that drain)the)reservoir)and)relieve)overpressure.)This)model)thus)

predicts)oscillating)patterns)of)monogenetic)regional)volcanism)and)central)vent)

eruptions.

We)test)predictions)of)the)magmatic)lensing)model)with)data)from)Mount)

Mazama)in)the)Oregon)Cascades)that)document)central)vent)eruptions)and)regional)

monogenetic)volcanism)over)the)past)400)ka)(Bacon)and)Lanphere)2006,)Bacon)

2008).)There)are)significant)patterns)in)the)volume,)melt)composition)(silica)

content),)and)spatioOtemporal)occurrence of)eruptions)that)are generically

consistent)with)episodic)focusing)of)rising)melt)by)the)Mazama)magma)storage)zone.)

These)patterns)may)reflect)unsteady)melt)supply)into)the)Mazama)system,)and)a)

gradual)increase)in)crustal)modulation)of)rising)melt,)culminating)in)the)climatic)

calderaOforming)eruption)that)formed)Crater)Lake)caldera at)~7.7)ka.)We)suggest)

that)a)detailed)characterization)of)monogenetic)versus)central)vent)eruptions)in)

combination)with)simple)models)has)the)potential)to)provide)important)constraints)

on)both)the)timeOevolving)melt)influx)and)size/geometry)of)crustal)plumbing)at)

active)volcanic)centers.)
MODELING MAFIC LAVA FLOWS WITH AN EYE TO EMERGENCY RESPONSE. L. P. Keszthelyi1

1

Astrogeology Science Center, U.S. Geological Survey (2255 N. Gemini Dr., Flagstaff, AZ 86001; laz@usgs.gov).

Introduction: Models that estimate the extent of 

lava flows from a volcanic eruption can be useful in 

planning for the emergency response to a future volcanic eruption in the American Southwest. In particular, they can help determine the extent to which experiences in Hawai’i can be relied on. However, the 

models all have limitations that must be wellunderstood before they are used to make decisions that 

affect the life and well-being of people. 

Here, two key questions are considered. (1) How 

far can a lava flow be expected to reach? And (2) 

When will it be safe to begin reconstruction efforts 

after a lava flow has covered an area? The second is 

easier to anwer and is addressed first. 

Lava Flow Cooling: Reopening roads covered by 

lava flows usually starts with removing some part of 

the lava flow with heavy earth-moving equiptment. In 

Hawai’i, the tracks on a bulldozer were damaged when 

this was attempted on a solidified but still hot lava 

flow. The time required to cool a typical lava flow to a 

safe temperature, say below 70°C or 160 °F, is of the 

order of years. This time is primarily controlled by the 

thickness of the lava flow and the amount of rainfall. 

If the cooling is primarily by conduction of heat 

through an insulating crust of lava, then the time is 

proportional to the square of the lava flow thickness 

(double the thickness = 4 times the time to cool) [1].

However, if there is substantial cooling by rain, this 

rule is violated and the flow cools more linearly (double thickness = 2 times the time to cool). Rain can be a 

very important effect on the wet side of Hawai’i, but 

should be negligible in the American Southwest. 

Figure 1: model calculations for the thickness of a 

pahoehoe crust on a basaltic lava flow for various rainfall rates. Straight lines indicate cooling dominated by 

conduction with little effect from rain. Model is based 

on [2-3]. 

The take-home message from this analysis is that it 

can easily take a decade or more for a typical lava flow 

to naturally cool to a safe temperature. This time can 

be greatly shortened by pouring large amounts of water 

onto the flow (inundate with the equivalent of a few 

times the thickness of the lava flow). 

Modeling the Length of Lava Flows: There are 

many models, some very simple, that purport to establish a relationship between the final length of a lava 

flow and a few basic parameters about the lava and/or 

the eruption. Despite their apparent pedigree in terms 

of numbers of peer-reviewed papers using them, no 

generic model can be trusted. 

In the broadest sense, lava flows stop when they 

solidify too much to flow. Thus a balance between the 

heat (a) being added by new lava coming out of the 

ground and (b) being lost out of the lava flow should 

allow a generic model for how long a lava flow can be

[4]. The problem is that how lava flows loose their 

heat is very different between open flows and insulated 

flows and between sheet flows and narrow 

tubes/channels [5]. Within each basic type of lava 

flow, there are some empirical relationships that relate 

parameters such as erupted volume, effusion rate, lava 

viscosity, and slope to the length of the flow. 

While such semi-generic models can give a rough 

sense of what to expect, individual lava flows can behave in very unpredicted manners. For example, the 

direction that a lava flow takes is generally downhill. 

However, topographic obstacles only a fraction the 

height of the final lava flow can substantially divert the 

flow. Perhaps more problematic for accurate prediction is the fragility of the lava transport conduits. Even 

short-lived (hours to days) stoppages or surges in lava 

flux can irreparably damage lava tubes or channels in 

difficult to predict locations [6-7]. This essentially 

resets the location of the lava vent to a new location 

along the existing tube/channel. Since the total erupted 

volume is a key element in estimating the final length 

of a lava flow, there is no practical way to predict the 

length of a lava flow before the eruption ends. 

References: [1] Hon K. et al. (1994) GSA Bull., 

106, 351-370. [2] Keszthelyi L. and Denlinger R. 

(1996) Bull. Volcanol., 58, 5-18. [3] Keszthelyi L. and 

McEwen A. S. (1997) GRL, 24, 2463-2466. [4] Griffiths R. W. (2000) Annu. Rev. Fluid Mech., 32, 477-

518. [5] Keszthelyi L. et al. (2006) J. Geol. Soc. Lon., 

163, 253-264. [6] Kauahikaua et al. (2003) USGS Prof. 

Pap. 1676, 63-88. [7] Crisp J. and Baloga S. M. (1994)

JGR, 99, 1819-1831.

19
Relationship between dike and volcanic condiut distribution in a highly eroded 

monogenetic volcanic field: San Rafael, Utah 

Koji Kiyosugi1, Charles Connor1, Paul Wetmore1, Brian Ferwerda1, Aurelie Germa1, Laura 

Connor1

and Amanda Hintz*2

* presenting author 

1 Department of Geology, University of South Florida, Tampa, Florida 

2 Utah Geological Survey, Salt Lake City, Utah 

A relatively young, potentially active monogenetic volcanic field (Black Rock Desert, Utah) and 

a relatively old, eroded sub-volcanic plumbing system composed of dikes and sills (San Rafael 

Swell, Utah) were examined for patterns of conduit distribution and validity of statistical 

methods to perform probabilistic hazard assessments on monogenetic volcanic fields globally. 

We mapped 63 conduits, ~2000 dike segments, and 12 sills in the San Rafael sub-volcanic field, 

where this Pliocene magmatic system is eroded to a depth of ~0.8 km and is exceptionally well 

exposed. Although the number of mapped conduits, dikes, and sills might represent minimums, 

depending on the level of erosion and exposure, mapped dikes are more numerous around the 

areally extensive sills and interact with sills and conduits in complex ways. We analyze conduit 

distribution using kernel density methods and compare results with dike and sill distribution. We 

find that the distribution of conduits matches the major features of dike distribution, including 

development of clusters and distribution of outliers. These statistical models are then applied to 

the distributions of volcanoes in several recently active volcanic fields, where intrusion 

distributions must be inferred from very sparse data, and compared with San Rafael conduit 

distribution. This comparison supports the use of statistical models in probabilistic hazard 

assessment for distributed volcanism. Specifically, renewed dike intrusion and potential 

eruptions in active basaltic systems can be assessed probabilistically from the distribution of 

older volcanoes in dispersed volcanic systems. 
Capabilities of University of Utah Seismograph Stations for Monitoring Seismicity in Utah 

KOPER, Keith D., koper@seis.utah.edu, University of Utah Seismograph Stations; Kristine L. 

Pankow; Relu Burlacu; Katherine M. Whidden; James C. Pechmann; J. Mark Hale; Paul M. 

Roberson 

The University of Utah Seismograph Stations (UUSS) monitors seismicity in Utah using data 

from a network of 253 seismograph stations deployed in Utah and neighboring states. These 

stations generate 786 channels of seismic data from various combinations of broadband, strongmotion, and short-period sensors. UUSS processes the incoming data in near real time, with 

nearly all events larger than M 3 automatically detected, located, and publicized within 10 

minutes of the origin time. Most earthquakes occur within Intermountain Seismic Belt (ISB), a 

100- to 200-km-wide band of seismicity that extends southward into Arizona and northward into 

Montana; however, a significant number of small, mining-induced earthquakes occur within the 

coal-mining belt of central Utah. The current uniform detection threshold for the network is 

estimated to be M 1.5 within the ISB in Utah and M 2.0 to 2.5 elsewhere in the state. In an 

average year in Utah, UUSS locates one earthquake of M 4 or larger, 12 of M 3-4, 200 of M 2-3, 

1200 of M 1-2, and 300 of M 0-1. An M 5 or larger earthquake occurs on average every 5 years, 

although the last such event was in 1992. The ISB and its associated faults are responsible for 

most of the seismic hazard and risk in Utah, which is concentrated along the five central 

segments of the Wasatch fault in the northern Utah Wasatch Front urban corridor and along the 

Hurricane fault in southwestern Utah. 

Three features of UUSS operations are especially relevant to monitoring potential volcanism in 

Utah. The first is that UUSS routinely computes full moment tensors for Utah seismic events 

larger than about M 3.5. This includes statistical tests to assess the significance of any isotropic 

component that appears in the solution. This capability was developed because of the need to 

identify and model mine collapses, which are not purely deviatoric, and would be seamlessly 

applicable to dilatational volcanic sources. Second, UUSS currently maintains a network of 8 

infrasound arrays across Utah, with continuous telemetry to the UUSS data center. Three UUSS 

personnel have expertise in infrasound analysis and would be able to process and interpret any 

infrasonic signals generated by volcanic activity. Third, UUSS maintains approximately 6 

portable seismograph stations that could be deployed by UUSS technicians to most regions of 

Utah within approximately 24 hours. Therefore, once unusual volcanic activity had been 

identified, UUSS could quickly augment the permanent network in the region of interest. 
InSAR mapping of Holocene volcanoes in the western conterminous U.S. – preliminary 

results 

Z. Lu1, C.Y. Zhao2, W.J. Lee2, L.Y. Ji2, M. McLay1, and D. Dzurisin1

1) USGS/CVO, Vancouver, WA 98607 (lu@usgs.gov); 

2) Visiting scholars at USGS/CVO, Vancouver, WA 98607. 

We have processed ERS, Envisat, and ALOS PALSAR radar images to map long-term ground 

surface deformation from 1992 through 2010 at about 25 volcanoes in the western conterminous 

US that have erupted during the Holocene. We have used multi-temporal radar images and 

averaged many interferometric synthetic aperture radar (InSAR) images to improve the signal-tonoise ratio of our deformation analysis. Our preliminary results indicate persistent subsidence 

over Medicine Lake volcano and Lassen volcanic center at a rate of ~1 cm/year, but no 

significant deformation at the other volcanoes. Deformation fields driven by geothermal 

exploration or development and large earthquakes have also been identified near several of the 

volcanoes. Our results represent the first attempt to systematically map deformation over 

Holocene volcanoes in the western conterminous U.S. and will be updated regularly with future 

radar acquisitions. 
Pondering)the)consequences)of)an)eruption)in)the)American)Southwest:))Challenges)for)emergency)

management)and)scientific)response

Christina)Neal,)U.S.)Geological)Survey,)Alaska)Volcano)Observatory)

4230)University)Drive)

Anchorage,)AK))99508)))

tneal@usgs.gov))))tel)907H786H7458

The)last)volcanic)eruption)in)the)Four)Corners)region)of)the)American)Southwest)occurred)~1000)years)

ago.)Today,)even)a)modest)eruption)within)the)range)of)plausible)events)has)potential)to)threaten)lives)

and)property,)disrupt)economic)activity)and)lifelines,)and)impact)the)environment,)possibly)for)years.))

Hazards)of)concern)span)a)large)range)of)classic)volcanic)phenomena)with)the)added)potential)for)

largeHscale)forest)fires,)something)of)special)concern)in)the)arid)Southwest.))While)the)exact)time)and)

place)of)the)next)eruption)are)unknown,)it)will)with)certainty)pose)new)and)complex)challenges)to)

responding)agencies,)particularly)because)very)few)residents)or)official)responders)living)in)the)region

today)have)firstHhand)knowledge)of)eruptions)and)associated)hazards.)

Volcanic)crises)can)have)protracted)and)erratic)precursory)periods)that)demand)heightened)vigilance)

over)long)periods)of)time)(weeks,)months,)years).))Especially)where)monitoring)is)skeletal)and)baselines)

are)lacking,)a)significant)challenge)for)responders)is)to)communicate)useful)information)despite)

significant)uncertainties)about)the)probability)of)an)eruption,)as)well)as)its)timing,)size,)severity,)and)

duration.))At)the)same)time,)the)web)of)federal,)state,)and)local)agencies,)universities,)and)the)private)

sector)may)have)overlapping)spheres)of)response.)Plans)that)clarify)roles)and)protocols)are)vital)to)

avoid)conflicting)messages.))While)public)safety)and)mitigation)of)impacts)are)primary)objectives)of)

planning,)plans)should)also)consider)critical)science)opportunities)and)outline)mechanisms)to)facilitate)

a)strategic)research)response)to)episodes)of)volcanic)unrest)or)eruption.)))

Any)eruption)in)the)American)Southwest)would)unleash)a)deluge)of)attention,)severely)taxing)the)

resources)and)capabilities)of)scientific)agencies,)law)enforcement,)emergency)management,)and)land)

managers.))Strain)will)be)magnified)if)the)period)of)unrest)and)eruption)continues)for)months)or)years,)

interspersed)with)pauses)of)variable)duration.))The)Internet,)24/7)news)cycle,)exploding)social)media)

and)future)incarnations)of)surveillance)and)communication)technology)will)complicate)and)enhance)

the)ability)of)agencies)to)manage)the)situation)in)ways)difficult)to)anticipate.)))

Preparing)for)volcanic)eruptions)in)the)Southwest)necessarily)competes)with)higher)probability)hazards)

such)as)drought)and)wildfire.))Given)the)small)likelihood)of)an)eruption)in)the)lifetime)of)a)typical)

interagency)response)plan,)what)investment)in)planning)and)preparation)for)a)volcanic)crisis)is)

reasonable?))At)what)scale)should)such)planning)occur?))Can)these)efforts)be)dovetailed)with)other)

natural)hazard)assessment)and)risk)mitigation)efforts)to)leverage)scarce)resources?))Discussions)at)this)

meeting)will)begin)answering)these)questions)by)identifying)probable)eruption)scenarios,)impacts,)

current)response)protocols,)and)critical)gaps)in)science)and)preparedness.)
Abstract

Volcanism(in(the(American(Southwest((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((

October(18720,(2012(((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((

Flagstaff,(AZ

Osiensky,!Jeffrey!M.1

,!Birch,!Scott 2!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 1

NOAA/NWS(Alaska(Region(Anchorage,(AK((

2(NOAA/NWS(Western(Region(Salt(Lake(City,(UT

Volcanic!ash!plumes!and!its!impact!to!aviation!in!the!Western!United!States

Volcanic(eruption(plumes(and(drifting(ash clouds(from(Western(U.S.(volcanoes(have(caused(aviation(

concerns and(delays(in(flight(operations(nationwide.((A(jet(cruising(through(an(ash(plume(can(encounter

a(wide(variety(of(impacts(ranging(from(surface(and(windscreen(abrasion(to(engine(flameout,(depending(

on(the(material(encountered(and(exposure.((Large(volcanic(eruptions(in(the(Pacific(Northwest(and(

California(have(the(potential(to(transport(ash(into(the(Southwestern(United(States.((In(addition(to(the(

airborne(ash(hazard(to(aviation(there(exists(another(hazard,(namely(ash(fallout(on(the(ground.(( Volcanic(

threat(areas(in(southern(California(from(the(Long(Valley(Caldera(to(the(Salton(Buttes(pose(a(direct(risk(to(

public(health(and(infrastructure(in(the(Southwest(U.S.(((

There(are(many(volcanic(ash(hazards(to(aviation and(the(public.(( This(paper(will(explain(the(hazards(and(

what(is(being(done(both(nationally(and(internationally(to(mitigate(the(threat(of(volcanic(ash.((Federal,(

state(and(local(agencies(are(working(together(to(better(understand(the(hazards(and(find(the(best(ways(

to(deal(with(them.((State(and(local(emergency(responders(will(be(the(folks(who(deal(with(the(impacts(

from(the(volcanic(ash(and(need(to(know(what(resources(are(available(to(assist(in(their(decision(making(

process.

The(question(is(not(“if”(but(“when”(will(the(next(volcanic(ash(event(take(place(which(impacts(the(

Southwestern(U.S.?((In(order(to(be(prepared,(there(needs(to(be(a(plan(in(place(which(outlines(the(roles(

and(responsibilities(of(the(local,(state(and(federal(agencies(involved.((In(addition,(there(needs(to(be

training and(frequent(collaboration(to(ensure(proficiency(in(dealing(with(such(a(low(frequency,(high(

impact(event.((((
Abstract(for:(Volcanism(in(the(American(Southwest,(October(18:20,(Flagstaff,(AZ

Spatial(Database(of(Holocene(and(Latest(Pleistocene(Volcanic(Vents(in(the(Western(Conterminous(U.S.

By(David(W.(Ramsey(and(Connie(L.(Driedger

The(U.S.(Geological(Survey (USGS)(National(Volcano(Early(Warning(System((NVEWS)(has(identified 28(

volcanoes(and(volcanic(centers(in(the(western(conterminous(U.S.(as(posing(moderate,(high,(or(very(high(

threats(to(surrounding(communities(based(on(their(recent(eruptive(histories and(their(proximity(to(

vulnerable(people,(property,(and(infrastructure.((To(better(understand(the(extent(of(potential(hazards(at(

these(and(other(volcanoes(and(volcanic(centers,(the(USGS(Volcano(Science(Center((VSC)(is(compiling(a(

spatial(database(of(all(known(Holocene(and(Latest(Pleistocene(volcanic(vents(in(the(western(

conterminous(U.S.((The(database(records(vent(location((latitude/longitude(coordinates),(vent(type(

(cinder(cone,(maar,(etc.),(lithology,(age,(geographic(feature name,(mapping(source,(and,(where(

available,(spatial(database(source.((USGS(geologic(maps,(USGS(Data(Series,(the(Smithsonian(Global(

Volcanism(Program((GVP)(catalog,(and(published(journal(articles(are(the(main(data(sources(cited.((

Locations(in(this(compilation(can(be(spatially(compared(to(located(earthquakes, used(as(generation(

points(for(numerical(hazard(models(or(hazard(zonation(buffering,(and(analyzed(for(trends(in(regional(

magmatism(and(more(localized(eruptive(activity(through(time.((The(spatial(database(will(eventually(be(

available(online as(a(USGS(Data(Series publication.(
Experimental determination of H2O and CO2 solubility in basalt and basaltic andesite

Kurt Roggensack1 and Gordon Moore2

1

School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-

1404 (kurt.roggensack@asu.edu)

2

Department of Chemistry, Arizona State University, Tempe, AZ 85287-1604; now at 

Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109 

(gmmoore@umich.edu)

H2O and CO2 are the most abundant volatiles in mafic magmas and their solubility 

influences volcanic degassing and the eruptive process. A series of piston-cylinder 

experiments have been conducted to investigate H2O and CO2 solubility of mafic 

compositions commonly found in olivine-hosted melt inclusions. The starting material 

used in experiments are natural samples, a basalt from a Guatemalan cinder cone and a 

basaltic andesite from Fuego volcano, Guatemala. The samples were crushed and melted 

twice in a gas-mixing furnace at NNO to produce crystal-free, homogeneous glass prior 

to experimentation. All experiments were volatile-saturated with either pure H2O or a 

mixed H2O-CO2 fluid in Au80Pd20 capsules and heated with a graphite furnace to 1190  ̊C 

at pressures from 300 to 600 MPa. The intrinsic fO2 of our piston-cylinder assembly is ~ 

NNO+1. The analysis of the run products includes low-temperature, vacuum manometry 

of the residual H2O and CO2 fluid, electron microprobe analysis of the glass and FTIR 

spectroscopy of H2O and CO2 in the glass. Pressure calibration of the piston-cylinder is 

based on the solubility of H2O and CO2 in rhyolite. Among successful experiments, only 

those capsules with accurate fluid analysis (i.e. measurement of both CO2 and H2O; 

sensible mass balance) were included in the final data set. Our results improve upon H2OCO2 solubility of basalt and now allow distinction between H2O-CO2 solubility of 

basaltic andesite. At similar experimental conditions water and CO2 solubility are greater 

in basalt as compared to basaltic andesite. At 300 MPa with a pure H2O fluid the 

solubility of water in basalt is 6.3 wt.% versus 5.2 wt.% for basaltic andesite (based on 

near-IR molar absorptivities of Dixon et al., 1994 and those calculated from Mandeville 

et al. 2002, respectively). Direct comparison of our CO2 solubility results is simplified by 

interpolation of fugacity-CO2 abundance. Our experiments indicate that a pure CO2 fluid 

at 300 MPa (i.e. CO2 fugacity of 5945 bars) would equilibrate with 2,500 ppm CO2 in 

basalt and 2,000 ppm CO2 in basaltic andesite (molar absorptivity calculated from Dixon 

& Pan, 1995). At these same conditions the SolEx model predicts ~1,500 ppm CO2 in 

basalt, whereas the Papale et al. (2006) model predicts 3,300 ppm CO2 for basalt. In 

conclusion, our results show that there is a significant compositional dependence on H2OCO2 solubility in basalts and basaltic andesites with solubilities being greater in more 

mafic compositions. These data with complete characterization of gas fugacity will 

improve our ability to accurately interpret melt inclusion suites and model degassing 

processes.
Scenario for an eruption in the San Francisco Peaks or similar volcanic field: Effects on 

Northern Arizona and beyond 

Stephen Self

Office of Nuclear Material Safety and Safeguards, US-Nuclear Regulatory Commission, Washington DC 20555, 

USA; stephen.self@nrc.gov [also at Dept. of Earth and Environmental Sciences, The Open University, UK]

There is a chance of an explosive basaltic volcanic eruption in the foreseeable future from one of the ~ 

20-30 monogenetic volcano fields in the SW United States that have been active within the past 

100,000 years. It could be an eruption from fields in SW Nevada or California, or from the Black 

Rock Desert Field of SW Utah or the Raton Volcanic Field of New Mexico, or from the local San 

Francisco Volcanic Field (SFVF), Arizona, to name but a few. Both dry (magmatic) and wet 

(phreatomagmatic, i.e., involving groundwater) eruptions have occurred in these volcanic fields in

recent geologic times. 

An interpretation of the style, duration, and effects of a dry eruption can be based on the AD 1085 

eruption of Sunset Crater, the youngest eruption from the SFVF. Results from on-going studies on the 

deposits of this eruption could serve as a scenario for planning in case of future volcanic events. 

Sunset’s deposits suggest it was the largest recent eruption from a monogenetic basaltic volcano field

in the continental US, and one of the most explosive, meaning that it spread pyroclastic scoria and ash 

fall-out deposits over a wider area than in many similar eruptions. The duration of activity is not 

known precisely but can be bracketed between a few weeks to perhaps 2-3 years. Notable features of 

significance to hazards are: the 10-km-long eruptive fissure on which Sunset scoria cone grew; the 

relatively large eruptive magmatic volume (almost 1 km3

) apportioned between the broad (~ 2-kmwide, 300-m-tall) Sunset scoria cone, the scoria-and-ash fall deposit, and three lava flows (maximum 

11 km long); and the widespread dispersal of some scoria fall units. In another volcanic field in SW 

Nevada evidence from Lathrop Wells cone and fall deposits (~ 75,000 years old) suggest an eruptive 

style that was equally explosive and yielded some layers of finer ash deposits than seen at Sunset.

In terms of hazard scenario planning, the main facts to be considered for this style of explosive 

volcanism are:

- The main phase may last intermittently for last months to years, with declining activity dwindling on 

for several more years. 

- Eruption clouds laden with ash could reach altitudes up to 16 km above the volcano ( ~ 60,000 ft)

while spreading up to 100s km downwind, affecting flying aircraft. There would be ash impacts on 

local airports, on flights crossing the region at ~ 35 000 ft, and on aircraft heading in and out of ABQ, 

LVA, PHX, and SLC airports, dependent on wind-directions. 

- Ash fall-out deposit areas may be > 500 km2 for 10 cm thickness of ash and up to 1000s km2 for ~ 1 

cm. Despite this, there would be only a trace of fine ash fall-out beyond N Arizona for an eruption 

from SFVF, again dependent on wind-directions. Surface-wind-induced re-distribution of ash could 

also occur for months to years after the eruption has finished. Ash causes disruptions to surface 

transport systems and many services, is an abrasive nuisance, and in suspension can cause respiratory 

problems. However, basaltic ash is not recognized to carry minerals that cause severe health hazards. 

- On the longer term there may be ash-deposit-induced changes in soil properties, such as moisture, 

dependent on the location of the next eruption and the local geologic setting. 

This talk also reflects the work of many colleagues working on the Sunset and related deposits, 

including Michael Ort, Amanda Clarke, Fabrizio Alfano, Chelsea Allison, Greg Valentine, and, of 

course, Bob Amos. The views expressed are those of the author and not of the US-NRC.
The View from Social Science: 

How people will think and behave during an extended crisis with large uncertainties

Katherine F. Thompson, Columbia University Center for Research on Environmental Decisions

As scientists who are accustomed to interpreting probabilities, margins of error, and other statistical 

uncertainties, seismologists and volcanologists may well feel that such precise, scientific presentations 

of data are the most accurate formats through which to communicate information to the public when a

potential volcanic crisis threatens. 

Probabilities may seem like a natural format to use—after all, many Americans use weather forecast 

information on a near-daily basis. But research shows that a surprising percentage of the population 

critically misunderstands statements like, “there is a 30% chance of rain tomorrow.”1

 Other psychology 

studies show us that people tend to systematically misinterpret, ignore, distort, or misuse probability 

information, even when given clear verbal guidelines about the meaning of the numbers that they’re 

seeing.2-5 

This talk will introduce several psychological biases and tendencies that may affect the way the public 

understands (or even whether they pay attention to) the kind of information that might be provided by 

scientists or emergency managers during an extended period of volcanic unrest in the American 

Southwest. In addition to systematic distortions in probability perception, this talk will address:

• why long time horizons make people unlikely to act;

6

 

• how the “finite pool of worry” can cause us to ignore environmental dangers;

7

• how learning probabilities through personal experience (sampling) results in very different 

decisions than learning from verbal descriptions (summary statistics);

3

• how hedonic reappraisal, or adjusting to the “new norm,” may interfere with warnings or 

evacuation orders;

8

• and how critically important it is that people perceive instrumentality: the idea that their actions 

can and will have an effect on their situation.

9

Although many psychological biases tend to work against people’s willingness to invest in preparation 

and mitigation measures, those practitioners who understand the social science behind hazard 

warnings and information campaigns can easily avoid common pitfalls, and at times even harness 

some of these biases to improve the public’s ability to understand and use warning information.

References

1. Gigerenzer, G., Hertwig, R., Van Den Broek, E., Fasolo, B., & Katsikopoulos, K. V. (2005). “A 30% chance of 

rain tomorrow”: How does the public understand probabilistic weather forecasts? Risk Analysis, 25(3), 623-

629.

2. Kahneman, D. & Tversky, A. (1979). Prospect Theory: An Analysis of Decision under Risk. Econometrica,

XLVII: 263-291.

3. Hertwig, R., & Erev, I. (2009). The description-experience gap in risky choice. Trends in Cognitive Science, 

13(12), 517-523.

4. Lichtenstein, S., Slovic, P., Fischhoff, B., Layman, M., & Combs, B. (1978). Judged frequency of lethal events. 

JEP: Human Learning and Memory, 4, 551-578.

5. Budescu, DV, Weinberg, S & Wallsten, TS (1987). Decisions based on numerically and verbally expressed 

uncertainties. Journal of Experimental Psychology: Human Perception and Performance, 14(2), 281-294.

6. Trope, Y., & Liberman, N. (2011). Construal level theory. In P. Van Lange, A. W. Kruglanski, and E. T. Higgins 

(Eds), Handbook of Theories of Social Psychology. London: Sage Publications.

7. Hansen, J., Marx, S., & Weber, E. U. (2004). The role of climate perceptions, expectations, and forecasts in 

farmer decision making: IRI.

8. Brickman, P., & Campbell, D. T. (1971). Hedonic relativism and planning the good society. In M. 

H. Appley (Ed.), Adaptation level theory: A symposium (pp. 287–302). New York: Academic Press.

9. Spence, A., Poortinga, W., Butler, C., & Pidgeon, N. F. (2011). Perceptions of climate change and willingness 

to save energy related to flood experience. Nature Climate Change, 1(1), 46-49.
Basaltic volcanism in the American Southwest over the last million years: what 

happens here, how often, and why? 

Greg Valentine1 and Michael Ort2 

1

Department of Geology, 411 Cooke Hall, University at Buffalo, Buffalo, NY 14260

2

SESES, Box 4099, Northern Arizona University, Flagstaff, AZ 86011

The southwestern United States has over forty volcanic fields containing ~1400 Quaternary basaltic 

volcanoes. The volcanoes within the fields are predominantly monogenetic, each having produced only 

one eruptive episode that might last for days to years. The majority of Quaternary eruptions in the 

Southwest have occurred along a northwest-southeast-trending band that stretches from the Potrillo field 

in southern New Mexico, through four fields in Arizona, to the Lunar Crater field in Nevada (Figure 1); 

these six fields account for ~2/3 of the Quaternary events. Most of the remaining volcanoes occur around 

the margins of the Basin and Range Province, although a few are in the interior of the Province or 

scattered outside of it. The level of detailed study varies markedly from field to field, suggesting that a 

concerted hazards-oriented program of characterization and modern geochronology would be useful. The 

average interval between monogenetic eruptions in the entire region, based upon existing data, is ~700-

1000 years, depending upon whether one focuses on events <50 ka or on the last 2 Ma, and is comparable 

to the repose intervals between eruptive episodes at individual intermediate-composition stratovolcanoes. 

The potential hazards, while 

appreciable, are less extensive than at 

a reawakening stratovolcano, but 

assessment is complicated by the fact 

that a new eruption could occur at an 

unknown location within a broad area

with widely varying land use patterns. 

Conceptual models of volcanic field 

behavior in the Southwest range from 

large scales, which relate volcanism to 

rift zones, lithosphere-upper mantle 

coupling around the Colorado Plateau 

margins, deformation-induced 

focusing of pre-existing melts in 

lithospheric mantle, and shear-driven 

upwelling of asthenosphere. At 

smaller scales, the location of 

individual volcanoes and clusters is

related to crustal structure and, it is 

hypothesized, to small-scale compositional heterogeneities in source mantle material. Geochemical and 

petrologic data suggest that many eruptions are fed by magmas that rose quickly through the crust with 

little or no stalling, which implies that the lead time from monitoring might be relatively short (weeks?), 

if precursor signals are detected at all. Given the wide area with the potential for eruptions and its 

generally low population density, choosing where to monitor on an ongoing basis is problematic. Remote 

sensing using satellites, perhaps using InSAR, may be the best option for monitoring over such a large 

area. Recent work indicates that explosive basaltic eruptions with extensive ash-laden plumes might be 

common. Although often assumed to be relatively benign, eruptions at small-volume volcanoes can 

exhibit a range of styles (including phreatomagmatic) and produce all of the hazard types (tephra plumes, 

tephra fall, pyroclastic density currents, ballistics, lava flows, shock waves, and modification of 

landscapes and sediment budgets) that can occur at other types of volcanoes.

Snake

Plain

Cascade Range

32o 

28o 

24o 

20o 

16o 

36o 

40o 

44o 

48o 

120o 116o 112o 108o 100o 104o 

P 

J 

X 

U.S.A.

Estados Unidos 

de México 

Canada

120o 116o 112o 108o 100o 104o 

Pacific

Ocean

0 200 400 

kilometers

Pinacate

 (400,6)

N

Ubehebe

(3,3)

Pisgah

(1,1)

Dotsero

(2,1)

GeronimoSan Bernardino

(130,4)

San Francisco

(120,3)

Uinkaret

(213,2)

Black Rock

Desert (17,4)

ZuniBandera

 (55,5)

Carrizozo

(3,2)

Sentinel

(2,0)

Springerville

(350,0)

Amboy

(1,0)

AuroraBodie (4,0)

Big Pine

(24,3)

Inyo 

Craters

(35,12)

Coso

(19,1)

Cima

(30,3)

Buffalo

Valley

(13,0)

Clayton

Valley

(1,0)

Lunar

Crater 

(111,1)

SheldonAntelope

(4,0)

Soda Lakes

(8,2)

Southwest

Nevada

 (8,0)

Albuquerque (4,0)

Lucero (5,0)

Quemado

(14,0)

Potrillo

(124,6)

Taos

Plateau

(6,0)

RatonClayton

(15,1)

Ocate

Mount (2,0)

Taylor (2,0)

Diamond

Craters

(1,1)

Four

Craters

(3,3)

Jordan

Craters

(4,1)

Bald Knoll (3,3) Hurricane

 (10,0)

Markagunt

Plateau (6,1)

Santa Clara

(14,1)

Utah

Leucite Hills

(12,0)

Nevada

California

Oregon

Arizona

New Mexico

Colorado

Wyoming

Idaho

Sonora

Chihuahua

Mineral Mtn/

Cove Fort

 (7,0)

Mexico

U.S.A.

>100 Quaternary basaltic volcanoes

10-100 Quaternary basaltic volcanoes

<10 Quaternary basaltic volcanoes

(20,2) - (# Quaternary volcanoes, # <50 ka volcanoes)

Figure 1

Valentine et al

Fig 1.pdf
Timing&of&late&Pleistocene&volcanism&at&Big&Pine&volcanic&field:&insights&from&volcanic&

stratigraphy,&cosmogenic&36Cl&dating,&and&paleomagnetism.&

J.A.&Vazquez&1

,&J.M.&Woolford2,&Alana&Zohar2,&E.A.&NagyJShadman3,&D.E.&Champion1

1.&US&Geological&Survey,&Menlo&Park,&CA&

2.&California&State&University,&Northridge&

3.&Pasadena&City&College&

The&Big&Pine&volcanic&field&(BPVF)&is&one&of&several&Quaternary&volcanic&fields&located&

along&the&tectonically&active&Owens&Valley&of&eastern&California.&&Previous&

geochronology&establishes&an&~1.3&Ma&history&of&volcanism&at&BPVF,&but&the&ages&and&

distribution&of&volcanic&products&associated&with&the&youngest&eruptions&are&poorly&

resolved.&&To&delimit&the&timing&and&products&of&the&youngest&volcanism&at&BPVF,&we&

combine&field&mapping,&cosmogenic&36Cl&dating,&and&paleomagnetism&of&lavas&and&

pyroclastic&deposits&in&the&area&surrounding&the&town&of&Aberdeen&where&basaltic&lavas&

with&wellJpreserved&flow&structures&and&morphology&are&concentrated.&&Mapping&and&

petrography&reveal&that&approximately&fifteen&vents&and&six&principal&flow&fields&occur&in&

the&Aberdeen&area.&&Discrete&basalt&units&are&distinguishable&using&phenocrystJxenolith&

composition&and&mode,&and&overlapping&flow&margins&establish&the&relative&ages&of&most&

of&the&flows.&&For&cosmogenic&36Cl&dating,&samples&were&taken&from&pahoehoe&flow&

surfaces,&nearJvent&tumuli,&and&the&tops&of&meterJscale&accretionary&lava&balls.&&Using&

the&scaling&model&of&Desilets&and&Zreda&(2003)&and&assuming&erosion&rates&of&<3&mm/ka,&

36Cl&exposure&ages&for&lava&flows&from&the&top,&middle,&and&bottom&of&the&volcanic&

stratigraphy&are&ca.&15&ka,&25&ka,&and&40&ka,&suggesting&multiple&episodes&of&late&

Pleistocene&volcanism.&&These&ages&agree&with&cosmogenic&3

He&and&40Ar/39Ar&ages&from&

previous&studies,&and&are&relatively&insensitive&to&choice&of&scaling&model&or&erosion&rate.&&

Samples&from&the&three&stratigraphically&youngest&flows,&which&cover&much&of&the&area&

south&of&Taboose&Creek&and&north&of&Division&Creek,&yield&36Cl&ages&of&ca.&15&ka.&&This&

youngest&episode&of&volcanism&erupted&olivine&to&plagioclaseJpyroxene&phyric&basalt&

from&at&least&four&vents&along&the&Sierran&front&and&separated&by&up&to&5&km.&&

Paleomagnetic&directions&for&the&lavas&are&consistent&with&the&distinct&episodes&of&

volcanism&implied&by&the&36Cl&ages.&&The&youngest&lavas&yield&nearly&indistinguishable&

paleomagnetic&directions,&suggesting&that&the&youngest&episode&may&have&erupted&

compositionally&diverse&basalt&over&decadal&to¢urial×cales.&The&young&36Cl&ages&

and&high&concentration&of&vents&relative&to&other&areas&of&BPVF&indicate&that&late&

Pleistocene&volcanism&has&migrated&to&the&westJcentral&portion&of&the&volcanic&field.&
Data compiled by the Smithsonian about volcanoes in the 

southwestern United States

Edward Venzke (Global Volcanism Program, Smithsonian Institution) 

A database of volcanoes with Holocene activity, referred to as the Volcanoes of the World

(VOTW) database, is maintained by the Smithsonian’s Global Volcanism Program (GVP). The role of GVP 

is to compile data about volcanoes world-wide, providing a standardized and accessible source of 

information that can be used by a wide range of researchers, officials, and the public. Referenced 

sources are varied, but material is primarily extracted from published research papers.

There are 10 volcanoes from the states of Nevada, Utah, Colorado, Arizona, and New Mexico 

(table 1) thought to have been active in the last 10,000 years. Data collected includes the basics of 

location, elevation, primary name, synonyms, feature names, morphological type, and captioned 

photographs. GVP staff also writes a paragraph summarizing the geological and volcanological history of 

each volcano. All known eruptions are listed, with dates (when available), location and deposits, and 

types of eruptive events.

Three of the ten volcanoes have no dated eruptions, but are believed by researchers to be 

Holocene based on other evidence. Another six have only one dated eruption each in the Holocene. 

Zuni-Bandera has two eruptions known, at 1170 BCE ± 300 years and 8710 BCE ± 300 years. In addition, 

there are another 28 volcanic areas that were active in the Pleistocene epoch; two of those, Steamboat 

Springs (Nevada) and Valles Caldera (New Mexico), have exhibited recent fumarolic activity.

The GVP database schema has recently been redesigned in a variety of ways to allow increased 

flexibility and the ability to compose complex search queries. Submissions of new research findings are

always welcome from the volcanological community to improve and expand the database.

Table 1. List of Holocene volcanoes in Nevada, Utah, Colorado, Arizona, and New Mexico. Last known eruption, 

primary morphological type, new VOTW 4.0 volcano numbers , and legacy volcano numbers (as previously 

published) and are shown.

Name State Last Known 

Eruption

Primary Volcano

Type

Volcano

Number

Legacy

VNum

Soda Lakes Nevada Unknown Maars 326010 1206-01-

Santa Clara Utah Unknown Volcanic field 327010 1207-01- 

Bald Knoll Utah Unknown Cinder cones 327030 1207-03- 

Markagunt Plateau Utah <= 1050 CE Volcanic field 327040 1207-04- 

Black Rock Desert Utah 1290 CE ± 150 Volcanic field 327050 1207-05- 

Dotsero Colorado 2200 BCE ± 300 Maar 328010 1208-01- 

Uinkaret Field Arizona 1100 CE ± 75 Volcanic field 329010 1209-01-

Sunset Crater Arizona 1075 CE ± 25 Cinder cone 329020 1209-02-

Carrizozo New Mexico 3250 BCE ± 500 Cinder cones 327110 1210-01-

Zuni-Bandera New Mexico 1170 BCE ± 300 Volcanic field 327120 1210-02-
2012 meeting: Volcanism in the American southwest

Uncertainties regarding explosive maar-diatreme eruptions within volcanic fields 

James White, University of Otago, Dunedin, New Zealand 

Maar-diatreme volcanoes are small volcanoes having a central crater cut into the ground 

surface and surrounded by a tuff ring. Buried beneath the crater floor is a deep vent structure 

filled with debris, called a diatreme. Basaltic eruptions produce maar-diatreme volcanoes 

when groundwater fuels explosions in the subsurface. Initial explosions occur at shallow 

depths, while many later explosions occur deeper within the sub-crater diatreme structure, 

contributing to growth of the diatreme but not necessarily adding material to the tuff ring 

surrounding the syn-eruptive crater. 

Observed maar-forming eruptions at Taal and Tarawera both began with weakly explosive 

growth of scoria cones, with explosive maar excavation beginning later in the eruptions when 

laterally propagating dikes intersected groundwater in a way that produced explosive magmawater interaction. In contrast, many other small volcanoes in volcanic fields show evidence 

that initial eruptions involved explosive magma-water interaction and excavation of substrate 

country rock, but that as the eruptions continued explosivity declined and eruption style 

changed to produce scoria cones and lava flows that buried the initial crater. 

Despite decades of attention and careful laboratory work on magma-water explosions, there 

remain significant gaps in our knowledge of the precise conditions that facilitate explosive 

magma-water interactions in real eruptions. There is a known ratio of magma to water that 

has maximum potential for generation of vapor from magmatic heat, and hence maximum 

explosive potential, which is often expressed as an optimal magma:water mass ratio of ~3:1. 

The ratio is simply that at which all water can be vaporized while cooling the magma to the 

vaporization temperature. Both experiments and observations of eruptions in water show, 

however, that this ratio has little or no relationship to the quantities of magma and water that 

are available at the site of an eruption. 

It is known that in laboratory experiments with basalt, a small trigger is needed to initiate 

explosive magma-water interaction, but the nature and scale of equivalent triggering 

requirements for natural systems are not known. Laboratory studies show that interaction of 

magma with clay-water slurries differs qualitatively from its interaction with clear water, and 

though there is good geological evidence that slurries such as liquefied sediment are 

encountered in eruptions, how they affect magma-water explosivity is not understood. 

In summary, magma interacting with groundwater is needed to form basaltic maar-diatremes, 

but neither the magma-supply conditions, nor the characteristics of the aquifer, that are 

needed to produce these explosive eruptions are sufficiently well understood to support 

confident prediction of whether, and when, a dike transiting an aquifer will drive explosive 

phreatomagmatic eruptions. This implies that when assessing potential hazard of a new 

eruption in a volcanic field with groundwater, it should be assumed that eruptions may begin 

with violent magma-water explosions, and also that even initially quiet eruptions may 

subsequently become violent if conditions change to initiate magma-water explosions. 
Petrogenetic Processes in the Lunar Crater Volcanic Field, Nevada

E. Widom1*, C. Rasoazanamparany1, G.A. Valentine2, E.I. Smith3, J.A. Cortes2, D. 

Kuentz1, R. Johnsen3

1

Department of Geology, Miami University, Oxford, USA, widome@muohio.edu (*presenting author) 2

Department of Geology, State University of New York, Buffalo, USA, gav4@buffalo.edu

3

Department of Geoscience, University of Nevada, Las Vegas, USA, gene.smith@unlv.edu

The Lunar Crater volcanic field, Nevada, is located in the central Great Basin at the 

northern end of a NNE-trending belt of Pliocene to Quaternary mafic volcanism. The 

volcanic field contains >200 vents, including cinder cones, tuff rings and maars, with 

eruptive activity as recently as ~40 ka [1]. Our studies are investigating the petrogenetic 

processes leading to compositional variations within single monogenetic eruptions, as well 

those of closely spaced monogenetic vent clusters, with a focus on the relative roles of 

mantle source heterogeneity, variable degrees of partial melting and fractional 

crystallization, and shallow lithospheric assimilation. In this context, we have analyzed 

~20 relatively high-MgO (7-11%) basalts/trachybasalts from four volcanic centers in the 

northern LCVF: the Marcath volcano, which is the youngest in the volcanic field, and 

three other volcanoes referred to as YMB (younger megacryst-bearing), OPB (older 

phenocryst-bearing), and PB (plagioclase-bearing) [2] that are located within ~500 m of 

one another and ~6 km NE of Marcath. Major element variations within the sample suite 

indicate that the magmas are compositionally distinct, although the Marcath and YMB 

samples may be related to one another by fractional crystallization of olivine, 

clinopyroxene, and minor plagioclase and Fe-Ti oxide. Trace element variations further 

delineate two distinct compositional endmembers, both of which have OIB-type 

characteristics: the OPB/PB group which is broadly similar to HIMU with Nb-Ta 

enrichment and LILE depletion; and the Marcath/YMB group with overall higher 

abundances of highly incompatible trace elements and enrichments in Cs, Rb and Ba 

similar to EMI. Isotopic analyses reveal a limited range in Nd and Hf isotope ratios, but 

significant variations in Sr and Pb isotopes, and superchondritic Os isotopic signatures. 

The samples exhibit a strong negative correlation between Sr and Pb isotopes that could be 

attributed to lower crust assimilation. However, the lack of correlation of isotopic 

signatures with indices of fractionation, and high (OIB-like) Nb/U ratios that exhibit a 

positive correlation with 187Os/188Os argue against an important role for either upper or 

lower crustal assimilation. Instead, the trace element and isotopic data support a model in 

which the basalts are generated by partial melting of an enriched and heterogeneous 

mantle source, with variable degrees of mixing between HIMU and EMI-type 

endmembers. The OPB/PB group magmas have HIMU-like trace element patterns and SrPb isotope signatures that are consistent with derivation from a mantle source containing a 

component of ancient recycled oceanic crust. The Marcath/YMB group samples, which 

exhibit comparatively high Ba, Rb and Cs, lower 206Pb/204Pb, and higher 87Sr/86Sr, are 

derived from an EMI-like mantle source that may have been generated by recycled 

oceanic crust plus a minor sediment component [3]. These results indicate that the mantle 

in this region is characterized by chemical and isotopic heterogeneity over very small 

spatial scales, likely related to ancient subduction processes.

[1] Shepard et al. (1996) Geology 23, 21-24; [2] Valentine et al. (2011) EOS Fall AGU V33C-2657; 

[3] Rasoazanamparany et al. (2012) Goldschmidt Conference, Montreal.
Postcaldera magmatism at three Rio-Grande-rifted calderas: Implications for assessing volcanic 

hazards at active caldera systems in the USA 

Matthew J. Zimmerer(1) and William C. McIntosh(1)

(1) – New Mexico Bureau of Geology and Mineral Resources, New Mexico Institute of Mining 

and Technology, Socorro, NM 87801, USA 

 Understanding the timing and duration of postcaldera magmatism is important for 

assessing potential hazards at active caldera systems. Ages of postcaldera volcanic and plutonic 

rocks from three Rio-Grande-rift faulted caldera shed light on the timescales of postcaldera 

magmatism. Rio Grande rifting has exposed intracaldera sequences and silicic intrusions at the 

Organ caldera (southern NM), the Questa caldera (northern NM), and the Mt. Aetna caldera 

(central CO). Exposures at these systems allow for assessing the timescales of postcaldera 

magmatism not possible at younger, less-dissected active calderas. In general, ages indicate that 

postcaldera volcanism began immediately (within analytical error) after the caldera-forming 

event and continued for several 100 ka to several Ma. Postcaldera intrusions were emplaced 

concurrently with postcaldera volcanism, but intrusive activity continued for several Ma after 

volcanism ceased. Thermochronology of exposed intrusions indicates reheating events as much 

as 10 Ma younger than the caldera forming event, suggesting that subcaldera environments may 

act as pathways for much younger and perhaps unrelated magmatism. At these three systems 

postcaldera magmatism was concentrated within or along caldera faults, though some magma 

was emplaced and erupted several kilometers outside of the caldera margins. 

 Volcanic deposits from the Yellowstone, Long Valley, and Valles calderas crop out in the 

western USA. The probability of a catastrophic caldera-forming eruption from these Quaternary 

systems is extremely low. More probable volcanic hazards are small volume lava flows and 

pyroclastic eruptions associated with postcaldera domes. Considering our research on the midTertiary Rio-Grande-rifted calderas and the youthful nature of these Quaternary systems, 

postcaldera magmatism at these three calderas is likely to continue for several 100 ka to several 

Ma. A protracted period of subcaldera magma emplacement without an accompanying volcanic 

eruption is also expected at these three Quaternary systems. Additional work focusing on the 

durations of postcaldera magmatism, the recurrence intervals between postcaldera eruptions, and 

the relationships between post- and syncaldera volcanism is necessary to develop a 

comprehensive understanding of the hazards associated with postcaldera magmatic activity. 
Volcanism in the American Southwest

October 18-19, 2012 

Meeting Location:

U.S. Geological Survey 

2255 North Gemini Drive 

Flagstaff, AZ 86001 

Meeting Purpose: Bring together volcanologists, network operators, land managers, and 

emergency managers to start a conversation about southwestern volcanoes and identify 

how to best prepare for future activity. 

Organizers: Jake Lowenstern, Laz Kestay, SAFRR Project: Science Application for 

Risk Reduction (Sue Perry and John Bwarie) all from USGS; Nelia Dunbar

NMBGMR; Greg Valentine, University at Buffalo, Michael Ort, Northern Arizona 

University 

Meeting Outcomes: 

• Communicate who would be responsible for what during a crisis 

• Communicate the roles and limitations of USGS 

• Communicate the roles of other federal agencies (NOAA, FAA, military) 

• Raise understanding of resources available to state and local EM 

• Use discussion panels to determine what else could be needed (e.g., regional plans 

regular ongoing activities, etc.) 

• Increase awareness of volcanism and vulnerabilities in the American Southwest. 

• Ponder eruption probabilities in regions with rare, distributed, volcanism. 

October 18, 2012 

7:45-8:00 “Registration”, coffee, etc. 

8:00-8:10 Introduction to the Flagstaff Campus and meeting logistics Laz Kestay, 

and Jake Lowenstern, both at USGS

8:10–8:30 Self-introductions, facilitated (Name, agency, relevant responsibilities) 

8:30–9:00 Pondering the consequences of a volcanic eruption in the American 

Southwest: Tina Neal, USGS

9:00–9:30 Scenario for an eruption in the San Francisco Peaks Volcanic Field: 

Effects on Northern Arizona and beyond: Steve Self, NRC
9:30–10:00 Volcanism in the American Southwest over the last million years: What 

happens here, how often, and why? Greg Valentine, University at Buffalo 

and Michael Ort, Northern Arizona University

10:00–10:20 BREAK (10:18 is GREAT ARIZONA SHAKEOUT!). 

10:20–10:50 From the trenches: Anecdotes from actual eruptions and crises in the US 

and abroad. John Ewert, USGS

10:50–11:20 Scenarios for eruptions in New Mexico: Valles Caldera, Taos, ZuniBandera, etc.: Nelia Dunbar, New Mexico Bureau of Geology and 

Mineral Resources

11:20–11:50 Seismic and other networks in the southwest: How would we monitor 

volcanic unrest? Paul Earle, USGS

Lunch (11:50–13:10): 

13:10–13:40 An Introduction to incident response and the Incident Command System: 

Ellis Stanley, Dewberry

13:40–14:40 3 Minute Presentations (Sixteen poster presenters give quick overviews of 

what they’ll show at their poster)

14:40–15:40 Poster session: Attendees circulate through the first 12 posters. 

Coffee served during poster session 

15:40-16:10 Eruption potential and hazard, Valles Caldera, New Mexico: Fraser Goff, 

Ret., Los Alamos National Laboratory 

16:10–17:10 Panel Discussion: Incident Response in the context of volcanic unrest in 

AZ, NM, UT: Incorporating science into decisions for public safety: Lou 

Trammell, Director of AZDEM, Robert Rowley, Coconino County; Alan 

Sinclair, BIA; Ellis Stanley, Dewberry; Wendy Blackwell, NMDHSEM 

17:10-17:40 Capstone Talk: Impact of Sunset Crater eruption on prehistoric groups in 

Northern Arizona: Lessons on human adaptation to disasters: Mark Elson, 

Desert Archaeology, Inc.

17:40 Adjourn for Day. Dinner on your own. 
Day 2 October 19, 2012 

8:00–8:30 Small group planning: identifying challenges of Southwest volcanism.

8:30–9:00 The view from social science: How people will think and behave during an 

extended crisis with large uncertainties: Katherine Thompson, Columbia 

University

9:00–9:30 Monitoring dike intrusions with GPS networks: Past experience and future 

potential: Bill Hammond, University of Nevada, Reno

9:30–10:00 3 Minute Presentations (8 final posters) 

10:00–10:20 Break 

10:20–11:20 Panel Discussion: Seismic and geodetic monitoring in the southwest: 

What do networks need to do and to provide? Panel members Keith 

Koper, UU; Paul Earle, USGS; Bill Hammond, UNR; David Brumbaugh, 

NAU; Rick Aster, New Mexico Tech

11:20–11:50 Volcanic ash plumes and their impact to aviation in the Western United 

States: Jeff Osiensky and Scott Birch, NOAA/National Weather Service

 

11:50-13:00 Lunch 

13:00–14:00 Discussion: What (if anything) should we do next? 

14:00-14:10 Volcano Readiness Wrap-Up John Bwarie, USGS SAFRR

AFTERSESSION: SOUTHWEST VOLCANO PROBABILITIES 

14:10–14:40 Modeling mafic lava flows with an eye to emergency response (Laz 

Kestay, USGS) 

14:40-15:45 Poster session: Attendees circulate through the day's posters. 

Coffee served during posters. 

15:45–16:45 Panel Discussion: Geology, geochronology, and probabilistic modeling of 

volcanism in the U.S. Interior (Greg Valentine, U. Buffalo; Bill McIntosh, 

NMT; Duane Champion, USGS; Chuck Connor, U. S. Florida; Jorge 

Vazquez, USGS) 
16:45–17:15 Overview of the field trip for 10/20: Michael Ort, Nancy Riggs, Northern 

Arizona University)

Adjourn 

Day 3 October 20, 2012 

Optional field trip to Sunset Crater National Monument