.c.Death Valley, California


Titles of Investigations:

I.  Climate Change and Neotectonic History of Death Valley

II.  Alluvial Fan Evolution in the Western Great Basin

III.  Development of a Technique to Relate Eolian Roughness
to Radar Backscatter Using 
    Multi-Parameter SIR-C Data

IV.  Evaluation of SIR-C/X-SAR Imagery for Geologic Studies
in Arid and Semi-arid Regions

V.  Comparative Lithological Mapping Using Multipolarization,
Multifrequency Imaging 
     Radar and Multispectral Optical Remote Sensing

VI.  SIR-C Surface and Subsurface Responses from Documented
Test Site Localities in Death 
    Valley, the Sahara, Namib, and Kalahari Deserts, Africa,
and the Jornada del Muerto, 
    New Mexico 

Principal Investigators:

I.  Dr. Tom Farr
  Jet Propulsion Laboratory

II.  Dr. Allan Gillespie
  University of Washington

III.  Dr. Ron Greeley
  Arizona State University

IV.  Dr. Huandong Guo
  Academia Sinica

V.  Dr. Fred Kruse
  University of Colorado

VI.  Dr. Gerald Schaber
  US Geological Survey

Site Description:

 Death Valley is a N-S trending fault-bounded valley in the
southern Great Basin. Elevations 
range from 70 m below sea level to more than 3300 m above
sea level (Telescope Peak). Climate 
and vegetation vary accordingly, from subalpine pine forest
at higher elevations, to arid creosote 
on the piedmonts, to sparse salt-tolerant plants in the valley
bottom. Surficial process 
investigations are concentrating mostly on the piedmont and
valley floor. They include studies of 
the formation of alluvial fans through climatic and tectonic
effects, the nature and rates of 
weathering processes on the fans, soil formation, and the
transport of sand and dust by the wind. 
These are long-term studies with the goal of better understanding
the record of past climatic 
changes and the effects of those changes on a sensitive environment.
This may lead to a better 
ability to predict future response of the land to different
potential global climate-change 
scenarios.
  Death Valley is a good site for development and testing
of techniques for remote lithologic 
mapping because of the wide range of rock types exposed in
a range of environments. The 
Panamint Mountains, bounding the valley on the west and the
Grapevine Mountains in the north 
part of the valley, are composed of a variety of igneous,
metamorphic, and sedimentary rock 
types. In addition, there are known areas of alteration that
have created economic deposits of 
minerals. 
 As part of the secondary objectives, Death Valley has been
used as a test site for the 
development of radar interferometric techniques. At present,
both Seasat and TOPSAR data sets 
are available and ERS-1 interferometer images will be acquired
in 1993. In addition, a SPOT 
stereo-pair has been acquired and is being reduced to digital
topography for comparison to the 
interferometric data. These data are now being used in the
studies described above. Soils have 
developed in Death Valley in a wide range of salinity. This
makes possible studies of the radar 
signature of soils that have suffered a buildup of salt-
a growing problem in marginal lands. 
Finally, at the north end of the valley lies Ubehebe Crater,
a series of volcanic craters (maars) 
created by explosion with very little associated lava. Volcanologists
can study the radar 
signatures of the craters and explosive deposits. 
 
Objectives:

I.  a) The goal of the proposed research is to determine
the history of Quaternary climate 
change for a portion of Death Valley for inclusion in global
paleoclimate models and 
reconstructions of the tectonic history of the area.

  b) Compare surface modification processes that have operated
in Death Valley to those 
in similar areas of northwestern China.

II.  a) Describe systematic morphologic changes with surface
age in terms of 
multiparameter radar backscatter.

  b) Construct for the studied fans a depositional and weathering
history based on SAR 
and other images and field investigations.

  c) Use the depositional and weathering history of the study
area to constrain 
paleoclimatic interpretations.

  d) Use project as prototype for paleoclimate study of entire
Great Basin or other 
geomorphic provinces.

  e) Test the hypothesis that spectral mixing analysis can
be applied to multiparameter 
SAR images of alluvial fans in arid and semiarid regions.

  f) Define radar endmembers physically, in terms of Bragg
scattering, volume scattering, 
specular and corner reflectors, and dielectric constant,
etc..

  g) Develop and test mixing models for comparative analysis
of images spanning 
multiple spectral regions.

III.  a) To develop a technique to obtain values of aeolian
roughness for geologic surfaces 
from values of surface roughness determined from SIR-C/X-SAR.

  b) Define the optimal combination of radar parameters from
which aeolian roughness 
can be derived.

  c) Gain an understanding of the physical processes behind
the empirical relationship.


IV.  a) Conduct a radar penetration study be measurement
for typical surficial covers.

  b) Develop a theoretical model of radar scattering for
penetration study.

  c) Develop a limited inversion of radar scattering model
for applications of SIR-C/X-
SAR data.

V.  a) Develop a better understanding of depositional and
erosional processes through a 
study of compositional and geomorphic variation.

  b) Develop a better understanding of the current geomorphic
expression of rock 
surfaces; characterize the geometry, and indirectly, the
composition of rock units.

  c) Compare radar characterization with visible/infrared
characterization of surface 
materials for both vegetation-free and vegetated areas.

  d) Evaluate multidimensional image processing techniques
for analyzing multispectral/ 
multipolarization/multiple incidence angle radar data.

  e) Evaluate the utility of precision radargrammetry to
improve lithological mapping 
capabilities.

  f) Map the character and distribution of lithological variation
with SIR-C/X-SAR.

  g) Provide hands-on radar remote sensing experience to
graduate students.

VI.  a) Determine the optimum SIR sensor configuration for
detection of desert duricrust 
and to use this understanding to reconstruct the paleoclimatic
history for a portion of 
Death Valley.

Secondary objectives include: tests of interferometry and
use of digital topography, studies of soil 
salinization, and volcanology studies.

Field Measurements:

I.  a) Establish of a few key "calibration" sites at which
ages of geomorphic surfaces will be 
determined, remote sensing signatures of the surfaces measured,
and the variation of 
surfaces between and within drainage basins examined.

II.  a) Select study site(s) in Owens Valley/Death Valley
to exploit existing geomorphic, 
soils, and geochronology data, for a sequence of alluvial
fans deposited during the 
last 0.5 Ma.

  b) Make precise measurements of integrated weathering rates
for each dated surface, 
which can then be analyzed jointly to construct a history
of weathering rates and rate 
changes for selected parameters (e.g., oxidation, hydration,
clast disintegration, and 
aeolian silt redistribution).

III.  a) Collect wind data and microtopography measurements
at key sites in Death Valley.

  b) Compute statistical descriptions of surface roughness
from large- (m) and small- (cm) 
scale topographic profiles measured in the field on each
surface.

IV.   No field measurements are planned.

V.   a) Field work will include measurements of surface roughness,
dielectric constant(s), 
surface visible and infrared spectral measurements.  In addition,
geologic maps will 
be used to determine geomorphic units.

  b) Supporting remote sensing data include: AIRSAR data,
digital elevation models 
(DEMs) for the field site, co-registered AVIRIS, TM, and
TIMS data, helicopter stereo 
pairs for selected geomorphic surfaces, and color aerial
photographs.

VI.  a) Extend laboratory measurements and the SIR-A/B geometric
scatter model for 
calichified sediments in arid, sand-covered terrains to higher
frequencies and a wider 
range of sample physical parameters.

  b) Document and establish limits on SIR-C/X-SAR signal
behavior in hyperarid-to-
semiarid regions.  Specifically, document the effects of
surficial and subjacent 
geologic conditions on SIR-C response in various sensor configurations.

Crew Observations:

1) Crew Journal:  Describe sand or dust storms, weather at
the site, alluvial fans surface and 
dune orientations.

2) Cameras: Hercules and Hasselblad will be used to obtain
color photographs of the site.  A 
polarizing filter and infrared film are requested during
some orbits.


Coverage Requirements:

 The minimum coverage requirements for this are three passes
at incidence angles of 30-50, 
and one pass in quad polarization mode.

Anticipated Results:

I.  a) Maps of geomorphic surfaces with ages attached to
them will be a major step toward 
understanding the climatic history of this region of the
earth.

  b) Comparisons of this climate record with climate records
from the oceans and other 
continents will help advance the global synthesis of climate
change.

  c) Answers to the questions of how unique and how globally
representative remote 
sensing signatures are will directly affect our future ability
to extrapolate the 
signatures to global studies of climate change.

  d) Determination of past slip rates on some active faults
in Death Valley by a 
knowledge of the ages of offset surfaces.

II.  a) New technique for "unmixing" multiparameter radar
images into meaningful 
components (e.g., volume-scattering surfaces or "vegetation",
Bragg-scattering 
surfaces, etc.).

  b) An alternative to "extended spectral signatures" for
joint analysis of disparate images 
spanning multiple spectral regions.

  c) Better history of bajada surface evolution than available
from chemical weathering 
studies alone.

  d) Improved knowledge of Pleistocene paleoclimate in the
western Great Basin.

  e) Test of predictive models for climate/paleoclimate and
for inferences from 
paleoecological studies.

III.  a) Determination of an empirical relationship between
measurements of 
microtopography, aerodynamic roughness, and microwave energy.

  b) Development of an equation expressing this relationship.
 This expression will form 
the basis of a technique for using spaceborne SAR data to
determine a roughness 
parameter for use in aeolian sand transport rate equations.

  c) The results also will be used to validate models of
aeolian response to surface 
roughness.

IV.  a) Dependence of radar penetration depth.

  b) Interpretation of SIR-C/X-SAR imagery over areas of
Death Valley.

  c) Evaluation of quantitative application of SIR-C/X-SAR
data.

V.  a) A better understanding of processes involved in deposition
and erosion of 
sedimentary and igneous rocks.

  b) An improved understanding of lithological variation
and its relation to geomorphic 
expression of rock surfaces.
  c) Improved understanding of the relation of multiparameter
radar image 
characteristics to rock/soil/vegetation physical properties.

  d) An improved understanding of the strengths and weaknesses
of multispectral/ 
multipolarization/multiple incidence angle radar and how
it can be used to 
compliment visible/infrared remote sensing.

  e) Development of extended spectral signatures for geologic
materials and vegetation.

  f) Improved lithological mapping capabilities.

  g) Innovative image processing algorithms and analysis
techniques for multispectral/ 
multipolarization/multiple incidence angle radar.

VI.  a) An improved understanding of radar backscatter and
penetration in hyperarid-to-
semiarid terrains that was initiated during our SIR-A/B investigations
(Elachi, Roth 
and Schaber, 1984; Schaber et al., 1986).

  b) Refinement of synergistic remote methods to identify
various types and stages of 
datable, authigenic CaCO3 deposits related to successive
changes in climate and 
surface geologic processes during the Quaternary.

  c) Improved models of geometric scattering effects on SIR
signal penetration.

  d) New data on the spatial and chronological distribution
of semiarid paleoclimatic 
zones in Africa.