I. John Anderson – Welcoming Remarks
1. What will EarthScope gain from it multidisciplinary nature, making the whole greater than the sum of the parts?
2. What integrated data products do we want from the EarthScope facility?
3. What would you like to see as the EarthScope legacy in the Great Basin?
II. Kaye Shedlock, NSF EarthScope Program Director.
See Kaye's PowerPoint slides.
Kaye is the new Program Director for EarthScope. She explained the structure of EarthScope, including the roles of the EarthScope Science and Education Committee, the EarthScope Facility Executive Committee (and the three currently funded parts of the program – SAFOD, USArray, and PBO), and the research grants program. NSF would like to see working groups develop from the GreatBREAK Workshop to propose research projects. There will be an EarthScope Education Coordinator in the EarthScope Office to coordinate E&O across the program, to maintain the excitement, enthusiasm, and participation of the educational network community.
The first solicitation for EarthScope received 151 proposals for $45 million. 72 project proposals and 9 workshop proposals were reviewed; 19 projects and 6 workshops have been supported with $3.6 million awarded. The new RFP is out with $4 million available for the upcoming year.
III. Greg van der Vink, EarthScope Facilities Director
See Greg's PowerPoint slides.
IV. Gene Humphreys, Evolution of the Great Basin: Issues and Challenges in the Context of EarthScope
How much of the variation in the western North America is due to local effects (inherited from geologic past) versus far-field (imposed by plate tectonic) effects?
Great Basin must be weak (to be extending) and have a high potential energy.
Magmatism may be a controlling factor in weakening the lithosphere and aesthenosphere.
1. The Mid Atlantic and Artic Ridges push North America (NA) against the Pacific Plate and compress NA.
2. Rood drag of the craton resists about ¼ of ridge push; this reduces compression on western NA.
3. The gravitational potential energy of the topographically high western US overcomes compression and drives extension.
4. Transform entrainment superimposes a strong shear field on western NA.
5. Cascadia accommodates dilation of the interior; shear of the margin (that is, the southern Cascades is rotating clockwise and moving over the subducting plate).
Low P-wave velocity of the Great Basin relative to the Sierra Nevada (higher) at 100 km.
The hinge line separating the eastern edge of the Great Basin (and the Rocky Mountains-Colorado Plateau (with depleted mantle and Precambrian crust to the east versus fertile mantle to the west) and the Sr-isotope 706 line define the Paleozoic margin 600 MA ago, when North America and Australia separated.
The linkage between the center of the Columbia River basalt eruptions (Walawala Mountains?, which is still an area of high velocity) and the related Yellowstone magma system are affecting at least the northern part of the Great Basin. Extraction of basalt from the mantle on the edge of the Yellowstone area can explain mantle seismic velocities. There may not be a simple plume beneath Yellowstone (unless it is a small structure); it may be more a set of blobs, rather than a continuous plume.
Anisotropy of olivine in the mantle suggests a possible feature centered in the north-central part of the Great Basin.
There is too much information for one person or group of people from a discipline to be able to integrate all the data. That is, EarthScope provides an opportunity to change the culture of Earth science investigations by better integrating information from various disciplines.
V. Geoff Blewitt, Geodesy in the Great Basin: Highlights, Possibilities, and Challenges
See Geoff's PowerPoint slides.
Some questions geodesy might address:
1. How is strain accommodated in the Great Basin?
2. What might this new information imply? (for various issues, including geothermal exploration and Yucca Mountain)
3. Ground-water issues in the Great Basin (aquifer deformation, artificial recharge)
VI. John Anderson, Seismicity and Seismic Hazards of the Great Basin: What we know, don't know, and what EarthScope might give us.
See John's PowerPoint slides.
In general, geologic data from faults in the Great Basin (broadly defined) seems to underestimate seismic hazard (relative to seismic and geologic data).
VII. Larry Brown, Elements of Lithospheric Structure in the Basin and Range
See Larry's PowerPoint slides.
Why is the Moho so flat in the Great Basin? (Klemperer et al., 1986, suggested mafic underplating; EarthScope could better quantify the thickness of magma at depth.)
Time lapse (4D) seismic experiments are wise – in magmatic areas and along faults.
VIII. Greg Arehart, Economic Geology, and How EarthScope Might Play a Role
See Greg's PowerPoint slides.
He stressed the redistribution of elements in the Earth's crust.
What new and refined techniques will help both the extractive industries and the scientific communities?
There is a lot of potential for access to private-sector data that may help.
IX. Rick Aster, Outreach in the Great Basin: Highlights, Possibilities, and Challenges
See Rick's PowerPoint slides. EarthScope is a continental-scale initiative with a decadal time scale. There is an opportunity to promote Earth science as a high profile and high-tech discipline.
Tuesday Morning – Grand Challenges
X. Steve Wesnousky
See Steve's PowerPoint slides.
Understanding the accumulation and release of strain in the Great Basin is one of the grand challenges.
XI. Brian Wernicke
How does the geodetic strain rate (10 yr) compare with long-term strain rates (measurable at ten to ten million years)? We really have no idea what the physical processes are. EarthScope will give us many surprises. The theory will follow. There are already unexplained surprises (e.g., apparent compression at site LEWI and apparent slowing of westward motion at site EGAN). Geodetic data can now be presented in terms of not only velocities but also accelerations.
XII. Geoff King
Geoff discussed propagation of faults, using the Altyn Tagh fault (China) and North Anatolian fault (Turkey-Aegean Sea) as analogs to the Owens Valley - Death Valley – Panamint Valley faults, and the Carson Sink – Dixie Valley area. He described a jump inland of the southern San Andreas fault (at 5 Ma and beginning of the Garlock fault), with major motion of the Owens Valley – Death Valley – Panamint Valley faults (as dip-slip faults) and 3 to 1 Ma volcanism (including Long Valley), then transfer of strain into the central Nevada seismic belt. Neither block nor continuum models are correct. All continental lithosphere is already damaged – no faults are new. His group looks at the lithosphere as an elastoplastic material (like tooth paste or jelly) versus elastic (like honey).
XIII. Bob Smith
See Bob's PowerPoint slides. He discussed the eastern Basin and Range. The Yellowstone hot spot has reconstructed much of the Basin and Range. The tectonic parabola centered on Yellowstone has affected much of the northern Basin and Range province. Observed shear-wave anisotropy fits well with the Snake River plain, but there is a "circular" zone in the central part of Nevada that doesn't fit with surface geology.
What is the role of upper mantle flow with respect to surface manifestations?
XIV. James Davis
See Jim's PowerPoint slides. Velocity errors of about 0.1 mm/yr are achievable, but even the errors have assumptions regarding continuous, linear-in-time motions. We'll work to reduce the errors, as long as the geophysicists don't call the error "geodetic error."
XV. Elizabeth Miller
See Elizabeth's PowerPoint slides.
XVI. Richard Carlson
See Rick's PowerPoint slides.
Why does volcanism occur where and when it occurs in the Basin and Range?
XVII. Phil Wannamaker
See Phil's PowerPoint slides. EM data can help to image melt or high-temperature zones in the upper mantle.
XVIII. Craig Jones
How do you make a region with thin crust stand high and keep on extending after 40-50 million years? How do we make the mantle buoyant? How do we thin the lithosphere?
XIX. Karl Karlstrom
See Karl's PowerPoint slides. He focused on Proterozoic inheritance and connections between water quality (xenowhiffs – looking at CO2 concentrations and He and Sr isotopic ratios) and mantle tectonics.
XX. Jim Faulds
See Jim's PowerPoint slides. How does a strike-slip fault system develop and why? What controlled distribution of strain? Coupling between the upper mantle and crust? Dynamic and kinematic links with the plate boundary?
XXI. Wayne Thatcher
See Wayne's PowerPoint slides. An achievable goal for the next decade: map the kinematics of deformation. Force + Rheology = Deformation. PBO ought to be able to constrain deformation. Internal forces can be determined to an extent from USArray. Rheology will be more difficult to constrain.
XXII. Dennis Harry
See Dennis's PowerPoint slides. Geodynamic modeling – most outstanding issues also relate to rheology. A finite-element model has the crust and lithospheric mantle thinning over 40 million years, with strain moving from the center to the margins of the region. Slab windows, mantle drips (or tacos), and delamination need to be considered.
We need a geodynamic modeling tool that can be used by non-geodynamicists.
Scientists also need to be better educated on doing outreach.
XXIII. Tom Jordan
See Tom's PowerPoint slides. He spoke about EarthScope science integration. He calls for an EarthScope collaboratory to house data and computer codes and to produce data products, all of which could be used by other scientists (and educators). SCEC's goal is to develop better seismic hazard analysis. They are using a physics-based modeling approach, rather than a simple empirical approach.
Tom suggests a focus for (Great Basin) EarthScope on regional tectonics and hazards. Develop community data products and models, Use interactive working groups. Develop a collaboratory infrastructure (for code validation, standardization of products). Have regular forums (workshops and annual meeting). Develop funding to support collaboration.
Wednesday Morning
Workshop Breakouts
See PowerPoint summaries and overheads.
Persistence and evolution of mantle features, mantle upwelling, magma bodies, partial melt, and implication for future volcanism.
Transfer of force between the mantle and crust, and lower crustal flow.
The Research Committee of the Society of Exploration Geophysicists could help to get oil company seismic data in the Great Basin (Shell and other companies).
Is the Great Basin going up or down?
Where is extension occurring?
Some better targets for the flexible array may be revealed after interpreting data from the Bigfoot array.
There will be an EarthScope National Meeting at Tamaya Resort, Santa Ana Pueblo, New Mexico (near Albuquerque) – Tuesday, March 29, through Friday, April 1, 2005. Results of this workshop should be presented at this meeting, and follow-up discussions on EarthScope in the Great Basin can be scheduled as part of the meeting.
1. What will EarthScope gain from it multidisciplinary nature, making the whole greater than the sum of the parts? – self-organization
An annual science meeting – geophysics in the Great Basin
Work together to develop an Earth model
Have a modeling environment – computer codes to share
Test Bed (e.g. Socorro)
Ongoing Forums
John Anderson agreed to put a student on putting together a master Web link to Web sites for everyone doing geophysical work in the Great Basin. This could also be linked to the Web site of the Great Basin Center for Geothermal Energy.
Working groups could be formed to deal with various issues, including:
(a) The Earth model for the Great Basin (allowing for multiple working hypotheses – different models rather than one, most widely accepted model – Tom Jordan noted that the SCEC community model for southern California allows for multiple hypotheses; Anke Friedrich stressed the need for the international aspects of EarthScope – the fact that EarthScope will attract international collaborators and will have implications for science in other parts of the world).
(b) Fault geometry – link with the WSSPC-NEHRP-USGS effort to characterize and evaluate active faults (also consider major non-active faults, which can be significant geophysical boundaries; take advantage of SCEC's models and experience).
2. What would you like to see as the EarthScope legacy in
the Great Basin? In other words, what
are the key large-scale scientific problems to solve (simply stated with
achievable goals, including locations to solve multiple objectives at once)?
The Earth model – (for all of (U.S.) North America)
The reinvigoration of the Earth science community. (Rick Aster)
Amazing discoveries – we are already seeing it. (Geoff Blewitt)
3. What processes control the emplacement and eruption of magma [within the Great Basin (or, more broadly, the Basin and Range province)]?
4. How does the lower crust deform, relative to the upper crust and mantle, and how do fluids move through the crust?
5. How is the Pacific-North American plate boundary evolving?
(The world's best place for a distributed plate boundary)
6. Formation and collapse of orogenic plateaus
What is the relationship of geophysical observables and the actual 3D geology?
Integrating deformation in the western U.S., including Cenozoic evolution of the western U.S. – kinematics and dynamics through time.
Lew Gustafson: At some point, there needs to be a geographic focus, which will then bring people together who have different perspectives on the same area.
Several people advocated focusing on processes.
Bob Phinney advocated building the Earth model incrementally, rather than trying to worry about a top-down approach.
Geoff Blewitt advocated co-location of instruments (e.g., seismicity and geodesy).
My answers to some questions.
1. What will EarthScope gain from it multidisciplinary nature, making the whole greater than the sum of the parts? – Self-organization
2. What integrated data products do we want from the EarthScope facility?
Interpreted data that can easily be used by the broad Earth Science community in academia, government, and industry and by the science education committee:
(a) From USArray "Bigfoot" – 3D models of the crust and mantle (and core) below North America
(b) From USArray flexible instruments: 3D models of any area studied in detail. We would hope to see studies of several areas within the Great Basin, particularly
(i) the Walker Lane
(ii) The areas including and between major trends of gold deposits (Carlin, Battle Mountain-Eureka, Getchell, Independence Mountains)
(iii) Quaternary-Tertiary basins experiencing significant population growth (Las Vegas, Reno, Carson City, Minden-Gardnerville, Pahrump, Mesquite, Laughlin)
(c) From GPS data - velocity-vector (including vertical component) and strain-rate maps for the western North America – with the Great Basin in its broader context.
(d) From all of EarthScope activities – up to date databases, in GIS and 3D visualizations, on surface and subsurface geology; geochronology and distribution of igneous rocks; geochronology (e.g., C-14 dating) of significant geomorphic surfaces and features; active and inactive faults (including detailed information on slip rates, geometry, displacements and characteristic sizes of earthquakes – largely using the USGS Quaternary Fault and Fold Database); imagery (low sun-angle aerial photography, true color, hyperspectral and other special satellite imagery, :LIDAR imagery, detailed topography, InSAR scenes, etc.); distribution of precarious rock (as indicators of areas that experienced limited ground shaking from earthquakes in Holocene time); geothermal resource information (locations of hot and warm springs and wells, known geothermal resource areas, heat-flow measurements, etc.); gravity, magnetic, seismic, and other available geophysical data, including data donated by industry; well data from geothermal, oil and gas exploration, and other deep wells. Some of this data is currently available through the USGS, Nevada Bureau of Mines and Geology, Utah Geological Survey, and Great Basin Center for Geothermal Energy, which is compiling data on a Web site for easy access.
3. What would you like to see as the EarthScope legacy in
the Great Basin? In other words, what
are the key large-scale scientific problems to solve (simply stated with
achievable goals, including locations to solve multiple objectives at once)?
4. What processes control the emplacement and eruption of magma [within the Great Basin (or, more broadly, the Basin and Range province)]?
Answering this question will help resolve the discrepancy between heat flow measurements and locations of Quaternary volcanoes, with the Lunar Crater basalt field more or less in the middle of a regional heat-flow low. Another areas that would be particularly good for detailed study of the current distribution of magma at depth is the Crater Flat-Lathrop Wells-Amargosa Valley field of basaltic cinder cones, flows, and sills, for which the presence of magma has significant implications regarding the performance of Yucca Mountain as a repository for nuclear waste (and therefore there may be interest from the Department of Energy in at least partial funding of geophysical studies in this area. Several locations within and near the Walker Lane could take advantage of other studies being proposed to unravel the evolution of Pacific-North American plate interactions, including the region around Silver Peak and Clayton Valley (site of a Late Quaternary basaltic cinder cone, active faulting in a pull-apart basin that is coincidentally the site of only lithium mine currently operating in the United States, gold deposits associated with a Miocene metamorphic core complex and low-angle extensional faults, and fault-related geothermal activity), Soda Lake (near Fallon in the Caron Sink area, where two basaltic maars that are probably the youngest volcanoes in Nevada, less than 7,000 years in age, are part of a larger Quaternary volcanic field, and where subsurface geothermal resources are not fully understood); and the Lake Tahoe – Reno area, which has evidence of some of the youngest rhyolitic volcanism in the Great Basin (approximately 1 million-year-old domes, perhaps associated with the active geothermal system) and for which recent seismic and geodetic data suggest active injection of magma deep within the crust.
5. How does the lower crust deform, relative to the upper crust and mantle, and how do fluids move through the crust?
This question can tie together many interests. These include the following questions:
How do metamorphic core complexes evolve?
How do range-bounding faults at the surface change in geometry with depth?
Is the Carlin trend is in the hanging wall of the decollment of the Ruby Mountains metamorphic core complex?
Does a deep crustal structure exist below the Carlin trend or other major mineral trends, and if, so, how has it been deformed by post-Eocene extension?
How has the deep crustal structure of the Northern Nevada Rift and subparallel basaltic dike trends been deformed by post-Miocene extension?
How does fluid from the mantle, particularly 3He locally seen in geothermal springs along range-bounding faults, move through the ductile lower crust?
6. How is the Pacific-North American plate boundary evolving?
This question calls for detailed studies in the Walker Lane.