The GeoTraverse Workshop
Held at the
first EarthScope National Meeting
March 28,
2005
Conveners:
Ben van der
Pluijm (University of Michigan); vdpluijm@umich.edu
Participants:
Ramon Arrowsmith (Arizona State), Sam Bowring (MIT), Mike
Brown (Maryland), Cathy Busby (Santa Barbara), Rick Carlson (Carnegie), David
Evans (Yale), Gary Fuis (USGS), Kevin Furlong (Penn State), George Gehrels
(Arizona), John Geissman (New Mexico), Robert Hatcher (Tennessee), Kip Hodges
(MIT), Dan Holm (Kent State), Mary Hubbard (Kansas State), Gene Humphries
(Oregon), Jim Knapp (South Carolina), Luc Lavier (Texas Inst Geophysics),
Thorne Lay (Santa Cruz), Chris Marone (Penn State), John Oldow (Idaho), Roberta
Rudnick (Maryland), Jane Selverstone (New Mexico), Christian Teyssier
(Minnesota), Martyn Unsworth (Alberta), Mike Williams (Massachusetts), Kelin
Whipple (MIT), Robert Wintsch (Indiana).
Find contact information at end of the report.
Index
Background
and Motivation................................. 1
Schedule.................................................. 2
Breakout
groups........................................... 3
Details
of the GeoTraverse concept........................ 3
Results
of the workshop................................... 4
Models
for Geological involvement......................... 4
I. Strict GeoTraverse..................................... 5
II. CD-model.............................................. 6
III.
Flexible GeoTraverse................................. 7
Summary
of the GeoTraverse concept........................ 7
Participants
............................................. 9
GeoTraverse
is a cross-continent, transect-based research concept that supports integrated, multidisciplinary (geologic and
geophysical) study of the three-dimensional structure and temporal
evolution of the crust and uppermost mantle of the
The
purpose of the GeoTraverse workshop was to evaluate a geologically-based scheme
on how to design and coordinate one or more transects for high-resolution,
coast-to-coast coverage of the conterminous
A
group of ~30 experienced geoscientists from a broad spectrum of the community
were invited to explore the possibility of the GeoTraverse concept. The workshop was held at the Tamaya Resort at Santa Ana Pueblo, New Mexico, on the day
before the first annual EarthScope meeting.
The preliminary outcomes of the workshop were presented during a
15-minute presentation on the first day of the EarthScope meeting (see http://www.earthscope.org/meetings/assets/es.natl.meeting/presentations/Vanderpluijm.ppt ).
2:00p Welcome and workshop goals
van
der Pluijm - Introduction and Logistics
Tikoff – details of
GeoTraverse concept
2:30p
Selected presentations.
Humphreys – The role of active
source seismology
Fuis – The role of active
source seismology
Selverstone – The role of
petrology and geochemistry
Teyssier – The role of
structure and rheology
3:30p
Break
3:45p
Two break-out groups (pre-arranged grouping)
4:45p
Break-out group feedback on GeoTraverse concept (detailed discussion after
dinner)
5-7
Dinner and break; opportunity to meet with other ES meeting participants
7:00p
Plenary session: Discussion of break-out groups'
discussions
8:00p
Toward a "white-paper" on GeoTraverse and
meet with representatives of other, interested groups
9:00p
Adjourn
The
break-out groups were asked to explore questions that examine both process and
research. These questions were:
1. What process-oriented, geologic questions can be answered
though imaging of the
2. Specific questions
about the GeoTraverse, including: a) Where are particular places to locate a
traverse?; and b) What is the best strategy for a
traverse (large swath, a few small swaths, multiple lines)?
3. How does one organize a traverse and should there be an
(small) organizational superstructure?
4. Given realistic resolution of passive source seismology
(~10 km), how critical is active source seismology?
5. How can we utilize data delivery structure of EarthScope
to collect/distribute geologic information in a digital format?
Details of the GeoTraverse concept
A
GeoTraverse is a coast-to-coast geologic transect across the conterminous US
that focuses on 3-D visualization of the crust and uppermost mantle. We distinguish between literal transects and conceptual
transects. A literal transect is a specific path on a map that combines
targeted studies, and best captures the intent of the GeoTraverse concept as
proposed. Conceptual transects focus on specific
regions of the continent in which studies will be conducted, although no
specific data are collected across regional boundaries. The latter might also be viewed as
mini-traverses, following past and current integrated continental dynamics
projects.
Any
form of the GeoTraverse is not a one-dimensional line, but rather a swath with
varied degrees of resolution along and perpendicular to the swath. We envision a ~100 km wide (or broader?)
passive source swath that represents a significantly enhanced spacing from the
70 km spacing utilized by the USArray Bigfoot array. To provide greater crustal resolution, the
GeoTraverse must locally add an active-source component that specifically
includes reflection profiling, allowing the integration of geology, seismology
and other geophysical approaches.
A
GeoTraverse is not necessarily straight, nor oriented
EW. Rather, a GeoTraverse is likely
curved and occasionally segmented to link scientific targets and include
critical geographic logistics. Importantly,
any form of GeoTraverse would ideally proceed in concert with planned USArray
deployment to optimize outcomes and maximize the outreach potential,
country-wide research opportunities.
The
GeoTraverse concept could fundamentally change how geologists carry out
continental science. By identifying a
national priority for obtaining geologic information, the community would
embrace a “data-collection” model of operation, similar to that in the
geophysics community. The GeoTraverse
must cultivate interaction among different geologic sub-disciplines.
Perhaps
equally important to intellectual, science-driven considerations, the
GeoTraverse will be a key element in the Education and Outreach component of
EarthScope, as observable geological phenomena strongly interest the public and
students. Therefore, GeoTraverse should
incorporate, where possible, recognized natural laboratories and iconic
settings, such as National Parks and Monuments. Further, because of national extent
of a GeoTraverse, it could potentially link EarthScope to urban
populations. Passing a transect or swath
through an urban area would make a significant contribution to the visibility
of EarthScope, with obvious links to area high school science programs, science
museums, and other educational outlets.
The
geologic community has a reputation for being individualistic, partially in
response to the demands of field-based study by small groups and the fact that
large collaborations are considered less critical for collecting geologic data.
Initial responses at the workshop typically reflected this perspective. In
particular, individual participants were concerned about the fact that
identifying research targets would necessarily require that some areas would
not get attention and/or that a particular process may not be examined in the
best location. Illustrating the
diversity, an informal poll of target areas and research topics resulted in a
list with as many specific features as participants. The realization that this culture may have to
change in the EarthScope environment was understood and grew significantly
during the course of the meeting. Given the short duration of the workshop,
many participants lacked definitive opinions and positions, but verbalized both
the positive and negative features of the GeoTraverse concept. Subsequent comments further shaped
discussion.
Notably,
the GeoTraverse concept, as broadly defined, was recognized for its very
appealing components. First, the
potential, longer-term benefits of a broad research framework could outweigh
initial reservations, especially when carefully coordinating regional
interests. Specific priorities were
discussed in regional workshops, and these results must be considered in
determining the path of a GeoTraverse.
Second, the participants emphasized that the geologic component of
EarthScope does not have any organizing intellectual framework, and that a
GeoTraverse could provide this context.
Last, it was generally agreed that geologists could benefit from a
change in their approach to community-wide science, and that GeoTraverse may
provide this opportunity.
In
general, the workshop concluded that EarthScope offers a tremendous opportunity
to the geological community, but that utilization and involvement of this
community is presently limited in scope and purpose, and requires a broader
framework to be established.
Models
of geological involvement in the USArray component of EarthScope
A
major question facing the USArray initiative is whether part or all of the
flexible array instrument pool should be systematically deployed to focus study
on specific areas of the coterminous
We
briefly summarize three plans that were discussed at the workshop: A strict GeoTraverse
“swath” across the country, a Continental Dynamics (CD) model approach, and a
modified GeoTraverse approach.
Option 1: A “Strict” GeoTraverse
We
describe selected benefits of a coast-to-coast, planned traverse. We neither specify the traverse location nor
the equipment utilization, but rather advance the concept of a continent-wide
traverse in anticipation of community discussion on specific location(s).
1) It would provide the portal for a geologic component into
EarthScope. Geologists working together
would provide the continent-scale approach that is compatible with the
EarthScope initiative’s goals.
2) It would highlight transitions between different tectonic
provinces, rather than focusing exclusively on problems, often of parochial
interest, specific to a region. This is
perhaps the richest intellectually, yet least recognized potential of the
GeoTraverse concept, given the unusually diverse tectonic settings in the
3) All areas of the country would be covered, thereby
enhancing the involvement of geoscientists in the EarthScope initiative. This nationwide involvement can only increase
the possible success of EarthScope.
4) It would engage the broader geologic community by
offering a framework that embraces regional activities and opportunity for new
discoveries. This motif is broadly summarized under the heading “Building a
continent” (Structure and Evolution of the North American Continent).
5) It would transform how geologists do continental science,
as it would specifically recognize “data-collection” as a complementary aspect
of “hypothesis-testing” science. This
approach, used by the geophysical community, would undoubtedly allow us to
recognize new process-based questions, to test new hypotheses that would
otherwise not be possible.
6) It would facilitate the inclusion of numerous geologists,
rather than selected groups, because an individual can contribute to data
collection along the specified transect.
7) It would offer a highly visible framework for outreach
and education, by tying observable geologic phenomena (geology) to deeper
lithospheric processes (determined from geophysics) across the entire
continent. The diversity of tectonic
setting guarantees that interest will remain high during the project’s tenure.
8) Given the cost of studying the crust with active-source
seismology and other techniques and the declining budgets that earth science
institutions are currently facing, it is important that efforts be concentrated
in a study such as GeoTraverse to maximum EarthScope results.
We
recognize that there are several major challenges to adoption of the
GeoTraverse concept by the geological (and geophysical) community.
1) How is a traverse located to optimize the outcomes,
including both process- and discovery-oriented science? As opposed to solely PI-driven research, in
which the reviewers ultimately determine those areas/processes that are funded,
the location of the transect will limit what can be
studied. Therefore, it is crucial that
the process of choosing the transect is determined carefully by maximizing the
amount of new information to be learned, given the exposure of the field area,
resolution of specific seismic instruments, and logistics of their
installation.
2) How will a location be decided upon in collaboration with
regional groups? Several regional groups
have prioritized geologic problems in a particular area, and this information
should be included in any larger, more encompassing initiative. We recognize, however, that different
regional groups may have geographically disparate areas that do not allow
inclusion into any specific GeoTraverse (e.g., Southern Rocky Mountains and
3) How many seismometers should be utilized in the
GeoTraverse initiative? Two-dimensional
coverage along a GeoTraverse will require a large part of the USArray
seismometers, yet excellent scientific arguments can also be made for areas
outside the specific traverse. We
recognize that some compromise is required for these competing needs, which
should be possible within the GeoTraverse concept.
4) How is the logistical effort realized? Because a GeoTraverse requires putting
instruments on a grid, it will require a major permitting and installation
effort. If and how this effort could be
coordinated with the USArray Bigfoot array must be determined.
5) How can we integrate both the geophysical and geologic
communities? The GeoTraverse approach
requires the participation of both the active and passive source seismology
communities. There are many enthusiastic
supporters of this effort in these communities and we recognize that their
cooperation is essential. The multidisciplinary, multi-institutional, and often
multi-national transects that have been conducted to date, including
LITHOPROBE, the Trans-Alaska Crustal
Transect, and the trans-European transects, have provided excellent models for
GeoTraverse.
We view the CD-model as the
“default” alternative to the GeoTraverse approach. This approach is essentially
“business-as-usual” for the tectonics community, with competing (individual or
small team) PI-driven projects. As is
seen below, the benefits are less numerous, but so are the challenges.
Benefits
1) It provides the least
change in how geologists are accustomed to preparing proposals and conducting
science.
2) It provides a focus on process-driven
science and effort can be concentrated on areas that appear the most promising
to provide information about aspects of continental processes and tectonic
assembly of
Challenges
1) It is unclear how to
combine results from different areas to provide a synthetic view of orogenic
processes at the continental scale.
2) Can geologists compete
successfully for funding with geophysics-only projects in this system? The scale of USArray is larger than that of
any individual group of geologists working in detail. Further, it is not clear how to tie geologic
data directly to questions about mantle structure and physical properties (with
notable exceptions, such as xenolith studies).
Option 3: A “flexible” GeoTraverse
The concept of a “flexible” GeoTraverse is to provide some
consistency on how the flexible part of USArray is employed across the
country. As such, this is a hybrid
between a literal GeoTraverse model and the CD-model. The benefits and challenges are intermediate
between the two lists, depending on the exact nature of the “flexible”
GeoTraverse and will not be repeated below.
Rather, we summarize only the salient points.
For a “flexible” GeoTraverse, the geological
community must provide its focus and define questions associated with a range
of length and time scales, associated with a flexible portion of USArray
equipment. Geological input is clearly essentially for dealing with
issues related to time-specific questions, including the evolution of the North
American lithosphere. Geological
research will provide the link between larger scale processes in the mantle and
smaller scale deformation in the crust.
The geological community will also provide the link to deformation
processes, by working at all intermediate scales, from that of the crust to the
microscopic scale relevant to the experimental deformation community.
Three main challenges exist for formulating
such a “flexible” Geotraverse. (1) An
overarching theme or themes must make the Geotraverse a single entity rather
than multiple individual problems (CD-model). This overarching theme may be
crust-mantle interaction or time scales of deformation. (2) Higher
resolution seismic data will be needed in the focus areas and these will be
expensive. (3) A novel way to interact and a strong data
gathering/storing infrastructure needs to be developed by geologists. Integrative tools to link this information to
geophysical data and for input into geodynamic models will be necessary, which
fall more logically to GEON or CIG (Computational Infrastructure in
Geodynamics).
Summary of the GeoTraverse
concept
The
GeoTraverse concept – in either its literal or more flexible form - takes full
advantage of the unique opportunity provided by EarthScope, providing a
synoptic, integrative, and four-dimensional view of the North American
continent. The flexible form has the logistical
advantage that it is a more organized form of how the geological community has
done science in the past. The
GeoTraverse concept has the possibility of fully integrating the geological
component into EarthScope and thereby broadening how the geological community
does research. It also provides for the
possibility of significantly enhancing the education and outreach components of
EarthScope, potentially with collaboration of the National Parks. Adoption of the GeoTraverse concept will
require compromises with other research activities, but the benefits are
huge. GeoTraverse would more fully
integrate geology into EarthScope, distribute geologic investigation throughout
the
June 10, 2005
Participants
|
|
Affiliation |
Email |
|
|
|
|
|
Ben van der Pluijm (co-conv) |
|
|
|
Cathy
Busby |
UCSB |
|
|
Chris
Marone |
|
|
|
Christian
Teyssier |
|
|
|
Dan Holm |
|
|
|
David
Evans |
Yale |
|
|
Gary Fuis |
USGS |
|
|
Robert
Hatcher |
|
|
|
Robert
Wintsch |
|
|
|
|
|
|
|
George
Gehrels |
|
|
|
Jane
Selverstone |
|
|
|
Jim Knapp |
|
|
|
John
Geissman |
|
|
|
John Oldow |
|
|
|
Kelin
Whipple |
MIT |
|
|
Kevin
Furlong |
|
|
|
Kip
Hodges |
MIT |
|
|
Luc
Lavier |
|
|
|
Mary
Hubbard |
|
|
|
Mike
Brown |
|
|
|
Mike
Unsworth |
|
|
|
Mike
Williams |
|
|
|
Ramon
Arrowsmith |
|
|
|
Rick
Carlson |
Carnegie |
|
|
Robert
Hatcher |
|
|
|
Robert
Wintsch |
|
|
|
Roberta
Rudnick |
|
|
|
Sam
Bowring |
MIT |
|
|
Thorne
Lay |
|
|