Maggi Glasscoe
NASA
New investigations
of the spreading of Earth's crust in
Antarctica may change existing estimates of tectonic plate
motion around the Pacific Ocean Basin.
Tectonic deformation
in western Marie Byrd Land and the
Ross Embayment area apparently occurs as the continent
separates. Possible causes of the deformation include the
separation and crustal uplift caused by isostatic rebound
following the last glacial maximum, about 14,000 years ago.
Isostatic
adjustment is vertical movement caused when weight is added or
subtracted from parts of the Earth's crust. When a glacier is
at its heaviest, the crust falls; as it melts or moves from that
part, the crust rises.
"It is
widely accepted that the Ross Sea region is
undergoing active deformation, but the rates and causes of deformation
are essentially unknown. Tectonic extension may be occurring in
the Ross Embayment during the current separation of West and East
Antarctica," said Dr. Bruce Luyendyk, principal investigator
and chair of the Geology Department, University of California
Santa Barbara.
To measure
isostatic rebound and tectonic deformation,
researchers have installed three autonomous, continuously recording
global positioning system (GPS) stations on outcrops in western
Marie Byrd Land in concert with a series of stations in the Transantarctic
Mountains. This enables scientists to collect data from a large
area across the Ross Embayment. Data has been acquired since 1998
and will continue to be monitored for the next several years.
Scientists
plan site visits to evaluate and upgrade equipment and to collect
data.
"So far,
the data indicate that spreading is occurring
across the Ross Embayment," said Dr. Andrea Donnellan, co-investigator
of the project at NASA's Jet Propulsion
Laboratory, Pasadena, Calif. "Future measurements will refine
the number."
The joint
JPL and UCSB project brings together experts in
Antarctic geology and tectonics, tectonic geodesy, and
lithospheric deformation. Funding is from the National
Science Foundation Office of Polar Programs and NASA's Office
of Earth Science Enterprise, Washington, D.C. Donnellan and Luyendyk
are co-authors of a paper to be presented at the American Geophysical
Union meeting in San Francisco on December 18. JPL is managed
for NASA by the California Institute of Technology in Pasadena.
More information is available at http://geodynamics.jpl.nasa.gov/antarctica/mblproject.html
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