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 .