March GEOLOGY and GSA TODAY media ...(rowth of large subsurface structures tha...)

Date:2/29/2008

rowth of large subsurface structures that form the hydrocarbon traps for the significant oil discoveries in the area. These subsurface structures also created gravity disequilibria in the overlying tectonic wedge, triggering further gravitational readjustments. Subsequently, as shortening ceased even at depth, crustal extension became dominant (from the Middle Pleistocene to the present).

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Neogene extension and basin deepening in the West Antarctic rift inferred from comparisons with the East African rift and other analogs

Wesley LeMasurier, Institute of Arctic and Alpine Research, University of Colorado at Boulder, 1560 30th St., 450 UCB, Boulder, Colorado 80309-0450, USA. Pages 247-250.

The West Antarctic rift is a region of volcanic activity and crustal stretching that is roughly the size of the western United States (from Salt Lake City to the Pacific Ocean). About 98 percent of it is buried beneath glacial ice, up to 2.5 miles thick, and bedrock beneath the ice is 20003000 feet below sea level over large areas. All of this makes it a difficult region to study. It is interesting nevertheless, because volcanic eruptions beneath the ice could destabilize the ice sheet, leading to as much as 25 feet of sea-level rise. How likely is it that this could happen is a question scientists have debated for over a decade. LeMasurier addresses the question by comparing the West Antarctic rift with similar areas of crustal stretching elsewhere in the world. The comparison shows that volcanic activity in rifts is most common where the land is a mile or more above sea level, and rising, which can readily be seen in Antarctica along the Transantarctic Mountains, and in the Pacific coast mountains of Marie Byrd Land. The large sub-sea-level interior of the rift does not, therefore, seem to be a likely place for present-day volcanic activity. This is good news, because the sub-sea-level base of the West Antarctic ice sheet is alread
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Contact: Ann Cairns acairns@geosociety.org 303-357-1056 Geological Society of America Source:Eurekalert

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