May 27, 2009

‘Blob’ of material found beneath Nevada

Arizona State University researchers say they have discovered a large cylindrical blob of cold material far below the surface of central Nevada.

Led by geologist John West, the scientists determined the blob was formed when portions of the lithosphere -- the Earth's crust and uppermost mantle -- had sunk into the more fluid upper mantle beneath the U.S. Western Great Basin.

West said it was an extremely unexpected finding in a location that showed no corresponding changes in surface topography or volcanic activity.

The Great Basin in the western United States is a desert region largely void of major surface changes. The area consists of small mountain ranges separated by valleys and includes most of Nevada, the western half of Utah and portions of other nearby states.

For tens of millions of years, the Great Basin has been undergoing extension -- the stretching of Earth's crust. It was while studying the region's extension that West and his colleagues made their discovery of the so-called lithospheric drip that formed the approximately 60-mile by 300-mile blob.

The findings provide important insights into fine-scale mantle convection processes, and their possible connections with volcanism and mountain-building on Earth's surface, Greg Anderson of the National Science Foundation said.

The study that included Jeff Roth and Associate Professor Matthew Fouch appears in the journal Nature Geoscience.