What lies beneath: Studying a U.S. impact crater and its effects on groundwater


  • Anonymous


NASA Langley Research Center, Hampton, Va., August 3, 2000 Today, the team drilling for its version of gold hauled up another 18 meters of sediment samples as super-hardened carbide disks welded onto a coring bit pushed through a Virginia unit of the St. Mary's Formation, which dates from the Late Miocene Epoch 8 5 million years old. The drilling, which began on July 23 and is expected to grind on at this site until September, has now reached about 107 meters below land surface.

The scientists and heavy equipment handlers hope that by the end of August they will reach the layer of the Chesapeake Bay impact crater where breccia lies. This is a jumble of redistributed and angular broken rock fragments they expect to find that was deposited in the aftermath of a bolide strike 35 million years ago, during the Late Eocene epoch. The breccia could lie anywhere from 640 to 820 meters down, scientists believe. Drillers working the coring rig may continue down as far as 1370 or 1675 meters to take up a long sample of underlying crystalline rocks, according to geologist Greg Gohn of the U.S. Geological Survey (USGS), a co-leader of the Chesapeake Bay Impact Crater (CBIC) project.