Abstract: 3D Seismic and the Discovery of California's First Meteorite Impact Crater, Sacramento Valley
BLAKE, RICHARD G., Consulting Geologist, Pleasanton, CA
The first meteorite crater ever found in California was discovered as a buried feature in the Sacramento Valley, about seven miles southwest of the City of Sacramento. The crater is about 4300 feet in diameter and lies 2500 feet below ground surface. It was located using a 3D seismic survey intended for natural gas exploration. The crater has been formally named the Cowell Crater, after the S. H. Cowell Foundation which owns the property where the discovery was made. The Cowell Crater is almost identical in size to the Barringer Crater near Flagstaff, Arizona, a surface crater that was made about 50,000 ago. Studies by the USGS suggests that a meteor of this size would eject about 100 million tons of rock by the impact of a meteor between 100 to 200 feet in diameter. The impact would be equivalent to a 30 megaton explosion, or 30 times bigger that the atomic bombs dropped on Japan during World War II. The meteor would have struck at a speed of about 12 miles per second, which is fast enough to cross the continental United States in two or three minutes. The meteorite smashed into the ancestral Sacramento River flood plain during Miocene time about 25 to 30 million years ago. It was eventually buried by runoff from the Sierra Nevada Mountains. Several other craters found in North America are of similar age, according to NASA, and may suggest that the earth passed through a major meteor field during Miocene time.
AAPG Search and Discovery Article #90935©1998 AAPG Pacific Section Meeting, Ventura, California