Oil exploration in California, USA reveals giant impact crater

March 22, 2007

Researchers in San Joaquin County, California have discovered what appears to be a massive impact crater made by an asteroid nearly 50 million years ago, while exploring the area for possible oil deposits. The period in which it struck the Earth, say researchers, is called the Eocene Epoch.

Images from a seismic survey has shown the crater is about 3 miles (6 kilometers) wide, buried under sediment at nearly 4,300 feet and may even still contain the asteroid which is said to still be inside the crater nearly 10 miles below the Earth's surface. The crater is reported to be below an area previously covered by water.

"Analyses of a 3-D seismic survey and well logs in the southwestern Sacramento basin, San Joaquin County, California, have revealed a subsurface, circular, 3 mile (~5.5-km-) diameter anomaly that may represent a previously unrecognized complex impact crater. This unique anomaly, buried 4,500-5,000 ft (1,490–1,600 m) below sea level under the southwestern part of the Sacramento-San Joaquin Delta, is provisionally named the Victoria Island structure for an overlying surface geographic feature," J. R. Morrow of San Diego State University during the 38th Lunar and Planetary Science Conference, held in Houston, Texas.

In the images, researchers found that the crater contained a "central uplift," or the peak near the center, which researchers say is a good sign that the discovery is a crater created by an asteroid.

Researchers plan to look at rock samples that will be retrieved during a drilling mission surrounding the impact area. They hope to find shocked quartz, melted rock and glass. The element known as iridium is also expected to be found in elevated levels.

This is the second such crater to be found in the central valley of California. The "Cowell structure" which is said to be 0.8 miles wide, is said to be nearly 25 million years old.

Researchers now call the crater "The Victoria Island Structure." The impact would have been as strong as 100,000 nuclear bombs all going off at once.