The impact is estimated to have occurred 375 million years ago, during the Devonian period, when much of what is now the Catskills was either river delta or a shallow sea. The crater lies 2,640 feet (800 m) below the surface, is 6 miles (10 km) wide, and lies directly under the mountain. The meteorite that struck is believed to have been roughly one-half mile (1 km) wide, striking with a force equivalent to 11 trillion tons (9.9 trillion tonnes) of TNT.