A scar on the Deccan Traps
Sometime during the Pleistocene Epoch, a meteorite traveling at hyper-velocity slammed into a 65-million-year-old flood basalt plain in what is now Maharashtra, India. The impact created the Lonar Crater, a near-circular depression with a mean diameter of 1.2 kilometers (3,900 ft) and a rim that rises about 20 meters (65 feet) above the surrounding plain. The crater floor sits roughly 137 meters (449 ft) below the rim. While age estimates vary, argon-argon dating suggests the impact occurred around 570,000 years ago.
For many years, its location within the Deccan Traps, a massive field of volcanic basalt—led geologists to believe it was a volcanic crater. The confirmation of its impact origin came with the discovery of specific shock-metamorphism features. The most definitive of these is maskelynite, a type of natural glass. Maskelynite formed when the mineral plagioclase is subjected to the extreme pressures of a high-velocity impact, a process that does not occur in volcanism. This glassy material, previously identified in lunar rock samples and meteorites, provided clear evidence of the crater's extraterrestrial origin. The presence of shatter cones and an ejecta blanket surrounding the crater further supports the impact theory. Lonar is one of only four known hyper-velocity impact craters in basaltic rock on Earth.