On June 30, 1908, a little after 7:00 AM in the area that is now Krasnoyarsk Krai on the Lower Tunguska River, a huge explosion flattened more than 80 million trees on 830 square miles of Siberian taiga. The explosion was estimated at one-thousand times greater that the atom bomb dropped on Hiroshima, Japan in 1945. The cause of the explosion is not known for sure, but some scientists surmise that it was a large comet or meteor striking the Earth. The evidence does not support that contention, however, but pictures of the site look more like an air-burst than an impact since there is no crater to support the impact theory.