The Tunguska Event was a massive explosion that occurred near the Tunguska River in Siberia, at about 7:14 a.m. on June 30, 1908. The explosion was most likely caused by the air burst of a large meteor or comet fragment at an altitude of 5-10 kilometers above the earth’s surface. There are a number of estimates as to the size of the meteor, but it is generally agreed that it was about 50 meters wide. Although the meteor or comet exploded in the air rather than colliding with the earth's surface, this event is still referred to as an impact.

The explosion had a blast range of an estimated 30 megatons or about 1000 times as powerful as the bomb dropped on Hiroshima and about one third the power of the Tsar Bomb, the largest nuclear weapon ever detonated. The explosion knocked over an estimated 80 million trees in a 2,150 square kilometer area. An explosion like this is capable of destroying a large city. The Tunguska Event is believed to be the most powerful explosion on land in earth's recent history.