Tunguska Explosion

On June 30, 1908, an enormous explosion flattened about 500,000 ac of pine forest near the Stony Tunguska River in central Siberia. Its energy is estimated to have been equivalent to that of about 15 megatons of TNT.

Uncertain evidence suggests that a meteoroid or, less likely, a comet disintegrated in the atmosphere high above Earth's surface, creating a fireball and blast wave but no crater. Eyewitnesses spoke of a fireball lighting the horizon, initially visible from about 500 miles away, followed by trembling ground and hot winds strong enough to throw people down and shake buildings.