At 7:15am on June 30, 1908, a blue-white fireball flew over the remote region of central Siberia near the Stony Tunguska River and exploded with the force of a 10- to 15- megaton hydrogen bomb. The explosion wiped out approximately 60 million trees across an area of 2,000 square kilometers. Witnesses from hundreds of miles away saw an immense pillar of fire and heard thundering claps. Those closest to the blast were deafened by the noise and knocked off their feet when the thermal wave swept through the area. Miraculously, no one was killed.

Since then, the scientific community has come up with a plausible reason for the blast––a mid-air comet or meteor explosion. Despite this, there are those who believe that the explosion was caused by a very large UFO, although there was no evidence of spacecraft debris. Scientists did find rocks embedded in the ground and the trees that are consistent with the material found in meteorites.

Further Reading: Tunguska Explosion
Tunguska - Fire in the Sky
James Oberg: Tunguska Echoes
1908 Siberia Explosion: Reconstructed