The Tunguska Event, sometimes referred to as the Tunguska explosion, was a massive explosion that occurred near the Podkamennaya (Under Rock) Tunguska River in what is now Krasnoyarsk Krai of Russia, between 7:00 and 8:00 AM on June 30, 1908.

The explosion was most likely caused by the airburst of a large (around 20 m (66 ft) across) meteoroid or comet fragment at an altitude of 5 to 10 kilometers (3-6 mi) above the Earth's surface. Although the meteor or comet is considered to have burst prior to hitting the surface, this event is still referred to as an impact event. The energy of the blast was estimated to be between 10 and 20 megatons of TNT, 1,000 times more powerful than the bomb dropped on Hiroshima, or equivalent to Castle Bravo, the most powerful nuclear bomb ever detonated by the US.

The Tunguska explosion felled an estimated 80 million trees over 2,150 square kilometers (830 sq mi). An overhead satellite view, from nearly a century later, centered at 60°55 N, 101°57 E (near ground zero for this event) shows an area of reduced forest density with a clearly visible, irregular clearing of somewhat less than one square kilometer in area. It is estimated to have measured 5.0 on the Richter scale.

The Tunguska event is the largest impact event in recent history. An explosion of this magnitude had the potential to devastate large metropolitan areas should it occur over a large city. This has helped spark discussion of ways to potentially stop large asteroids or comets from hitting Earth.
(source:http://www.crystalinks.com/tunguskaevent.html)

Lintaskan!