Tunguska Event

The Tunguska Event, or Tunguska explosion, was a powerful explosion that occurred near the Podkamennaya (Lower Stony) Tunguska River in what is now Krasnoyarsk Krai of Russia, at around 7:14 a.m.^[1][2] on June 30, 1908 (June 17 in the Julian calendar, in use locally at the time).^[2]
Although the cause of the explosion is the subject of debate, it is commonly believed to have been caused by the air burst of a large meteoroid or comet fragment at an altitude of 5–10 kilometres (3–6 miles) above the Earth's
surface. Different studies have yielded varying estimates of the
object's size, with general agreement that it was a few tens of metres
across.^[3]
Although the meteor or comet burst in the air rather than directly hitting the surface, this event is still referred to as an impact. Estimates of the energy of the blast range from 5 megatons^[4] to as high as 30 megatons^[5] of TNT, with 10–15 megatons the most likely^[5]—roughly equal to the United States' Castle Bravo thermonuclear explosion set off in late February 1954, about 1,000 times as powerful as the bomb dropped on Hiroshima, Japan and about one-third the power of the Tsar Bomba, the largest nuclear weapon ever detonated.^[6] The explosion knocked over an estimated 80 million trees over 2,150 square kilometres (830 square miles). It is estimated that the shockwave from the blast would have measured 5.0 on the Richter scale. An explosion of this magnitude is capable of destroying a large metropolitan area.^[7] This possibility has helped to spark discussion of asteroid deflection strategies.
Although the Tunguska event is believed to be the largest impact event on land in Earth's recent history,^[8] impacts of similar size in remote ocean areas would have gone unnoticed^{[dubious – discuss][citation needed][9]} before the advent of global satellite monitoring in the 1960s and 1970s.