The Tunguska event was a large explosion that occurred near the Podkamennaya Tunguska River in Yeniseysk Governorate (now Krasnoyarsk Krai), Russia, on the morning of 30 June 1908 (NS). The explosion over the sparsely populated Eastern Siberian Taiga flattened 2,000 square kilometres (770 square miles) of forest, yet caused no known human casualties. The explosion is generally attributed to the air burst of a meteor. It is classified as an impact event, even though no impact crater has been found; the object is thought to have disintegrated at an altitude of 5 to 10 kilometres (3 to 6 miles) rather than to have hit the surface of the Earth.
Something from outer space had hit the atmosphere. Such
things have happened in the past, as shown for example by the
huge meteor crater in Arizona, which was the result of a lump of
rock, a small asteroid, hitting the earth. However the Tunguska
event, as it has become known, was different, as became apparent
years later when the first adventurous investigators, led by
the Czechoslovakian scientist Leonid Kulik in 1927, reached the
remote site. Had it been an asteroid, a lump of rock from the solar
system that had smashed into the earth, then some tell-tale hole in
the ground should have been there. However, there was no sign of
any crater. They discovered that immediately below the explosion
was a vast mud plain as if a thousand bulldozers had cleared the
forest to prepare the foundations for a city the size of London.