Tunguska, 1908: the great explosion
Eighty million trees flattened, and no crater.
On the morning of 30 June 1908, a huge explosion shook the forest near the Podkamennaya Tunguska River in Siberia. People 60 km away were knocked off their feet, and the shock was recorded by instruments across Europe. Night skies glowed for days afterwards.
An asteroid or comet fragment, probably 50 to 60 m across, exploded several kilometres above the ground. The blast flattened about 2,000 km² of forest, some 80 million trees. Estimates of its energy are typically 10 to 15 megatons.
The first expedition, led by Leonid Kulik, reached the site only in 1927 and found trees lying in a vast radial pattern but no crater and no meteorite. Tunguska is the largest impact event in recorded history, and the reason 30 June is now marked each year as Asteroid Day.