On the morning of 30 June 1908, a large explosion flattened 2,000 km2 of forest near the Stony Tunguska River in Eastern Siberia. There were no recorded human casualties.
Fallen trees at Tunguska, 1927
In 1930, a scientific expedition, lead by Leonid Kulik, recorded the testimony of S Semenov:
At breakfast time I was sitting by the house at Vanavara Trading Post [65 kilometres/40 miles south of the explosion], facing north. […] I suddenly saw that directly to the north, over Onkoul’s Tunguska Road, the sky split in two and fire appeared high and wide over the forest.
The split in the sky grew larger, and the entire northern side was covered with fire. At that moment I became so hot that I couldn’t bear it as if my shirt was on fire; from the northern side, where the fire was, came strong heat.
I wanted to tear off my shirt and throw it down, but then the sky shut closed, and a strong thump sounded, and I was thrown a few meters.
I lost my senses for a moment, but then my wife ran out and led me to the house. After that such noise came, as if rocks were falling or cannons were firing, the earth shook, and when I was on the ground, I pressed my head down, fearing rocks would smash it.
When the sky opened up, hot wind raced between the houses, like from cannons, which left traces in the ground like pathways, and it damaged some crops.
Later we saw that many windows were shattered, and in the barn, a part of the iron lock snapped.
Most scientific investigations of this event conclude that the explosion was caused by the disintegration and airburst of a meteoroid at an altitude of about 5 to 10km. Estimates of the size of the meteroid vary between 60 and 190m.
The explosion was equivalent to 500 to 1000 times that of the Little Boy atomic weapon used at Hiroshima, and the shock would have measured about 5.0 on the Richter Scale.
Similar events have occurred:
- 13 August 1930 over the area of Curuçá River in Brazil (explosion approximately 1/5th the size of Tunguska)
- Chelyabinsk in the Ural district of Russia on 15 February 2013 (explosion approximately 1/10th the size of Tunguska) causing 1,200 injuries, mostly from falling glass.
There are alternative theories for the explosion at Tunguska including the release and explosion of 10 million tons of natural gas from within the Earth’s crust.