Portal:Disasters/Selected article/October 2006
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The Tunguska event was an explosion that occurred at , near the Podkamennaya (Under Rock) Tunguska River in what is now Evenk Autonomous Okrug, at 7:17 AM on June 30, 1908. The event is sometimes referred to as the great Siberian explosion.
The explosion was probably caused by the airburst of a meteorite or comet 6 to 10 kilometers (4–6 mi) above the Earth's surface. The energy of the blast was later estimated to be between 10 and 15 megatons of TNT, which would be equivalent to Castle Bravo, the most powerful nuclear bomb ever detonated by the US. It felled an estimated 60 million trees over 2,150 square kilometers (830 sq mi).
At around 7:15 a.m., Tungus natives and Russian settlers in the hills northwest of Lake Baikal observed a column of bluish light, nearly as bright as the Sun, moving across the sky. About 10 minutes later, there was a flash and a loud "knocking" sound similar to artillery fire that went in short bursts spaced increasingly wider apart. Eyewitnesses closer to the explosion reported the sound source moving during each barrage, east to north. The sounds were accompanied by a shock wave that knocked people off their feet and broke windows hundreds of miles away. The majority of eyewitnesses reported only the sounds and the tremors, and not the sighting of the explosion; to different eyewitnesses the sequence of events and their overall duration is also different.
The explosion registered on seismic stations across Eurasia, and produced fluctuations in atmospheric pressure strong enough to be detected by the recently invented barographs in Britain. Over the next few weeks, night skies were aglow such that one could read in their light. In the United States, several observatories noted a decrease in atmospheric transparency that lasted for several months.
