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2 #12 reveals the Tunguska Event was part of an ancient cabal of powerful immortal rulers using a magic ceremony to create a powerful animal/human creature (a character called 'The Bear', introduced in an earlier " flashback" Iron Man). In the main 616 continuity, as part of the Original Sin crossover, Mighty Avengers vol.Warren Ellis, as a rule, does his research. In this universe the Tunguska explosion was said to have happened in 1904 instead of 1908, and Word of God is that the date was moved to make it a century before the release date of the comic in 2004. He (she?) was quickly taken into Russian custody and dissected so its Organic Technology could be used to kickstart a Super Soldier project, which means no one learned about Gah Lak Tus until about a year before he was supposed to eat Earth. The Ultimate Marvel Ultimate Galactus Trilogy miniseries revealed in the first mini ( Ultimate Nightmare) that the Tunguska Incident was caused by the Vision crash-landing to Earth.It has been speculated the Tunguska Event might have been due to a really big build-up of subterranean methane that found its way out. It has also been noted that recent explosions in Siberia, leaving impressive craters and downed trees, are due to pockets of methane being released from defrosting tundra global warming is speeding up this process and creating another interesting consequence. Other less credible, but more interesting, theories suggest that the event was caused by: a deuterium-rich meteorite causing an all-natural thermonuclear explosion a chunk of antimatter a miniature black hole passing through the Earth an alien spacecraft crashing or discharging some kind of superweapon psychic experiments or magic rituals gone wrong or a test run of Nikola Tesla's Death Ray. There's some debate over whether the exploding space rock came from a comet (which would explain lack of a solid meteorite body) or an asteroid. While such air-bursts are common at higher altitudes, they are rarely close enough to Earth's surface to cause damage.
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Today, most scientists agree that The Tunguska Event was caused by a meteoroid exploding in mid-air rather than directly impacting. As of 2013 the meteorite still hasn't been found. But this hypothesis requires further investigation. It's absent from 19th century maps (albeit rather inaccurate ones) and appears only from 1929 onward, it has unusual shape, and it's only 8 km from the epicenter. In 2007 a small lake Cheko has been suggested to have an impact origin.
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