Wednesday, June 27, 2007

A possible impact crater for the 1908 Tunguska Event

In 1908, something crashed into a remote forest in Russia. 770 square miles of trees were flattened in an instant. Over the last 99 years, there have been many theories about what happened including an asteroid strike, a mini-black hole, and even a UFO crash. However, the mystery may have been solved.

A possible impact crater for the 1908 Tunguska Event by L. Gasperini, F. Alvisi, G. Biasini, E. Bonatti, G. Longo, M. Pipan, M. Ravaioli, R. Serra has some of the details. It was published in the journal Terra Nova.

The abstract of the article notes, "The so-called 'Tunguska Event’ refers to a major explosion that occurred on 30 June 1908 in the Tunguska region of Siberia, causing the destruction of over 2000 km2 of taiga, globally detected pressure and seismic waves, and bright luminescence in the night skies of Europe and Central Asia, combined with other unusual phenomena. The ‘Tunguska Event’ may be related to the impact with the Earth of a cosmic body that exploded about 5–10 km above ground, releasing in the atmosphere 10–15 Mton of energy. Fragments of the impacting body have never been found, and its nature (comet or asteroid) is still a matter of debate. We report results from the investigation of Lake Cheko, located 8 km NNW of the inferred explosion epicenter. Its funnel-like bottom morphology and the structure of its sedimentary deposits, revealed by acoustic imagery and direct sampling, all suggest that the lake fills an impact crater. Lake Cheko may have formed due to a secondary impact onto alluvial swampy ground; the size and shape of the crater may have been affected by the nature of the ground and by impact-related melting and degassing of a permafrost layer."

Not everyone is convinced. Another article notes, "Many are skeptical about the discovery, though. For example, there are trees surrounding Lake Cheko. An impact should have blown down all these trees as well. Any object that created an airburst with the energy of 1,000 Hiroshima bombs should have dug out a much larger crater. Lake Cheko is also missing a characteristic flap of material that's ejected on the opposite side of an impact crater."

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