|Lake Cheko (Чеко)|
|Location||near Podkamennaya Tunguska River, Siberia|
Lake Cheko (Russian: Чеко) is a small freshwater lake in Siberia, near the Podkamennaya Tunguska River, in what is now the Evenkiysky District of the Krasnoyarsk Krai. It is a small bowl-shaped lake, 708 metres long, 364 metres wide and about 50 metres deep, and has been connected by some scientists to the Tunguska event. They postulate that it was created by a chunk of the exploding meteorite that struck the ground.
Age of the lake 
Some scientists have speculated that Lake Cheko was created during the Tunguska event, an explosion on 30 June 1908 that destroyed more than 2,000 km2 (800 sq mi) of Siberian taiga. It is suggested that the lake, which lies approximately 8 kilometres north-north-west of the event hypocenter, was formed by a fragment which struck the ground.
Varied evidence 
By contrast, in 2009, researchers from the University of Bologna investigated the lake bed  and concluded that the sediments, isotopes and pollen "suggest that Lake Cheko formed at the time of the Tunguska Event." Their recent research suggests that only a meter or so of the sediment layer on the lake bed is "normal lacustrine sedimentation", indicating a much younger lake of about 100 years. Acoustic-echo soundings of the lake floor offer some further support for the impact hypothesis, revealing a conical shape for the lake bed, which could be consistent with an impact crater. Also, the lake's long axis points to the hypocenter of the Tunguska explosion, about 7.0 km away. Magnetic readings also indicate a possible meter-sized chunk of rock below the lake's deepest point, which may be a fragment of the colliding body.
A BBC News story on the 100th anniversary of the Tunguska Event mentioned that researchers at Imperial College London had pointed out that many of the trees surrounding the lake are older than 100 years, which suggests that the lake could not have been created by an impact in 1908. In their response to the Bologna group's theory, the researchers had also pointed out other problems, including the morphology of the lake and the surrounding terrain, the lack of impactor debris and ejecta, and that the characteristics of the impactor required by the impact theory are inconsistent with existing models of the known features of the event.
- Rincon, Paul (2007-06-26). "Team makes Tunguska crater claim". BBC News. Retrieved 2013-02-15.
- Florenskiy, K. P. (1963). "Preliminary results from the 1961 combined Tunguska meteorite expedition". Meteoritica 23: 3–29. Retrieved 2007-06-26.
- Gasperini, Luca et. al. (2009). "Sediments from Lake Cheko (Siberia), a possible impact crater for the 1908 Tunguska Event". Retrieved 30 June 2010.
- Gasperini, Luca, et. al.; Bonatti, Enrico; Albertazzi, Sonia; Forlani, Luisa; Accorsi, Carla A.; Longo, Giuseppe; Ravaioli, Mariangela; Alvisi, Francesca et al. (December, 2009). "Sediments from Lake Cheko (Siberia), a possible impact crater for the 1908 Tunguska Event". Terra Nova (Blackwell Publishing Ltd.) 21 (6): 489–494. doi:10.1111/j.1365-3121.2009.00906.x. Retrieved 30 June 2010.
- Gasperini, L. et al. (2001). "Geophysical/sedimentological study of a lake close to the center of the great 1908 Siberian (Tunguska) Explosion". NGF Abstracts and Proceedings (1): 29–30. Retrieved 2008-05-27.
- Gasperini, L. et al.; Bonatti, Enrico; Longo, Giuseppe (April 2008). "Reply - Lake Cheko and the Tunguska Event: impact or non-impact?". Terra Nova 20 (2): 169–172. doi:10.1111/j.1365-3121.2008.00792.x. Retrieved 2008-05-27.
- Gasperini, L. et al. (June 2008hyp). "The Tunguska Mystery". Scientific American: 80–86. Retrieved 2008-06-08.
- Rincon, Paul (2008-06-30). "Fire in the sky: Tunguska at 100". BBC News. Retrieved 2008-07-01.
- Collins, G. S., et al.; Artemieva, N.; Wünnemann, K.; Bland, P. A.; Reimold, W. U.; Koeberl, C. "Evidence that Lake Cheko is not an impact crater". Terra Nova (Blackwell Publishing Ltd.) 20 (2): 165–168. doi:10.1111/j.1365-3121.2008.00791.x. Retrieved 15 February 2013.
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