An unexplained explosion that occurred in 1908 in Russia.
The cause of the explosion has not yet been clarified. It is assumed that the meteor exploded 5 kilometers above the ground and completely destroyed the forest within 2,000 km2,  without a visible crater.

http://imgur.com/IgYHcCh.jpg

Professor Leonid Kulik Aleksejvič the first expert who led the expedition in 1927 to investigate this event these are his photos.
http://imgur.com/2BrQ8VZ.jpg

http://imgur.com/brDQvYr.jpg

http://imgur.com/iUCqo1G.jpg
Research continued in modern times, tunguska is even proclaimed a protected park and is tracking forest recovery.
No new research is available for the public.

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