On 30th June, 1908 at about 7:14am an extremely large and powerful explosion occured at Podkamennaya Tunguska River in Russia.
The explosion occured is said to be the largest impact event that has ever occured in the Earth’s recorded history. To give you an idea of the scale of the explosion we are talking about, it is estimated to be 1000 times more powerful than the bomb that was dropped on Hiroshima.
The explosion knocked down an estimated 80 million trees over over an area of 2150 square kilometres.
The seismic activity caused the explosion was felt all over Europe and an air pressure change was detected all the way in Great Britian.
Several expeditions have been carried out and there are many theories. All incomplete. None with proof.
This occurence is known as the Tunguska Event.
Look it up 
Do you know of any other unexplained phenomenon that have occured throughout Earth’s history?
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Only queerio could come up with that.