Tunguska The Mysterious

This is a picture from a 1927 expedition to the site of the Tunguska incident in Siberia. It occurred on June 30th, 1908. It was originally thought to be a meteor impact, but it left a butterfly-shaped area of flattened trees and nothing else. However, some scientists say that a lake nearby could be the real impact crater, although it is rather uncertain. Here's a link to more information:

Tunguska Information