Tunguska event

The violent impact of what is thought to have been a comet or meteorite in the Tunguska region of Siberia on 30 June 1908. Though the event caused devastation over a large area, no remains of an impacting body or any crater have been discovered, perhaps because the object exploded in the atmosphere before an actual impact; the height of such an explosion has been estimated at 8.5 kilometres. Observers reported seeing a fireball as bright as the Sun. It exploded with a deafening sound and caused a shock wave that shook buildings and caused damage, though there was no loss of human life. The first expedition to the remote area of the explosion did not take place until 1927. It was found that a forest of trees had been snapped in half over a region 30-40 kilometres (20-25 miles) in radius. Over a region of radius 15-18 kilometres (9-11 miles) from the apparent "impact" site, trees had been flattened radially and stripped of their branches. No totally satisfactory explanation of the event has been found.