Tunguska event
What happened is called air burst today. At the time, the energy involved was estimated to be between 10 and 30 megatons of TNT, depending on the height in which the air burst happened. Simulations that have been done with modern computers have found that the energy involved was probably between 3 and 5 megatons of TNT.  Taking 15 megatons, this would mean that the energy involved was 1.000 times that of the atomic bomb dropped on Hiroshima, in 1945. The shock wave is considered to be that of an earthquake with a magnitude of 5.0 on the Richter scale. For these reasons, the Tunguska event is considered the largest impact event on Earth in recorded history.