2. Tunguska Event
On June 30,1908, a gigantic airburst occurred near the Tunguska River (present-day Krasnoyarsk Krai, Russia). The most plausible theory is a 20m in diameter comet fragment or meteorite that broke up before hitting the ground. The energy released during the event was between 10 and 20 megatons of TNT or one thousand times more powerful than the atomic bomb that leveled Hiroshima. More than 80 million trees fell on 2,150 square kilometers of deeply forested area. Today, we can still identify remnants of the devastation with latest satellite images.