In June 1908, a ball of fire exploded in a remote area of Russia, shaking the ground and instantly flattening 770 square miles of forest. Known as the Tunguska event because of its close proximity to a river of the same name, the blast reached 15 megatons of energy, about a thousand times more powerful than the Hiroshima bomb. Recent research suggests a meteor is to blame, as evidenced by a nearby lake that some scientists believe was created by the meteor’s impact. However, other scientists believe the lake was there before the event. What is certain is that the event was the most powerful natural explosion in recent history.