Tunguska event, illustration. The Tunguska event was a massive explosion that took place at 07:17 on 30 June 1908, in Siberia, Russia. A fireball was observed low in the sky, moving north-west, followed by a series of loud knocking sounds and a shock wave that was felt hundreds of kilometres away. Expeditions to the area found immense damage, with over 3000 square kilometres of forest flattened. It is thought that the explosion was a meteorite or comet breaking up and exploding above the surface.