On the morning of June 30, 1908, an explosion ripped through the sky above a remote area in Siberia, near the Podkamennaya Tunguska river. The earth was said to tremble as far away as the UK, and 830 square miles of forest (approximately 80 million trees) were leveled, with burned reindeer carcasses littered throughout the destruction. The 15-megaton blast was 1,000 times greater than the atomic bomb dropped on Hiroshima, Japan.
The investigation into the explosion found no central crater or origin site, so what happened? Due to the remote region and harsh seasons where it took place, this strange occurrence wasn't studied until almost 20 years after it happened, leaving lots of speculation over what really took place. Was this the beginning of atomic testing by Russia? No. This incident became known as "The Tunguska Event," and was caused by what's known as an "air burst." When a large meteor (this one was the size of an eleven-story building) explodes while traveling through the atmosphere, it causes a destructive blast of air to thrust down upon Earth's surface.
A similar event happened again over Russia that helped to fill in the story, this time in February of 2013. A giant fireball lit up the sky over the town of Chelyabinsk and was recorded on thousands of cameras and scientific instruments. Like Tunguska, airwaves collided with Earth's surface after the meteor exploded, this time resulting in shattered and blown-in glass windows, and fallen human structures. The intense light from the fireball was momentarily 30 times brighter than the Sun and caused over 180 cases of eye trauma and reports of intense sunburn. A roof at a factory collapsed due to the shock wave, and a total of 1,200 people were hospitalized with blast-related injuries.
While the Chelyabinsk blast has offered up new scientific data to help piece together the Tunguska event, it must be noted that the Chelyabinsk blast was more than 30 times smaller than Tunguska. Scientists say Earth only encounters a meteor the size of Tunguska once every 300 years.