Tunguska Event

The Tunguska Event was an event on Earth, also known as the Tunguska blast (TV: In the Forest of the Night) or Tunguska disaster. (COMIC: The Hyperion Empire)

It was believed to have been caused by a meteor impact in the Tunguska province of Russia on 30 June 1908. The "meteor" was, in actuality, half of the TARDIS. It had split in half, then time rammed itself. The energy released by the impact caused the Great Divide to open in Russia, allowing some of the Charrl to enter that time period from 22,000. (PROSE: Birthright)

According to the Twelfth Doctor, the Tunguska blast should have blown the Earth off its axis, but instead, it simply knocked "a few tens of thousands of trees" over. The trees in the region protected the Earth from the impact by "filling the atmosphere with oxygen, pumping it up, like a massive, inflammable airbag", and the impact burnt off the excess oxygen. (TV: In the Forest of the Night)

The Third Doctor attempted to take Liz Shaw and Jo Grant to witness the meteor impact but the TARDIS instead materialised in St Petersburg in December 1916. (PROSE: The Wages of Sin)

After her defection from the Soviet Union to the United Kingdom in 1958, the Czech scientist Dr Nadia Červenka provided the Sen-Gen Facility with a neuro-chemical hallucinogen developed using a yellow fungus which was discovered in the crater. It was believed to be extraterrestial in origin. (AUDIO: Artificial Intelligence)

Aftermath
After the Tunguska Event, Nicholas II set up the KVI. (PROSE: Trace Memory)