The Tunguska province was a region of Russia.
In 1908, the region experienced a mysterious explosion that denuded a forest in and around the Tunguska Basin. The explosion was never completely explained. One account said that the TARDIS had split in half, then time rammed itself. (PROSE: Birthright) According to another, a 21st century human named El Ape accidentally set off a nuclear explosion in the valley while travelling with the Seventh Doctor in search of the Monk. (COMIC: Follow That TARDIS!) According to the Twelfth Doctor, the forest in the region prevented the blast from blowing the Earth off its axis 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)