An avalanche was a rapid flow of material down a sloping surface.

Davis and Walters triggered an avalanche near Brittanicus Base when they tried excavating the body of a buried Ice Warrior. Davis was killed in the avalanche. (TV: The Ice Warriors)

In 1777, a Swiss village disappeared in an apparent avalanche. However, the inhabitants were taken away to be experimented on by the inhabitants of a dark planet. (PROSE: The Dark Planet)

Harding Wellman was killed in an avalanche while mountaineering in the Swiss Alps in 1913. (AUDIO: Winter for the Adept)

The Monk took Lucie Miller to the planet Questus, where he planned to kill the parents of a dictator in an avalanche to prevent the dictator's birth. After being dragged out of the avalanche, she tired of the Monk's meddling. He then "dumped" her on Deimos Moonbase in the 23rd century. (AUDIO: The Resurrection of Mars)