Safety in numbers . . . served us well through the eons when lions, tigers and bears were our greatest fear . . . Our herding instinct has the opposite effect in avalanche terrain.
Bruce Tremper
Introduction to Snow Safety
The word avalanche is derived from the Latin word meaning to "slip, glide down, and flow." Although almost anything that slides down a mountain or hillside (mud, ice, or rocks) can be called an avalanche, the term most commonly refers to snow slides.
Avalanches are classified on an international scale. Size 1 avalanches are relatively harmless to people. At the other end of the spectrum, size 5 avalanches are the largest snow avalanches known. They could destroy a village or a forest of 100 acres and typically involve a shifting snow mass of 100 000 tonnes.
It is the union of terrain, weather and snow variables that make avalanches possible.
Avalanche Hazard Triangle
The people or facilities at risk at the centre of this triangle create the hazard.