Dirt and rocks litter an avalanche area in Alaska.

Avalanche in springtime, in a Pyrenees valley. Dirty snow, broken trees, and giant rocks moved by the strength of the snow.

A chunk of the unstable lava dome at Sinabung volcano in Sumatra, Indonesia collapses causing a pyroclastic flow to form.

Fast moving and dangerous pyroclastic flow sweeps down the side of Sinabung volcano in Sumatra, Indonesia on 19th June 2015.

A large cloud of volcanic ash erupts from Sinabung volcano in Sumatra, Indonesia during a major eruption on 19th June 2015.

A large and destructive pyroclastic flow sweeps over farmland on the flanks of Sinabung volcano in Sumatra, Indonesia on 19th June 2015.

A large and fast moving pyroclastic flow sweeps down Sinabung volcano in Sumatra, Indonesia during a major eruption on 19th June 2015.

A large and dangerous pyroclastic flow sweeps down the side of Sinabung volcano in Sumatra, Indonesia during a major eruption on 19th June 2015.

A large and dangerous pyroclastic flow sweeps down the side of Sinabung volcano in Sumatra, Indonesia during a major eruption on 19th June 2015.

A large and dangerous pyroclastic flow sweeps down the side of Sinabung volcano during an eruption on 19th June 2015.

Wide shot of a skier, he falls and is hit by a wall of snow. Avalanche carries man down slope

Skier struck by wall of snow

Skier is swept down slope over crevasse

Avalanche in springtime, in a Pyrenees valley. Dirty snow, broken trees, and giant rocks moved by the strength of the snow.

Avalanche protection, Lawinenschutz, Sicherung, S�lden (Austria)

Snowboarder rotates in mid air

Snowboarder walking on the mountains edge

Danger of Avalanches, Lawinenwarnung, S�lden (Austria)

Avalanche protection, Lawinenschutz, Sicherung, S�lden (Austria)

Danger of Avalanches, Lawinenwarnung, S�lden (Austria)

An avalanche slides down a mountainside.

Snowboarder doing powder turn

Snowboarder performs a trick

Winter hiking with crampons and axes