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Avalanches are huge masses of ice and snow that breaks away from the side of a mountain and surges downward at great speed. Scientists have grouped avalanches into three main kinds: wet-snow, dry-snow and slab avalanche. Wet-snow avalanches begins in rocky areas and occur in spring. The melting snow gathers together to form a large boulder of snow. The rocks warms up under the sun, causing snow around to melt and fall downhill. Such type of snow becomes very hard after they finallys stop. Dry-snow avalanches are more deadly. They can close to the ground or lift off the ground and swirl through the air, hundreds of feet high. The snow is powdery unlike those in wet-snow avalanches. A destructive blast of air may be sent out as the snow travels. A huge slab of solid snow breaks away from a slope when slab avalanches occur. Layers of loose snow crystals lie below and this slab slides across it. The front of the slab soon starts to break up. They usually occur on slopes that are protected from the wind as the snow collects in deep piles. |