All avalanches share some common elements. Every avalanche must have a trigger--either human, animal or a natural cause--and a start zone where the avalanche begins. They also always have a slide path and a debris deposit of accumulated snow, a place where the slide comes to rest.
There are three main types of avalanches. A slab avalanche is the most common and causes the most deaths because it is human caused. They occur when there is a break in the weak layer of snow after new snow has been deposited. The slab breaks free and causes the slide.
Wet avalanches occur when wet snow builds up and breaks from the surface. These avalanches resemble the look of water but move slowly and are made of snow, rock and ice.
The powder avalanche is the most destructive avalanche because it can travel as fast as 100 mph. Made up of snow that has the consistency of powder, these avalanches are triggered by a small object, such as falling rock or ice.
A great way to prevent avalanches is to be educated about them. If you plan to head to the backcountry, take a avalanche certification course. Ski patrols at ski resorts take great care in preventing avalanches with blasting and other preventive measures.