Have you thought about how a avalanche starts? Well I'll tell you how.
There are two things needed to start a avalanche. One is a snow covered
slope; another is a trigger like a strong winds, a skier, or a person's voice.

         Did you know that there are more than 1 kind of avalanche? One is called a sluff.  It  starts when the weak layer of snow is on top of the the snowpack. A snowpack is when the snow that is falling hits the ground and the pressure of the snow on top makes it pack together like a snowball to make a snowpack.  The sluffs aren't very dangerous because they do not carry a lot of snow with them.

          Slab avalanches are a lot more deadlier than a sluff. Why is because the weak layer of snow is deep in the snowpack so when it hits the snow that is packed together strikes first. While it is traveling down a mountain the speeds of a slab can reach up to 200 MPH. When it stops it as hard as concrete. That is 1 reason why the slab is a lot deadlier than a sluff because it's a lot harder to dig somebody out if they get caught under the snow.