Technically, an avalanche is any am

Technically, an avalanche is any amount of snow sliding down a mountainside. It can be compared to a landslide, only with snow instead of earth. Another common term for avalanche is “snowslide”. As an avalanche becomes nearer to the bottom of the slope, it gains speed and power, this can cause even the smallest of snowslides to be a major disaster.
There are two common types of avalanches, a Surface Avalanche that occurs when a layer of snow with different properties slides over another layer of snow. For example, when a layer of dry loosely packed snow slides over a dense layer of wet snow. The other common avalanche is known as a Full-Depth Avalanche which, as it’s name would lead you to believe, occurs when an entire snow cover, from the earth to the surface, slides over the ground.
An avalanche can be composed of many different kinds of snow depending on the region, temperature and weather. It could be compiled of loosely packed light fluffy snow, which can still be very dangerous even though it may not appear threatening. It could also consist of a thick “slab” which is an area of tightly packed together snow that separates itself from the surroundings.