Here's why:

* Avalanches are primarily driven by gravity: They occur when a mass of snow or ice on a slope becomes unstable and slides downwards due to gravity.

* The terrain plays a crucial role: The shape and composition of the slope, the amount of snow accumulation, and the presence of weak layers within the snowpack all contribute to the likelihood of an avalanche.

* Atmospheric conditions can influence avalanches: Factors like wind, precipitation, and temperature changes can affect the stability of the snowpack, but they are not the primary drivers of the avalanche itself.

While atmospheric conditions can play a role in triggering avalanches, the fundamental process of snow and ice sliding down a slope is inherently geological.