Glaciers form when accumulating snow compresses into firn and eventually turns into ice. In some cases, perennial snow accumulates on the ground and lasts all year. This makes a snowfield and not a gl...Glaciers form when accumulating snow compresses into firn and eventually turns into ice. In some cases, perennial snow accumulates on the ground and lasts all year. This makes a snowfield and not a glacier since it is a thin accumulation of snow. Snow and glacial ice actually have a fair amount of void space (porosity) that traps air. As the snow settles, compacts, and bonds with underlying snow, the amount of void space diminishes.
