How Do Glaciers Form?

Glacier formation begins in areas where more snow falls each winter than melts each summer. Over years, the weight of accumulating snow compresses lower layers, squeezing out air and transforming fluffy snow into granular firn, then into solid glacial ice. When the ice reaches a thickness of about 30-50 metres, the pressure causes it to become plastic and flow — slowly deforming and moving downhill under gravity. This process typically takes decades to centuries. Valley glaciers flow like slow rivers through mountain valleys, while ice sheets (like those in Antarctica and Greenland) spread outward under their own immense weight. Glaciers currently store about 69% of the world fresh water.