Glaciers are large, slow-moving masses of ice that form from compacted snow. They are found in mountain ranges and polar regions. Glaciers are sensitive to climate conditions and influence sea levels and water resources. They are categorized based on their thermal characteristics, behavior, and location. Alpine glaciers are confined to valleys while continental glaciers span entire regions. As glaciers accumulate more snow than melts, they grow, but melting exceeds accumulation in warmer periods, causing glaciers to recede.