Glaciers are masses of ice that flow over land under their own weight. They currently exist in Greenland, Antarctica, and mountain ranges. Glaciers are important for understanding past climate changes as they are sensitive to small changes in temperature and precipitation. During glacial periods, large ice sheets covered vast areas of the Earth's surface. Glaciers erode and transport material, depositing it in distinctive landforms like moraines, eskers, and drumlins. The cyclic growth and decay of glaciers over the past few million years, known as glacial and interglacial periods, has significantly impacted the Earth's landscape and climate.