Glaciers and Ice Ages

Earth has experienced multiple ice ages — extended periods when ice sheets covered significant portions of the continents. The most recent ice age peaked 20,000 years ago (Last Glacial Maximum) when ice sheets 3-4 km thick covered most of Canada, Scandinavia, and northern Europe. Sea levels were 120 meters lower — you could walk from Siberia to Alaska, Britain to France, and Australia to Papua New Guinea. Glaciers today cover 10% of Earth's land surface (mostly Antarctica and Greenland) and contain 70% of Earth's fresh water. Glaciers are retreating worldwide — at current rates, the Alps will be largely ice-free by 2100 and Montana's Glacier National Park will have no glaciers. The potential melting of the West Antarctic Ice Sheet alone would raise sea levels by 3.4 meters — threatening coastal cities globally. Ice cores drilled from Antarctica contain climate records from 800,000 years of snowfall.