Glacial Info • A glacier is a perennial mass of ice which moves over land • A glacier forms in locations where the mass accumulation of snow and ice exceeds ablation over many years • Glacier ice is the largest reservoir of fresh water on Earth, and is second only to oceans as the largest reservoir of total water • Glaciers cover vast areas of the polar regions and are found in mountain ranges of every continent including Australasia • Glaciers are indicators of climate and are important to world water resources and sea level variation
Alpine Glaciers • Alpine glaciers form on mountain slopes and are also known as mountain, niche, or cirque glaciers. An alpine glacier that fills a valley is referred to as a valley glacier. Larger glaciers that cover an entire mountain, mountain chain, or volcano are known as an ice cap or ice field, such as the Juneau Ice field. Ice caps feed outlet glaciers, tongues of ice that extend into valleys below, far from the margins of the larger ice masses
Ice Sheets • Ice sheets are the largest glaciers. These enormous masses of ice are not visibly affected by the landscape as they cover the entire surface beneath them, with possible exception near the glacier margins where they are thinnest. Antarctica and Greenland are the only places where continental ice sheets currently exist. These regions contain vast quantities of fresh water. The volume of ice is so large that if the Greenland ice sheet melted, it would cause sea levels to rise six meters (20 ft) all around the world. If the Antarctic ice sheet melted, sea levels would rise up to 65 meters (210 ft).Ice shelves are areas of floating ice, commonly located at the margin of an ice sheet. As a result they are thinner and have limited slopes and reduced velocities.
Tidewater glaciers • Tidewater glaciers are glaciers that terminate in the sea. As the ice reaches the sea pieces break off, or calve, forming icebergs. Most tidewater glaciers calve above sea level, which often results in a tremendous splash as the iceberg strikes the water. If the water is deep, glaciers can calve underwater, causing the iceberg to suddenly leap up out of the water. The Hubbard Glacier is the longest tidewater glacier in Alaska and has a calving face over ten kilometers long. Yakutat Bay and Glacier Bay are both popular with cruise ship passengers because of the huge glaciers descending hundreds of feet to the water. This glacier type undergoes centuries-long cycles of advance and retreat that are much less affected by the climate changes currently causing the retreat of most other glaciers. Most tidewater glaciers are outlet glaciers of ice caps and ice fields.