Glacier - Types of Glaciers

Types of Glaciers

Glaciers are categorized in many ways including by their morphology, thermal characteristics or their behavior. Alpine glaciers form on the crests and slopes of mountains and are also known as "mountain glaciers""niche glaciers", or "cirque glaciers". An alpine glacier that fills a valley is sometimes called a valley glacier. Larger glaciers that cover an entire mountain, mountain range, or volcano are known as an ice cap or ice field, such as the Juneau Icefield. Ice caps feed outlet glaciers, tongues of ice that extend into valleys far below the margins of the larger ice size

The largest glacial bodies, ice sheets or continental glaciers, cover more than 50,000 km² (20,000 mile²). Several kilometres deep, they obscure the underlying topography. Only nunataks protrude from the surface. The only extant ice sheets are the two that cover most of Antarctica and Greenland. 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 metres (20 ft) all around the world. If the Antarctic ice sheet melted, sea levels would rise up to 65 metres (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. Ice streams are fast-moving sections of an ice sheet. They can be several hundred km long. Ice streams have narrow margins and on either side ice flow is usually an order of magnitude less. In Antarctica, many ice streams drain into large ice shelves. However, some drain directly into the sea, often with an ice tongue, like Mertz Glacier.

Tidewater glaciers are glaciers that terminate in the sea, including most of the ones flowing from Greenland, Antarctica, Baffin and Ellesmere Islands in Canada, Southeast Alaska and the Northern and Southern Patagonian Ice Field to the Pacific in Chile. 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. 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. Humboldt Glacier, in North West Greenland is the widest tidewater glacier in the Northern Hemisphere; its front is 110 km (68 mi) wide. The Hubbard Glacier is the longest tidewater glacier in Alaska and has a calving face over 10 km (6.2 mi) 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.

In terms of thermal characteristics, a temperate glacier is at melting point throughout the year, from its surface to its base. The ice of a polar glacier is always below freezing point from the surface to its base, although the surface snowpack may experience seasonal melting. A sub-polar glacier has both temperate and polar ice, depending on the depth beneath the surface and position along the length of the glacier.