What types of glaciers are there?

 

Mountain glaciers

Historic photograph of Variegated Glacier, Alaska, 1965Variegated Glacier is a valley glacier that winds through the Saint Elias Mountains in Alaska, terminating near Yakutat Bay. —Credit: Photograph by Austin Post. 1965. Variegated Glacier: From the Glacier Photograph Collection. Boulder, Colorado USA: National Snow and Ice Data Center. Digital media.

These glaciers develop in high mountainous regions, often flowing out of icefields that span several peaks or even a mountain range. The largest mountain glaciers are found in Arctic Canada, Alaska, the Andes in South America, and the Himalaya in Asia.

Valley glaciers

Commonly originating from mountain glaciers or icefields, these glaciers spill down valleys, looking much like giant tongues. Valley glaciers may be very long, often flowing down beyond the snow line, sometimes reaching sea level.

Tidewater glaciers

As the name implies, these are valley glaciers that flow far enough to reach out into the sea. Tidewater glaciers are responsible for calving numerous small icebergs, which although not as imposing as Antarctic icebergs, can still pose problems for shipping lanes.

Piedmont glaciers

Historic photograph of Lamplugh Glacier, Alaska, 1941A classic tidewater glacier, Lamplugh Glacier terminates in a small embayment in Alaska's Glacier Bay National Park and Preserve. —Credit: Photograph by William Osgood Field. 1941. Lamplugh Glacier: From the Glacier Photograph Collection. Boulder, Colorado USA: National Snow and Ice Data Center. Digital media.

Piedmont glaciers occur when steep valley glaciers spill into relatively flat plains, where they spread out into bulb-like lobes. Malaspina Glacier in Alaska is one of the most famous examples of this type of glacier, and is the largest piedmont glacier in the world. Spilling out of the Seward Icefield, Malaspina Glacier covers about 3,900 square kilometers (1,500 square miles) as it spreads across the coastal plain.

Hanging glaciers

When a major valley glacier system retreats and thins, sometimes the tributary glaciers are left in smaller valleys high above the shrunken central glacier surface. These are called hanging glaciers. If the entire system has melted and disappeared, the empty high valleys are called hanging valleys.

Cirque glaciers

Cirque glaciers are named for the bowl-like hollows they occupy, which are called cirques. Typically, they are found high on mountainsides and tend to be wide rather than long.

Ice Aprons

These small, steep glaciers cling to high mountainsides. Like cirque glaciers, they are often wider than they are long. Ice aprons are common in the Alps and in New Zealand, where they often cause avalanches due to the steep inclines they occupy.

Rock Glaciers

Satellite image of the Larsen Ice Shelf, Antarctica, 1998This satellite image shows the Larsen Ice Shelf, Antarctica, in 1998, four years before the shelf disintegrated. Taken at the beginning of the Antarctic winter, the ice shelf is clearly visible. Notice that sea ice is forming over the ocean to the right the ice shelf. —Credit: NSIDC, data from the Moderate Resolution Imaging Spectroradiometer (MODIS)

Rock glaciers sometimes form when slow-moving glacial ice is covered by debris. They are often found in steep-sided valleys, where rocks and soil fall from the valley walls onto the ice. Rock glaciers may also form when frozen soil creeps downslope.

Ice shelves

Ice shelves occur when ice sheets extend over the sea and float on the water. They range from a few hundred meters to over 1 kilometer (0.62 mile) in thickness. Ice shelves surround most of the Antarctic continent.

Icefields

Icefields are similar to ice caps, except that their flow is influenced by the underlying topography, and they are typically smaller than ice caps.

Ice caps

Ice caps are miniature ice sheets, covering less than 50,000 square kilometers (19,305 square miles). They form primarily in polar and sub-polar regions that are relatively flat and high in elevation.

Ice streams

Photograph of the Southern Patagonian IcefieldThe Southern Patagonian Ice Field spans the border between Argentina and Chile and covers 12,363 square kilometers (4,773 square miles). —Credit: NASA

Ice streams are large ribbon-like glaciers set within an ice sheet—they are bordered by ice that is flowing more slowly, rather than by rock outcrop or mountain ranges. These huge masses of flowing ice are often very sensitive to changes such as the loss of ice shelves at their terminus or changing amounts of water flowing beneath them. The Antarctic ice sheet has many ice streams.

Ice sheets

Found now only in Antarctica and Greenland, ice sheets are enormous continental masses of glacial ice and snow expanding over 50,000 square kilometers (19,305 square miles). The ice sheet on Antarctica is over 4.7 kilometers (3 miles) thick in some areas, covering nearly all of the land features except the Transantarctic Mountains, which protrude above the ice. Another example is the Greenland ice sheet. In the past ice ages, huge ice sheets also covered most of Canada (the Laurentide Ice Sheet) and Scandinavia (the Scandinavian Ice Sheet), but these have now disappeared, leaving only a few ice caps and mountain glaciers behind.