Hanging Valleys

A hanging valley is a tributary (a stream or river that does not flow directly into the sea or ocean) valley with the floor at a higher place than the main channel into which it flows.  They are mostly associated with U-shaped valleys when a tributary glacier flows into a bigger glacier. The main glacier erodes a U-shaped valley with almost vertical sides, while the tributary glacier, makes a shallower U-shaped valley.  Since the surfaces of the glaciers were originally at the same height, the shallower valley seems to be ‘hanging’ above the main valley. Often waterfalls form at the hanging valleys.

Cirques

Cirques are a steep bowl-shaped hollow occurring at the end of a valley glacier by erosion.

   The formation of a cirque

Cirques are found among mountains as a result of alpine glaciers (alpine glaciers form the crests and slopes of a mountain). Cirques may get up to a square kilometer in size usually on the high mountain side near the firn line. The firn line is the ‘line’ where firn (a type of snow that has been left over past seasons that has been recrystallised. It is ice that is the stage between snow and glacial ice) is found at the altitude that it accumulates.

Cirques are surrounded by on three sides by steep cliffs. The highest cliff is called a headwall. The fourth side is called the lip, threshold or sill and is the side which the glacier flowed away from the cirque. Many glacial cirques contain tarns (a mountain lake or pool, formed in a cirque) dammed by either till (debris) or a bedrock threshold. When enough snow accumulates it can flow out the opening of the bowl and form valley glaciers which may be several kilometers long.

Continental Ice Caps

A continental ice cap is basically a very large ice cap (an ice cap is a huge block of ice that covers large areas) and can get up to 50, 000 km squared and are several kilometers deep. As continental ice caps are very large, if one were to melt it would cause the earth’s oceans to rise about 6ft, depending how big the continental ice cap is.

The only thing exposed in a continental ice cap would be a nunatak. A nunatak is an exposed, often rocky element ridge, mountain or a peak that is not covered with snow. Nunataks are only found in continental ice caps or ice sheet.