Glacial Features

MacGillycuddy's Reeks is a sandstone and siltstone mountain range in the Iveragh Peninsula in County Kerry, Ireland. Stretching 12 miles, from the Gap of Dunloe in the east, to Glencar in the west, the Reek's is Ireland's highest mountain range. Situated near the centre of the range is Carrauntoohil, Ireland's highest mountain standing at a height of 1,038.6 metres (3,407 ft). The range was heavily glaciated which carved out deep corries, U-shaped valleys and sharp aretes and ridges.

Cirque: A Cirque is a large hollow that is found high up in a mountain. It has three steep sides and may contain a lake. It was the birthplace of a glacier. It is formed when snow collects in mountain hollows and is compressed to form ice. The ice plucks from the sides of the hollow, causing the walls to become steep . These rocks are then used as a tool to deepen the hollow by abrasion. The ice builds up until it overflows the hollow and begins to flow downhill under its own weight. When the ice melts, a lake called a tarn is trapped in the cirque.

Arete: A narrow , steep-sided ridge. When two cirques develop side-by-side or back-to-back, the ground between them is gradually eroded backwards until just an arete remains.

Pyramidal Peek: When three or more cirques form around a mountain, only a steep-sided peak, with several aretes, remains as a result of erosion.

U-shaped valley: A wide, flat floor and steep sides. When the glacier moves out of a cirque, it takes the easiest route down the mountainside. This is usually through a former river valley. The glacier uses its load to reshape the river valley by plucking and abrasion. The glacier widens, deepens and straightens the V-shaped valley, changing it to a U-shaped valley. In doing this, it cuts the heads off the interlocking spurs, leaving them as truncated spurs.

Hanging valley: A small tributary valley that hangs above the main glaciated valley. Once occupied by a small glacier that was unable to erode as deeply as the main glacier. When the ice melted, the floor of the tributary valley was left high above the floor of the main valley. If a stream leaves the hanging valley, it drops into the main valley as a waterfall.

Truncated spur: A truncated spur is a spur, which is a ridge that descends towards a valley floor or coastline from a higher elevation, that ends in an inverted-V face and was produced by the erosional truncation of the spur by the action of either streams, waves, or glaciers.

Tarn Lake: A tarn is a mountain lake, pond or pool, formed in a cirque, and excavated by a glacier. A tarn is created when either river or rainwater fills up a cirque. The depressions that have been carved out from weak rocks are then occupied by a series of rock-basin lakes.

Ribbon Lake: A ribbon lake is a long and deep, finger-shaped lake, usually found in a glacial trough. Formed when a glacier flows over the land, it flows over hard rock and softer rock. Softer rock is less resistant, so a glacier will carve a deeper trough. When the glacier has melted, water will collect in the deeper area and create a long, thin lake called a ribbon lake.