Physical Geography - glaciation Flashcards
What are some features of glaciation?
Corries, truncated spurs, arete, pyramidal peak, hanging valley, u-shaped valley, misfit stream, ribbon lake
What is a pyramidal peak and how is it formed?
Pyramidal peaks or horns have a sharp summit and steep slopes on at least three sides. A pyramidal peak may form where three or more corries erode back so far that they produce aretes with a pyramidal peak in between.
What is an arete and how is it formed?
An arête is a narrow knife-edged ridge where two corries have eroded back to back. That is, when the back walls of a corrie have been eroded back so far that only a narrow ridge separates them.
What is a ribbon lake and how is it formed?
A ribbon lake is a large, narrow lake occupying a u-shaped valley. It forms in a hollow when a glacier has more deeply eroded less resistant rock or it may fill up a valley behind a wall of moraine across the valley.
What are truncated spurs and how is it formed?
Truncated spurs are rounded areas of land which have been cut off. They are often rounded at the top but steep at the bottom. They are formed when glaciers move through the main valley and cut off spurs.
What is a misfit stream and how is it formed?
Misfit rivers meander through the flat, wide U-shaped floor. They did not erode the valley, as they formed in the valley after glaciation had carved out the U-shaped valley.
What is a hanging valley and how is it formed?
A hanging valley is a smaller side valley left ‘hanging’ above the main u-shaped valley. A waterfall can often be seen. During glaciation the smaller side valley contains less ice than the main glacial valley, which is why it is not as deeply eroded.
What is a u-shaped valley and how is it formed?
U-shaped valleys have steep sides and a wide, flat floor. They are usually straight and deep. U-shaped valleys are formed in river valleys which, during the ice age, have been filled by a large glacier. These glaciers have deepened, straightened and widened the valley by plucking and abrasion.
What is a corrie and how is it formed?
A corrie is an armchair shaped hollow, high on a mountain with steep back and side walls. After glaciation, the hollow may be filled by a small lake or tarn. Snow gathers in mountain hollows, especially north facing hollows, where there is more shade. This snow builds up and compacts to ice (neve). The action of gravity means the ice moves down the hill. As it goes, it sticks to back walls and plucks rock from the surface. Rocks on the backwalls are loosened by freeze-thaw action. A gap between the wall and the ice develops, called a bergschrund. Ice moving with loose rock acts like sandpaper and deepens the hollow by abrasion. Most erosion is where the weight of the ice is the heaviest. Stones frozen in the base of the ice grind or abrade the corrie base, deepening it. Ice in a corrie has a rotational movement which means that the front of the corrie is less eroded, and a lip forms. The glacier retreats and melts, often leaving a Tarn/glacial lake in the base of the corrie.
What are some land uses in glaciated upland areas?
Farming, forestry, industry, ,military, recreation and leisure, tourism, water storage and supply.
What is plucking?
Plucking occurs when rocks and stones become frozen to the base or sides of the glacier and are plucked from the ground or rock face as the glacier moves. It leaves behind a jagged landscape.
What is abrasion?
Abrasion occurs when rocks and stones become embedded in the base and sides of the glacier. These are then rubbed against the bedrock (at the bottom of the glacier) and rock faces (at the sides of the glacier) as the glacier moves. This causes the wearing away of the landscape as the glacier behaves like sandpaper. It leaves behind smooth polished surfaces which may have scratches in them called striations. Striations are carved out by angular debris embedded in the base of the glacier.
What is freeze-thaw weathering?
The process is sometimes assisted by water. There are two main types of physical weathering: Freeze-thaw occurs when water continually seeps into cracks, freezes and expands, eventually breaking the rock apart.
What are some examples of glaciated uplands?
Cairngorms
Sowdonia
Lake District / Cumrian mountinsh
