H Geography - Physical Unit - Lithosphere - Glaciated Upland Features

How many erosional glaciated uplands features are there?

There are 6 erosional glaciated uplands features

What are the 6 erosional glaciated uplands features

The 6 erosional glaciated uplands features are;

• Corrie

• Arête

• Pyramidal peak

• U-shaped valley

• Hanging valley

• Ribbon lake

Formation of a corrie

• A corrie is an armchair shaped hollow on the North facing side of a mountain

• The glacier moves downhill due to gravity

• A bergschrund crevasse opens up at the back of the hollow, this allows meltwater and rock fragments to get to the base of the glacier, increasing erosive power.

• Rotational sliding overdeepens the central part of the hollow.

• Friction causes ice to slow at the front edge, allowing a rock lip to form which traps rainwater.

• Once the glacier has melted, this hollow can fill with water to form a lochan or a tarn

• An example of a corrie is the Coire an Lochan Uaine in the Cairngorms

• + Formation of glacier and glacial processes

Arête formation

• An arête is a sharp ridge between two corries

• The glacier moves downhill due to gravity

• Rotational sliding over deepens the hollow

• An arête is formed when two corries erode back towards eachother.

• Freeze thaw weathering can make the ridge more pronounced, and can cause scree slopes to develop.

• An example of arête is Stridling Edge in the Lake District

• + Formation of glacier and glacial processes

Pyramidal peak formation

• A pyramidal peak is a sharp peak where three or more corries have eroded back to back

• Over time, rotational sliding deepens the central part of the corrie.

• Further freeze-thaw weathering will make the peak more pointed, scree slopes may also form.

• An example of a pyramidal peak is Helvellyn in the Lake District

• + Formation of glacier and glacial processes

U-shaped valley formation

• A U-shaped valley is a valley with steep sides and a flat and wide floor.

• They form following the existing V-shaped river valleys.

• Former interlocking spurs may be cut off by the glacier, this leaves crags and exposed rock faces at the side of the valley. This results in steep crags and truncated spurs.

• Over time, the valley becomes straightened, widened, and deepened.

• After glaciation the previous river may return, this is known as a misfit stream.

• An example of a U-shaped valley is Great Langdale Valley in the Lake District

• + Formation of glacier and glacial processes

Hanging valley formation

• A hanging valley is a smaller valley that hangs on the side of a main U-shaped valley

• Smaller tributary glaciers are less powerful glaciers which do not erode as deeply. This often leads to a waterfall forming

• Interlocking spurs are truncated by the power of the glacier. This leaves crags or exposed rock faces at the sides of the valley.

• An example of a hanging valley is Little Langdale in the Lake District

• + Formation of glacier and glacial processes

Ribbon lake formation

• A ribbon lake is a large narrow lake that occupies a U-shaped valley

• The glacier moves downhill due to gravity

• Former interlocking spurs may be cut off by the glacier, resulting in steep crags or truncated spurs.

• Ribbon lakes form where softer bedrock is eroded more deeply than the surrounding area

• Ribbon lakes can form where terminal or recessional moraine creates a dam.

• An example of a ribbon lake is Lake Windermere in the Lake District.

• + Formation of glacier and glacial processes

How many depositional glaciated uplands features are there?

There are 3 depositional glaciated uplands features

What are the 3 depositional glaciated uplands features

The 3 depositional glaciated uplands features are;

• Terminal moraine

• Drumlin

• Esker

Formation of terminal moraine

• Moraine is the material transported and deposited by the glacier as it moves downslope.

• Terminal moraine is a ridge across a valley and is made up of till, which is usually rocks of different shapes and sizes, this is unsorted

• As the glacier moves downhill it acts like a bulldozer, pushing sediment in front of the snout as it goes

• On reaching lower altitudes or when temperature rises, the glacier melts and loses power, depositing moraine at its snout

• Terminal moraine marks the furthest point that the glacier reaches. Once the ice has retreated, the terminal moraine can often form a natural dam, creating a ribbon lake.

• + Formation of glacier and glacial processes

Formation of a drumlin

• Drumlins are elongated hills of glacial deposits, formed when the glacier is still moving.

• Drumlins are made up of unsorted material and consist of glacial till.

• Drumlins are formed as the glacier becomes overloaded with sediment and deposits it, streamlining the sediment as it flows over it.

• If there is a small obstacle on the ground, it may act as a trigger point and till can build up around it.

• Drumlins may be reshaped by further ice movements after being originally deposited.

• On reaching lower altitudes or when temperature rises, the glacier melts

• The steep stoss slope faces up valley and the more gently sloping lee slope faces down valley. This shows direction of travel

• Drumlins are found in swarms or in a basket of eggs topography

• An example of a swarm of drumlins are Glasgow’s Drumlins

• + Formation of glacier

Formation of an esker

• Eskers are meandering ridges along a valley floor formed by meltwater streams in or underneath a glacier

• They are made up of meltwater sands and gravels. These are sorted by size because heavier stones are dropped first by flowing water

• The stones also tend to be more rounded than glacial deposits, because of the action of flowing water rounding the edges by erosion

• On reaching lower altitudes or when temperatures rise, the glacier begins to melt, and sub-glacial streams deposit in the tunnels.

• + Formation of glacier and glacial processes

Formation of a glacier

• Snow accumulates in north facing hollows when more snow falls in winter than melts in the summer

• North facing slopes are more shaded, so snow lies longer with accumulated snow compressed into névé

What is plucking?

Plucking is when ice freezes on to bedrock, pulling loose rocks away from the sides

What is abrasion in glaciation?

Abrasion in glaciation, is when the angular rock embedded in the ice grinds the valley floor

What is freeze-thaw?

Freeze-thaw is when water in cracks in the rock freezes, expands, and contracts. This weakens the rock until fragments break off