Glaciation Flashcards
Describe the formation of the Glacier.
1) Snowflakes collect or accumulate in a hollow in the mountainside usually north facing.
2) With more snowfall events, the weight compresses the snow further, into solid ice of much greater density.
3) If the ice does not melt and snow continues to fall the ice mass will become bigger and heavier.
4) As the glacier moves it erodes (wears away) the landscape on either side and underneath it altering the landscape
Describe Plucking
plucking (1 mark) when ice freezes on to
bedrock, pulling loose rocks away from the
backwall (1 mark)
Describe Abrasion
abrasion (1 mark) when the angular rock
embedded in the ice grinds the hollow (1
mark)
Describe Freeze-Thaw Weathering
Freeze-Thaw Weathering occurs in Upland areas when the temperature regularly rises and forms below 0 degrees .when water collects in the cracks in rocks.Water collects in cracks and overnight freezes and expands, this puts pressure and stress on the rocks. During the day when the temperature rises again the ice thaws and contracts relieving the pressure on the rock. This happens repeatedly until eventually the rock crumbles and breaks off
Describe the formation of a corrie.
Snow accumulates in north-facing hollows at high altitudes as these areas are normally colder.
North-facing slopes are more shaded so snow lies longer with accumulated snow compressed into neve and eventually ice.
Plucking when ice freezes on to bedrock, pulling loose rocks away from the back wall.
Abrasion when the angular rock embedded in the ice grinds the hollow.
Frost shattering/freeze-thaw weathering when water in cracks in the rock freezes, expands and contracts weakening the rock until fragments break off.
Glacier moves downhill due to gravity
The weight of the glacier pushes down causing
rotational sliding, which over deepens the
hollow
After the ice is melted and arm chair shaped hollow is left in the mountainside this is called a Corrie
A lip is formed when less pressure is exerted by the glacier or there has been a temporary loss of energy as the glazier has had to deposit material.
an example is Brown Cove.
Describe the formation of an Arete
Describe the formation of a Corrie
Then ADD…
After the ice melts, two armchair shaped hollows, or
corries are left in the mountainside; the knife-edged
the ridge in between these is an arête.
The ridge is further sharpened by freeze-thaw with scree developing on the lower slopes
Example Striding Edge in the Lake District.
Describe the formation of a Pyramidal Peak
Describe the formation of a Corrie
Then ADD…
After the ice melts three or more corrie are left in the mountainside the highest point in the center of the corries is called a pyramidal peak.
Example the Matterhorn in Switzerland
Describe the formation of a U-Shaped Valley.
Before glaciation, a river runs through a v-shaped valley.
Freeze-thaw weathering weakens the rock at the sides
and base of the valley.
This is when water in cracks in the rock freezes expands and contracts to weaken the rock until fragments break off
During Glaciation, a glacier moves through the V-shaped valley. As it does so it pulls huge amounts
of rocks away from the sides and base of the valley, steepening it (known as plucking ).
Abrasion occurs when the angular rock embedded in the ice grinds the hollow, smoothing them like
sandpaper. This deepens the base of the valley.
After glaciation, a huge valley is left with very steep sidewalls and a very wide, valley floor.
The interlocking spurs that once alternated across the
the valley has been ‘cut off’ and are now called TRUNCATED SPURS
The river will return but it no longer ‘fits’ the wide valley and so is known as “ misfit stream ”.
Example Glen Van
Describe the formation of a Hanging Valley.
Describe the formation of a U-shaped valley
Then ADD…
Hanging valleys form from tributary rivers that flow into the main river below. During glaciation, these tributary valleys are filled with small glaciers. These glaciers do not have the same power as the valley glacier and so do less vertical erosion.
After glaciation, the tributary valleys have been cut off by the main valley glacier and so are left “hanging” above the main valley. When the rivers return, the hanging valley is usually marked with a waterfall.
Describe the formation of a Ribbon Lake.
Ribbon lakes can form where a terminal or recessional moraine creates a dam.
When a glacier moves along its valley, changes in the rate of flow caused by extension or compression may lead to increased deepening of sections of the valley floor. Areas of softer rock may also experience increased deepening. When the glacier retreats, the deepened sections fill with meltwater and become lakes. These lakes remain long after glaciation has ended, supplied by rainfall and subsequent streams and rivers.
Example is Lake Windermere
