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CfE H Geography: Lithosphere - Glaciation Revision
Transcript of CfE H Geography: Lithosphere - Glaciation Revision
During Glaciation certain parts of
the U-shaped valley floor were over eroded.
After Glaciation these areas will fill up
with water to create a long-narrow 'ribbon-lake'.
Just like rivers, glaciers have tributaries. As the main glacier erodes deeper into the valley, the tributary is left higher up the steep sides of the glacier. U-shaped valleys ending with a water fall at the cliff-face are called hanging valleys.
Before Glaciation gentle sloping
hill sides sloped down to the river.
These were called 'interlocking spurs'.
During Glaciation the glacier bulldozed through the interlocking spurs. Chopping them off to create steep sided 'truncated spurs'.
Remember you should use this revision Prezi alongside your class notes and can-do checklist to focus your revision. This isn't designed as a one-stop revision tool.
HIGHER GROUND = LOWER TEMPERATURES
Glaciated landscapes are found in upland areas. This means that they are much higher above sea-level. Remember that temperature drops by around 1C for every 100m in height - this helps the process of FROST SHATTERING to take place.
Formation of a Corrie
Snowfall builds up in a north-facing hollow in a mountainside. Over time, 30-40 years, it compacts to form firn and eventually glacial ice. The backwall is steepened through FREEZE-THAW and PLUCKING. This plucked moraine from backwall deepens the corrie through the process of ABRASION. After glaciation, the ice melts and can leave a Corrie-Loch or Tarn. The rock-lip acts as a natural dam. FREEZE-THAW continues on the steep backwall causing lots of weathered rock to create a 'scree-slope'.
Formation of Arêtes and Pyramidal Peaks
When two adjacent corries erode backwards or sideways towards each other, the land between them becomes narrower, until a rocky, knife-edged ridge called an arête is formed. The ridge is sharpened by frost shattering.
If three or more corries develop on the sides of a mountain, a pyramidal peak or horn may be developed. This has steep sides and several arêtes radiating from the central peak.
Formation of U-Shaped Valleys / Glacial Troughs
Rivers in Mountains carved out V-shaped valleys. A glacier flowed down the old V-shaped river valley. The ice eroded the sides and floor of the valley through PLUCKING and ABRASION. This deepened and widened the valley into U-shape. The U-shape Valley formed has a wide, flat valley floor with very steep sides. As the ice has all melted rivers begin to flow through these valleys. The rivers are too small for the size of the valley and are called 'misfit streams'
Formation of a Hanging Valley
When the valleys are occupied by ice, less ice is found in the tributary valley. Less ice results in less erosion. After glaciation, the tributary valley is left hanging above the floor of the main valley. This is known as a hanging valley. The valley often contains a river which results in a waterfall into the main valley.
Formation of Drumlins
Drumlins are large, smooth, elongated mounds of glacial till. They were thought to have been formed when the glacier became overloaded with material and had to deposit some. They were later streamlined by further ice movement. They are almost symmetrical across their long axis, which is parallel to the direction from which the ice came. The highest point is nearest to the stoss side, which faces the direction from which the ice came. Drumlins usually occur in swarms.
Formation of Eskers
Long, narrow, sinuous ridges of sorted sands and gravels. They were deposited by subglacial streams during ice retreat. These tend to be well sorted as the largest pieces of material are deposited first as the stream loses its energy. As it continues to lose energy smaller and smaller material is then deposited.
Formation of Kames and Kame Terraces
Kames are undulating mounds of sand and gravel deposited unevenly by meltwater like a series of deltas along the front of a stationary or slowly melting ice sheet. Kame Terraces are ridges of sand and gravel found along the sides of valleys. They are deposited by the meltwater streams flowing between the glacier and the valley wall (these are sorted whereas lateral moraines are not).
ARETES / PYRAMIDAL PEAKS
Remember to quote Case Study examples!
ARETE: STRIDING EDGE
PYRAMIDAL PEAK: HELVELLYN
Remember to look for the words 'cirque', 'cwm', 'tarn', 'lochan'
FEATURES PRODUCED BY EROSION
FEATURES PRODUCED BY DEPOSITION
GLACIAL FEATURES ON A MAP
Questions in the exam will most likely be in the following format:
EXPLAIN the CONDITIONS AND PROCESSES involved in the formation of [one of the features]
You must mention conditions and if possible all 3 processes.
FREEZE-THAW / FROST SHATTERING
Water in cracks in the rock freezes and expands by 9%, forcing the crack to widen. When the ice melts (thaws) more water can get into the crack and freeze again. The process repeats making the crack bigger and the pieces off rock are eventually broken off.
Glacial ice freezes into the cracks and crevices made by the freeze-thaw process and as the glacier moves, loose pieces of rock are pulled or torn out.
Abrasion occurs when pieces of rock debris that are embedded in the ice rub away at the rocks on the valley floor and sides like 'sandpaper'.
HIGHER GROUND = MORE RELIEF RAINFALL
Glaciated landscapes are found in upland areas with mountainous terrain. This means that they will be subject to high levels of precipitation (RAIN/SNOWFALL) which allows snow to build up and increased precipitation levels can also aid FROST SHATTERING.
Areas that have well-jointed rocks are more easily attacked by the process of FROST SHATTERING.
You can also use your 'can do' checklist before your revision to check which areas you should focus your revision on or after you completed revision to check your learning.
STRIDING EDGE & HELVELLYN,