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Introduction Higher Geography

Introduction Higher Geography. INTRO. As more snow falls the pressure makes the earlier snowflakes melt. Repeated melting and re-freezing forms granules called firn or névé. Further compression forms larger crystals of glacial ice.

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Introduction Higher Geography

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  1. Introduction Higher Geography

  2. INTRO • As more snow falls the pressure makes the earlier snowflakes melt. • Repeated melting and re-freezing forms granules called firn or névé. • Further compression forms larger crystals of glacial ice. • It can take 30 to 40 years for snow to form dense glacial ice. • Gravity now moves the glacier downslope.

  3. INTRO Ice erodesin the upland areas using three main processes and creates a number of interesting features The products of erosion- moraine and other material- are transported to lower ground where they are deposited in areas in specific shapes.

  4. EROSION PROCESS 1 Freeze-thaw/ frost shattering At night temperatures drop below freezing and the water changes into ice as it expands by 9%. • Water expands when frozen and forces the crack wider. When it warms, ice melts and the wider crack can hold even more water. • After several sessions, the rock shatters. • Sharp, angular pieces of rock called scree fall to the foot of the slope. • This is a repeated process Water from melted snow collects in cracks and crevices in rocks above glaciers.

  5. EROSION PROCESS 2-Plucking • 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. Note; This rock has joints and bedding planes!

  6. EROSION PROCESS 3-Abrasion 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.

  7. EROSION Striations are scratches made on the existing surface by rocks that are embedded in the bottom of the glacier as it moves forward. The rock is scratched, polished, smoothed and eventually worn away by the scouring action.

  8. Features of erosion CORRIES Snow collects in hollows, especially on the less sunny north and east facing slopes, turns to glacial ice and moves downwards under the force of gravity Rocks are plucked out and the hollow is widened by abrasion to become a corrie. A corrie is a deep, rounded hollow with a steep back wall.

  9. Features of erosion

  10. Features of erosion Formation of a corrie Describe and explain the formation of a corrie 8 marks

  11. Before: During the ice age and especially in the winter months snow will gather on natural hollows in the landscape. This gathering of snow usually occurs in the less sunny north and east facing hills as it has less sun the glacier does not have a chance to melt. During: The weight of the glacier turns the snow into ice and once the ice reaches an uneven equilibrium it will start to move downhill by gravity. When moving the glacier erodes the landscape through plucking and abrasion (here explain plucking and abrasion). These processes deepen and widen the hollow. As the glacier moves some ice will still be stuck to the back wall making the bergschrund.

  12. After: Frost shattering still occurs once the ice age has left. (explain frost shattering). This makes the jagged summit and means scree continues to form in the Corrie Lochan. Morraine left by the glacier can hold in the water at the edge of the corrie.

  13. Features of erosion Back wall scree lip Once the glacier retreats, the corrie may be filled with water. A small, generally circular loch is formed. This is known as a tarn or corrie lochan.

  14. Features of erosion On an OS map, corries are shown as horseshoe-shaped features. scree Note the east-facing aspect; snow lasts longer before melting. N Note the contours are very close together, especially on the steep backwall. Note also the bare rock symbol. tarn

  15. Features of erosion Red Tarn

  16. Features of erosion ARETE An arete is a narrow, sharp-edged ridge which forms the side walls of corries or separates different glacial valleys. Continually eroded by frost shattering.

  17. = arete scree bare rock horn Features of erosion On a map an arete is hard to see. It is a long ridge between to corries or valleys. The red lines mark the spines of the three aretes. These corries and aretes are in the Cairngorms.

  18. Features of erosion arete Striding Edge Striding Edge arete on Helvellyn, Lake District

  19. Features of erosion MATTERHORN Pyramidal peaks are also called horns.

  20. Corrie formation

  21. Pyramidal peaks are formed when three or more corries cut backwards into the same mountain. Formation of a pyramidal peak arête The Ridge is the ARETE tarn corrie

  22. Features of erosion Stages in the formation of a U-shaped valley

  23. Features of erosion These are the actions that form this feature. a) A glacier flows into an earlier 'V' shaped valley with interlocking spurs. b) The glacier abrades and plucks the sides and floor of the river valley. c) The valley is greatly deepened, widened and straightened. d) When the ice melts the valley is 'U' shaped with truncated spurs. e) It now has very steep sides and a fairly flat floor. f) Any rivers are called 'misfit streams’ because they are far too small to have cut the valley.

  24. Features of erosion Truncated spurs Former hill spurs are ‘truncated’- their ends are cut off by the ice action to form steep, sheer cliffs. The yellow lines show where the spurs were before they were chopped off! Note how they defined a V-shaped valley.

  25. Features of erosion A U-shaped valley in Canada.

  26. Features of erosion When a glaciated valley is submerged or drowned by a rise in sea level, a fiord is formed. The sea lochs of western Scotland are the best examples of fiords in the British Isles. Fiord/fjord

  27. Features of erosion A hanging valley Vertical erosion in the main glacier is far greater than in the tributary glaciers. So the valleys are not the same depth. After the glacier has retreated, rivers flowing down the tributary join the main valley via a waterfall Can you spot the river delta,too?

  28. Features of erosion When a glacier moves along the valley, some parts are deepened more than others due to softer rock. When the glacier retreats, the deepest parts fill with water and become lakes. The English Lake District owes its character to these narrow ribbon lakes along its valley floors. Ribbon lakes

  29. Erosion/ deposition Caused when a stream falling from a side valley reaches flatter ground on the valley floor. Material is dropped at the ‘break of slope’ to form this fan shape. An alluvial fan (This is really a depositional feature.) alluvium = silt deposited by a river

  30. Erosion/ deposition A crag and tail Edinburgh Castle crag tail Plug of volcanic rock These are partly erosional, partly depositional features. The rock face facing the ice is steepened by glacial erosion. Softer rock on the other slope is protected from erosion to form a tail of boulder clay.

  31. Supra-glacial deposition TYPES OF MORAINE Lateralmoraine is found on the sides of the glacier. Scree, from frost shattering, is an important source. Ground moraine is found at the base (bottom) of the ice. It is also called till or boulder clay. Englacial moraine is found inside the ice itself. Medial moraine is found down the middle of the glacial surface and occurs when the inner lateral moraines of two glaciers join. Terminal moraine is found in front of the snout of the glacier if it is stationary. It represents the maximum advance of the ice.

  32. deposition

  33. deposition Terminal moraine Snout of glacier

  34. Before the ice melts At the front of the glacier (known as the snout) a large pile of rocks and boulders has been “bulldozed” into a large pile.

  35. After the ice has melted The glacier has now gone, and a pile of rocks and stones known as terminal moraine is left. Sometimes this mound can block streams from a melting glacier, and moraine-dammed lakes are formed.

  36. deposition Erratics are large rocks that are completely different from the type of rocks on which they rest ERRATICS They were carried by the ice-sheet, sometimes for hundreds of kilometres and then deposited.

  37. deposition ESKER Glacial streams are found under the ice.They are loaded with debris (sand and gravel) carried by the meltwater.As the ice retreats, the river deposits its load. The built-up river bed is called an Esker. This river has dried up!

  38. deposition An esker is a steep-sided, long, winding ridge, made up of gravel and sand. Most are tree-covered.

  39. deposition DRUMLIN Side view Drumlins are smooth, rounded mounds of ground moraine. The steep (stoss) side faces the direction the ice moved from. Drumlins often occur in swarms or groups on the valley floor. Plan view

  40. Exam style questions

  41. Question 1 • Corries are landscape features present in glaciated upland areas. • Explain the conditions and processesinvolved in the formation of a corrie. 8 Marks • You may use diagrams to illustrate your answer. Fully annotated diagrams can receive full marks.

  42. Question 2 • As a glacier moves downhill it can create a massive glacial trough. • Explain the conditions and processesinvolved in the formation of a glacial trough. • You may use diagrams to illustrate your answer. Fully annotated diagrams can receive full marks.

  43. Question 3 • Terminal moraine can be found at the end of the glacier. • Explain how it forms, the conditions of the land and what the land can be used for after the glacier retreats. • You may use diagrams to illustrate your answer. Fully annotated diagrams can receive full marks.

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