LITHOSPHERE GLACIATION 1 Introduction Higher Geography

LITHOSPHERE GLACIATION 2  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.  As more snow falls the pressure makes the earlier snowflakes melt. INTRO

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

LITHOSPHERE GLACIATION 4 Water from melted snow collects in cracks and crevices in rocks above glaciers. PROCESS 1 Freeze-thaw/ frost shattering EROSION  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 At night temperatures drop below freezing and the water changes into ice as it expands by 9%.

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

LITHOSPHERE GLACIATION 6 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. PROCESS 3-Abrasion EROSION

LITHOSPHERE GLACIATION 7 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. EROSION

LITHOSPHERE GLACIATION 8 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. CORRIES Features of erosion

LITHOSPHERE GLACIATION 9 Features of erosion

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

LITHOSPHERE GLACIATION 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.

LITHOSPHERE GLACIATION 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.

LITHOSPHERE GLACIATION 13 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. lip Back wall scree Features of erosion

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

LITHOSPHERE GLACIATION 15 Red Tarn Features of erosion

LITHOSPHERE GLACIATION 16 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. ARETE Features of erosion

LITHOSPHERE GLACIATION 17 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. scree bare rock horn = arete Features of erosion

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

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

LITHOSPHERE GLACIATION 20 Corrie formation

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

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

LITHOSPHERE GLACIATION 23

LITHOSPHERE GLACIATION 24 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. Features of erosion

LITHOSPHERE GLACIATION 25 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. Truncated spurs Features of erosion

LITHOSPHERE GLACIATION 26 A U-shaped valley in Canada. Features of erosion

LITHOSPHERE GLACIATION 27 The sea lochs of western Scotland are the best examples of fiords in the British Isles. When a glaciated valley is submerged or drowned by a rise in sea level, a fiord is formed. Fiord/fjord Features of erosion

LITHOSPHERE GLACIATION 28 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 A hanging valley Can you spot the river delta,too? Features of erosion

LITHOSPHERE GLACIATION 29 The English Lake District owes its character to these narrow ribbon lakes along its valley floors. When the glacier retreats, the deepest parts fill with water and become lakes. When a glacier moves along the valley, some parts are deepened more than others due to softer rock. Ribbon lakes Features of erosion

LITHOSPHERE GLACIATION 30 alluvium = silt deposited by a river An alluvial fan 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. (This is really a depositional feature.) Erosion/ deposition

LITHOSPHERE GLACIATION 31 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. Edinburgh Castle A crag and tail Plug of volcanic rock crag tail Erosion/ deposition

LITHOSPHERE GLACIATION 32 TYPES OF MORAINE deposition Lateral moraine is found on the sides of the glacier. Scree, from frost shattering, is an important source. Medial moraine is found down the middle of the glacial surface and occurs when the inner lateral moraines of two glaciers join. 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. Supra-glacial Terminal moraine is found in front of the snout of the glacier if it is stationary. It represents the maximum advance of the ice.

LITHOSPHERE GLACIATION 33 deposition

LITHOSPHERE GLACIATION 34 Terminal moraineSnout of glacier deposition

LITHOSPHERE GLACIATION 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.

LITHOSPHERE GLACIATION 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. After the ice has melted

LITHOSPHERE GLACIATION 37 Erratics are large rocks that are completely different from the type of rocks on which they rest They were carried by the ice-sheet, sometimes for hundreds of kilometres and then deposited. ERRATICS deposition

LITHOSPHERE GLACIATION 38 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. ESKER This river has dried up! deposition

LITHOSPHERE GLACIATION 39 An esker is a steep-sided, long, winding ridge, made up of gravel and sand. Most are tree-covered. deposition

LITHOSPHERE GLACIATION 40 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. DRUMLIN deposition Side view Plan view

Exam style questions

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

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

LITHOSPHERE GLACIATION 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.