GEOGRAPHY GCSE REVISION

So using the whiteboard on your table can you…. List as many glacial landforms as you can List the 2 main types of erosion So using the whiteboard on your table can you…. Say whether they are erosional or depositional? List the 3 main types of transportation

Place your screenshot here Glacial Landscapes Where would we find glacial landforms? What conditions do the processes need? How are erosional and depositions landforms different?

What feature am I? Look at the features that appear. Can you easily name them? Do you know how they were formed? ?

LANDFORM ESSENTIALS YOU MUST… Know the sequence or order in which something happens. SO think about what you did when you got up this morning – got out of bed, went to toilet, shower etc. That is what got you here….but what about a river landform? We need all the detail about how that was made! YOU MUST… Understand and be able to talk about the processes of erosion, weathering, transportation and deposition that cause the feature to form in this way. And it is with these processes that we are going to start!

River Processes Deposit Transport Erode ***Freeze-Thaw weathering helps break the rock down also and provides materials for erosion.

Erosion Abrasion Plucking This is a sandpaper effect caused by the huge weight of the glacier scouring the valley floor. This process leaves a very smooth, polished surface. Sometimes scratches or lines called striations can be seen on the bedrock. These are caused by smaller rock stuck in the ice scraping along. Plucking When meltwater beneath a glacier freezes and bonds the base of a glacier to the surface, it acts a bit like glue. When the glacier tries to move it rips or plucks out any loose rocks – a bit like extracting teeth. This leaves behind a jagged surface. These plucked rocks can then be used in abrasion.

Freeze-Thaw Weathering Temperature falls over night and freezes water causing volume to expand by 9% Over time, the rock will break off to form sharp jagged material called scree. 3 conditions are needed: Crack in rock Water Fluctuating temperature above and below 0°C Water enters crack in rock This puts pressure on the rock Repeated freezing and thawing occurs as the temperature fluctuates above and below 0°C

Transportation Basal Slip This is when, in the summer, meltwater lubricates the glacier, enabling it to slide downhill. Rotational Slip In hollows, high up on the valley sides, the basal slip is different. It is more curved. Internal Deformation In winter the glacier becomes stuck to the rock. When this happens the sheer weight of the ice and gravity cause individual ice crystals to change shape in a plastic-like way. Bulldozing As the glacier moves forward, it pushes any material in its path ahead and downhill. Moraine Rock fragments from plucking, abrasion and freeze-thaw are called moraine.

Deposition Boulder Clay/Till Outwash As a glacier slowly retreats it leaves behind a bed or broken rock fragments called till. As there is no water to transport and order the rock, it is unsorted, with jagged rock of all sizes. Till is also called boulder clay. Outwash In front of the glacier, meltwater will carry sediment away. Attrition in the outwash, makes the rocks smaller and more rounded. It is also sorted more meaning larger material close to the snout and finer material further away.

Erosional Landforms The erosional landforms you need to know are: Corries Aretes Pyramidal Peaks U-shaped valleys/Glacial Troughs Truncated Spurs Hanging Valleys Ribbon Lakes You need to: Recognise them Know the processes that act on them Explain how they are formed (using diagrams if necessary)

Corries This is a large bowl/armchair shaped depression on the upper slopes of glaciated valleys. Snow accumulates in a hollow on a hillside. The snow compacts to form firn/neve and then eventually ice. Through rotational slip, the glacier abrades and over deepens the hollow (like an ice cream scoop). Plucking and freeze-thaw take place at the back wall making it jagged and steep and adding more material in for abrasion to take place. The ice at the front is thinner and less erosive and loses power as it moves of the raised lip. Sometimes moraine may be deposited here. A tarn or corrie lake may form in the bottom of the corrie.

Aretes An arete is a knife-edge ridge often found at the back of a corrie or separating 2 glaciated valleys. They are very narrow and popular with walkers. As 2 corries erode back-to-back, the land in between becomes narrower and narrower.

Pyramidal Peaks If 3 or more corries erode back-to-back a pyramidal peak is formed. The aretes separate the corries and form the basis for the pyramidal peak which is a single peak and very distinctive.

U-Shaped Valleys Most glaciers flow along existing river valleys (V-shaped). Unable to flow around obstacles, glaciers are very powerful and carve a straight course. Freeze-thaw weathering occurs at the sides of the valley providing material in the form of scree to the glacier sides. The process of abrasion occurs on the glacier bottom and side as it scrapes along in a sandpaper actions. Plucking will also occur on the glacier bottom providing further material for abrasion. These processes create a distinct flat valley bottom and steep sides, or ‘U’ shaped valley. Within this valley may other glacial features are found.

Hanging Valleys A smaller tributary (secondary) glacier joins the main valley glacier. This tributary glacier is smaller and therefore has less erosive power. As a result, it is not able to erode down to the same level as the the main glacier. When the ice finally melts, a glacier valley is left perched on the main valley side often with a spectacular waterfall.

Truncated Spurs The river flows around existing interlocking spurs. The glacier is unable to flow around these spurs due to its lack of flexibility. Instead it cuts straight through them, eroding them and forming steep-edged truncated spurs.

Ribbon Lakes There are two main reasons why a ribbon lake may have formed. Either a band of softer rock across the valley floor has become over deepened as it is eroded more deeply…or… Tributary glaciers have joined the main glacier giving it more erosive power and causing it to over deepen. As a result a long depression along the valley floor it created which becomes visible when the glacier melts. Often a band of moraine may form a dam allowing water to build up in the depression behind.

Depositional Landforms The erosional landforms you need to know are: Moraine – Terminal/Medial/Lateral/Ground Drumlins Erratics You need to: Recognise them Know the processes that act on them Explain how they are formed (using diagrams if necessary)

Lateral Moraine Glaciers behave like giant conveyor belts carrying weathered and eroded rocks from the mountains to the lowlands. These rocks can be carried on top of the ice, within the ice or beneath the ice (where the carry out abrasion). The term moraine is applied to these angular and poorly sorted deposits. Lateral moraine forms at the sides of the glacier. It is mostly scree material that has fallen off the valley sides due to freeze-thaw weathering. When the ice melts, the moraine forms a low ridge on the valley side.

Medial Moraine A tributary glacier joins the main glacier. Both a producing lateral moraine at the sides of the glaciers. 2 lateral moraines will merge to produce a single line of sediment that runs down the centre of the main glacier. On melting, the medial moraine forms a ridge down the centre of the valley.

Ground Moraine Quite simply this is the material dragged underneath the glacier and left behind when the ice melts. It often forms uneven hilly ground. The ice melts and retreats up the valley leaving a moraine strewn across the valley.

Terminal Moraine Huge amounts of material pile up at the snout of a glacier. The glacier acts like a huge bulldozer pushing the moraine. This forms a high ridge often tens of metres in height across the valley. This is the furthest point the glacier has reached hence the name terminal. The ice melts and retreats up the valley leaving a moraine stretching across the valley.

Drumlins Drumlins are smooth egg shaped hills about 10m high and several hundred metres long. They are found in clusters or ‘swarms’ on the floor of a U-shaped valley. They are sometimes referred to as a basket of eggs topography. They are made of moraine. This moraine has been streamlined and shaped by the moving ice. Drumlins usually have a blunt end facing up valley. This tells us the direction the glacier was travelling.

Erratics An erratic is a huge boulder that is out of place, resting on a different type of rock. Scientists use erratics to trace the history of glaciation in the UK. By studying a geology of an area, it is possible to work out where the erratics came from and what route they followed as they were carried by glaciers. Most large erratics were probably transported on or in glaciers.

So using the whiteboard on your table can you…. List as many glacial landforms as you can List the 2 main types of erosion So using the whiteboard on your table can you…. Say whether they are erosional or depositional? List the 3 main types of transportation