1. Cold Environments Processes in a glacial environment

2. Learning objectives By the end of the lesson you will be able to: 1.Identify different types of glaciers and how Britain's landscape is effected by them. 2.Explain how glaciers erode through the processes of plucking and abrasion. 3.Determine the factors that will effect the rate of glacial erosion. Key words – Rouche Mountonee, Striations, Chatter marks, Divergent Flow

3. Types of glacier Which type of glacier is the largest? How was/is Britain effected by past glacial phases? Which glacier will have the most erosive power?

4. Glaciation Currently, 10% of the continental surface is covered permanently by snow and ice. Twenty thousand years ago almost one-third of the land surface was covered in snow and ice, including most of northern Europe and Canada. Like rivers, glaciers carry out erosion, transportation and deposition and create a number of different landforms.

5. The power of the glacier… Glaciers have the ability to erode huge sections of land. The evidence of which is still present today. Glacial Trough – Lake District

6. The power of the glacier… A glacier’s load comes from material falling onto the glacier as a result of mass movement and weathering. The load then helps the glacier to erode the land. Glaciers erode because they are mobile and they contain material at their base and sides. Little erosion occurs in polar glaciers because they are too static – fast, moving warm glaciers have high rates of erosion.

7. 1. Plucking (Quarrying) The ripping out of material from the bedrock. The more fractured and broken the bedrock, i.e. the more freeze- thaw there has been, the more effective plucking becomes. Think about blue tack on painted walls. Mainly at the base of the glacier but also at the sides. Plucking involves downward pressure caused by the weight of the ice then downhill drag as the ice moves, slow enough for melt water to freeze onto obstacles. Once the material has been prised out of the bedrock, it can be used for abrasion of the landscape.

8. Plucking (Quarrying) 1.A small rock outcrop at the base of the glacier will cause frictional resistance to the ice flow. 2.The upstream side will experience high pressure, which results in some melting. 3. Melt water will run into joints in the rock, on the downstream side where pressure is lower, freezing will occur. 4. Therefore as the glacier moves forward rock will be plucked along joints in low pressure areas.

9. Plucking (Quarrying) What is it?

10. Abrasion Think of it as the sandpaper effect – the erosion of the bedrock by material carried by the glacier. This material is derived from physical weathering and mass movements in areas exposed above the ice and from erosion by glaciers themselves. The larger and more angular the load, the great potential for erosion.

11. The coarser material will scrape, scratch and groove the rock – leaving STRIATIONS and CHATTER MARKS. The finer material will smooth and polish the rock.

12. Write a brief description of Abrasion in books. Add the two pictures of striations and chatter marks and add the following definitions: Striations: Scratch marks on a rock caused by abrasion. Chatter marks: Discontinuous scratch marks on a rock cause by abrasion. Sketch the roches mountnnees diagram to explain the difference between plucking and abrasion.

13. Glacial Erosion What factors influence the rate of glacial erosion? 1.Geology – well fractured, jointed bedrocks are easily plucked. Example – Carboniferous limestone of the Burren in County Clare, Ireland. 2.Velocity of glacier – Dependent on the gradient – areas of fast flowing ice lead to increased erosion. 3.Load – the amount of load carried by the glacier – coarse, resistant and angular load will erode more than a fine, weak and rounded load. 4.Temperature of Glacier – cold based glaciers little erosion – need some meltwater. Ice Protectionst Theory – the ice protects the landscape underneath. May be true for cold based glaciers, but warm, fast moving glacier erode at a faster rate. Example – Antarctica – ice in valleys can be highly erosive but ice on a plateau is thin and slow moving therefore protects the bed from erosion.

14. Homework Research the following terms and find out what they mean and their relevance to glaciers: Congelifraction, Ice-lensing, Nivation and Solifluction.