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© Boardworks Ltd 2005 1 of 26 These icons indicate that teacher’s notes or useful web addresses are available in the Notes Page. This icon indicates the.

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Presentation on theme: "© Boardworks Ltd 2005 1 of 26 These icons indicate that teacher’s notes or useful web addresses are available in the Notes Page. This icon indicates the."— Presentation transcript:

1 © Boardworks Ltd of 26 These icons indicate that teacher’s notes or useful web addresses are available in the Notes Page. This icon indicates the slide contains activities created in Flash. These activities are not editable. For more detailed instructions, see the Getting Started presentation. 1 of 26 The Upper Course of a River © Boardworks Ltd 2005

2 2 of 26 What are the main processes that operate in the upper course? What landforms occur in the upper course of a river? How are the landforms created? Learning objectives

3 © Boardworks Ltd of 26 Processes of river erosion Study this photo. How do you think this river can erode the landscape? Erosion is the wearing away of the land.

4 © Boardworks Ltd of 26 Processes of river erosion Hydraulic action Attrition Corrosion Abrasion

5 © Boardworks Ltd of 26 Definitions Hydraulic Action This process involves the force of water against the bed and banks. Abrasion/Corrasion This is the process by which the bed and banks are worn down by the river’s load. The river throws these particles against the bed and banks, sometimes at high velocity. Attrition Material (the load) carried by the river bump into each other and so are smoothed and broken down into smaller particles. Corrosion This is the chemical action of river water. The acids in the water slowly dissolve the bed and the banks.

6 © Boardworks Ltd of 26 Do you know your processes of erosion?

7 © Boardworks Ltd of 26 What are the main processes that operate in the upper course? What landforms occur in the upper course of a river? How are the landforms created? Learning objectives

8 © Boardworks Ltd of 26 river disappears from view hidden by this spur of land River Conwy (near Mignant Moor) Landforms in the upper course V-shaped valleys and interlocking spurs Rapids Waterfalls

9 © Boardworks Ltd of 26 What are the main processes that operate in the upper course? What landforms occur in the upper course of a river? How are the landforms created? Learning objectives

10 © Boardworks Ltd of 26 Why do V-shaped valleys occur?

11 © Boardworks Ltd of 26 Interlocking spurs In the upper course the river does not have a huge amount of energy to erode as it does not have a high discharge and it has to transport large pieces of sediment. When the river meets areas of harder rock that are difficult to erode it winds around them. A series of hills form on either side of the river called spurs. As the river flows around these hills they become interlocked. So, a series of interlocking spurs are often found in the upper course of a river valley.

12 © Boardworks Ltd of 26 Techniques! – 1. Fieldsketching…. Produce an annotated fieldsketch to show that this is part of an upland river valley.

13 © Boardworks Ltd of OS Maps Identify v-shaped valleys and spurs of land.

14 © Boardworks Ltd of 26 Waterfalls! Seljalandsfoss, SW Iceland

15 © Boardworks Ltd of 26 Waterfall formation

16 © Boardworks Ltd of 26 Waterfalls

17 © Boardworks Ltd of 26 How does a waterfall form? Rearrange the stages of formation into the correct order:

18 © Boardworks Ltd of 26 Draw and annotate a diagram to explain the formation of a waterfall. Suggested labels: 1.More resistant rock 2.Less resistant rock 3.Plunge Pool 4.Unsupported rock 5.Fallen rocks 6.Gorge Your labels should contain detailed explanations! Waterfalls

19 © Boardworks Ltd of 26 An example of a waterfall – Gulfoss, Iceland

20 © Boardworks Ltd of 26 Gulfoss is located in Southwest Iceland on the Huita River. Gulfoss has two ‘steps’ to its waterfall. These steps are made by basalt lava while the rocks between these layers are softer, sedimentary rocks. Its gorge is 70m deep and 3 km long! Gulfoss

21 © Boardworks Ltd of 26 plunge pool grey basalt conglomerate tillite sandstone mudstone Which of these different rocks do you think is the most resistant? The geology of Gulfoss is more complex!

22 © Boardworks Ltd of 26 What are rapids and how do they form? Rapids are formed due to a sudden steepening of the stream gradient, but without a sufficient break in slope to form a waterfall, or from the river flowing over a series of thin layers of hard and soft rock. Rapids are part of a river where the water is relatively shallow but the flow of the water is quite fast and turbulent as the water descends over a series of small steps. River Rhône

23 © Boardworks Ltd of 26 Rapids

24 © Boardworks Ltd of 26 Examination question X Y Study the map of a river valley below: Sketch a cross-section of the river valley from X to Y. Label two features of this river valley. State at what stage of a river’s course you would expect to find this type of valley. Give reasons for your answer. Height (m) XY

25 © Boardworks Ltd of 26 What do you know about upland river valleys?

26 © Boardworks Ltd of 26 Key ideas Erosion is the main process operating in the upper course of a river. The direction of erosion is vertical. There are four main types of erosion – hydraulic action, attrition, abrasion and corrosion. Valleys are v-shaped with interlocking spurs. Waterfalls are formed where a river meets a band of less resistant rock. Plunge pools and gorges are features associated with the formation of waterfalls. Rapids are smaller scale features formed where finer bands of varying resistance of rock are found.


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