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The Upper Course of a River

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BIG PICTURE: How do waterfalls and gorges form?

• WHAT: Identify and locate features from the upper course of a river on an OS map.

• HOW: By explaining the processes involved in the formation of waterfalls and gorges.

• WHY: So I can create a model to represent the formation of key geological features in the upper course.

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Processes of river erosion

Hydraulic action

Abrasion

Attrition

Corrosion

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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.

Hydraulic Action

This process involves the force of water against the bed and banks.

Corrosion

This is the chemical action of river water. The acids in the water slowly dissolve the bed and the banks.

Attrition

Material (the load) carried by the river bump into each other and so are smoothed and broken down into smaller particles.

Processes of river erosion

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river disappears from view hidden by this spur of land

Upper Valley - River Conwy (near Mignant Moor)

Landforms in the upper course

V-shaped valleys and interlocking spursRapidsWaterfalls

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Connect: Identify v-shaped valleys and spurs of land from this OS map

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Rapids

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Rapids on the Rhone

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Waterfalls!

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Waterfall formation

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The waterfall retreats back forming a gorge (steep sided valley)

Overhang becomes unsupported and falls into the plunge pool

http://www.curriculumbits.com/prodimages/details/geography/waterfalls.html

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Can you add the correct labels correct labels to show the key features of a waterfall?

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An example of a waterfall – Gulfoss, Iceland

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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

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plunge pool

grey basalt

grey basalt

conglomerate

tillite

sandstonemudstone

Which of these different rocks do you think is the most resistant?

Demonstrate: The geology of Gulfoss (Iceland) is a little more complex! Can you explain how the Geology of the land contributes to the formation of water falls?

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Reflect: Think about what you have learnt about the resistance of different rock types today…Can you name this feature and explain how it is formed?