IB Geography Topic A.1.4 River Landforms Revision Notes (SL/HL)

IB Geography Topic A.1.4 River Landforms Revision Notes (SL/HL) | RevisionDojo

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Waterfalls Are Created by Differential Erosion

Waterfalls are created by differential erosion, which occurs when a river flows over layers of rock with varying resistance to erosion.
Here’s how it works:
1. Hard and Soft Rock Interaction
  1. A river flows over a layer of resistant hard rock (e.g., granite) underlain by softer rock (e.g., shale).
  2. The softer rock erodes more quickly due to the processes of hydraulic action(the force of water breaking rock apart) and abrasion (rock particles scouring the surface).
2. Undercutting
  1. As the soft rock erodes, the hard rock above it becomes unsupported and eventually collapses.
3. Waterfall Retreat
  1. Over time, this process causes the waterfall to retreat upstream, leaving behind a steep-sided gorge known as a gorge of recession.

Example

Niagara Falls is a classic example of a waterfall formed by differential erosion, where the harder dolomite cap rock overlays softer shale.

Hint

Remember: Waterfalls are temporary features in the landscape, as they retreat upstream due to ongoing erosion.

Floodplains Are Flatlands of Fertility

Floodplains are the wide, flat areas on either side of a river, often rich in nutrients and ideal for agriculture. But how are these fertile lands formed?
1. Overbank Flow
  1. During periods of flooding, a river overflows its banks, spreading water and sediment across the surrounding land.
2. Deposition
  1. As the floodwaters slow down, they lose energy and deposit their load.
  2. Coarser materials settle closer to the river channel, while finer particles (like silt and clay) are carried further, creating a flat, fertile plain.

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IB Geography A.1.4 River Landforms Notes

Waterfalls Are Created by Differential Erosion

Floodplains Are Flatlands of Fertility

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Waterfalls Are Created by Differential Erosion

Floodplains Are Flatlands of Fertility

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1 Changing Population3 subtopics

2 Global Climate - Vulnerability and Resilience3 subtopics

3 Global Resource Consumption and Security3 subtopics

4 Power, Places and Networks (HL only)3 subtopics

5 Human Development and Diversity (HL only)3 subtopics

6 Global Risks and Resilience (HL only)3 subtopics

Option A Freshwater - Drainage Basins4 subtopics

Option B Oceans and Coastal Margins4 subtopics

Option C Extreme Environments4 subtopics

Option D Geophysical Hazards4 subtopics

Option E Leisure, Tourism and Sport4 subtopics

Option F The Geography of Food and Health4 subtopics

Option G Urban Environments5 subtopics

IB Geography A.1.4 River Landforms Notes

1 Changing Population3 subtopics

2 Global Climate - Vulnerability and Resilience3 subtopics

3 Global Resource Consumption and Security3 subtopics

4 Power, Places and Networks (HL only)3 subtopics

5 Human Development and Diversity (HL only)3 subtopics

6 Global Risks and Resilience (HL only)3 subtopics

Option A Freshwater - Drainage Basins4 subtopics

Option B Oceans and Coastal Margins4 subtopics

Option C Extreme Environments4 subtopics

Option D Geophysical Hazards4 subtopics

Option E Leisure, Tourism and Sport4 subtopics

Option F The Geography of Food and Health4 subtopics

Option G Urban Environments5 subtopics

Waterfalls Are Created by Differential Erosion

Floodplains Are Flatlands of Fertility

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Waterfalls Are Created by Differential Erosion

Floodplains Are Flatlands of Fertility

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

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