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The broken up material is transported by water, wind and ice and deposited as new sediment. This fragmentary material makes the foundation for a new generation of sedimentary (and perhaps metamorphic) rocks in another turn of the Rock Cycle.
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Weathering is the distintegration of rock in situ by the action of elements of the weather, with little or no transport.
Types of weathering include
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Weathering breaks down or alters rocks into
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One of the most important aspects of weathering is the formation of soil. Without soil, there would be little food! The formation of soil depends largely on climate rather than rock type.
- Most rock types are made up a relatively few, chemically related minerals which will produce similar end products.
- On the other hand, climate is variable across the world, with different temperatures and rainfalls which affect the intensity of chemical weathering, and therefore the kind of soil which is developed.
For example
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Once the original rock has been broken up by weathering and soil formation, it is now an unconsolidated mass of small
fragments of minerals and rocks which makes its way downhill by mass movement.
Processes include
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Mass movement carries this loose material into rivers and onto glaciers. Moving water, ice and wind use this material for the various processes of erosion. As the weathered material is now at the bottom of the hill, the hill top and sides are lowered - part of the process of denudation, the wearing away of the landscape.
In a river, erosion is carried out by
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The processes of erosion are most easily demonstrated through pot-holing action and the formation of waterfalls.
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As a result of erosion, rivers and their valleys develop a number of characteristic river landforms, closely related to the way in which water behaves when confined to a channel at the bottom of a valley (as compared to a glacier which fills the valley).
| Landforms found in the hills, where downcutting is important, are different from those in the lowlands, where lateral erosion is dominant. |
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Over time, the longitudinal profile of the river will grade to a theoretical gradient relating the discharge and stream velocity to erosion and deposition.
This graded profile will be achieved if the base or sea level remains stable for a long period of time - which rarely happens. If there is a change in base level, the landforms of the valley are modified. It is these modifications which provide the evidence that the base level has changed - up or down; this can then be investigated.
A rise in sea level will flood former river valleys, resulting in
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If the land rises, the river will be lifted further above base level and can renew its erosion into the land
surface, forming
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- Change in Base Level
- Erosion
- Mass Movement
- River Land Forms
- Soil Formation
- Weathering
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