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Land based sub-aerial weathering

Page history last edited by Claire 13 years, 10 months ago

 

Sub-aerial weathering means 'under the air', weathering that happens to the coastline above sea level.

 

Physical Weathering

Freeze-Thaw

Water enters a line of weakness, such as a crack, then as it freezes the water expands by 9%. This puts pressure on the crack and the surrounding rock. The repeated fluctations in pressure break off pieces of rock.

 

Pressure release

Jointed rocks can be weathered as the pressure from the surrounding rocks is removed, causing the rock to expand and cracks to appear. e.g. Granite Tors

 

Biological Weathering

Living things are involved, growing through the rocks, cracking and expanding the rocks.

 

Chemical Weathering

Tends to occur where there is wetting/drying cycle, for example the base of cliffs - low/high tide.

 

Oxidation

Rocks are exposed to the oxygen in the air, the rock is oxidised as the oxygen reacts with the minerals. e.g. iron and oxygen form iron oxide, or rust.

 

Hydration

The rock absorbs water and swells, making it more susceptible to decomposition. Its most effective in intertidal zones.

 

Hydrolysis

The H+ and OH- ions in the water combine with ions in the minerals and result in the rocks breaking down.

 

Carbonation

Carbon dioxide dissolves into the rainwater, producing carbonic acid. This reacts with the calcium carbonate in limestone and other rocks, with the soluble product being washed away. NATURAL PROCESS.

 

Solution

The dissolving action of water on rocks.

 

Acid Rain

HUMANS. Produce lota of carbon dioxide, nitrogen dioxide, and sulphur dioxide. This dissolves in the rainwater to form acids and reacts with the rocks.

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