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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