Sub-aerial weathering Flashcards
What are sub-aerial processes?
Land-based processes that shape the coastline (e.g weathering or mass movement).
What 3 types of sub-aerial weathering are there?
Mechanical/physical weathering.
Biological weathering.
Chemical weathering.
What is mechanical weathering?
Processes that occur at coasts depending on the nautre of the climate.
E.g in latitudes where temperatures fluctuate above and below freezing, freeze thaw is apparent as there is a ready supply of water.
What is biological weathering?
Processes that lead to the breakdown of rocks by the action of vegetation and coastal organisms.
E.g - Some marine organisms such as the piddok (a shellfish) have specially adapted shells that enable them to drill into solid rock. Particularly active in areas with chalk geology where they can form sponge-like rock.
- Seaweed attaches itself to rocks and the action of the sea can be enough to cause swaying seaweed to prise away loose rocks from the sea floor.
- Algae secretes chemicals capable of promoting solution.
- Some animals can weaken cliffs as they burrow or dig into them such as rabbits or some cliff-nesting birds.
What is chemical weathering?
Occurs where rocks are exposed to air and moisture so chemical processes can breakdown the rocks. Solution is the main chemical process.
Name two types of chemical weathering.
(Any two of the following)
Oxidation.
Hydration.
Hydrolysis.
Carbonation.
What is oxidation?
Oxygen dissolved in water reacting with rock minerals, forming oxides and hydroxides, especially affecting iron-rich rocks.
What is hydration?
Makes the rocks more susceptible to further chemical weathering, although it involves a physical addition of water to minerals in the rock. This causes the rock to expand, and can cause the rock to disintegrate, widening cracks and joints.
What is hydrolysis?
Mildly acidic water reacting or combining with minerals in the rock to create clays and dissolvable salts; degrading the rock.
What is carbonation?
CO2 dissolved in rainwater makes a weak carbonic acid which reacts with calcium carbonate found in rocks like limestone and chalk to create calcium bicarbonate which dissolves easily in water.
