Consists of physical actions such as the growth of plant roots or chemical processes such as chelation by organic acids.
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Tree roots
Tree roots grow into cracks or joints in rocks and exert outward pressure, causing the rock to split.
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Organic Acids
These may be secreted molluscs, released during the decay of organic matter or released by algae. These acids can react with rock minerals.
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Carbonation
Rainwater is a weak carbonic acid. this reacts with calcium carbonate in rocks such as limestone to produce calcium bicarbonate, which is soluble.
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Salt weathering - crystallisation
solutions of salt in the sea water can enter pore spaces in porous rocks. the salt precipitate, forming crystals, and the growth of these crystals creates stress in the rock causing it to distintegrate.
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Wet-dry weathering- hydration
water molecules added to rock minerals create new minerals of a larger volume. this happens to anydrite, forming gypsum.
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Freeze-thaw Weathering
Water enters cracks/joints and expands by nearly 10% when it freezes. This exerts pressure on the rock causing it to split or causing pieces to break off.
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Chemical Weathering
The breakdown of rocks by chemical processes such as oxidation, solution and hydroliysis
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Oxidation
Some minerals in rock react with oxygen, either in the air or in the water. The rock becomes soluble under strongly acidic conditions and the original structure is destroyed.
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Solution
some minerals are soluble in water and as they dissolve they weaken the structure of a rock.
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Hydrolysis
This is a chemical reaction between rock minerals and water. Silicates combine with water producing secondary minerals such as clay.
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Other cards in this set
Card 2
Front
Tree roots grow into cracks or joints in rocks and exert outward pressure, causing the rock to split.
Back
Tree roots
Card 3
Front
These may be secreted molluscs, released during the decay of organic matter or released by algae. These acids can react with rock minerals.
Back
Card 4
Front
Rainwater is a weak carbonic acid. this reacts with calcium carbonate in rocks such as limestone to produce calcium bicarbonate, which is soluble.
Back
Card 5
Front
solutions of salt in the sea water can enter pore spaces in porous rocks. the salt precipitate, forming crystals, and the growth of these crystals creates stress in the rock causing it to distintegrate.
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