Water enters joints and cracks and expands when it freezes. This exerts pressure on the rock causing it to break off.
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Frost shattering
At extremely low temperatures, water trapped in pores freezes and disintegrates the rock to small particles.
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Pressure release
When the weight of the overlying ice is lost due to melting, underlying rock then expands and fractures parallel to the surface.
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Oxidation
Minerals in the rock react wth O2 (from air/water). Rock becomes soluble under extremely acidic conditions and the structure is destroyed.
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Carbonation
Rainwater cobines with dissolved CO2 to produce a weak carbonic acid. This reacts with calcium carbonate in rocks such as limestone to produce calcium bicarbonate (soluble)
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Solution
Any process by which a mineral dissloves in water.
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Hydrolysis
This is a chemical reaction between rock minerals and water. E.g Silicates combine with water to produce secondary minerals such as clay.
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Hydration
Water molecules added to rock minerals create new minerals of a larger volume. This happens to anhydrite forming gypsum. This causes surface flaking in many rocks.
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Plucking
When meltwater seeps into joints in the rock of the valley floor/sides. It freezes and becomes attached, when the glacier advances it pulls pieces of rock away.
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Abrasion
As a glacier moves across the surface, the debris in its base scours surface rock, wearing them away.
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Tree roots
Tree roots grow into cracks or joints in rocks and exert outward pressure. When trees topple they can exert leverage on rock and soil, exposing them to further weathering. Burrowing animals may have a similar effect.
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Organic acids
Organic acids produced during decomposition of plant and animal litter cause soil water to become more acidic. This can react with minerals- chelation.
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Nivation
Thought to include a combination of freeze-thaw action, solifluction, transport by running water and chemical weathering.
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Other cards in this set
Card 2
Front
At extremely low temperatures, water trapped in pores freezes and disintegrates the rock to small particles.
Back
Frost shattering
Card 3
Front
When the weight of the overlying ice is lost due to melting, underlying rock then expands and fractures parallel to the surface.
Back
Card 4
Front
Minerals in the rock react wth O2 (from air/water). Rock becomes soluble under extremely acidic conditions and the structure is destroyed.
Back
Card 5
Front
Rainwater cobines with dissolved CO2 to produce a weak carbonic acid. This reacts with calcium carbonate in rocks such as limestone to produce calcium bicarbonate (soluble)
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