Weathering and erosion Flashcards
(17 cards)
What are the different processes of mechanical weathering?
- Freeze - thaw
- Salt crystallization
What are the 3 processes of chemical weathering?
1.Carbonation
2. Hydrolysis
3. Oxidation
What are the 2 processes of biological weathering?
- Plant roots
- Rock boring
What is freeze-thaw?
Water expands by 9% in volume when freezing, exerting a force within cracks and fissures; repeated cycles force cracks open and loosen rocks.
What rocks are vulnerable to freeze-thaw?
Any rocks with cracks and fissures, especially high up cliffs away from salt spray. Freezing is relatively uncommon on UK coastlines especially in the south and salt spray and reduce its effects even further.
What is salt crystallization?
The growth of salt crystals in cracks and pore spaces can exert a breaking force, although less than for freeze thaw.
What is carbonation?
The slow dissolution of limestone to rainfall (weak carbonic acid, pH 5.6) producing calcium bicarbonate in solution.
What rocks are vulnerable to carbonation?
Limestone and other carbonate rocks.
What is oxidation?
The addition of oxygen to minerals, especially iron compounds, which produces iron oxides and increases volume contributing to mechanical breakdown.
What rocks are vulnerable to oxidation?
Sandstone, siltstones and shales often contain iron compounds that can be oxidised.
What rocks are vulnerable to salt crystallization?
Porous and fractured rock, the effects in greater in hotter, direr climates are where evaporation and the precipitation of salt crystals in more pronounced.
What is hydrolysis?
The breakdown of minerals to form new clay minerals, plus materials in solution, due to the effects of water and dissolved CO2.
What rocks are vulnerable to hydrolysis?
Igneous and metamorphic rocks containing feldspar and other silicate minerals.
What is plant roots in the context of biological weathering?
Trees and plants roots growing in cracks and fissures forcing rocks apart.
What rocks are vulnerable to plant roots?
An important process on vegetated cliff tops that can contribute to rockfall.
What is rock boring?
Many species of clams and mollusks bore into rock and may also secrete chemicals that dissolves rocks.
What rocks are vulnerable to rock boring?
Sedimentary rocks, especially carbonate rocks (limestone) located in the inter-tidal range
