EQ2-Weathering And Erosion Flashcards
What are the 3 types of weathering?
-Mechanical
-Chemical
-Biological
What are the 2 different types of mechanical weathering?
-Freeze-thaw
-salt crystallisation
What is freeze-thaw?
-When water expands by 9% in volume when freezing, exerting a force within cracks and fissures
-repeated cycles force cracks open and loosen rocks
What types of rocks are more likely to be susceptible to freeze-thaw?
-Any rocks with cracks and fissures, especially high up cliffs away from salt spray
-Freezing is relatively uncommon on Uk coasts, especially in South and salt spray can reduce its effect even further
What is salt crystallisation?
The growth of salt crystals in cracks and pore spaces can exert a breaking force, although less than for freeze thaw
What types of rocks are susceptible to salt crystallisation ?
-Porous and fractured rocks e.g. sandstone
-the effect is greater in hotter, drier climates where evaporation and the precipitation of salt crystals is more pronounced
What are the different types of chemical weathering?
-carbonation
-hydrolysis
-oxidation
What is carbonation?
The slow dissolution of limestone due to rainfall (weak carbonic acid, pH 5.6) producing calcium bicarbonate in solution
What types of rocks are susceptible to carbonation?
Limestone and other carbonate rocks
What is hydrolysis?
The breakdown of minerals to form new clay minerals, plus materials in solution due to effect of water and dissolved CO2
What types of rocks are susceptible to hydrolysis?
Igneous and metamorphic rocks containing feldspar and other silicate minerals
What is oxidation?
The addition of oxygen to minerals, especially iron compounds, which produces iron oxides and increases volume contributing to mechanical breakdown
What types of rocks are susceptible to oxidation?
Sandstones, siltstones and shakes often contain iron compounds that can be oxidised
What are the different types of biological weathering?
-plant roots
-rock boring
What is meant by “plant roots”?
Trees and plant roots growing in cracks and fissures forcing rocks apart
What types of rocks are susceptible to plant roots weathering?
An important process on vegetated cliff tops that can contribute to rockfalls
What is rock boring?
Many species of clams and mollusks bore into rock and may also secrete chemicals that dissolve rocks
What types of rocks are susceptible to rock boring?
-sedimentary rocks, especially carbonate rocks (limestone) located in the interior tidal range
