subaerial processes (weathering) Flashcards

1
Q

difference between weathering and erosion

A

-weathering is in situ
-erosion is the movement of broken down sediment

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2
Q

what does sub aerial mean

A

processes occurring at the land surface

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3
Q

what do weathering processes do

A

-mechanically disintegrate and/or chemically decompose rocks where they are in (in situ)
-increase vulnerability to mass movement

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4
Q

2 processes of mechanical weathering

A

-freeze-thaw
-salt crystallisation

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5
Q

whats freeze thaw

A

-when water expands in volume when freezing
-exerts force within cracks and fissures
-repeated cycles force cracks open

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6
Q

what rocks are vulnerable to freeze thaw

A

-any rocks w cracks/fissures

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7
Q

which mechanical process is more common on the UK coast

A

-salt crystallisation
-freeze thaw is uncommon

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8
Q

what is salt crystallisation

A

-growth of salt crystals in cracks and pore spaces
-exert a breaking force (although less than for freeze thaw)

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9
Q

what rocks are vulnerable to salt crystallisation

A

-porous and fracture rocks
-effect is greater in hotter, drier climates where evaporation and precipitation is more pronounced

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10
Q

what are the 3 chemical weathering processes

A

-carbonation
-hydrolysis
-oxidation

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11
Q

what is carbonation

A

-dissolution of limestone due to rainfall

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12
Q

what rocks are vulnerable to carbonation

A

-limestone and other carbonate rocks

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13
Q

what is hydrolysis

A

-breakdown of minerals to form new clay minerals

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14
Q

what rocks are vulnerable to hydrolysis

A

-igneous and metamorphic rocks

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15
Q

what is oxidation

A

-addition of oxygen to minerals
-produces iron oxides and increases volume contributing to mechanical breakdown

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16
Q

what rocks are vulnerable to oxidation

A

-sandstones
-siltstones
-anything that contains iron compounds that can be oxidised

17
Q

what are the biological processes of weathering

A

-plant roots
-rock boring

18
Q

effect of plant roots - weathering

A

-trees and plant roots growing in cracks and fissures forcing rocks apart

19
Q

effect of rock boring

A

-species of clams and molluscs bore into rock and may secrete chemicals that dissolve rocks

20
Q

what’s the name for when organic acids from plant roots and decaying mater bind to metal ions (resulting in rocks decomposing)

A

-chelation

21
Q

where is weathering a dominant process

A

-low energy
-low tidal range coasts
-such as the Mediterranean

22
Q

what influences weathering

A

-meteorological factors such as annual temperature and rainfall

23
Q

example of the influence of lithology on weathering

A

-basalt
-weathers at 1-2mm per 1000 years

24
Q

what type of weathering dominates in cold climates

A

mechanical

25
Q

what kind of weathering dominates in hot and wet climates