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Geography > Weathering > Flashcards

Weathering Flashcards

1
Q

Define weathering

A

Breakdown of rocks by physical (mechanical), chemical or biological means. The weathered rock (scree) stays in situ

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2
Q

Define scree

A

Weathered rock

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3
Q

Define in situ

A

Not removed from the area

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4
Q

Define erosion

A

Breakdown of rocks by wind, water or glacial action. The broken down rock may be transported to another location

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5
Q

What are two types of physical weathering?

A

Freeze thaw action and exfoliation (onion weathering)

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6
Q

What is the main factor that causes freeze thaw action and exfoliation?

A

Temperature

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7
Q

What are the ideal conditions for freeze thaw action?

A

Upland, mountainous areas that drop below 0°C

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8
Q

What are the ideal conditions for exfoliation?

A

Desert climates that are 45°C+ during the day and below 0°C at night

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9
Q

What is chemical weathering?

A

Reaction of minerals in rocks to chemical agent. Rocks dissolve

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10
Q

What are the different types of chemical weathering and what rock type do they affect?

A

*Oxidation - Sandstone
* Carbonation - Limestone
* Hydrolysis - Granite
* Hydration - Granite

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11
Q

In what climate does chemical weathering speed up?

A

Hot humid climates

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12
Q

What is biological weathering?

A

Plant/animal life that leads to the breakdown of rock

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13
Q

What are some different causes of biological weathering?

A
  • Trees: Growing up through rocks. Tree roots break rock.
  • Animals: Burrowing
  • Fungi/Lichen/Moss: Attach to rock and break it down
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14
Q

What are the processes of fluvial and marine erosion?

A

Hydraulic action, attrition, solution and abrasion

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15
Q

What are the processes of glacial erosion?

A

Plucking, abrasion

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16
Q

Where does freeze thaw action occur?

A

Mountainous regions eg. Croagh Patrick

17
Q

During what periods does freeze thaw action occur?

A

Glacial periods - Now and 12,000 years ago

18
Q

What factors affect freeze that action?

A
  • Temperature: above and below 0°C
  • Altitude: Higher up is more effective
  • Rock type: Permeable rocks and rocks with natural fractures/pore spaces affected more
19
Q

Explain the steps of freeze thaw action

A
  • Water fills the cracks of the rocks during the day
  • At night temperatures fall below 0°C and water turns to ice, expanding by 9-11%, putting pressure on the rock
  • Over time this cycle causes rock to fracture and break off, creating scree
20
Q

Where does exfoliation occur?

A

Desert and arid climates

21
Q

Give an example of somewhere exfoliation occurs

A

Sahara Desert, Africa

22
Q

What happens during exfoliation?

A

The outer layer of rock heats and expands, then cools and contracts repeatedly. This causes is to fracture and peel away

23
Q

What factors affect exfoliation?

A
  • Temperature: Large diurnal range eg. 40°C day, 0°C night
  • Lack of vegetation: Nothing to cover rocks/provide shade
  • Lack of cloud cover: Blue skies during day (hot) and loss of heat during night
  • Stone colour: Dark rock attracts heat causing it to expand more rapidly
24
Q

Give an example of somewhere carbonation occurs

A

The Burren, Co. Clare

25
Q

What is the area of the Burren?

A

250 km squared

26
Q

What kind of landscape is the Burren?

A

Karst landscape - exposed limestone, no soil or vegetation

27
Q

Explain the process of carbonation

A
  • Rainwater (H20) mixes with Carbon Dioxide (CO2) to form a weak carbonic acid (H2CO3)
  • Limestone is a permeable rock. The limestone in the Burren is made up of 55% Calcium Carbonate
  • Calcium Carbonate is insoluble however when H2CO3 comes into contact with it it turns it into the soluble Calcium Bicarbonate
  • It dissolves and is washed away in solution
28
Q

Draw a diagram of carbonation

A

N/A

29
Q

Explain hydration

A
  • Soil-forming minerals in rock absorb water causing them to expand
    *This causes stress to build in the rock, eventually leading to it fracturing and shattering
    *Mechanical weathering furthers the disintegration
30
Q

Explain hydrolysis

A

*Carbonic acid causes rock-forming minerals eg. feldspar to turn into softer weaker kaolin
* Kaolin doesn’t bond well and breaks down easily, weakening rocks structure, eventually causing it to break down and decompose

31
Q

Explain oxidation

A

Oxygen dissolved in water reacts with metal in rocks to produce oxides of iron (rust) in rock particles

32
Q

Explain two types of physical weathering with reference to examples from Ireland (30m)

A

See notes

Geography (8 decks)

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