Weathering

Question 1

Weathering is influenced by what factors?

Answer 1

1. Rock type
2. Climate
3. Topography (upland areas more exposed)

Question 2

Physical weathering

Answer 2

• breakdown of rock by physical forces into smaller particles
• no change in chemical make up
• most likely to occur in areas that have little or no vegetation
• free thaw action (temp change)
• exfoliation (temp change)

Question 3

Freeze-thaw action

Answer 3

-common where temps move above and below freezing point (0)
- water fills spaces in rocks during day (warmer)
- water freezes at night (_ freezing)
- as water —> ice, volume expands by 9%
- pressure is put on rock forcing gaps to open
- sequence of freeze and thaw, slowly weakens the rock. Eventually, particles (scree) break off
- eg sugar loaf, alpine environments

Question 4

Exfoliation (onion)

Answer 4

-process helps strip off outer layers of rock (most effective when rocks have strata)
- occurs in areas with great daily temp change (deserts)
- day, temp high (^40) (no clouds) - heats the surface, expands the rock
- no clouds + no vegetation = rapid loss of heat at night (0) - layers of rock close to surface cool + contract
- heating + cooling doesn’t occur equally. Outer layers heat and cooled faster than layers further in
- dark rocks - absorb heat faster
- fractures + flacking occur (outer layers peel off like onion)
- scree
- cycle of exfoliation
- eg. Yosemite National park

Question 5

Chemical weathering

Answer 5

-decomposition/decay or rocks
- make up is changed (minerals dissolved/change into new minerals)
- moisture (areas of precipitation)
- carbonation
- hydrolysis

Question 6

Carbonation

Answer 6

• rainwater absorbs carbon dioxide as it falls through atmosphere
• as water passes through soil, absorbs even more carbon dioxide
• ^^^ forms weak carbonic acid
• reacts with minerals in the rocks and either dissolves them/turns them into other minerals
  -limestone/chalk -calcium carbonate
• calcium carbonate reacts with weak carbonic acid to form calcium bicarbonate (soluble)
  -limestone weaknesses (joints etc)
• carbonation produces karst landscape (limestone)
• burren

Question 7

Hydrolysis

Answer 7

• water reacts with chemicals in rocks and breaks them down
• creates new substance that is softer and weaker then original
• fine grained rock = weather faster than course grained because they have larger surface area that is open to weathering
• occurs faster in hot,wet conditions (tropics)
• v effective w granite (feldspar, mineral,Easily absorb water, Kaolin)
• kaolin poor at bonding (crumbles easily, weakening rock)
• quartz and mica in granite not held together bc of kaolin
• important for soil-forming (most solis contain high amount of clay minerals)
• the Leinster batholiths