weathering

Question 1

what is weathering

Answer 1

natural breakdown, decomposition and disintegration of rock material by means of pressure release, exposure to fluctuating temperatures, oxygen in air and water

Question 2

mechanical weathering

Answer 2

disintegration of rock by processes that do not alter chemical composition, usually in areas without water and vegetation

Question 3

Chemical weathering

Answer 3

decomposition of rock via chemical reactions that lead to chemical change of parent material , occurs in places with moisture and heat

Question 4

frost shattering

Answer 4

water enters joints and crevices in rock, then freezes at night, ice has more volume than water causing crack to widen, eventually causing rock to shatter from main body

Question 5

salt crystallisation

Answer 5

if water entering pore spaces in rocks is saline when it evaporates it forms crystals. as crystals grow , it exerts stress upon rock, causing it to disintegrate

Question 6

pressure release

Answer 6

rocks form under high pressure, when exposed to atmosphere, there is a release in pressure which weakens rock allowing agents to enter rock
results in sheeting - crack develops parallel to surface , peeling away layers

Question 7

thermal expansion

Answer 7

outer layers of rock warm up faster and cool faster than inner ones , causing outer layers to peel off in a process called exfoliation

Question 8

biological weathering

Answer 8

tree roots grow along bedding plane , filling and widening joints until rock becomes detached

Question 9

oxidisation

Answer 9

occurs when rocks are exposed in air or water, changing oxidation state of ion and colour of rock causing it to crack and crumble easily

Question 10

hydration

Answer 10

rocks, especially ones containing salts, can absorb water or lose it, making rock swell up and exert pressure and changes chemical composition. this causes it to become vulnerable to future breakdown

Question 11

hydrolysis

Answer 11

H+ or OH- ions replace ions in rock minerals creating a totally different compound. increase in H+ ions increases hydrolysis rate

Question 12

carbonation

Answer 12

rainwater contains carbon dioxide in solution which produces carbonic acid (H2CO3) which reacts with rock composed of calcium carbonate (limestone) causing it to dissolve

Question 13

Acid Rain

Answer 13

Human activities increases carbon dioxide , sulphar dioxide and nitrogen oxide in atmosphere, gases then form acids in solution with rain water. this acid rain causes increased hydrolysis in soil, release of toxic metals in rock, and attacks limestone and sandstone