Weathering and Rocks

Question 1

Freeze thaw weathering

Answer 1

when water in joints and cracks freeze at 0 degrees
expands by 10%
exerts pressure

most effective where moisture is plentiful so frequent fluctuations above and below freezing

common in peruglacial and alpine regions

Question 2

Pressure Release

Answer 2

Overlying rocks are removed by erosion
causes underlying rocks to expand and fracture parallel to the surface
removal of a great weight e.g. glacier has the same effect

Question 3

Heating and cooling

Answer 3

different minerals expand and contract at different temperatures

grandiose disintegration i rocks composed of different minerals
eg granite contains feldspar mica and quartz

block disintegration happens when the rock consists of a single mineral

Question 4

Salt Crystallisation

Answer 4

the decomposition of rock by solutions of salt

in areas where temperatures fluctuate around 26-28 degrees sodium carbonate and sulphate expand by 300%
creates pressure on joints forcing them to crack

water evaporates leaving salt crystals behind
the temperature rises salts expand and exert pressure on rock

Question 5

where is salt crystallisation found?

Answer 5

hot desert regions
low rainfall
high temperatures

Question 6

Disintegration

Answer 6

Rock heats up in day and contracts at night
rocks of conductor of heat
stressed only occur on the outer layers
peeling or exfoliation thus occurs
moisture is essential

Question 7

Where does disintegration occur

Answer 7

Hoy desert areas
large diurnal temperature range
deserts temperatures exceed 40 degrees and drop below freezing at night

Question 8

where does physical weathering occur

Answer 8

at or near the earths surface

Question 9

where does chemical weathering occur

Answer 9

sub surface

percolating water has gained organic acids from soil and vegetation

Question 10

Carbonation (solution)

Answer 10

Occurs in rocks with calcium carbonate
eg chalk or limestone

rainfall columbines with dissolved carbon dioxide or organic acid to form weak carbonic acid

calcium carbonate reacts with acid water and forms calcium bicarbonate which is soluble and removed in solution by percolating water

Question 11

Hydration

Answer 11

a process whereby certain minerals absorb water expand and change

eg shales and mudstone increase in volume by the 100% when clay minerals absorb water

Question 12

Oxidation

Answer 12

when iron compounds react with oxygen to produce a reddish brown coating

dissolved oxygen in soil or atmosphere affects iron

oxidation is only under extreme acidity meaning it remains in many soils and rocks giving it a red colour

Question 13

Hydration

Answer 13

Certain rocks containing feldspar (GRANITE) reacts with acid water
to produce kaolin and leaving behind quartz and mica

Question 14

Organic Action

Answer 14

Acids derived from the decomposition of vegetation are termed humid acids

Bacterial activity and the respiration of plant roots raise carbon dioxide levels in soil siding solution

Question 15

what type of sediment is prone to oxidation

Answer 15

iron oxide based

Question 16

how can vegetating increase weathering

Answer 16

release of organic acids through root systems

solution of limestone is greater under soil than bare rock due to extra organic acids released by vegetation in soil

Question 17

how can grain size influence weathering

Answer 17

coarse trained rocks weather quickly due to large empty spaces and high permeability

fine grained rocks offer a greater surface area for weathering and may be highly susceptible to weathering

Question 18

vant hoffs law

Answer 18

the rate of chemical weathering increases 2/3 rimes for each increase of 10 degrees

Question 19

main processes of weathering for granite

Answer 19

freeze thaw

hydrolysis

Question 20

what is in granite

Answer 20

quartz
feldspar
mica

Question 21

how could a mudflow affect the shape of slopes

Answer 21

leave a bowl shaped scar where movement starts

depositional toe at base

stepened upper slope
decreased angle at the base as a result of depositional toe

flow tracks produced

Question 22

how can humans affect slopes

Answer 22

undercutting (roads, quarrying, mining)

vegetation removal (deforestation)

overloading slope (waste or resovoirs)

Question 23

describe the process of pressure release

Answer 23

creation of joints and other weakness in rocks by the removal of overburden and the release of pressure

Question 24

chelation

Answer 24

chemical weathering
of rocks
by organic acids and molecules

Question 25

how do fold mountains form (at both plate margarine)

Answer 25

sediments (accretionary wedges) are scraped off the ocean floor and rise over the higher plate