7. Geomorphological Processes

Question 1

at a lower altitude so is…

Answer 1

closer to sea level

Question 2

orographic rainfall is also known as

Answer 2

relief rainfall (rain shadow effect)

Question 3

where (and why) are geomorphological processes most prevalent?

Answer 3

the margins of cold environments

high precipitation (orographic rainfall) and temperatures that fluctuate around 0°C

Question 4

outline the process of freeze-thaw weathering

Answer 4

1. precipitation fills a crack in a rock
2. water freezes when temperatures drop (e.g. at night) and expands by 9%, extending the crack
3. steps 1-2 repeat many times
4. the rock splits apart

Question 5

by how much does water expand when frozen?

Answer 5

9%

Question 6

what happens to the pieces after freeze-thaw weathering takes place?

Answer 6

form a scree slope

Question 7

what is the impact of freeze-thaw weathering on glacial landscapes?

Answer 7

at the margin: (where temperatures fluctuate above/below 0°C)
prevents vegetation from growing as unstable ground

Question 8

name some geomorphological processes

Answer 8

freeze-thaw weathering
acid rain
plant root action
nivation

Question 9

outline the process of acid rain

Answer 9

1. carbon dioxide is released by human activities such as the burning of fossil fuels
2. this CO₂ dissolves in the water vapour in clouds
3. this forms carbonic acid which can corrode sedimentary rocks such as chalk and limestone

Question 10

what happens to the pieces after acid rain takes place?

Answer 10

runs off as rainwater (minerals dissolved)

Question 11

what is the impact of acid rain on glacial environments?

Answer 11

minimal as glaciers are typically igneous rock (as tectonic fold mountains) and acid rain affects sedimentary rocks

Question 12

outline the process of plant root action

Answer 12

plant roots find weaknesses in rocks and crack them open

Question 13

what happens to the pieces after plant root action takes place?

Answer 13

they just lie there

Question 14

what is the impact of plant root action on glacial environments?

Answer 14

minimal as too inhospitable for plant life (no plants = no roots)

Question 15

outline the process of nivation

Answer 15

1. in hollows filled with snow (which face the directions which receive the least sunlight i.e. north- and east- facing in the northern hemisphere), freeze-thaw weathering and chemical weathering disintegrate the rock beneath the snow
2. in spring, the meltwater flushes the rock away
3. this process repeats annually to create nivation hollows

hollows fill with snow as snowfall is protected by the small depressions, which begins the formation of the glacier

Question 16

what happens to the pieces after nivation takes place?

Answer 16

the rock is flushed out by meltwater each spring/summer

Question 17

what is the impact of nivation on glacial environments?

Answer 17

creates nivation hollows which look like craters on the landscape

Question 18

what are the scratches left by abrasion called?

Answer 18

striations

Question 19

erosion vs. weathering

Answer 19

weathering is in situ (so the pieces stay there)

Question 20

what is plucking?

Answer 20

ice acts like wax due to regelation, freezing around rocks and then pulling them out of the bedrock

this drags the rock along the glacier, leaving behind a jagged landscape

Question 21

controlling factors of ice movement

Answer 21

(mgsinA)

temperature of ice (more water = more plucking/abrasion as everything moves faster –> lubricant)
g
m
friction (meltwater = lubricant)

Question 22

define subglacial

Answer 22

beneath the glacier (once englacial, but snow accumulated around it)

Question 23

define englacial

Answer 23

within the glacier

Question 24

define supraglacial

Answer 24

on the surface of the glacier (where weathering occurs)

Question 25

where does glacial deposition occur?

Answer 25

the zone of ablation; close to the glacier's snout

Question 26

what is material deposited by ice known as?

Answer 26

till