glaciation

Question 1

glacials and interglacials?

Answer 1

glacials are warm phases and interglacials are warm phases

Question 2

what theories are there for the cause of ice ages

Answer 2

• variations in sunspot activity may increase or decrease amount of radiation received
• volcanic dust ejected into the atmosphere reflect and absorb radiation from the sun
• increased co2 by greenhouse gases can be absorbed by the sea in time leading to an overall drop in world land temperatures
• changes in ocean currents or jet streams
• earths position in space, its tilt and its orbit effect incoming radiation

Question 3

what is the snow line?

Answer 3

level above which snow will lie all year

Question 4

why is the snow line in northern hemisphere at lower altitudes on north facing slopes?

Answer 4

these receive less insolation than south facing slopes

Question 5

what is a firn?

Answer 5

compacted snow which has experienced one winters freezing and survived a summers melting. it is composed of randomly orientated ice crystals separated by air passages

Question 6

how are glaciers formed?

Answer 6

summer meltwater percolates into the firn only to freeze either at night or during the following winter… forming an incredibly dense mass

Question 7

cirque glaciers

Answer 7

small masses of ice occupying armchair shaped hollows in mountains, often overspilling to feed valley glaciers

Question 8

valley glaciers

Answer 8

large masses of ice which move down from either an ice field or a cirque basin source. they usually follow former river courses and are bounded by steep sides

Question 9

piedmont glaciers

Answer 9

formed when valley glaciers extend onto lowland areas, spread out and move

Question 10

ice caps or ice sheets?

Answer 10

huge areas of ice which spread outwards from central domes.

Question 11

nunataks

Answer 11

exposed summits of high mountains

Question 12

ice shelves

Answer 12

form when ice sheets reach the sea and begin to flirt

Question 13

upper part of of the glacier where inputs exceed outputs

Answer 13

zone of accumalation

Question 14

zone of ablation

Answer 14

lower part where outputs exceed inputs

Question 15

zone of equilibrium

Answer 15

where the rates of accumulation and ablation are equal, and it corresponds with the snow line

Question 16

polar glaciers

Answer 16

occur in areas where no melting occurs and where relief is usually gentle. base is much colder than pressure melting point so no melting occurs

Question 17

temperate glaciers

Answer 17

occur in areas with milder summers allowing melting to occur and where relief is steeper. the base of a temperate glacier is about the same temperature as the pressure melting point

Question 18

internal flow

Answer 18

in very cold climates glacier will be frozen to its bed. without any friction or pressure increase there will be no more melting. such glaciers move only 1 - 2cm per day with minimal erosion

Question 19

basal slippage

Answer 19

if glacier moves, pressure and friction increases with the bedrock. this raises temperature and basal ice may melt, resulting meltwater will act as lubricant enabling glacier to move more rapidly at 2-3m per day

Question 20

creep?

Answer 20

obstacle in path of glacier increases pressure and stress. as this builds up, ice behaves like plastic and flows around or over the obstacle

Question 21

extending and compressing flow?

Answer 21

compressing flow - where there was a reduction in gradient of the valley floor, ice would slow down and become thicker
extending flow - valley gradient steepened and ice accelerates and becomes thinner

Question 22

surges

Answer 22

result of an excessive build up of meltwater, can move glacier by 300m in one day

Question 23

pressure melting point

Answer 23

temperature at which ice is on the verge of melting

Question 24

by which 4 processes does movement in a glacier take place

Answer 24

basal flow, creep, extending - compressing flow and surges

Question 25

in what 3 ways do glaciers move debris

Answer 25

supraglacial debris, englacial debris, subglacial debris

Question 26

supraglacial debris

Answer 26

carried on the surface as lateral and medial moraine. consists of material that has fallen onto glacier from valley sides

Question 27

englacial debris

Answer 27

material carried within the body of the glacier

Question 28

subglacial debris

Answer 28

moved along the floor of the valley either by the ice or meltwater streams formed by pressure melting

Question 29

what are the processes associated with glacial erosion

Answer 29

frost shattering, abrasion, plucking, rotational movement, and extending and compressing flow

Question 30

what is frost shattering

Answer 30

produces loose material that will fall from the valley sides to form lateral moraine
then either covered all falls down crevices to be transported as englacial debris

Question 31

abrasion?

Answer 31

sandpaper effect of material rubbing against valley sides while be transported, creating smooth gentle landforms

Question 32

plucking

Answer 32

process involves the glacier freezing onto rock outcrops, after which ice movement pulls away masses of rock

Question 33

a bergschrund?

Answer 33

large crevasse like feature found near the head of some glaciers

Question 34

rotational movement?

Answer 34

downhill movement of ice, pivots about a point. increase in pressure is responsible for the over deepening of the cirque floor

Question 35

Aretes and Pyramidical peaks?

Answer 35

Arete - when two adjacent erode backwards or sideways toward each other, the previously rounded landscape is transformed into a narrow, rocky, steep sided ridge
Pyramidical Peak - if three or more cirques develop develop on a mountain, having several aretes and steep sides radiating from a central peak

Question 36

glacial troughs

Answer 36

steep sided flat floored valleys

Question 37

ribbon lakes and rock steps?

Answer 37

overdeepening of the trough floor, creating river like features, or may leave less eroded, more resistant rock steps.

Question 38

truncated spurs?

Answer 38

cliff like features formed by abrasion by englacial and subglacial and plucking along the valley sides to remove the tips of preglacial interlocking spurs

Question 39

hanging valleys

Answer 39

results from differential erosion between main glacier and its tributary. floor of tributary deepened at a slower rate than the main channel, as ice melts, tributaries are left high above the main vallley