Glacial Processes and Landforms

Question 1

What percentage of earth’s freshwater is stored in glaciers?

Answer 1

around 70%

Question 2

what percentage of earths surfaces covered in ice?

Answer 2

around 10%

Question 3

where on earth is ice stored?

Answer 3

ice sheets (Antarctica, Greenland)
valley glaciers

Question 4

What areas were covered by ice sheets during the last ice age?

Answer 4

large parts of north america and Europe

Question 5

glaciers have a strong control on…?

Answer 5

average global sea level

Question 6

what do glacial deposits lead to?

Answer 6

construction aggregate

important aquifers

Question 7

ice flows under its own weight due to …..

Answer 7

gravity

Question 8

If downslope force (shear stress, τ) > resisting force (shear strength), then…

Answer 8

ice flows as a plastic

Question 9

what are some features of glaciers?

Answer 9

zone of accumulation
equilibrium line (line between net gain and net loss)
zone of ablation
crevasses
snowlayers

Question 10

How does snow become glacial ice?

Answer 10

becomes more dense - contains less air

Question 11

what is the lower limit of the zone of accumulation?

Answer 11

the equilibrium line

Question 12

what is the zone of ablation defined by?

Answer 12

net loss by melting

Question 13

if accumulation > ablation

Answer 13

glacier advances

Question 14

if accumulation < ablation

Answer 14

glacier retreats

Question 15

ice within a glacier always flows in which direction?

Answer 15

forwards (even when retreating)

Question 16

how do glaciers move?

Answer 16

creep

basal slip

Question 17

how fast does the ice in a glacier move?

Answer 17

metres/yr to 100 metres/yr

Question 18

what are the different types of glaciers?

Answer 18

valley (also tributary/tidewater) glaciers
ice sheets
(they are classified by size/location)

Question 19

how hard is ice?

Answer 19

1.5 hardness on mosh scale

can be scratched by a fingernail

Question 20

How do glaciers erode?

Answer 20

Glaciers scour & erode rock

Question 21

how do glaciers scour & erode rock?

Answer 21

Ice pressure + sediment abrasion

(1) As ice flows, it entrains & ‘pushes’ sediment
- > Abrasion, ‘bulldozing’, & plucking
2) Glacial meltwater
- > Meltwater flow (outwash plains & rivers)
- > Pressurised sub-glacial flow

Question 22

What landforms result from glacial erosion?

Answer 22

cirques
truncated spurs
horns
tarns
arête
hanging valleys
glacial trough (u-shaped)

Question 23

what is a roche moutonnée?

Answer 23

Streamlined bedrock mound parallel to ice flow

‘Plucking’ on lee side (freeze/thaw)

Question 24

What deposits do glaciers leave behind?

Answer 24

(1) Till
(2) Glaciofluvial deposits
(3) Glaciolacustrine deposits
(4) Glacial erratics

Question 25

what is till?

Answer 25

poorly-sorted mixture of many different sediment sizes and striated rocks [material left behind after transport on/in/under ice]

Question 26

what are glaciofluvial deposits?

Answer 26

sands/gravels deposited by meltwater channels

Question 27

what are glaciolacustrine deposits?

Answer 27

fine-grained sediment, with dropstones. Deposited in lakes.

Question 28

what are glacial erratics?

Answer 28

ice-transported boulders, not derived from underlying bedrock

Question 29

What landforms result from glacial deposition

Answer 29

``` eskers (glaciofluvial feature) ground moraines drumlins kettle lakes recessional moraine terminal moraine outwash plain (glaciofluvial deposition) ```

Question 30

how are moraines formed?

Answer 30

Debris deposited on ice, up-valley (mass wasted) Transported on surface, down-valley, down-ice Leaves train of deposits (till) on margins of glacier, and eventually its front (toe)

Question 31

what are lateral moraines?

Answer 31

moraines that form along the sides of a glacier

Question 32

how do medial moraines form?

Answer 32

lateral moraines become medial moraines when two valley glaciers meet

Question 33

what does a terminal moraine mark?

Answer 33

the furthest advance of the glacier

Question 34

when are recessional moraines formed?

Answer 34

while terminus of receding glacier remains temporarily stationary

Question 35

during the last glacial maximum which ice sheet covered all of BC?

Answer 35

cordilleran ice sheet

Question 36

what is an effect of continental ice sheet on the crust?

Answer 36

During glaciation: crust pushed down After deglaciation: crust rebounds ->uplift [isostatic rebound] Forms raised beaches (e.g. Hudsons Bay - still rebounding today)

Question 37

rate of isostatic rebound is proportional to.....

Answer 37

the viscosity of the underlying mantle (asthenosphere)

Question 38

what is the global average in temperature fluctuations in the past million years?

Answer 38

around 10 degrees Celsius

Question 39

what are the milankovitch cycles?

Answer 39

``` eccentricity tilt precession (variations in earths orbit) they lead to variations in energy received from the sun ```

Question 40

what is eccentricity?

Answer 40

where earths orbit fluctuates between circular and elliptical over a 100,000 year cycle

Question 41

what is tilt?

Answer 41

where earths tilt fluctuates between 22.5 degrees and 24.5 degrees over a 41,000 year cycle

Question 42

what is precession?

Answer 42

where earth "wobbles" on its axis over a 26,000 year cycle