W8L1 Glacial Processes

Question 1

strongest erosional agent

Answer 1

ice

Question 2

ice sheets and glaciers are

Answer 2

large masses of recrystallised ice

Question 3

ice sheets and glaciers persist

Answer 3

all year round

Question 4

ice sheets and glaciers move

Answer 4

byinternal dynamics

Question 5

ice sheets and glaciers form

Answer 5

at high latitudes or high altitufe
cold local climate
persistemt snowfall
no summer melt

Question 6

ice preserves

Answer 6

environmental conditions

precipitation (rain from atmosphere) so icesheets can measure atmsopheric change

Question 7

glacial ice forms

Answer 7

Year on year, snow accumulates in a north-facing sheltered hollow (cirque) -
with increasing overburden pressure, the ice undergoes diagenesis and metamorphoses
compacts
recrystallises
grains grow with time
pore space reduces
ice eventually flows out of the cirque

Question 8

Glacier Dynamic accumulation zone

Answer 8

Accumulation Zone
higher latitude or altitude
sublimation
little/no summer melt
ice moves by internal pressure to - ablation zone
need pressure!

Question 9

Glacier ABlation zone

Answer 9

lower latitude or altitude
ancient ice slowly exhumed
melting and iceberg calving

Question 10

glacier sublimation

Answer 10

sublimation. the transition of a substance from the solid phase directly to the vapor phase, or vice versa, without passing through an intermediate liquid phase.

Question 11

ice sheet albedo

Answer 11

large ice area changes albedo effect

Question 12

ice sheet force

Answer 12

mass is the motive force

Question 13

ice sheet flow

Answer 13

will flowuphill if overburden pressure in maintained

Question 14

ice sheet viscosity

Answer 14

extreme viscosit of ice means powerful erosive force and effiicient transport agent

Question 15

ice sheet sediment

Answer 15

glaciers & ice sheets create, transport & deposit huge quantities of sediment

Question 16

Periglacial features are

Answer 16

this is whats perserved thru rock, find things around the iceand what can be reconstructed

Question 17

ice dynamics reaction to pressure

Answer 17

Differential pressure produces different behaviour in the ice profile
in the upper 50 m, pressure & brittle strength are relatively low
cracks & crevasses
sediment falling on to ice surface is incorporated & transported
below 50 m, pressure is high & ductile strength is low
deformation & flow

Question 18

Wet vs . dry dynamics

Answer 18

temperate wet vs polar dry

Question 19

temperate glaciers

Answer 19

Temperate wet-based glaciers –

ice slips over a meltwater/sediment slurry

Question 20

polar glaciers

Answer 20

frozen to substrate

flow by internal ductile deformation

Question 21

erosional flow is

Answer 21

flow is from the accumulation zone to the ablation zone
individual ice crystals follow a curved trajectory
regardless of melting in the ablation zone or stalled flow at the ice front, th ice body flows as long as accumulation is sustained

Question 22

scouring erosion . and incorporation ofbedrock

Answer 22

occurs under the accumulation zone
as pressure slackens, melting occurs & sediments are released
melting beneath the ice leads to sediment dumping – lodgement till
sediment, carried on and in the ice, is dumped at ice front – terminal moraine
meltwater streams emerging from ice front carry sediment away to the outwash plain

Question 23

direction of flow

Answer 23

flows from accumulartion to deposition

Question 24

doiminant deposited mineral

Answer 24

quartz

Question 25

Sediment weathering and transport moraines

Answer 25

Freeze-thaw shattering supplies clasts to the surface of mountain glaciers
physical weathering - angular clasts - no change in mineralogy
slower ice flow at valley sides melting and sediment concentration
side moraines
central moraines result from the confluence of two or more valley glaciers

Question 26

clast and bedrock weathering

Answer 26

lasts incorporated through crevasses transported & weathered
reduction of grainsize & unstable minerals
clasts at the glacier base abrade the bedrock striations parallel to flow
upstream of obstruction flow slows ice freezes to bedrock
downstream of obstruction flow restarts clasts plucked from surface
best indicator of ice (geologcial past) : striations parallel to flow

Question 27

Erosional force

Answer 27

100s of vertical metres of rock are removed by glacial erosion
1000s of cubic kilometres
obstacles will be eroded by clasts in the ice and form valleeys or rivers

Question 28

Sediment Transport surface load

Answer 28

no change in grainsize or mineralogy

Question 29

sediment internal load

Answer 29

decrease of grainsize and unstable minerals

Question 30

clasts in contact with bedrock

Answer 30

extremely high weathering

Question 31

sediment transport

Answer 31

rock flour
clasts dumped when pressure slackens
terminal moraines
lodgement till

Question 32

Till and Tillite

Answer 32

All sizes of clast dumped beneath, beside and in front of the ice
unsorted
unstratified
compositionally & texturally immature
gravity flow: debris flow bcs nothing to distinguish
direct indicator: scratch marks
indiredct indicator: would be context, other glacial features around

Question 33

Glacial erratics

Answer 33

pushed/dragged/carried by the ice in some cases for kilometres
thought to be transported by swift-moving ice streams, then ice melted and rocks left behind
usually identified by anomalous rock type
protects bedrock from weathering processes

Question 34

Glacial outwash

Answer 34

moves / shifts around extremely large volume of material

Question 35

glacial outwash stream

Answer 35

Typical braided stream & forms outwash plain
stream full of sediment (rolling bedload & suspended load)
high capacity/ low competence

Question 36

bars and channels

Answer 36

rapid formation, filling, abandonment and reformation

Question 37

glacial outwash sediment

Answer 37

highly weathered clasts
highly rounded
clays, quartz sands, pebbles and cvobbles
compositionally and texturally mature
cross-bedded, sorted and deposited by seasonal braided streams
pebbles/cobbles are imbricated
river conglomerates, coarse marine gravels, glacial outwash sediments

Question 38

proglacial lakes

Answer 38

iceberg calving dropstones (ice-rafted debris)
a tell-tale sign of glaciation
two distinct seasons in proglacial lakes (frozen & meltwater) deposition of varves

Question 39

ice sheet at sea level

Answer 39

ice shelves extend from the land when ice sheet is grounded on the shelf

Question 40

ice sheets debris bcs of glaciation

Answer 40

the amount of ice-rafted debris in marine sediments is commensurate to intensity of glaciation

Question 41

glacial ice clast size

Answer 41

can transport any clast . size ions to cliff sized boulders

Question 42

glacial ice forms at

Answer 42

forms at high latitudes and altitudes

over 100s/1000s of years, snow transformed to ice by overburden pressure flows under its own weight

Question 43

glaciers flow

Answer 43

from accumulation zone (high pressure) to ablation zone (low pressure)

Question 44

glaciers in high altitudes

Answer 44

in high-altitudes frost-shattering supplies clasts to the ice surface

Question 45

glaciers accumulation zone

Answer 45

under the accumulation zone, plucking & abrasion erode the bedrock and incorporate clasts into the ice

Question 46

glacial sediment

Answer 46

sediment carried on and in the ice and is dumped where pressure slackens - unsorted, unstratified, mixed mineralogy till

Question 47

glacial ice front

Answer 47

at the ice front meltwater streams deposit sorted, stratified clays, quartz silts, sands & gravels
lowland glaciers can terminate in proglacial lakes

Question 48

varves

Answer 48

winter/summer contrast produces laminated sediment – ‘varves’

Question 49

ice shelves

Answer 49

ice at sea level is grounded on the shelf – ‘ice shelves’

cebergs transport ice-rafted debris into the ocean