Glacial processes

Question 1

Internal deformation

Answer 1

This occurs when the weight of glacier ice and gravity causes the ice crystals to deform, so that the glacier can move down hill slowly.

Question 2

Basal slip

Answer 2

Occurs when the base if the glacier is at the pressure melting point, which means the meltwater is present and acts as a lubricant, enabling the glacier to slide more rapidly over the bedrock.

Question 3

Glacial surges

Answer 3

The glacier can move up to 100 times faster than usual. Caused by the build-up of meltwater at the ice rock interface.

Question 4

Regelation creep

Answer 4

Obstacles on the valley floor cause increase in pressure, which makes the ice plastically deform around around the feature.

Question 5

Subglacial bed deformation

Answer 5

Occurs locally when a glacier moves over relatively weak or unconsolidated rock, and the sediment itself can deform under the weight of the glacier, moving the ice on top along with it.

Question 6

Active layer

Answer 6

The top layer of soil in permafrost environments that thaws during summer and freezes during winter.

Question 7

Factors that influence the distribution of permafrost

Answer 7

Proximity to water 
Slope orientation 
Character of ground surface 
Vegetation cover 
Snow cover

Question 8

Freeze thaw weathering

Answer 8

When water freezes in the cracks and joints of rock, it expands by up to 10% its volume, weakening the rock and causing disintegration through repeated freeze thaw cycles. This process is also know as frost action or frost shattering.

Question 9

Block fields

Answer 9

Accumulations of angular, frost-shattered rock, which pile up on flat plateau surfaces. They form in situ, created by frost heaving of a jointed bedrock and freeze thaw weathering

Question 10

Tors

Answer 10

Crowns hill tops, standout from block fields as they form where most resistant rock occur

Question 11

Scree or talk slopes

Answer 11

formed when rock fragments fall and accumulate on the lower slopes or base of cliffs. The larger the material that makes up the slope, the steeper its angle of rest tends to be. Some research suggests slope is more a reflection of the rock type, length slope and fragment shape, with shale/slates ‘packing’ together.

Question 12

Pro-talus ramparts

Answer 12

Created if a patch of snow has settled at the base of a cliff. When rocks fall, as they are shattered by frost action, the snow patch acts as a buffer. The rocks settle at the base of the snow patch, leaving a rampart of boulders when the snow melts.

Question 13

Rock glaciers

Answer 13

form when large amounts of frost shattered rock mixes with ice. On the surface rock glaciers look like stream/fans or angular rocks, but they are conjoined with interstitial ice below and move slowly like glaciers, at rates of up to 1m a year.

Question 14

Nivation

Answer 14

A combination of processes weakens and erodes the ground beneath a snow patch. These processes include freeze thaw weathering, solifluction and meltwater erosion.

Question 15

How is a nivation hollow formed

Answer 15

• Fluctuating temperatures and the presence of melt water promote frost shattering.
• summer meltwater will Cary away any weathered rock debris,to reveal an ever enlarging nivation hollow.
• as long as the freshly weathered material is removed by meltwater, the nivation hollow will continue to be enlarged.

Question 16

Frost heave

Answer 16

• soil chills more slowly than rock. The water under rock freezes and forms ice lenses. The expansion of the ice then forces the rock upwards after upward dislocation.
• the upward motion creates a dome on the surface, which causes larger rocks to roll outwards .
• when the slope is less than 6° stone polygons form, if the angle is greater then stripping occurs. any Angle greater than 30° results in no pattern

Question 17

Ground contraction (ice wedge polygons)

Answer 17

• In low temperatures the ground contracts and cracks from in the soil
• In the summer cracks fill with meltwater and the following writer the water freezes and expands, which increases the size of the crack
• After many repetitions of this process the cracks grow to a lager size.
• the cracks become the polygons(5-30 cm in width)

Question 18

Solifluction

Answer 18

The downslope movement of saturated active layer under the influence of gravity. It forms a younger shaped feature at the foot of a slope