Glaciation

Question 1

What is a glacier

Answer 1

Slowly moving mass or river of ice formed by the accumulation of snow on mountains or near the poles

Question 2

Ice cap

Answer 2

Mass that covers less than 50,000 km of land area

Question 3

Ice sheet

Answer 3

Mass of glacier that covers surrounding terrain and is greater than 50,000 km2

Question 4

Quaternary period

Answer 4

Last c.2 million years

Question 5

Pleistocene epoch

Answer 5

From 11,700-1.8 million years bp

Question 6

Holocene epoch

Answer 6

Last 11,700 years

Question 7

Describe the Pleistocene

Answer 7

• at the time the continents had moved to their current positions
• sheets of ice covered all of Antarctica, large parts of Europe, North America , South America and small areas inn Asia
  -consisted of about 20 cycles of glaciers retreating and thawing

Question 8

Evidence for climate change

Answer 8

-ice cores:ice cores contain information about past temperatures and many other aspects of the environment. They enclose small bubbles of air that contains sample of the atmosphere(co2 levels indicate global temperatures at the time
-oxygen isotopes: they indicate past climatic conditions. The technique involves the ratio between heavy and light oxygen in marine sediments

Question 9

Eccentricity

Answer 9

Earths orbit moving from circular to more elliptical, changing the amount of radiation the Earth receives. Occurs every 100,000 years

Question 10

Obliquity

Answer 10

Tilt of the earths axis which affects the earths seasonal extent . Occurs every 41,000 years

Question 11

Precession

Answer 11

The direction of the earths axis rotation it affects the timings of the seasons . It occurs every 21,000 years

Question 12

Other causes of climate change

Answer 12

• volcanic activity as it lowers global temperatures
  -variations in sunspot activity as sunspot activity significantly affects our climate

Question 13

Periglacial environment

Answer 13

Cold climate typically near glacial regions,often marginal to a glacial environment and is subject to intense cycles of freezing and thawing

Question 14

List the types of permafrost

Answer 14

Continuous
Discontinuous
Sporadic

Question 15

Permafrost

Answer 15

Where the ground is frozen for more than 2 years in a row

Question 16

Continuous permafrost

Answer 16

Sheet of frozen material

Question 17

Discontinues permafrost

Answer 17

Where the permafrost melts partially, usually the lower layer remains frozen

Question 18

Sporadic permafrost

Answer 18

Occurs at margins of periglacial environments and is usually very fragmented and only a few meters thick

Question 19

Characteristics of periglacial environments

Answer 19

-found close to glacial environments
-characterised by permafrost and cycles of intense freezing and thawing
- talik( upper part ) may thaw

Question 20

Periglacial environments

Answer 20

• frost heave: the concentration and cracking of rapidly freezing soils in which ice wedges and patterned ground are formed
  -suction: the migration of sub surface water to the freezing front which causes the formation of ice lens and pingos
  -solifluction: the mass movement of the saturated active layer downslope, largely by gravity,which leads to lobes and terraces
• frost shattering(freeze thaw ): it is the 9% water expansion of water upon freezing which forms block fields and screes
  -wind erosion: high winds disturb sediment which can build up in certain areas to create loess deposits

Question 21

Formation of glaciers

Answer 21

• Snow accumulates and compacts into an upland nivation hollow.
• Over 3-4yrs, water is squeezed out of the ice, percolates down and refreezes onto the bottom of
  the glacier (firn/nevé).
• Gravity and the weight of the ice above will gradually further compact the ice until it becomes
  glacier ice.
• The glacier will then begin to flow over the lip as a result of gravity and the gradient of the
  underlying slope.

Question 22

Glacier mass balance

Answer 22

The net difference between accumulation and ablation over the course of one year

Question 23

Basal slippage

Answer 23

Lower ice melts allowing glacier to move as one body (temperate glaciers)

Question 24

Deformation

Answer 24

Individual ice crystals moving within the glacier. Ice at the surface and in the middle of glacier move faster due to less friction (temperate and polar glaciers).

Question 25

Compressional flow

Answer 25

Reduction in gradient leads to glacier de-acceleration so ice thickens.

Question 26

Extensional flow

Answer 26

Gradient becomes steeper so glacier accelerates, and ice thins.

Question 27

Rotational flow

Answer 27

Ice in cirque pivots around a point which deepens corrie floor

Question 28

Regelation creep

Answer 28

Due to pressure melting point (melting point drops below 0 degrees), water melts, flows to an area of less pressure and re-freezes

Question 29

Glacial surge

Answer 29

Excessive build up of meltwater leads to ice moving forward rapidly.

Question 30

Factors affecting rate of movement

Answer 30

-thickness : a glacier moves because pressure generated by its own weight causes it to deform and/or slide, consequently, thick glaciers often flow faster than thinner glaciers.
- temperature: : in general, temperate glaciers flow at greater velocities than polar glaciers. This is because temperate glacial ice is warmer and is therefore able to deform more easily and, further, the presence of meltwater at their base promotes basal sliding
-bedrock: more rapid movement occurs over easily deformable rock, such as clay or shale, because bedrock deformation increases the rate of basal sliding. Greater velocities also occur over impermeable rock surfaces as compared to permeable since the percolation of meltwater into permeable rock masses will reduce lubrication at the ice/rock interface and retard flow.
- gradient: glaciers with steep surface gradient flow faster than those with gentler gradients, since the former are affected by greater gravitational forces.
-bedrock permeability: temperate glaciers move faster over impermeable surfaces as basal meltwater is retained – aiding slippage.

Question 31

Erosional processes

Answer 31

Abrasion=occurs when rocks and stoned become embedded in the base and sides of the glacier. These are then rubbed against the bedrock as the glacier moved. This causes the wearing away of the landscape as the glacier behaves like sandpaper

Plucking =occurs when rocks and stones become frozen to the base or sides of the glacier and are plucked from the groud or rock face as the glacier moves. It leaves behind a jagged landscape

Question 32

3 types of glacial transportation

Answer 32

-supra-glacial:it is mainly weathered material,carried on top of a glacier
-englacial:formally supraglacial material,but now carried by fresh snowfall and carried within the ice
-subglacial:is the material carried below the ice,which is dragged and pulverised by the overlying glacier.

Question 33

List the different glacial landform environments

Answer 33

-periglacial: exist at the edges of the glaciers and can be extensive in scale.Landforms which occur here are macro scale
-glacial:within the actual physical mass of the glacier ice,forming the glacier system,wichury includes the proces of flotę ,erosion and deposition
-marginal-at the side or end of the glacier.weathering and deposition operate here to create landforms such as moraines
-proglacial-in front of ,at,or immediately beyond the margin of a glacier.Fluvioglacial processes operate here,creating outwash plains , meltwater channels and proglacial lakes.

Question 34

Causes of glacial deposition

Answer 34

• as a result of ice melt , mainly in the ablation zone
  -when the glacier lacks the energy to continue to transport the material being carried

Question 35

Glacial drift

Answer 35

Collective name for all the sediments and debris deposited under glacial conditions

Question 36

Till

Answer 36

Material directly deposited by the glacier , such as moraines and intra-glacial material dropped in situ by retreating ice

Question 37

Landforms formed by cirque glaciers

Answer 37

-cirques,arêtes and pyramidal peaks

Question 38

Landforms formed by valley glaciers

Answer 38

-u shaped valley
-truncated spurs
-hanging Valleys
-ribbon lakes

Question 39

Landforms formed by ice sheet scouring

Answer 39

-basins
-knock and lochans
-Roche moutoness

Question 40

Formation of a cirque glacier

Answer 40

Snow accumulates in a nivation hollow where nivation processes enlarge and deepen it.As more ice accumulates ,over time it forms into glacier ice and begins to flow forming a cirque glacier.Freeze thaw weathering loosens material which is entrained and gathers as sub glacial basal ice.The rotational flow of the glacier deepens it while plucking of the back wall erodes it backwards creating an armed chair shape.Deposition take place where flow is weakest and a lip can form on the edge of the cirque.when the glacier retreats and melts it often fills with water to create a tarn.
When 2 cirques erode back it creates a knife edge ridge called an arête,whereas where 3 or more erode back it creates a pyramidal peak