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Glaciated Landscapes Flashcards

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1
Q

What are the characteristics of a glaciated landscape?

A

Formed by the action of glaciers
Include areas glaciated in the past
Usually classified as erosional/depositional
Glaciers now exist at high latitudes and high altitude

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2
Q

How can glaciated landscapes be viewed as systems?

A

Based on relationships within a unit - stores, processes, connections of energy/materials in varying timescales.
Open system - energy and matter can cross the boundary of the system to the surrounding environment

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3
Q

What are the energy inputs of the system?

A

Kinetic energy from wind/movement of ice
Thermal energy from the heat of the sun
Potential energy from material on slopes and processes of weathering, mass movement and deposition

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4
Q

What are the outputs of the system?

A

Glacial and wind erosion from rock surfaces - evaporation, sublimation and meltwater

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5
Q

What are the transfers of the system?

A

Stores of ice, water, debris
Flows of ice, water, debris under gravity

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6
Q

What does the system combine to form?

A

a distinctive landscapes made up of erosional and depositional landforms created by geomorphic processes and human activity

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7
Q

What do we mean when the glacier is in a state of equilibrium?

A

the inputs and outputs are equal (glacier will remain the same size)

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8
Q

What is positive feedback?

A

initial change bringing about further change away from equilibrium

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9
Q

What is negative feedback?

A

system returns to equilibrium

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10
Q

What is feedback?

A

self-regulation will occur to restore equilibrium

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11
Q

What is mass balance/glacier budget?

A

The difference between the inputs and outputs over a year

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12
Q

What are the inputs of the budget?

A

(accumulation) - direct snowfall, blown snow and avalanches

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13
Q

What are the outputs of the budget?

A

(ablation)- mass lost by melting and evaporation (gravity).

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14
Q

What are the zones of acccumulation/ablation and where are they found on the glacier?

A

Zone of accumulation - upper part of glacier, accumulation > ablation
Zone of ablation - lower part of glacier, accumulation < ablation

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15
Q

What is the equilibrium line?

A

boundary between the zone of accumulation and ablation

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16
Q

How do seasonal variations affect mass balance?

A

Seasonal variations - accumulation > ablation winter, ablation > accumulation summer. Weather changes from year to year cause variations over time. Long term natural climate fluctuations can cause large timescale changes

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17
Q

How does climate affect glaciated landscapes (PF)

A

Wind (aeolian processes)- picks up material and uses these in erosion, deposition, and transportation
Precipitation - provides snow, sleet and rain input - large seasonal variation
Temperature - affects inputs and outputs. Increased temperature causes melting. High altitude areas may be summer melting and high latitude may never exceed 0.

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18
Q

How does geology affect glaciated landscapes (PF)

A

Lithology - chemical and physical composition of rocks. Effects impacts of weathering, erosion and mass movement processes.
Clay - weak - erosion effective
Limestone vulnerable to chemical weathering due to calcium carbonate
Structure - existence of joints, bedding planes and faults. Permeability - primary permeability when a rock has pores that can absorb and store water e.g. chalk. Secondary permeability - water seeps into joints and cracks e.g. limestone. Angle of dip - e.g. horizontal strata results in steep profiles

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19
Q

How does latitude and altitude affect glaciated landscapes (PF)

A

High latitudes - e.g. Arctic/Antarctic, cold, dry climates - landscapes develop under stable ice sheets
Low latitude but high altitude - develop under dynamic valley glaciers e.g. Rocky Mts.

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20
Q

How does relief and aspect affected glaciated landscapes (PF)

A

Microclimate - affected by relief and aspect, steep relief = more energy due to gravity
Aspect - away from sun means temperatures remain lower for longer so less melting - positive balance. Facing sun means more melting

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21
Q

How does glacier ice form (nivation)?

A

Snow falls as flakes, creating low density layer
Where temperatures are low enough for snow to remain frozen annually, the lower layers compact to neve/firn.
Further compassion over 30-1000 years - air is forced out and ice formed (diagenesis).

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22
Q

What is the difference between a valley glacier and an ice sheet?

A

Glaciers - contained within valleys - outlets from ice sheets/fed from corries, follow course of existing valley
Sheets - large accumulations of ice with area >50,000km2 Antarctica and Greenland

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23
Q

What are the characteristics of a warm based glacier and where are they found?

A

Warm - occur in temperate areas e.g. Norway and Iceland
Small (metres to kms)
High rates of ablation in summer = more meltwater
Meltwater lubricates glacier causing more movement and so more erosion, deposition and transportation (movement of 20-200m per year)
All ice is at or above pressure melting point (temp at which ice melts when under pressure. Pressure caused by ice mass leads to ice melting at temps below freezing)due to warmer atmospheric temperature, weight of the ice and effect of geothermal heat in bedrock

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24
Q

What are the characteristics of a cold based glacier and where are they found?

A

Cold - polar areas e.g. Arctic and Antarctic
Vast ice caps and sheets cover hundreds of km2
Areas of low precipitation and snow - low levels of accumulation and no melting
All ice has temperature below pressure melting point
Little meltwater - slow movement (few metres per year)
Glacier often frozen to bedrock - less erosion, transportation and deposition

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25
Q

What are basal sliding and internal deformation affected by and what are the different zones of the glacier?

A

Move due to gravity but influenced by:
Gradient - steeper gradient = more movement
Ice thickness - affects basal temperature and pressure melting point
Balance - positive balance causes advance
Upper zone - ice is rigid and brittle so breaks to form crevasses
Lower zone - ice deforms due to pressure
Top and middle move more rapidly than the sides and base due to frozen areas and friction

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26
Q

Describe basal sliding, what type of glacier?

A

Warm based glaciers
Slippage - circular motion that can cause ice to move away from back wall/hallows
Creep - slow downwards movement of loose rock and soil down a gentle slope
Bed deformation - movement of soft sediment beneath ice. More effective in temperate areas as underlying material is water saturated

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27
Q

Describe internal deformation, what type of glacier?

A

Cold based glaciers
Intergranular flow - individual ice crystals move relative to each other
Laminar flow - individual ice crystals move along layers within the glacier

28
Q

How are glacial landforms developed?

A

A variety of interconnected climate and geomorphic processes

29
Q

Describe the 3 processes in mechanical weathering

A

Freeze thaw - water enters cracks, freezes and expands 10% - pressure causes split
Frost shattering - low temperatures water in pores freezes and expands - disintegration
Pressure release - weight of overlying ice falls due to melting - rock expands and fractures

30
Q

Describe the 5 processes in chemical weathering

A

Oxidation - some minerals will react with oxygen from air or water
Carbonation - rainwater dissolves CO2 from atmosphere to produce carbonic acid which reacts with calcium carbonate
Solution - mineral dissolves in water
Hydrolysis - chemical reaction between rock minerals and water
Hydration - water molecules added to rock minerals to create new larger minerals

31
Q

Describe the 2 processes in biological weathering

A

Tree roots - grow into cracks/joints and exert outwards pressure
Organic acids - produced during plant decomposition and animal litter cause soil water to become more acidic and react with minerals - chelation

32
Q

What are mass movement processes and what are the 2 different types?

A

The movement of above ground material (regolith) down a slope
Rockfall - slopes of 40 degrees or more - material falls to base of of the slope by gravity
Slides - may be linear with movement along a fault or bedding plane, or rotational with movement along a curved or slip plane

33
Q

What is mass movement dependent on?

A

Dependent on: slope angle, particle size, temperature, saturation

34
Q

Which 3 processes work together to erode advancing glaciers?

A

Abrasion - material embedded in the glacier rubs away at the valley sides and floor. Striations left behind. Fine debris is called rock flour
Plucking - glacier freezes on and into rock. As ice moves it pulls away the rock. Mainly happens at the base where jointed rocks have been weakened by freeze-thaw action - jagged left
Nivation operates under patches of snow - freeze-thaw and chemical weathering loosen rock with meltwater removing debris. This repeated melting/freezing forms nivation hollows

35
Q

What are advancing erosional processes affected by?

A

presence of basal debris, debris size and shape, hardness of particles, ice thickness, basal water pressure, sliding of basal ice, movement of debris at the base, removal of fine debris

36
Q

What is glacial transportation and what are the 3 types?

A

Carry large amounts of debris which can come from wide range of sources such as rock falls, avalanches, debris flow, aeolian deposits, eruptions, plucking and abrasion
Supra-glacial - movement on the surface
En-glacial - movement within the ice
Sub-glacial - movement at the base of the glacier

37
Q

What is glacial deposition and where does it occur?
What is till?

A

Where ice melts at the snout, material is deposited
Drift →till or outwash →till becomes lodgement till (pressed into floor in advance) or ablation till (left behind during retreat)
Till - angular, unsorted, unstratified vs outwash - smooth, sorted, stratified

38
Q

What are corries and what are the 5 steps in its formation? Erosional/depositional?

A

Armchair shaped rock basins with rock lip that occur on north/east slopes due to less insolation and greater accumulation
1. Nivation on mountains creates a small hollow, this collects snow and enlarges annually. At a critical depth the ice rotates
2. Plucking steepens the back wall and adds debris - retreats due to freeze-thaw weathering
3. Abrasion occurs at the base as it flows forward and down - deeper depression
4. Meltwater and debris from freeze-thaw weathering above the corrie glacier drop down a deep crevasse that opens up between the glacier and back wall - causes movement as lubricates base causing more abrasion
5. Glacier rotates and more erosion deepens basin, at the outlet, ice moves upwards so less erosion forms a lip
erosional

39
Q

What are aretes? Erosional/depositional?

A

Sharp ridge formed where two corries erode back-to-back or alongside each other
erosional

40
Q

What are pyramidal peaks? Erosional/depositional?

A

Back walls of three or more corries erode a hill or mountain top, the back walls meet to create a sharp central mass
erosional

41
Q

What is a glacial trough? Erosional/depositional?

A

Troughs are formed when glaciers flow down pre-existing river valleys. Deepen and change the v-shape to a u-shape. Straight, wide-based, steep-sided
erosional

42
Q

What is a hanging valley? Erosional/depositional?

A

result of the valley of a tributary being eroded at a slower rate than main river
erosional

43
Q

What are roche moutonnees? Erosional/depositional?

A

Ice, meltwater and sub-glacial debris combined have huge erosive power forming:
Areas protruding from the river valley sides (spurs) removed forming truncated spurs
Areas of resistant rock on the valley floor are not completely removed and left as RMs, smooth up-valley side created by abrasion and jagged down-side due to plucking.
erosional

44
Q

What are striations and what do they indicate? Erosional/depositional?

A

Scratches or grooves made by debris embedded in the base of the glacier
Indicate the direction of ice flow
erosional

45
Q

What are ellipsoidal basins and how are these different to other landforms? Erosional/depositional?

A

Formed by an ice sheet
Huge erosional depressions in the landscape created by the erosive action of ice sheets such as the Laurentide Ice Sheet
erosional

46
Q

What are moraines (3 types) and how are they made? Erosional/depositional?

A

Landforms created when debris carried by glacier is deposited
Lateral - from frost-shattering of valley sides, carried at the edge of the glacier, when melting happens a side embankment is formed
Terminal - high mound extending across the valley to mark the maximum advance
Recessional - mark an interruption in the retreat of the ice
depositional

47
Q

What are erratics? Erosional/depositional?

A

Individual pieces of rock picked up and carried by ice over kms to be deposited in areas with different geology. Pebble → boulder
depositional

48
Q

What are drumlins and how are they thought to be created?
Erosional/depositional?

A

Smooth, elongated mounds of unsorted till (rock, clay, sand). Long axis runs parallel to ice flow and often found in swarms
Only theoretical theories but could include
Logement of subglacial debris, reshaping of previously deposited material by ice, material accumulating around an obstruction, deposition of material as ice thins
Depositional

49
Q

What are till sheets? Why are they different?Erosional/depositional?

A

Huge, wide, flat areas where there is a covering of till (sand/gravel).
Composition varies and depends on nature of rock the ice has moved over
Created by ice sheets
depositional

50
Q

How do glacio-fluvial landforms evolve over time as climate changed?

A

Glacio-fluvial landforms exist as a result of climate change - produced by meltwater during deglaciation - high velocity flow - loss of energy due to decrease in discharge causes deposition

51
Q

What are the 2 main geomorphic pocesses that change in interglacial periods?

A

When global temperatures rise, glacial periods end and interglacial periods begin 10,000-15,000 years. Rivers deposit outwash:
Small pieces of material carried by meltwater streams which have less energy than ice
Smooth and rounded particles
Sorted - larger material further up valley
Stratified vertically with distinct seasonal and annual layers
Sudden melting can cause high discharge - large amounts of sediment deposited (jokulhlaup)

52
Q

Are glacio-fluvial landforms erosional or depositional?

A

Depositional

53
Q

What are Kames (2 types) and how are they formed?

A

Undulating, winding mounds of unevenly deposited sand and gravel that follow ice movement
Delta - englacial streams emerge at snout - lose energy and deposit. Supra-glacial streams flow to the edges of glaciers and flow into lakes at ice margin. Stream loses energy as it meets static water and deposits
Kame terraces - supra-glacial streams on the edge of a glacier pick up and carry lateral moraine material, gets deposited when glacier retreats (rounded and sorted)

54
Q

What are eskers and how are the formed?

A

Long, narrow ridges of sorted and stratified course sand and gravel
Form when water in subglacial tunnels deposits what it is carrying when glacier melts and retreats
Deltaic deposits left when meltwater flows into a lake trapped by moraine deposits

55
Q

What are outwash plains and how are they formed (include braided streams)?

A

Large flat areas which contain deposits from pro-glacial streams and meltwater streams running out from the snout of the glacier - course material - found near to end of glacier and finer clay - carried across the plain and deposited
Meltwater streams that cross the plan are braided (divide as the channels become clogged) - kettle holes formed when blocks of ice that have been washed onto the plain melt and leave a gap in the sediments

56
Q

How are landforms modified by changes in climate?

A

Repeated retreat and advance of ice
Geomorphological processes such as weathering and erosion
Colonisation of vegetation in post-glacial times e.g. mosses/grasses
Rising temperatures lead to more melting and further expanses of outwash

57
Q

Why do periglacial landforms exist, what are they and where are they found?

A

a result of climate change
Areas with - permafrost (permanently frozen soil and regolith) discontinuos/sporadic, seasonal temperature variations with a brief ‘summer’ above 0, freeze-thaw cycles as dominant process
Found in high latitudes and altitudes

58
Q

What is frost heave?

A

Below the surface and leads to vertical sorting of material in the active layer
Stones in active layer heat up and cool down faster than surroundings
Water beneath the stones freeze and expand pushing stones to the surface

59
Q

What is ground ice?

A

During summer melting, water percolates down to subsurface geology
During winter months this freezes and expands 10% pushing ground surface up

60
Q

What is patterned ground and how is it formed?

A

Frost heave pushes larger stones to surface
Ground is domed so stones roll down to edges due to gravity - pattern of a network of stone polygons, on angled slopes polygons becomes stretched and enlarged into garlands

61
Q

What are pingos?

A

Dome shaped hill with core of ice two types

62
Q

How are closed system (MacKenzie Delta Type) pingos formed?

A

Found in areas of continuous permafrost
develop beneath lake beds
ice core growth is hydrostatic
Deep lakes over 2m may remain unfrozen in winter
Permafrost layer at lake bed insulated from cold and thaws
Area of unfrozen waterlogged ground now sandwiched between lake and permafrost
Lake drains - bed no longer insulated so waterlogged bed freezes
Localised differences in pressure between the lake, freezing lake bed and permafrost causes newly freezing water together forming an ice lens that expands, pushing the lake-bed sediments above it in a dome shape
Ice lens continues to grow as long as there is still unfrozen ground in the lake based as a source of pressurised water to add to the core

63
Q

How are open system (East Greenland Type) pingos formed?

A

Areas of discontinued permafrost
Found in valley bottoms
Growth of ice core is hydraulic
Water seeps into upper layers of ground and flows from higher surroundings areas under artesian pressure
Water accumulates in flat, low-lying areas between the upper areas of permafrost or soil and frozen ground beneath the water and freezes
Freezing ice core expands doming the overlying layers
Grow as pressurised water continues to flow in from surroundings

64
Q

What is solifluction and how does it alter periglacial environments?

A

Slow flow of saturated regolith down a gradient
Summer melt of water in upper layers of permafrost leads to large amounts of water which can’t drain due to permafrost.
Lubrication means soil is moved on slopes
Mass movement (soil creep) makes frost heave domes less obvious

65
Q

What does a rise in temperature change in periglacial environments?

A

Rise in temperature causes colonisation by vegetation
Pingos thaw and collapse, creating circular depressions called ognips

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