Location and Distribution of Cold Environments

LO: To be able to describe and located different cold environments.

Task 1Using pages 40 and 41 find definitions for the following terms:• Tundra/Periglacial• Alpine• Glacial• Ice Cap• Ice Sheet• Glacier

Task 2Using pages 40 and 41 shade the following types of cold environments on your map.• Tundra/Periglacial• Alpine• GlacialCreate a key so each area is clearly identified.

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Glacial Budgets

LO: To be able to identify how a glacier works as a system.

Task 1Using pages 44-45 (Philip Allen) and pages 48-50 (Nelson Thorne) find definitions for each of the key terms:• Mass Balance• Accumulation Zone• Ablation Zone• Equilibrium Line

• Sublimation• Steady State• Net Balance• Surge

Task 2Complete a fully annotated diagram showing a cross section of a glacier using the key terms from todays lesson.

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Ice Movement

LO: To be able to identify the different types of glacier and how they move.

Types of GlaciersWarm Based (Temperate/Alpine)• Melting occurs during the summer,

releasing meltwater.• Meltwater acts as lubricant reducing

friction at the base resulting in basal flow.• Glaciers can move between 20 and 200m

per year.• Has a large amount of erosion,

transportation and deposition.

Types of GlaciersCold Based (Polar)• Occur where the temperature remains

below 0°C and no melting occurs.• Glaciers are frozen to their bed.• Movement is through internal flow or

deformation.• Limited rates of erosion, transportation

and deposition.

Task 1Annotate your diagram adding descriptions of the following types of glaciers:• Niche• Cirque/Corrie• Valley

• Piedmont• Ice Cap• Ice Shelve

Types of Glacier Flow

LO: To be able to identify the different types of glacier and how they move.

How do glaciers move?• This all depends on the temperature of

the ice. At different parts of the glacier the ice can be at different temperatures.

• This difference in temperature is a result of the pressure melting point, this is ice that is on the verge of melting.

• At the surface this is normally 0°C, but this can be lower within the glacier due to the pressure being exerted.

Internal Deformation• Occurs within the glacier ice due to the

force of gravity.• Ice crystal align themselves in the

direction of glacier flow sliding past each other.

• Movement is faster at the surface than the base.

• Due to difference in speed, crevasses form at the faster moving surface.

Internal Deformation

Basal Sliding• The sliding of a glacier over bedrock.• Friction and pressure cause the base

to melt resulting in water acting as a lubricant.

• Can also occur due to creep, where pressure builds and the ice becomes more “plastic” and flows around the obstacle.

Compression/Extensional Flow

• Compression flow: occurs where the land is flatter causing the ice to decelerate. Resulting in the ice being thicker. High levels of erosion.

• Extensional flow: occurs where the gradient is steeper. The ice accelerates and becomes thinner, causing less erosion. This also results in crevasses and seracs.

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Erosional Landforms

LO: To be able to describe and explain the key highland erosional landforms.

What does a pre-glacial landscape look like?

What does a glacial landscape look like?

What does a post-glacial landscape look like?

How do glaciers get material?

Weathering• The main source of material is frost

shattering (or freeze-thaw). This process results in material breaking away from the surrounding mountains and falling onto the glacier. It can then be carried on the surface (supraglacial), base (subglacial) or within the glacier (englacial).

How do glaciers get material?

Plucking• When the glacier freezes on to the bed rock

and pulls material away as it moves. This can occur at the back of corries or where the glacier meets obstructions.

Abrasion• Angular material carried by the glacier rubs

at the valley side and floor gradually wearing it away. These rock can leave scratches called striations on the bed rock.

Highland Landforms

Corrie/Cirque• Snow collects in a natural hollow on

the side of a mountain. Over time, further snow collects in the hollow. This extra weight compresses the snow underneath, turning it into ice.

• The hollow is deepened and widened by the corrie glacier through the processes of abrasion and plucking.

• This over-deepening leads to an ‘armchair’ shape characteristic of a corrie and causes a ‘rock lip’ to be formed.

A Corrie in pictures! Cwm Idwal

TarnBowl-shaped corrie

Steep back-wall

Highland Landforms

Arête• An arête is a

knife edge ridge that forms where two or more corries erode back-to-back. Arete

Sharp knife edged ridge

between TWO corries.

CorrieAn arm chair

shaped hollow

widened and deepened by

a glacier.

Highland Landforms

Pyramidal Peak• Occurs where

three or more corries erode back-to-back.

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Geographical Skills: Corrie Orientation and Altitude Task

To find a corries orientation (aspect) locate a corrie on a map and find the tightest curve of contours on the back wall. Place a compass edge at right angles to the contours and turn the dial until the lines in it are aligned to the grid lines on the map.

Corrie Orientation

• What relationship did you find between elevation and orientation?

• Is there a pattern that emerges and what is it?

• How strong (statistically) is the relationship you have found?

Erosional Landforms

LO: To be able to describe and explain the key lowland erosional landforms.

Glacial Trough

• U-Shape Valley• Ribbon Lakes• Fjords• Hanging Valleys• Truncated Spurs• Roche Mountonne

Glacial Trough

Glaciers would have flowed down existing river valleys, gradually widening, deepening and straightening them. This would eventually lead to the formation of a U-Shape Valley.

Glacial Trough

Glacial troughs have a stepped profile, and typically have a steep back wall called a trough end. Above this you may find hanging valleys and corries.

Ribbon Lakes Where compressing flow took place or at the confluence of glaciers, erosion would be greater. This would over-deepen the valley forming a rock basin. Where the rock basins are filled with water you find elongated Ribbon Lakes (such as Wast Water in the Lake District).

FjordsFjords are glacial troughs that have been filled by water, as the sea level has risen since the end of the last glaciation. Since the last glaciation sea level has risen by almost 120m. Fjords are a common feature on the coast of Norway.

Hanging Valleys

In these valleys the glaciers were smaller and had less erosive power, meaning they did not erode the rock down to the same level as the main glacier. When the main valley glacier retreat, they were left hanging above the main valley floor. (Example: Milford Sound, NZ)

Hanging Valleys

Truncated Spur

Is the straightening of former pre-glacial river valleys. Any land (spurs) that projected in to the valley being removed.

Roche MountonnéeAre sections of bedrock which have been eroded by glaciers moving over the top of them. They have a gently sloping, polished, stoss slope as a result of abrasion. The lee slope is steep and jagged due to plucking taking place as a result of refreezing.

Roche Mountonnée

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Depositional Landforms

LO: To be able to describe and explain the key depositional landforms.

Till

Till (or boulder clay) is the generic name for material that has been transported and deposited by a glacier. Material can range in size from some particle to large house sized boulders. It is often angular in shape, and when deposited it is orientated showing the direction of glacier flow. It can be deposited in a variety of ways producing a range of features.

Till

Lodgement Till• Material deposited at the base by a

moving glacier (e.g. a drumlin).Ablation Till• Material deposited as a result of ice

melting (e.g. recessional or terminal moraine).

Till Fabric Analysis

AimTo determine the origin of the sediment deposit.HypothesisThe sediment is of fluvial origin.

Pebbles in a river are rolled along their ‘B-axis’. Therefore when they are deposited many of the pebbles will have their ‘A-axis’ orientated across the river. A glacier, on the other hand, carries pebbles frozen within the ice. They are transported with the A-axis orientated in the direction of ice flow.

Sediment Orientation

Till Fabric Analysis: Plenary

• What conclusions can you draw about the origins of the sediment in Glen Rosa?

• How did you come to this decision? Explain your ideas.

Depositional Landforms

LO: To be able to describe and explain the key depositional landforms.

Moraines

• Moraines are features deposited at the margins of glaciers. They occur in a variety of different place, and can represent a glacial advance or retreat.

• The main types of moraine are lateral, medial, terminal, recessional and push moraines.

Types of Moraine

• Terminal• Recessional• Push• Lateral• Medial

Moraines

Terminal Moraine• Is a ridge of material stretching

across the valley at right angle to the movement of the glacier, often in the shape of a crescent. They are steep side on the glacier side and can reach up 60m in height.

Moraines

Recessional Moraine• Are ridges deposited across the valley

as the glacier has stagnated during retreat. These are often parallel to terminal moraines.

Push Moraine• Are moraine that have been reworked

as a result of a glacier re-advancing during cold periods.

Moraines

Lateral Moraine• Are formed from material deposited at the

sides of glaciers and are parallel to the direction of glacier movement. They are often made of material that has fallen from the valley sides.

Medial Moraine• Where two glacier meet the lateral

moraines combine and form a feature between the two glaciers.

DrumlinsDrumlins are asymmetrical elongated mound of till. They can vary in size from 50m to 1km in length. It is believed that they are formed beneath a glacier by the pressure of ice at a time when the glacier could not carry material. They are orientated in the direction of glacier flow. They have a steep stoss end and a shallow lee slope. They often appear in swarms.

Erratics

Are rocks and material carried hundred of kilometers by a glacier and deposited on top of a different rock type.They are said to be ex situ (not in the correct place).

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Fluvio-glacial Processes

LO: To be able to describe and explain fluvio-glacial processes and landforms.

Outwash Plain/SandurAn outwash plain is the area in front of the glacier where meltwater streams flow. The gravels, sands and clays carried by the streams are deposited. The larger material is found close the glacier whereas the finer clays are carried further away.They may also be made up of other depositional features (such as moraines and eskers), which have been reworked by the streams.

The Role of Meltwater

During summer when ablation is at its greatest on temperate glaciers, vast rivers form. These can be fed by both subglacial and supraglacial streams. These rivers have a high velocity and can carry large amounts of sediment.In subglacial streams where there is greater pressure they can carve subglacial valleys up to 15m deep.

As the discharge in outwash streams decreases material is deposited forming many features including eskers, kames, outwash plains and (in lakes) varves.

Skeiðarársandur in Iceland is the largest outwash plain in world, covering an area approximately 1300km2. It also has many classic depositional features.

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Assess the role of meltwater erosion and deposition in the formation of fluvioglacial landforms. (8 marks)

MARK SCHEME

Eskers

EskersAre sinuous, stratified ridges of sediment running parallel to the flow of the former glacier. They can range in height from 5 to 20m.

Eskers were formed by subglacial streams as a result of the streams being cut off or the water supply slowly being reduced as ablation decreases.As the glacier retreats the ridge is left behind, they are often destroyed by erosion due to outwash streams.

Kames and Kame Terraces

Kames and Kame TerracesKame• Are deposits of sand and gravel left by streams

in small ponds at the front of a glacier or in crevasses on the glaciers surface. When the ice melts these collapse to form irregular mounds.

Kame Terrace• Are formed at the sides of glaciers where layers

of material are deposited by streams between the glacier and valley sides. When the glacier melts the material forms a terrace raised above the valley floor.

Kettle Holes

Kettle HolesWhen a glacier retreats it often leave blocks of dead ice which can be buried beneath fluvio-glacial deposits. Gradually the ice slowly melts and leaves a depression in the outwash plain. Depending on the level of the water-table this can be filled with water, resulting in a kettle lake. They are often associated with kames to produce a kame and kettle topography.

Proglacial Lakes

Proglacial LakesProglacial lakes form at the margins of glaciers. They often fill the over-deepened basin that has been left as glaciers retreat. They are filled as meltwater drains from the glacier. These lakes can be dammed by moraines, dead ice or other glaciers and occasionally cause catastrophic flooding, such as in the Himalayas and the Andes.

Within proglacial lakes (a lacustrine environment) sediments are deposited which form distinct characteristics and are known as Varves.During the spring and summer, when streams have more energy, larger, light coloured sand is deposited. In the autumn when discharge decrease the streams carry only darker coloured silt and clay. These can only be deposited in low energy environments.

Braided Streams

Braided StreamsWhen glacial ice melts, the water moves away from the glacial snout in fast flowing rivers. The water transports vast quantities of sediment and debris. If the sediment load is very large in relation to the velocity of the stream, the coarse material may start to block the stream, forcing it to change its course. The stream starts to diverge, splitting into numerous segments which split and join repeatedly. Braided streams are typically shallow and wide, surrounded by poorly sorted rock debris.

Periglacial Processes and Landforms

LO: To be able to describe and explain periglacial processes.

Periglacial Environments

Periglacial environments are areas which are exposed to extremely cold conditions with intense frost action, and have permanently frozen ground or permafrost.These regions have consistently low temperatures, short summers (max temp 15°C), and extremely cold winters (reaching -40°C).

PermafrostOccurs where the temperature of the subsoil remains below 0°C for at least 2 years. It is thought that permafrost covers 25% of the earths surface including areas such as Siberia, Northern Canada, Alaska and ChinaIf the temperature rises above 0°C in the summer the surface layer (up to 3m deep) can thaw, forming an active layer. As the ice melts this releases water in to the layer. Due to the frozen ground below the water cannot drain, saturating the ground leading to solifluction.

Types of PermafrostContinuous PermafrostFound in the coldest areas and can be extremely deep (up to 1500m in Siberia). Often there is little or no melting of this type of permafrost.Discontinuous PermafrostFound in slightly warmer regions, only the upper 20-30m of land is frozen. Gaps in the permafrost can be found under rivers, lakes and near the sea.Sporadic PermafrostFound where temperatures fluctuate around 0°C. This results in isolated patches of permafrost, where localised climatic conditions prevent thawing in the summer.

Continuous permafrost occurs in northern Russia, Canada, Alaska and Greenland.Discontinuous permafrost extends to 50°N in Siberia and East Canada.Sporadic (Alpine) permafrost occurs at very high elevations as far south as 30°N.

Freeze Thaw

In periglacial environments freeze thaw results in the build up of scree at the base of slopes as a result of frost shattering. In flat areas large angular boulders can be left known as blockfield or felsenmeer (sea of rocks).

Nivation

Takes place under patches of snow in hollows of bare rock, generally on north to east facing slopes. This can result from a variety of processes including; freeze-thaw, chemical weathering, solifluction and meltwater. The underlying rock disintergrates, then during the spring thaw loose material is carried away. This leaves a nivation hollow, which could eventually lead to a corrie.

SolifluctionSolifluction occurs when the surface layer of permafrost melts. Due to saturation the soil is heavily lubricated. This means on slopes as shallow as 2° the active layer begins to move downslope. This creates tongue like features forming terraces called lobes or solifluction sheets.

Frost Heave and Patterned Ground

Frost Heave and Patterned Ground

When the active layer refreezes, ice crystals begin to form. As they expand the volume of the soil increases and causes an upward expansion of the surface causing the surface to dome.Within the soil there are larger stones, these heat up and cool faster than the surrounding material. As a result the ground beneath the stones freezes faster and expands before the other material, pushing the stones towards the surface. The stones then roll to the bottom of the dome.

Frost Heave and Patterned Ground

This forms patterned ground. On shallow slopes (<6°) stone polygons are formed, on steeper ground they form stone stripes.

Groundwater Freezing: Pingo

When permafrost is thin or discontinuous, water can seep in to the upper layers of the ground. When it freezes it causes the overlying ground to heave upwards in a dome shape, called a pingo. They can reach height of up to 50m and be up to 500m wide.They are often found in sandier soils in area such as Greenland and are referred to as open system types.

Groundwater Freezing: Pingo

Groundwater Freezing: Pingo

Closed system pingos are typical of low lying areas with continuous permafrost. On the site of small lakes, ground water can be trapped by freezing water from above and by the permafrost below. As the water freezes and expands it pushes up the sediment above forming a the pingo. The center can collapse and may be in filled with water to form a small lake.

Ground Contraction

Freezing of the active layer causes the ground to contract and cracks open on the surface. During the following summer these cracks fill with meltwater and fine sediment. Over many years this repeats and forms an ice wedge, which can be up to 3m deep and 1m wide. On the surface polygon patterns can be formed by frost heaving.

Ice wedges in continuous permafrost, arctic Canada

Water and Wind ActionDue to the lack of vegetation rates of erosion by wind and water in periglacial landscapes can be very high.Water erosion results from seasonal streams which have a high discharge as a result of the water released form the active layer.In periglacial areas winds can reach high velocities, these winds carry material causing abrasion on the surface of bare rock, polishing and shaping them (ventifacts). Winds can also carry fine material from outwash plains long distances, resulting in deposits up to 300m thick (loess).

Groundwater Freezing

Groundwater Freezing: Pingo

Antarctica and the Southern Ocean

To understand where Antarctica is and why it is a special place.

Assess the threats and uses of Antarctica as a resource for exploration and exploitation

What and where is Antarctica?

Page 79 and the Atlas

Watch the clip and note down all of the physical and human features of Antarctica

• http://uk.youtube.com/watch?v=TemK6CF6lF0

• http://uk.youtube.com/watch?v=VwADGPfjerI

Fishing and WhalingProduce a timeline of fishing and whaling in the

Southern ocean using pages 79 and 80Date Event

1786

1830

1868

1925

1930s

1950

1960s

1964

1966

2008

Why are Krill so important to the Southern Ocean food chain? (page 80/1)

Tourism in Antarctica

1. What attracts tourists to Antarctica?2. How do they access this place?3. What has happened to the number of

tourists over time? (use the graph to help)4. What impact does tourism have on this

environment?5. Is tourism well managed in this region?

Opinion Line

• The Madrid Protocol, Banning Mining, should be scrapped

• It is justifiable to allow whaling• Antarctica remains a wilderness• Tourism to Antarctica should be banned• Tourism to Antarctica should be restricted

Homework

• Visit www.coolantarctica.com and research the facts and science section, look at the photographs as well.