3.1.3.4 Glacial Landscapes in the UK Flashcards
What was the glacial environment like in the UK?
- Snow and ice covering much of the landscape - very much part of the UK during the last ice ago
- Consistently low temperatures, barely getting above freezing
- Development of significant amounts of snow and ice leading to the formation of large glaciers and an ice sheet across the UK
- Huge glaciers radiated from the north and west and carved deep glacial valleys and troughs. Further east the land was permanently frozen with some meltwater rivers
What was a powerful force in the shaping of the physical landscape of the UK?
ice was a powerful force in the shaping of the physical landscape of the UK
In the last glacial period where did ice extend to?
- During the last glacial period ice advanced south in the Northern Hemisphere to cover large parts of Europe and North America
- In the last glacial period, the ice coverage across the UK reached its maximum extent around 18,000 years ago
- In the UK the ice spread as far south as the Severn estuary
- Southern England would have been completely frozen - like parts of northern Canada today
What happens between glacial periods (within an ice age)?
Between the glacial periods there were warmer interglacials which were at least as warm as today’s climate if not warmer
When did the UK experience an ‘Ice Age’ and what has this formed today?
- 2.5mn - 11,300 yrs ago - UK experienced a succession of glaciations - the ‘Ice Age’
- much of UK was periodically covered by ice sheets (glacial period) spreading from Scandinavia
- glaciers carved deep valleys forming today’s mountain landscapes e.g. The Lake District
Which part of the UK remained ice free during the Ice Age?
- only far south of UK remained ice-free
- temperatures here were low and the ground frozen (permafrost) for much of the year
Ice age:
a period of long-term cooling of the Earth’s atmosphere, resulting in the expansion of ice sheets and glaciers
When was the most recent ice age?
most recent ice age, the Pleistocene, began about 2 million yrs ago
What period are we currently in?
We’re currently in an interglacial period that began around 10,000 years ago
What % of the Earth’s land surface is covered by ice and how does this compare to 20,000 years ago?
- Today about 10% of the Earth’s land surface is covered by ice – the only ice sheets are the ones on Greenland and Antarctica
- Ice covered a lot more of the land around 20,000 years ago (during the last glacial period) – over 30% of the Earth’s land surface was covered by ice, including nearly all of the UK
Glacial processes:
- freeze-thaw weathering
- erosion
- movement and transportation
- deposition
What is the main weathering process in cold environments?
freeze-thaw weathering
Freeze-thaw weathering:
- water collects in cracks or holes (pores) in the rock (usually in Summer as there is more liquid water available unlike in Winter due to freezing temperatures)
- as temperature drops at night, this water freezes and expands
- this puts pressure on the rock at the side of the crack - makes crack in the rock bigger
- when the temperature rises and the ice thaws, water will seep deeper into the rock
- this process repeats many times
- eventually pieces of rock break off
Why is freeze-thaw weathering an important process in glacial environments?
- helps to shape jagged mountain landscapes
- rocks become weakened by freeze-thaw weathering making it easier for them to be eroded by glaciers
- piles of large angular rocks, called scree, collect at the foot of mountains - become powerful erosion tools when trapped under moving glaciers (abrasion)
Crevasse:
a deep, open crack found in a glacier
Diagram of freeze-thaw weathering:
Abrasion in glacial environments:
- the ‘sandpaper’ effect caused be the rocks within the ice scouring the valley floor
- abrasion leaves a smooth, polished surface
- scratches (striations) caused by large rocks beneath the ice can often be seen
Plucking in glacial environments:
- when meltwater beneath a glacier freezes and bonds the base of the glacier to the rocky surface below (like glue)
- as the glacier moves, loose fragments of rocks are ‘plucked’ away
- this process leaves behind a jagged rocky surface
Striations:
sharp, straight lines found in the valley where sharp rocks have grinded their way along
Diagram showing glacial erosion:
2 main ways that glaciers move:
- rotational slip
- basal slip
Rotational slip:
- where ice moves along a curved surface to enlarge and develop hollow
- in hollows high up - movement is more curved
Basal slip:
- in the Summer, meltwater acts as a lubricant to the the glacier enabling it to slide downhill
- this type of movement can be quite sudden - occurs more in Summer months
Internal deformation:
- In the winter, the glacier becomes frozen to the rocky surface
- The sheer weight of the ice and the influence of gravity cause individual ice crystals to change shape in a plastic-like way
- This process is known as internal deformation and causes the glacier to move slowly downhill
How do glaciers transport material?
- Rock fragments resulting from freeze-thaw eroded by the ice are transported by the glacier
- This sediment (called moraine) can be transported on the ice, in the ice (buried by snowfall) and below the ice
- As the glacier moves forwards it pushes loose debris ahead of it - transporting it down the hill - bulldozing
How do glaciers form and move?
- Snowflakes fall and accumulate in a hollow in the mountainside
- With more snowflakes, the weight compresses the snow together to form firm - a very firm type of snow
- As more snow falls and more weight is added this firm turns into ice
- The ice appears blue because of all the air that is squeezed out under pressure
- If ice does not melt and snow continues to fall, the glacier becomes bigger and heavier
- Then the force of gravity causes this large ice mass to move downhill very slowly
- As the glacier moves it erodes the valley on either side and underneath it, altering the landscape
Where is deposition of material carried by the glacier usually found and when does this happen the most
- as deposition occurs when ice melts and most melting occurs at the front/snout of the glacier
- deposition of material carried by the glacier is usually found at the snout
- during Summer as temperatures are higher - meltwater pours off the snout of some glaciers
How does glacial deposition occur?
- As a glacier slowly retreats is leaves behind a bed of broken rock fragments called till
- Due to the lack of water to transport it, till is poorly sorted with jagged rock fragments of all sizes - till is also known as boulder clay
OR
- Renewed further movement of the glacier pushes the material found at the snout downhill (bulldozing)
- This build up of sediment can form a hummock (small mound of sediment)
How does deposition occur ahead of the glacier?
- Ahead of the glacier, meltwater rivers will carry sediment away
- This process of attrition will cause rock fragment to become smaller and more rounded
- Sediment is well sorted with larger rocks deposited close to the ice and finer material carried many kilometres away
- This sandy and gravel material is called outwash
What does constant transport of new, debris laden ice into lowland areas result in?
- Constant transport of new, debris laden ice into lowland areas results in the widespread deposition of all of the eroded and weathered material from the uplands
- This deposited material is known as glacial till
Till:
- poorly sorted debris carried by the ice and then deposited when the ice melts
- will comprise of a range of particle sizes and will tend to be angular and having had little water transport
- outwash - carried by meltwater streams - tends to be more rounded and better sorted, with gradually finer material being deposited with distance away from the ice front
Moraine:
deposited material from a glacier
What do distinctive glacial landscapes result from?
distinctive glacial landscapes result from different physical processes
What can create spectacular landforms in mountainous areas?
- ice very powerful agent of erosion
- can create spectacular landforms in mountainous areas
Corrie:
- also known as cirques or cwms
- a deep hollowed-out depression found in a hillside in the upper course of glaciated valleys
What are corries characterised by?
- steep back wall and sides (still freeze-thaw in Winter)
- raised ‘lip’ at the front
- may contain lake - called a tarn
- jugged summit
- deep rock basin
How are corries formed?
- Snow accumulates in a sheltered hollow on a hillside
- Nivation (snow-related processes e.g. freeze-thaw weathering, meltwater and slumping) enlarges the hollow enabling more snow to collect
- Gradually the snow is compressed into ice and a small corrie glacier is formed
- Through rotational slip, (where meltwater lubricates the glacier) the glacier slides down and gouges out the deep hollow and through abrasion the glacier deepens the hollow
- The glacier steepens the back wall through plucking
- Reduced erosion at the front of the corrie, due to the ice being thinner and less erosive, forms a raised lip - sometime moraine may be deposited here
- A tarn (corrie lake) may form in the bottom of the corrie
- After the glacial period the corrie would have a jagged summit, steep back wall (still freeze-thaw in Winter - creates deposits of scree), scree, corrie lake (tarn), deep rock basin and a rock lip (can have moraine on top)
Diagram to show the formation of corries:
Arête:
- an arête is a knife edge ridge, steep drop on either side
- are often found at the back of a Corrie or separating two glacial valleys
How are arêtes and pyramidal peaks formed?
- forms when erosion in two back to back corries causes the land in between to become narrower
- if three or more corries have formed on a mountain, erosion can continue to lead to the formation of a single peak - pyramidal peak
Diagram of arêtes and pyramidal peak:
What do most glaciers flow along?
- most glaciers flow along pre-existing river valleys
- unable to flow around obstacles glaciers carve straight courses
Diagram of glacial valley landforms:
Ribbon lakes:
long, narrow lakes, often tens of metres deep, occupying a U-shaped valley
How do ribbon lakes form?
- Long and thin lakes that collect from melt water and rain water after the glacier has melted
- During glaciations the glacier erodes some parts of the valley floor more than others - this could be because of varying strengths of the bedrock or because there is thicker ice in one region of the glacier than another or because there is more sediment abrading the ground in one region than another
- When the glacier melts, water fills the depressions (holes) where the valley floor was eroded most
- These lakes can also form because melt water from receding glaciers is trapped behind Moraine (would form a shallow ribbon lake)
Glacial trough/U-shaped valley:
a steep-sided, wide and flat bottom valley, formed by abrasion
How are glacial troughs/u-shaped valleys formed?
- The glaciers change a V shaped valley into a U shape, by creating a steep sided, wide valley in the shape of the letter U
- They are formed by a glacier that moves down the valley because of gravity
- As the glacier moves down the valley it plucks the rock from beneath and those rocks then rub against the bed of the valley, eroding it further
- This deepens and widens the valley
Hanging valleys:
smaller tributary valleys above the main glacial trough
How are hanging valleys formed?
- Within glacial valleys there are main glaciers and smaller tributary glaciers (just like with rivers)
- The main glacier can erode its valley to a much greater extent because they are wider, deeper, have more mass and more sediment to use as erosive tools
- The tributary valley glaciers are smaller, have less mass and sediment and hence erode their valley less
- This means that the main valley is deeper, wider and steeper, and this becomes really evident post glaciation, when the tributary glacier is left hanging high above the main valley
- When rivers return, they often form waterfalls in these hanging valleys
Truncated spurs:
interlocking spurs without the land that interlocks
How are truncated spurs formed?
- As the glacier moves down the valley it plucks the rock from beneath and those rocks then rub against the bed of the valley, eroding it further
- This deepens and widens the valley
- At the front end of the glacier it acts like a bulldozer, shifting and removing soil, plucking rock from interlocking spurs and truncating them.
- This createstruncated spurs
- Originally, truncated spurs are created as a river erodes the upper valley it cuts down into the rock and meanders in and out of the surrounding roc
- During glaciations this rock is removed by descending ice sheets
How do glaciers transport material?
- as ice from higher areas descends in to lower areas, the snout (front) of the glacier bulldozes material
- rocks can be carried on the ice, within the ice or below the ice where they carry out abrasion
- soils, rock and boulders are shoved forwards by the force of the glacier
Drumlin:
- a drumlin is a small egg shaped hill, often found on the floor of a glacial trough
- they have a steep side known as the stoss and a gentle side known as a lee
- they are elongated features that can reach a kilometre or more in length, 500m or so in width and over 50m in height
What is a cluster of drumlins known as?
swarm
How are drumlins formed?
- Formed when the glacier deposited materials - as the glacier is carrying so much, it is overloaded and struggles to carry it as it is nearer the end and it is melting
- Small obstacles e.g. rocks, lead to moraine being deposited around them as the ice cannot overcome them and carry material
- The moraine moulds itself around the obstacle - the blunt end being the deposited material upstream of the ice and the tong tapered ice where the ice has flowed over the obstacle and trailed the moraine with it
Diagram of drumlins:
Erratic:
- Glacial erratics, often simply called erratics, or erratic boulders, are rocks that have been transported by ice and deposited elsewhere
- The type of rock (lithology) that the glacial erratic is made from is different to the lithology of the bedrock where the erratic is deposited
Example of an erratic:
an erratic could be a boulder of sandstone that is picked up by a glacier, transported, and deposited on top of a limestone bedrock
Why are erratics useful to scientists?
- Some erratics are useful to scientists because they are of a distinctive rock type, which means that their source outcrop can be identified and located
- Scientists can locate the origins of erratics and use this information to suggest the direction of ice movement
How are depositional landforms formed in glacial environments?
- Depositional landforms are produced when a glacier loses the ability to carry material
- When glacial icemelts, different types of rock are laid down that have been carried along by the glacier
- Piles of these deposits are calledmoraines
Moraines:
moraines are accumulations of rock debris and have distinct shapes
What are the 4 types of moraine?
- ground moraine
- lateral moraine
- medial moraine
- terminal moraine
Ground moraine:
- the material dragged under the glacier and left behind when the ice melts
- often forms uneven hilly ground
Lateral moraine:
- this moraine forms at the edges of the glacier]most scree material that has fallen off the valley sides due to freeze-thaw weathering
- when the ice melts, the moraine forms a low ridge in the valley side
Medial moraine:
- when a tributary glacier joins the main glacier two natural moraines will merge to produce a single line of sediment that runs down the centre of the glacier
- on melting, the medial moraine forms a ridge down the centre of the valley
Terminal moraine:
huge amounts of material pile up at the snout of a glacier to form a high ridge often tens of metres in height across the valley
Diagram showing different types of moraines:
Economic opportunities in glaciated environments:
- tourism
- eco-tourism, lodges
- natural environment → polar bears, Northern lights
- fishing
- Barents Sea
- geothermal energy
- e.g. Iceland
- oil drilling
- e.g. Trans-Alaskan pipeline
Economic opportunities in previously glaciated environments:
- farming
- tourism
- quarrying
- forestry
Why does farming take place in previously glaciated upland areas?
- in upland areas, glaciers scoured the land stripping away soil and vegetation
- as a result, soils in these areas are thin and acidic
- upland areas not ideal for farming, but mainly used for grazing
- sheep can tolerate the cold, wet and windy conditions and poor vegetation
Why does farming take place in previously glaciated valleys?
- soils in valleys thicker due to deposition
- flat-bottomed glacial troughs are ideal for using machinery and farming can be more productive
- typical crops include cereals and potatoes
- lot of land is used to grow grass for winter feed (silage and hay for livestock)
Why does farming take place in previously glaciated lowland areas?
- lowland glaciated areas may be covered by a thick layer of till - very fertile
- much of central and eastern Britain has productive farmland growing wheat, barley, potatoes and other crops
- flat/gently rolling landscape and warmer, sunnier climate these areas are well suited to intensive arable farming
Economic opportunities of farming in previously glaciated areas:
- arable farming = crops
- livestock
Why are previously glaciated upland areas used for tourism?
spectacular glacial scenery attracts tourists who enjoy outdoor activities and cultural heritage
Economic opportunities of tourism in previously glaciated landscapes:
- tourism can be most important economic activity and provide employment for 1,000s of people
- Aviemore, near Cairngorm, Mountains in Scotland, one of UK’s main activity centres
- people can mountain bike, ski and climb
- area is criss-crossed with footpaths and lots of wildlife to watch, photograph or draw
- wildlife park, folk museum, an adventure park and stream railway
- water sports
- hiking
- zip-wire
Why are previously glaciated upland areas used for quarrying?
- made of hard,, resistant rock
- this can be quarried and crushed to provide stone used in construction industry and for building roads
Why are previously glaciated lowland areas used for quarrying?
- in lowland areas, glacial deposits of sand and gravel deposited by meltwater streams, are also valuable in construction industry
- sand is used for making cement and gravel is used to make concrete
Economic opportunities from quarrying in previously glaciated areas:
- limestone makes up much of Penine Hills in central England
- valuable resource used in chemical industry, for conditioning soils or making cement
Why are previously glaciated upland areas used for forestry?
- well-suited to forestry
- large plantations of most coniferous (cone-bearing) trees have been planted throughout Scotland and across parts of northern England
Economic opportunities of using previously glaciated upland areas used for forestry:
- conifer trees are well adapted to cope with acidic soils
- one of few economic ways of utilising steep slopes
- once planted can be left to grow for 20-30 yrs before being felled
- conifers produce ‘soft’ wood used for timber in the construction industry for making paper
