Glaciation Flashcards
Describe plucking
As ice moves over the rock surface below, meltwater freezes around loose sections, pulling them away as the glacier moves forward
Describe abrasion
Rocks and boulders embedded in the base of the glacier act like sandpaper, scratching and scraping the rocks below. Large boulders can cause striations.
Describe freeze-thaw weathering
Water seeps into cracks in a rock face
Temp falls at night, cauisng water to freeze
Water expands as it turns to ice, putting pressure on rock either side of crack, causing it to tear open
Ice melts, sinks deeper into crack and freezes again
What are the erosion processes of glaciers?
Plucking and abrasion
Is freeze-thaw weathering an erosion process?
No, it isn’t caused by a moving force, it takes place in a particular place and remains of rock don’t move.
Evidence for freeze-thaw weathering
Scree slopes and blockfields
What is meltwater?
Ice at the base of glacier that has melted due to the pressure or water that has travelled from surface of glacier to base
How do glaciers move?
Rotational slip and basal slip
Describe rotational slip
At the top of glaciers, circular motion of ice can erode out hollows, which get deeper over time. This is how corries form
Describe basal slip
Meltwater beneath a glacier enables it to slide forward as a mass by a few metres each year.
How does a glacier transport material?
Bulldozing
Describe bulldozing
Rocks at the snout of a glacier are shoved forwards by the sheer force of the moving ice. Material is also carried on surface of glacier and inside.
Why would material be carried on the surface of the glacier?
Surface - Freeze-thaw weathering occurs on mountain-sides above glacier, causing rocks to become detached and fall onto the ice
Why would material be carried inside a glacier?
Plucking has torn away rock below the moving ice which is now embedded in the base of the glacier
Some rocks fall into crevasses at the surface of the glacier which reach deep into the glacier
Where on the mountain does glacial deposition take place and why?
Lowland areas, warmer climatic zones, causing more meltwater to flow.
Describe the two types of glacial sediment deposited
Till - range of sizes, angular shape, deposited by ice
Glacial outwash - Rounded rocks, sorted by size, deposited by meltwater
Describe how till is deposited
Melting takes place at front of glacier and is dumped on the ground. Because it is transported by solid mass of ice, it is unsorted
Describe how glacial outwash is deposited
In summer months, meltwater rivers flow from snout of glacier and carry outwash material . It is carried by water so it smaller (attrition) and sorted by size.
Suggest why material deposited by a glacier is mixed in size
Transported by ice which picks up all sizes of debris. Glacier bulldozes everything in its path.
Till has a wider range as it consists of materials moved by solid ice so everything is picked up
Explain the formation of a glacial trough
V-shaped is filled with ice.
Glacier moves through the valley eroding the valley floor and sides by abrasion and plucking.
Truncated spurs are formed as glaciers cut through interlocking spurs.
Glacier melts/retreats, leaving behind glacial trough.
Explain the formation of a corrie
Snow forms in a hollow and gets compressed, forming a dense mass of ice. Glacier moves downhill by rotational slip
As the ice pulls away from walls of the hollow, rocks are plucked.
Freeze-thaw weathering occurs on back wall of hollow, above the ice, causing rocks to fall on surface of ice. Retreating steep back wall is formed.
These rocks become embedded in the ice and abrade the hollow, making it deeper and wider.
Describe how an arrête occurs
When two corries are eroded back to back, the ridge in between them becomes narrower.
(Use explanation of formation of corrie)
Describe how a pyramidal peak forms
When three or more corries form on all sides of the mountain. Corries erode the mountain behind them, the remaining rock is freeze-thaw weathered into a sharp point
(Use explanation of formation of corrie)
Describe how a hanging valley forms
As a glacier moves through a V-shaped valleys, abrasion and plucking cut off the valley sides. Tributaries that used to flow down river valley sides exit abruptly through a gap in the valley wall. Water cascades from a high altitude, creating a waterfall.
Describe how a ribbon lake forms
(Use explanation of glacial trough)
Glacier makes straight sides and wide flat valley floor by abrasion and plucking.
Glacier melts, long narrow ribbon lake formed.
Describe terminal moraine
Often results from bulldozing. Marks the maximum extent of the glacier. Huge amounts of material build up at the snout to form a high ridge across the valley. The longer the snout stays in one place, the greater
the amount of material that is deposited.
Describe ground moraine
Uneven material that gets lodged and deposited underneath the glacier which is then deposited. It often forms an uneven hilly surface.
Describe medial moraine
Occurs when two glaciers meet and two lateral moraines merge together.
Describe lateral moraine
Ridge of material that runs along the edges of a glacial trough. Source of material is freeze-thaw weathering high on the valley sides. As ice melts and the glacier gets smaller, this material is slowly lowered and deposited on the valley floor.
Describe how drumlins are formed
Material is deposited underneath a glacier as ground moraine. This ground moraine is sculpted to form drumlin shapes by further ice movements.
How do drumlins tell us the direction of glacial movement?
Glacial moved from blunted (higher) end to tapered (lower) end
What are glacial erratics?
Large boulders that stand out because they are composed of a rock type not native to the area
What are moraines?
Formed by the deposition of poorly sorted, angular till that are dumped when ice melts
What is the difference between freeze-thaw weathering and plucking?
Freeze-thaw weathering is done in a particular place, and not by the glacier as it moves along. It isn’t an erosion process. Usually happens above surface of glacier.
Plucking is the opposite
What is the chosen example of a UK upland area with landforms?
Cadair Idris, Snowdonia, Wales
Example of a corrie/ tarn
Llyn Cau
Example of an arrete
Craig Cwn Amarch
Example of a pyramidal peak
At back of corrie containing Llyn Cau
Example of a glacial trough
Extends from Northeast to Southwest to the South of Cadair Idris
Example of depositional landforms
Many in the Tal-y-llyn valley
Describe farming as an economic activity in glaciated upland areas
Slightly limited
Soil is thin and infertile in mountains, waterlogged in valley bottoms.
Slopes are steep and often covered by scree
Harsh climate with high rainfall, low temp, strong winds.
Sheep grazing is widespread. Some crops are grown, primarily grass for hay.
Describe forestry as an economic activity in glaciated upland areas
Commercial forestry is widespread
Mostly conifer plantations
These trees are well suited to the harsh environment and can thrive on thin, acidic soils. Trees are used to provide wood for furniture and construction.
Some are chipped to use a biofuel.
Describe quarrying as an economic activity in glaciated upland areas
Upland glaciated areas are made of tough rocks
Lake District - Slate is used as roofing and decorative material. 13 active quarries
Describe tourism as an economic activity in glaciated upland areas
Provides 1000s of jobs and contributes to local economy through shops, hotels restaurants.
Opportunities for hiking, cycling, climbing, nature-watching.
Describe land use conflict between farming and tourism
Tourists use footpaths that cross farmland, leaving open gates which livestock can escape from. Loose dogs can worry sheep. Littering can harm animals
Describe land use conflict between quarrying and conservation
Quarrying damages natural environment, destroy habitats, make landscape unattractive, lorries used for transport can damage verges and create air pollution.
Describe land use conflict between wind turbines and local people
Ideal location for wind farms - cheap land, strong winds, low populations.
Local people don’t want visual pollution of wind turbines. Local businesses rely on tourists which might be deterred if landscapes are scarred by ugly wind farms.
Describe land use conflict between reservoir construction and conservation
Ideal location for reservoirs - high rainfall, deep (U shaped) valleys, low population density.
However, local people forced to relocate, destruction of habitats.
Describe land use conflict between forestry and conservation
Conifer plantations. few species of tree are planted, reduced biodiversity. As they grow, they block sunlight from reaching vegetation on forest floor. Low wildlife levels due to limited vegetation.
Case study for glaciated upland area used for tourism?
Lake District
Attractions for tourists in the Lake District
Boating, fishing, hiking on Lake Windermere (ribbon lake)
Helvellyn mountain for hiking and climbing
Gorge scrambling, abseiling.
Small towns, historic houses (Beatrix Potter’s house)
Social impacts of tourism in Lake District
(they are mostly negative)
50 million visitors a year, pressure on the roads. Congestion on narrow roads.
Local people are unable to afford houses due to purchase of second homes by wealthy tourists.
Jobs are poorly paid and seasonal.
Economic impacts of tourism in Lake District
(they are mostly positive)
Employment in tourism for 1000s of people boosts family incomes and leads to positive multiplier effect as more money to spend in local economy.
Businesses, such as adventure tourism, are promoted by tourism.
Tourists spend over £1000 million each year in hotels, restaurants, boosting local economy
Environmental impacts of tourism in Lake District
(they are mostly negative)
Pollution (traffic, litter) can be an issue
Walkers create conflicts with farmers when gates are left open or dogs worry livestock
Footpath erosion is an issue in popular locations
How is traffic congestion (caused by tourism) managed in the lake district?
Public transport is encouraged. Honister Rambler bus route for hikers and cyclists.
Traffic calming in villages
Some settlements (Ambleside) act as transport hubs with car parks, bus stops, cycleways.
How is footpath erosion (caused by tourism) managed in the lake district?
Volunteer groups such as Fix The Fells work with local landowners to restore footpaths using local stone and sheep’s wool.
Improved signage encourages people to not to stray off dedicated footpaths.
Re-planting of native plants and those able to withstand trampling to reduce erosion.
