Everything Flashcards
Kames
Mounds of sediment found on the floor of a glacial trough, resulting from fluvioglacial deposition in a marginal lake.
Meltwater channels
Often narrow and steep sided valleys formed by torrents of meltwater at the end of a glacial period.
Hanging valleys
Tributary glacial trough perched up on the side of he main glacial trough, often marked by a waterfall.
Frost heave
Small scale upwards displacement of soil particles, resulting from the freezing and expansion if the water just below ground surface.
Glacial trough
Glacially enlarged river valley, large broad flat surface floor with steep sides, U shaped.
Internal deformation
Ice crystals slipping and sliding over each other. They may become damaged or fractured and gradually move downhill due to gravity. Occur in cold and warm glaciers often at the same time as basal sliding.
Basal sliding
The movement of a large block of ice, usually by a series it short jerks. Occurs in warm glaciers where meltwater is present. Obstacles causes added pressure as the ice moves over them, this leads to melting called regelation slip.
Frost shattering
Water seeps into cracks and pores in the rock. Temperature drops to at least 0 degrees and the water freezes expanding in volume. The expansion stresses the rock causing the crack to enlarge. When the temperature rises to above 0 degrees the water melts and the process is repeated causing chunks of rock to beak off.
Describe the distribution of polar and alpine cold environments
Polar, high latitude 60-70 degrees north and South within the arctic and Antarctic circles. Alpine, lower latitude, under he influence of mountains, found along the west coast of the Americas and North of the Indian subcontinent.
Periglacial environments
Found of the ridges of polar and glacial environments, Siberia, Canada, and Greenland. Permanent frozen ground, the warmer summer allows the ground surface layer to thaw enabling some plants to grow.
Extensional flow
When there is a sudden increase in the gradient, the ice will flow faster and may become thinner as it is stretched.
Compressional flow
A reduction in the gradient further down the glaciers means the ice will move slower causing it to pile up and become thicker.
Terminal moraine
Marks the furthest extent of a glacier.
Ground moraine
The rocks grind along the base of the glacier, this moraine can be several metres thick.
Englacial moraine
Rock material buried within the ice having been buried over several year by layers of fresh snow and ice.
Lateral moraine
Consists largely of frost shattered rocks that have fallen onto the glacier from the valley sides.
Accumulation zone
There is a net gain of ice over the year, the inputs exceed the outputs.
Ablation zone
There is a net loss of ice over the year. The losses exceed the gains.
Rotational flow
Occurs in corries, the ice pivots around a central point and moves I’m a circular way, it deepens the area away from the lip.
Ice wedges
V-shaped ice filled features, formed by the enlargement if surface cracks by frost action, in time the crack will become in filled with sediment.
Plucking
Refreezing of meltwater freezes part of the underlying bedrock to the base of the glacier. Any loosened rock fragments will be plucked away when the glacier moves.
Medial moraine
When a tributary glacier joins up with a main glacier, two lateral moraines join up to form medial moraine. The line of debris them continues is journey towards the centre of the main glacier.
Solifluction lobes
Extended lobes of saturated soil formed by solifluction on a hillside.
Truncated spurs
Former interlocking spurs that have been eroded by a glacier to form steep valley sides.
Fragile enviroments
Natural environments where processes operate slowly and where ecosystems can be easily harmed and take a long time to recover.
Eskers
Sinuous ridges found of the floor of a glacial trough formed by fluvioglacial deposition in a meandering subglacial river.
Alpine environment
Mountainous areas such as the alps and the Rockies, they experience very cold winters with heavy snow. Due to high altitude the temperature can drop to -10 degrees or less, the extreme winter is replaced in the summer by warmer weather.
Weathering
Breakdown or disintegration of rock in its original position at or just below ground surface.
Polar environment
Most extreme cold environment, temperatures can often drop to -50 degrees. Include Antarctica and Greenland. Very dry due to low precipitation levels, there is an extensive area of sea ice.
Pingos
Ice cored mounds found in peri glacial environments formed by freezing if sub surface water bodies and subsequent swelling of the ground surface.
Solifluction
Gradual downhill slumping of saturated soil and rock, usually in summer when the upper surface zone melts and becomes heavy and waterlogged.
Out wash plains
Often a vast area of well sorted rounded sand and gravel deposits, extending for some distance in from of a glacier by meltwater.
Importance of meltwater
Melting snow helps to enlarge the shallow nivation hollows. Meltwater helps to lubricate the base of the glacier and overcome friction. It transports moraine beneath the ice and erodes channels and form depositional features.
Describe drumlins
Oval, elongated, smooth and rounded. Appear in swarms. They are large and can be up to 3km long. Tend to be wider and steeper at one end than the other. Maximum dimensions, 100m height, 3km long, 600m width.
Define permafrost
Permanently frozen ground. Depth varies, can be up to 700m in Canada but up to 1500m in Siberia. May be an active layer in the summer. Located in tundra or peri glacial environments.
Glacial environments
Associated specifically with glaciers. Most moving glaciers are found in alpine environments. Heavy winter snowfall provides ice to feed the glaciers. In the summer meltwater lubricates the glaciers helping them to move.
Surges
Rapid movements of ice that occur due to large levels of inputs or meltwater. Ice usually 60m thick before movement occurs. .
Glacial budget
Inputs and additions to the glacial system such as snowfall and avalanches. Also he outputs and losses from the system such as melting ice or ablation, evaporation and sublimation. Overall balance of inputs and outputs determines whether the glacier gets bigger or smaller.
Discontinuous permafrost
Forms is areas where the mean annual soil temperature is between -5 degrees and 0 degrees. Usually the below ground temperature is less variable than the air temp.
Extensive discontinuous permafrost
Where permafrost cores 50%-90% of the landscape, and is found in areas with temperatures of -2 to -4 degrees.
Sporadic permafrost
Permafrost cover is less than 50% of the landscape and occurs where mean annual temperatures are between 0 degrees and 3 degrees.
Scree slopes
Angular deposits of rock. The scree collects at the bottom of the slope and reduces the angle between the valley side and the valley floor. Caused by freeze thaw weathering and some biological weathering.
Push moraine
When a glacier extends again during a colder period it will push the terminal moraine left at the previous end of the glacier and leave it further down the valley.
Striations
Scratches that run parallel to the direction of ice movement. Usually found in groups. Measure between 1cm and 1m. Made by sharp angular rocks in the ice scratching the bedrock. Show movement of ice. Over time abrasion polishes the rock.
