glacial systems and landscapes

key terms

ablation

The loss of mass from the glacier, e.g., meltwater, avalanches, sublimation, evaporation.

Abrasion

Small rocks within the base of the glacier rub against the bedrock.

accumulation

The addition of mass to the glacier, usually as snow

Active layer

the top layer of soil above permafrost, which thaws annually in summer

Alpine regions

Areas of low temperature in high altitude, mointainous regions

Arete

a ridge formed between two corries

Basal Ice Melting

The weight of a temperate glacier causes meltwater, which will then erode the bedrock through fluvial erosion.

basal sliding

Glaciers sliding over bedrock, due to meltwater between the two surfaces.

Blockfields

Rock-strewn landscape caused by extensive frost action.

Cold based glacier

The glacier's temperature remains below zero degrees, so the base of the glacier remains frozen and moves very little.

Compressional flow

ice builds up and thickens due to friction as a glacier travels upwards along a shallow gradient

Corries

A round hollow in the side of a hill, widened from an initial smaller hollow by a glacier within the hollow.

crushing

the weight of the glacier causes fracturing in the bedrock

Drumlins

when a glacier hits an obstacle that cannot be eroded, deposition from underneath the glacier builds up behind the obstacle

environmental fragility

An environment is vulnerable or at risk, with low resilience or ability to adapt to changes.

Erratics

Boulders transported and deposited by a glacier. The type of rock that forms the erratic will usually differ from the rock types in the surrounding landscape.

Esker

a long winding ridge of glacial deposition

Extensional flow

Ice thins out, creating crevasses, due to an increase in the glacier's velocity down a shallow gradient

fluvial erosion

Water within the glacier erodes the base of the glacier over time through: hydraulic action, attrition, corrosion.

frost heave

the freezing and expansion of water beneath the ground, resulting in floor uplift

glacial budget

The difference between accumulation and ablation for a glacier.

glacial period

a period of colder average global temperatures causing the growth of ice cover, glacial advances and sea levels to fall

glacial trough

a u-shaped valley formed from a v-shaped river valley that becomes filled and eroded over time by a glacier

Hanging valleys

A valley with a wall at one end, due to the glacier that filled the valley previously being low energy.

Holocene Epoch

Our current glacial period of limited ice cover, lasting over 10,000 years.

ice wedge

Water infiltrates small cracks in the permafrost and expands on freezing repeatedly.

interglacial period

A period of time of warmer average global temperatures, resulting in reduced ice cover, glacial retreat and sea levels to rise.

internal deformation

Glacial movement caused by the weight of the glacier above deforming the ice.

Kames

Piles of material, sorted due to the differing weight of sediment, left on the valley floor after a glacier melts.

Milankovitch cycles

changes to the tilt and shape of the orbit will affect the average temperature of the earth

Meltwater channels

Streams of meltwater (melted glacier) formed by higher temperatures.

Moraines

deposits of eroded material that has been transported by a glacier. Moraines may be lateral, medial, ground, recessional or terminal

Nivation

A type of physical weathering in cold climates that involves the breaking away of rock by the action of water freezing and expanding in cracks in the rock base. Also called frost shatter.

orbital eccentricity

How far a planet's orbit is from being a perfect circle

outwash plain

Material is washed out and deposited due to large volumes of meltwater as a glacier recedes.

patterned ground

formed through the frost heave of stones in and underneath the active layer

Periglacial

landscapes found at the edge of glacier, polar and alpine regions. Permafrost occurs, with low precipitation and only highly adapted plant species survive

Permafrost

permanently frozen layer of soil beneath the surface of the ground

Pingos

A mound produced as ground is forced upwards through frost heave.

plucking

rocks on the bedrock are frozen within the glacier, as the glacier moves, the rocks are pulled from the bedrock and moved

polar regions

areas of maximum ice sheets and limited vegetation, located at high latitudes on earth

roche moutonnee

rock shaped by a glacier flowing over it and eroding it

Solifluction

the movement of water-logged soil, trapped between the active layer and permafrost

Solifluction lobes

As the active layer thaws, soil falls down the hillside in tongue-shaped lobes.

Terracettes

Ridges running parallel across a hillside, believed to be created by vegetation trapping sediment falling loose down the hillside, created through frost heave.

Thermokarst

Marshy, boggy wetlands caused when permafrost melts

till plains

An ice sheet detaches from the main glacier and melts, releasing all loose till and sediment across the bedrock.

Warm based glaciers

faster travelling glaciers due to basal meltwater trapped underneath the glacier, acting as lubrication to allow the glacier to move