Glacial Systems and Landscapes Definitions Flashcards
What is ablation?
The loss of mass from a glacier (e.g. iceberg calving, meltwater, sublimation).
What is abrasion?
Small rocks within the base of the glacier rub against and erode the bedrock, leaving behind striations.
What is accumulation?
The addition of mass to a glacier (e.g. direct snowfall, blown snow, avalanches).
What is the active layer?
The top layer of soil in periglacial environments above the permafrost, which thaws annually in summer.
What is an alpine region?
An area of low temperature in high altitude, mountainous areas (3000m+).
What is an arête?
A knife-shaped ridge formed between two corries.
What is basal ice melting?
The high pressure of a glacier causes meltwater, which will then erode the bedrock through fluvial erosion.
What is basal sliding?
The movement of a glacier due to lubrication from subglacial meltwater.
What is a blockfield?
A rock-strewn landscape caused by extensive freeze-thaw weathering.
What is a cold-based glacier?
Polar glaciers where the temperature remains below freezing and there is little ice movement as the glacier is frozen to the bedrock.
What is compressional flow?
Ice builds up and thickens as a glacier travels over a shallow gradient.
What is a corrie?
An armchair-shaped rock basin on the sides of mountains, formed through nivation and rotational slip in a hollow.
What is crushing?
The weight of a glacier causes the bedrock to fracture.
What is a drumlin?
A small dome-shaped hill formed due to deposition behind a resistant obstacle.
What is environmental fragility?
When an environment is vulnerable or at risk, with a low resilience and ability to adapt or recover from disruptions.
What is an erratic?
A large boulder deposited by a glacier in an area of completely different geology.
What is an esker?
A long, sinuous ridge of deposited glacial material which follows the path of a previous subglacial meltwater stream.
What is extensional flow?
Ice thins out and creates crevasses as a glacier travels over a steep gradient.
What is fluvial erosion?
Water within a glacier erodes the bedrock over time (e.g. hydraulic action, attrition).
What is frost heave?
The freezing and expansion of water in the soil, resulting in uplift and patterned ground.
What is the glacial budget?
The difference between annual accumulation and ablation (mass balance).
What is a glacial period?
A period of time with colder than average global temperatures, causing glacial advance and falling sea levels.
What is a glacial trough?
A U-shaped valley formed due to glacial scouring of a pre-existing V-shaped river valley.
What is a hanging valley?
A tributary valley from before glaciation is left hanging above a main valley due to the main valley glacier’s large erosive power.
What is the Holocene epoch?
The period of geological history with limited ice cover from 11,700 years ago to the present day.
What is an ice wedge?
Narrow cracks in the active layer formed through repeated infiltration and freezing of water.
What is an interglacial period?
A period of time with warmer than average global temperatures, causing glacial retreat and rising sea levels.
What is internal deformation?
Ice movement caused by ice crystals aligning under pressure and sliding over each other.
What is a kame?
A small mound of partially sorted sand and gravel left on the valley floor as a glacier melts.
What is a Milankovitch cycle?
Collective changes in Earth’s orbit, tilt and axis of rotation.
What is a meltwater channel?
A stream of meltwater formed through higher temperatures and pressure.
What is a moraine?
A ridge of deposited glacial material.
What is nivation?
Erosion underneath a patch of snow caused by alternating freezing and thawing.
What is orbital eccentricity?
How far a planet’s orbit is from being perfectly circular.
What is an outwash plain?
Large area of stratified and deposited fluvioglacial sediment at the snout of a glacier.
What is patterned ground?
Polygon-shaped cracks in the ground caused by frost heave of small stones within the active layer.
What is a periglacial environment?
A cold environment found on the edges of polar or alpine regions which contains permafrost.
What is permafrost?
Ground that remains below freezing for two continuous years in periglacial environments.
What is a pingo?
A dome-shaped mound formed as ground is forced upward due to frost heave.
What is plucking?
Rocks becoming dislodged as a glacier that was frozen onto the rock outcrop moves, causing erosion.
What is a polar environment?
Cold environments that are located at high latitudes with extremely low temperatures.
What is a roche moutonee?
A resistant rock which is eroded as a glacier moves over it.
What is solifluction?
The slow, downslope movement of soil which has become waterlogged during the summer thaw.
What is a solifluction lobe?
A tonge-shaped lobe in the soil formed due to solifluction and waterlogged soil.
What is a terracette?
A ridge of narrow steps with small treads which run parallel across a hillslide, formed as vegetation traps sediment created through frost heave.
What is a thermokarst?
A depression formed in the ground as permafrost melts and subsidence occurs.
What is a till plain?
A large expanse of glacial till formed behind terminal moraines in areas of flat relief.
What is a warm-based glacier?
Temperate glaciers where the higher temperatures create basal metlwater, allowing basal sliding to occur.
