DEFINITIONS Glaciated Landscapes

Define ablation

The loss of ice and snow through melting, evaporation, and sublimation

Define accumulation

The addition or gain of snow and ice to a glacier over time

Define active layer

The near surface layer in a periglacial environment which seasonally freezes and thaws

Define aggradation

The deposition of sediment in a river channel which results in a rise in the bed elevation

Define alases

Flat-floored, steep-side depressions in periglacial environments. Formed when the ice-rich permafrost thaws and the ground collapses due to the loss of ice support

Define alluvial fan

A cone of sediment deposited by a river or glacier where it leaves a steep upland course and enters a lowland area

Define anthropocene

The unofficial current geological period where humankind is the main driver of environmental change

Define arête

A narrow, ‘knife-edged’ ridge between two corries

Define aspect

The direction a slope faces

Define attrition

A type of erosion when rocks are carried in a river and knock against each other

Define chemical weathering

The breakdown of rocks and minerals due to chemical reactions, primarily involving water and other substances like oxygen and carbon dioxide

Define compressing flow

The movement of glacial ice down a gentler gradient than that of it’s previous slope, during which it thickens. Crevasses close up

Define deposition

The laying down of sediment transported by rivers, waves, glaciers, and wind as energy levels decline

Define diagenesis

The process by which snow becomes ice due to compression (from fresh density ~0.05g/cm3 to 0.9g/cm3)

Define dilitation

A mechanical weathering process - When the weight of overlying ice in a glacier is lost due to melting, or overlying rock lost to plucking, the underlying rock expands and opens up joints and fractures parallel to the surface

Define drift

The collective term for all glacial deposits, including till and outwash

Define drumlin

A large mound of glacial debris that has been streamlined into an elongated hill (egg shaped)

Define a dyke

A vertical or near vertical minor intrusion of magma/sedimentary hard rock through surrounding older rocks

Define dynamic equilibrium

When there is a long-term state of balance of inputs and outputs within a constantly changing system

(when the state of equilibrium is disturbed, the system undergoes self regulation and changes its form until equilbrium is restored)

Define erosion

The wearing away and/or removal of rock and other material by a moving force

Define esker

A long, sinuous ridge composed of stratified sand and gravel, parallel to ice movement

Define freeze-thaw

A mechanical weathering process caused by water, confined in rock joints, expanding by 9% as it freeezs, and as a result weakening and eventually breaking rocks into smaller particles

Define frost heave

The upward movement of soil and rocks due to the freezing and expansion of water in the soil.

Define frost shatter

At extremely low temperatures, water trapped in rock pores freezes and expands. This creates stress which disintegrates rock to small particles - it’s the result of freeze thaw

Define gelifluction

The slow, downslope mass flow of saturated regolith resting on a layer of permafrost.

Define geomorphic

Relating to the formation and shaping of landforms and landscapes by natural processes

Define geomorphic processes

The physical and chemical interactions between the earth’s surface and the natural forces acting upon it to produce landforms

Define a glacial

A prolonged cold climatic phase lasting for tens of thousands of years and causing continental glaciation in middle and high latitudes

Define glaciated landscape system

Parts of the Earth’s surface that have been shaped, at least in part, by the processes of glacial erosion, transport, and deposition that occur as a glacier moves through a lanscape

Define a glacier

A large mass of ice that moves slowly over land

Define a glacier mass balance

The difference between the amount of snow and ice accumulation and the amount of ablation occuring in a glacier over one year

Accumulation MINUS ablation

Define glacio-fluvial

Relating to meltwater from a glacier

Define granular disintegration

The breakdown of rocks by weathering into coarse, granular particles

Define hydrostatic pressure

The pressure exterted by a confined fluid, such as water under or in a glacier

Define ice-contact drift

Sediment deposited under or against ice

Define ice sheet

The largest accumulations of ice that extend for more than 50,000km²

Define inter-glacial

A period of climatic warming (lasting ~10,000 years) between glacials

Define kame

A rounded hill of deposited stratified sand and gravel laid down by glacial meltwater

Define kinetic energy

The capacity to do work as a result of motion

Define landscape

The visible features (landforms) of an area of the Earth’s surface

Define lateral moraine

A ridge of till running along the edge of a glacial valley

Define mass movement

The downslope movement of material (soil and rock) under gravity

Define nivation

A complex glacial process thought to include a combination of freeze-thaw, solifluciton, transport by water, and chemical weathering

Define nivation hollow

A depression formed by freeze-thaw and meltwater transport of weathered rock particles beneath a permanent snow patch

Define outwash

Material deposited by glacial meltwater

Define outwash plain

A flat expanse of glacio-fluvial sediment located beyond an existing or former glacier or ice sheet front

Define permafrost

Permanently frozen soil and regolith that has remained frozen for at least two years straight

Define physical weathering

The breakdown of rocks and minerals through physical forces without altering their chemical composition

Define a pingo

A conical ice-cored hill that only form in periglacial environments

Define positive feedback

An automatic response to change in a system which generates further change

Define a pyramidal peak

An angular, sharply pointed mountain peak which results from corrie erosion

Define recessional/stadial moraines

A series of ridges running transversely across a glacial trough which marks points in which the glacier was stationary for long enough to deposit sediment

Define regolith

A loose layer of rocky material overlying bedrock

Define striations

Scratches or grooves on rock surfaces formed by glacial abrasion

Define structure

The physical characteristics of rocks, including their jointing, bedding, faulting, angle of dip

Define a terminal moraine

A ridge of till extending across a glacial trough that marks the point of maximum advance of the glacier

Define thermal energy

The capacity to do work as a result of heat

Define trough

A steep sided U-shaped valley

Define till

Unsorted material deposited directly by glacial ice

Define transportation

The movement of material by the kinetic energy of a medium such as water or ice

Define valley glaciers

Confined by valley sides and follow the course of existing river valleys / corridors of lower ground

Define weathering

The in situ break down or dissolving of rocks and minerals on the Earth’s surface