Key Terms: Glaciers as Natural Systems (AQA A Level Geography): Revision Note

Glacial systems - key terms

Ablation – The process of ice and snow loss from a glacier through melting, evaporation, or calving.

Accumulation – The gain of ice and snow on a glacier through snowfall, avalanches, or frost.

Cirque glacier – A small glacier occupying a bowl-shaped hollow (cirque), usually at the head of a valley.

Cliff retreat – The backward movement of a cliff line over time due to erosion and mass movement processes.

Constrained glacier – A glacier whose flow is directed by the surrounding terrain, such as valley or cirque glaciers.

Continental glacier (ice sheet) – A vast, thick ice mass covering more than 50,000 km², not confined by topography.

Debris flow – The movement of rock, sediment, and ice within and across the glacier system.

Dynamic equilibrium – A state where inputs (e.g. snowfall) are balanced by outputs (e.g. melting), keeping the glacier’s mass stable over time.

Evaporation – A process in which liquid water changes to vapour, representing a loss of energy and water from the glacial system.

Feedback loop (positive) – A system process where a change leads to further changes in the same direction, such as melting exposing dark debris, increasing insolation and further melt.

Glacial movement – The flow of ice downhill under gravity, often shaping the landscape through erosion and deposition.

Glacial polish – A smooth surface on rock caused by fine sediment in ice scraping over it.

Glacial striation – Scratches or grooves on rock surfaces caused by larger rock fragments embedded in moving ice.

Ice cap – A mass of ice covering less than 50,000 km², usually centred on a high point like a mountain massif.

Ice shelf – A thick, floating sheet of ice attached to land, typically found in Antarctica or the Arctic.

Iceberg – A large piece of freshwater ice that has broken off from a glacier or ice shelf and floats in open water.

Insolation – Incoming solar radiation absorbed by sediment and ice, influencing melting rates.

Meltwater – Water produced by the melting of glacier ice, often stored within, beneath, or on top of the glacier.

Niche glacier – A small glacier found in a shaded hollow or crevice, often isolated and short-lived.

Nunatak – A mountain peak or rocky element that protrudes above an ice sheet or glacier.

Open system – A system with inputs (e.g. snowfall) and outputs (e.g. meltwater), such as glaciers interacting with the atmosphere and hydrosphere.

Outwash plain – A flat area formed by glacial meltwater depositing sediments beyond the glacier.

Piedmont glacier – A lobe-shaped glacier formed where valley glaciers spill out onto a flat plain and spread.

Positive feedback – A reinforcing loop where a change causes further effects in the same direction, amplifying the original process.

Rock flour – Very fine sediment produced by glacial erosion that gives meltwater a milky appearance.

Sublimation – The process where ice changes directly into vapour without becoming liquid.

Supraglacial lake – A body of meltwater that forms on the surface of a glacier.

Unconstrained glacier – A glacier whose flow is not restricted by surrounding topography, typically forming ice sheets or ice caps.

Valley glacier – A glacier confined within a valley, usually originating from a mountain glacier and flowing downslope like a river of ice.

Weathering – The breakdown of rocks in situ, contributing sediment to the glacial system.