Introduction to Glaciers

Glacier

A large mass of snow and ice that has accumulated and flowed over years.

Névé

First-year glacial snow that is granular and partially melted.

Firn

Accumulated snow that has survived one melt season, denser than névé.

Moulins

Narrow, near-vertical tubes in a glacier that carry meltwater to the base.

Calving

The process of ice breaking off from the edge of a glacier.

Mass Balance

The difference between accumulation and ablation of ice in a glacier.

Ablation Zone

The area of a glacier where annual melting exceeds accumulation.

Accumulation Zone

The area of a glacier where annual accumulation exceeds melting.

Tidewater Glacier

A glacier that flows into the sea, creating icebergs.

Ice Shelf

A thick floating sheet of ice formed by a glacier or ice sheet.

Terminal Moraine

A ridge of debris deposited at the furthest advance of a glacier.

U-Shaped Valley

A valley formed by glacial erosion that has a U-shape cross-section.

Plucking

The process where a glacier removes rocks from the valley floor.

Glacial Period

A period in Earth's history characterized by lower global temperatures and extensive glacier coverage.

Interglacial Period

The warmer periods between glacial periods when glaciers retreat.

Milankovitch Cycles

Natural variations in Earth's orbit that influence climate and glaciation.

Eccentricity

The variation in the circularity of Earth's orbital path around the sun.

Obliquity

The variation in the tilt of Earth's rotation axis.

Precession

The variation in the direction of Earth's axial tilt.

Oxygen Isotope Ratio

The ratio used to infer past temperatures and climate conditions based on variations between 16O and 18O isotopes.

Crag & Tail

A landform created when a glacier passes over a resistant rock, leaving a blunt peak with a tapered tail.

Siachen Glacier

A valley glacier located in the eastern Karakoram, contested between India and Pakistan.

Greenland Ice Sheet

The second largest ice sheet in the world, covering about 80% of Greenland's surface.

Larsen B

An ice shelf that collapsed in 2002, revealing instability due to warming.

Cirque

A bowl-shaped depression on a mountain formed by glacial erosion.

Drumlins

Streamlined hills formed by glaciers, typically found in groups.

Kettles

Depressions formed by melting ice blocks left behind by retreating glaciers.

Crevasses

Deep cracks in a glacier formed by brittle deformation.

Glacial Outburst Flood (GLOF)

A flood caused by the sudden release of a large volume of water from a glacial lake.

Ice Tongue

A glacier that extends rapidly out into the sea.

Supraglacial Streams

Water channels formed from surface melt on top of a glacier.

Englacial Channels

Water channels that form within the body of a glacier.

Subglacial Lakes

Bodies of freshwater situated beneath the ice of a glacier.

Paternoster Lakes

Linked lakes that form through streams connecting multiple tarns.

Cryoconite holes

Depressions on glacier surfaces formed by melting due to dark debris absorbing heat.

Ogives

Alternating crests and valleys in glacier ice linked to seasonal movement.

Tarn

A small lake that forms in a cirque after a glacier has melted.

Ice Rafting

The process of debris being transported by icebergs and deposited in water.

Snowball Earth Periods

Hypothetical periods during which the Earth was fully or nearly fully covered in ice.