dynamic planet glaciers

Crystal Structure of Ice

Ice in glaciers forms a hexagonal crystalline structure, aligning under pressure.

Density of Fresh Snow

Approximately 0.05–0.2 g/cm³.

Density of Firn

Approximately 0.4–0.83 g/cm³; it is the intermediate stage between snow and ice.

Density of Glacial Ice

Approximately 0.83–0.917 g/cm³; it is highly compacted and bubble-trapped.

Formation of Glacial Ice

Occurs when firn is compacted under pressure over time, expelling air and forming dense ice.

Ablation

Loss of ice and snow through melting, sublimation, or calving.

Accumulation

Addition of snow and ice through precipitation and avalanches.

Equilibrium Line (ELA)

The line on a glacier where accumulation equals ablation; above ELA the glacier grows, below it melts.

Basal Sliding

Ice slides over a thin layer of meltwater or deformable sediment at the base of the glacier.

Internal Deformation

Ice deforms and flows plastically under its own weight.

Valley/Alpine Glaciers

Glaciers that form in mountainous regions and flow down valleys.

Cirque Glaciers

Small glaciers occupying bowl-shaped hollows.

Hanging Glaciers

Glaciers that cling to steep mountain sides.

Ice Sheets

Vast, continental-scale glaciers that cover areas greater than 50,000 km².

Ice Streams

Fast-flowing sections of ice sheets.

Ice Shelves

Floating extensions of ice sheets over ocean water.

Calving

Breaking off of chunks of ice from the glacier terminus into water.

Milankovitch Cycles

Earth's orbital changes affecting climate, including eccentricity, obliquity, and precession.

Permafrost

Permanently frozen ground.

Glacial Lake Outburst Floods (GLOFs)

Sudden release of water from moraine or ice-dammed lakes.

Dropstones

Ice-rafted debris found in fine sediment.

Till

Poorly sorted, unlayered sediment left by glaciers.

Outwash

Sorted sediment that is deposited by glacial meltwater.

Varves

Annual layers of sediment in lakes, with summer layers being coarse and winter layers being fine.

Frazil Ice

Needle-like ice crystals formed in supercooled turbulent water.