DYNAMIC PLANET

glaciers, dynamic planet

Glacier Formation

The process by which snow accumulates, compacts, and transforms into glacial ice over time.

Neve

Granular snow that forms as snow compacts and begins to transform toward glacial ice.

Firn

Densely packed snow that develops from neve under pressure over decades.

Glacial Ice

Ice that forms from the compaction of firn under high pressure and recrystallization.

Crystal Structure of Ice

Ice forms hexagonal crystals which determine its strength and flow characteristics.

Density of Snow

Approximately 50–300 kg/m³.

Density of Firn

Approximately 550 kg/m³.

Density of Glacial Ice

Ranges from approximately 830–917 kg/m³, increasing with compaction.

Accumulation

The addition of snow and ice from processes such as precipitation and avalanches.

Ablation

The loss of ice through processes like melting and sublimation.

Equilibrium Line Altitude (ELA)

The altitude at which accumulation equals ablation in a glacier.

Positive Glacial Budget

Occurs when a glacier advances due to more accumulation than ablation.

Negative Glacial Budget

Occurs when a glacier retreats due to more ablation than accumulation.

Internal Deformation

The process where ice crystals slide past one another under pressure allowing the glacier to flow.

Basal Sliding

The movement of glaciers over a lubricant layer of meltwater at the glacier's base.

Glacial Flow Speed

Faster flow occurs at steeper slopes and higher elevations in glaciers.

Valley/Alpine Glaciers

Glaciers located in mountainous regions.

Cirque Glaciers

Glaciers that occupy bowl-shaped depressions.

Hanging Glaciers

Glaciers that end at steep cliffs.

Piedmont Glaciers

Glaciers that spread out at the base of mountains.

Ice Sheets

Massive glaciers covering large areas, such as those in Antarctica and Greenland.

Ice Streams

Fast-moving channels within ice sheets.

Ice Shelves

Floating extensions of glaciers that protrude from land.

Ice Caps

Smaller, dome-shaped glaciers covering less area than ice sheets.

Ice Tongues

Glaciers that extend into the ocean.

Crevices

Deep cracks in the surface of glaciers created by stress.

Ogives

Alternating bands of light and dark ice linked to seasonal flow.

Ice Falls

Steep descents of glaciers that resemble frozen waterfalls.

Calving

The process where icebergs break off from ice shelves into the ocean.

Marine Ice Sheet Instability

A phenomenon where ocean warming causes destabilization of ice sheets.

Ice Shelf Buttressing

The stabilization of inland glaciers provided by the presence of ice shelves.

Cirques

Bowl-shaped hollows carved by glacier erosion.

U-Shaped Valleys

Valleys formed by the erosive action of glaciers on valley walls.

Hanging Valleys

Tributary valleys left above the main U-shaped valley after glacial erosion.

Aretes

Sharp ridges formed between adjacent glacial valleys.

Horns

Pointed peaks shaped by glacial erosion on all sides.

Striations

Grooves in bedrock formed by rocks embedded in moving ice.

Roche Moutonnée

Smooth, asymmetrical bedrock features formed by glaciers.

Moraines

Accumulations of debris deposited by glaciers, categorized by position relative to the glacier.

Terminal Moraines

Deposits formed at the furthest extent of a glacier.

Ground Moraines

Deposits left underneath a glacier.

Kames

Mounds of sediment deposited by meltwater.

Drumlins

Streamlined hills of till formed by glacier movement.

Eskers

Long, winding ridges of sediment deposited by subglacial rivers.

Erratics

Large boulders transported and deposited by glaciers.

Tarns

Small lakes formed in cirques.

Kettles

Depressions formed by melting ice blocks that leave behind low-lying areas.

Moraine-Dammed Lakes

Lakes that form behind moraines blocking drainage.

Permafrost

Permanently frozen ground that remains at a temperature below 0°C for at least two consecutive years.

Pingos

Ice-cored hills resulting from groundwater freezing.

Frazil Ice

Needle-like crystals forming in calm water.

Pancake Ice

Circular slabs that form in turbulent water.

Draft vs. Freeboard

Comparison between submerged and above-water portions of ice.

Pressure Ridges

Ridges formed by the collision and deformation of ice.

Surface Melt

Seasonal melting that contributes to the formation of supraglacial lakes.

Moulins

Vertical shafts that transport meltwater to the base of glaciers.

Subglacial Lakes

Lakes located beneath glaciers, important for understanding glacial hydrology.

Greenhouse Gases

Gases like CO₂ and CH₄ that are released from melting ice, contributing to climate change.

Albedo Effect

The warming effect caused by the loss of reflective ice surfaces.

Isostatic Rebound

The rise of land that occurs after glaciers have melted away.

Milankovitch Cycles

Orbital changes that regulate solar energy distribution, influencing glacial cycles.

Varves

Annual layers of sediment deposited in glacial lakes, representing seasonal deposition.

Outwash

Sorted sediments that result from glacial meltwater activity.

Till

Unsorted debris deposited directly by glaciers.

Altimetry

A method to measure changes in ice surface height.

Radar

Technique used to reveal ice thickness and subglacial features.

Seismology

The study of icequakes and subglacial processes using seismic methods.

Gravimetry

Method of mapping gravitational variations to estimate ice mass.

Ice Cores

Cylinders of ice drilled from glaciers that contain gases and aerosols indicating past climates.

Glacial Hazards

Risks associated with glaciers, like ice avalanches and GLOFs (Glacial Lake Outburst Floods).