Glossary

Ablation: How glaciers and ice shelves lose mass. This can be through surface melting and runoff, calving icebergs, or melting at the base.

Accumulation: How glaciers gain mass, chiefly through precipitation. 

Advance: When a glacier grows longer because it is getting more snow at the top than it is melting at the bottom.

Arête: A narrow ridge of rock that separates two valleys. It is usually formed when two glaciers erode parallel U-shaped valleys.

Carbon dioxide: When a carbon atom joins with two oxygen atoms, a lot of carbon dioxide comes from burning things containing carbon

Cirque: A giant, bowl-shaped scoop carved out of the side of a mountain by a glacier.

Climate: The long-term pattern of weather in a particular area, typically averaged over a period of 30 years or more.

Climate Change: The rapid change in climate due to human activity (mainly burning fossil fuels) increasing heat-trapping greenhouse gases in the atmosphere.

Crevasse: A deep, dangerous crack in the glacier ice. They form because the ice stretches and breaks as the glacier moves over bumpy rocks.

Ecosystem: This is all the living (e.g. animals, plants) and non-living (e.g. light, water) things within a particular area

Erratic: Glacially-transported boulder that does not match the bedrock on which it sits (it is of a different origin).

Fiord: Formed when a glacier carves out a valley from the mountains to the sea. When the glacier melts, seawater fills the valley, creating a narrow inlet. Milford Sound is an example of a fiord.

Firn: Snow falls onto glacier surfaces, where the crystals change under the weight of snow above, turning into ice. The intermediate stage of multi-year hard snow is known as firn.

Glacials: Colder periods where ice sheets advance, global temperatures drop by roughly 5°C to 6°C, and vast amounts of water become locked up in ice, drastically lowering sea levels.

Glacier (Awa Kōpa): A huge river of ice that moves very slowly down a valley. They form when lots of snow falls in the mountains and packs down into ice over many years.

Glacier Milk: A milky, light-blue or grey river that flows out from the bottom of a glacier. It gets its colour from "rock flour," rock ground into a fine powder by the heavy, moving ice.

Global warming: When the average temperature on Earth rises.

Greenhouse effect: The natural way the Earth is warmed by gases in the atmosphere, known as greenhouse gases, which trap heat. If extra greenhouse gases are added to the atmosphere, such as from human activities, they absorb more heat, causing global warming.

Holocene: The last period of Earth’s history after global deglaciation. The last 10,000 years.

Horn: A sharply pointed, pyramid-shaped mountain summit, also known as a pyramidal peak. It forms when three or more glaciers erode the sides of a mountain. Each glacier carves out a deep, bowl-shaped hollow known as a cirque. As these ice scoops get deeper and deeper, the rock walls between them get steeper and skinnier, creating a horn.

Ice Age: A long period of Earth's history where global temperatures drop, causing the expansion of polar ice sheets and alpine glaciers. Surprisingly, our planet is technically still in an ice age that began about 2.6 million years ago.

Icefall: A section of the glacier that looks like a frozen waterfall. It happens where the mountain gets very steep, causing the ice to shatter into giant chunks.

Ice Shelf: Thick, permanent, floating sheet of ice that is derived from terrestrial tributary glaciers. Back pressure from an ice shelf stabilises its tributary glaciers, which may accelerate, recede, and retreat if the ice shelf melts away.

Ice Stream: Large outlet glacier moving at an order of magnitude faster than the surrounding ice. May be topographically confined. Ice streams transport 90% of the ice and sediment out of Antarctica. Their behaviour and stability are essential to the ice sheet's health.

Interglacial: Warmer interludes - like the current period we have been in for the last 11,000 years - when glaciers retreat, and the climate becomes much more temperate.

Last Glacial Maximum (LGM): The last time when the ice sheet reached its maximum extent, to the shelf break. In the Antarctic Peninsula, this occurred over 18,000 years ago.

Marine ice sheet: An ice sheet, such as the West Antarctic Ice Sheet, where the bed is below sea level. The bed gets deeper inland for the West Antarctic Ice Sheet, which may make it unstable.

Mass balance: Glaciers gain mass from precipitation and lose mass from melting. The zone where net accumulation exceeds net melting (ablation) is the accumulation zone. The zone where net melting exceeds net accumulation is the ablation zone. Mass balance is the balance between accumulation and ablation; if accumulation is greater, the glacier has a positive mass balance. If ablation is greater, then the glacier has a negative mass balance.

Moraine: A pile of rocks, dirt, and gravel that the glacier pushes along or leaves behind as it moves. It looks like a giant messy wall of dirt. It can form along the side of a glacier as lateral moraine, in the middle of the glacier as medial moraine, or at the end of a glacier as terminal moraine, where it shows the furthest point the ice ever reached.

Moulin: A deep, circular hole in the ice (like a giant plug hole) where melted surface water plunges into the inside of the glacier.

Nunatak: A mountain that protrudes above the surface of an ice sheet.

Outwash Plain: A broad, flat, or gently sloping plain formed by sediment deposited by meltwater streams at the end of a glacier. As glaciers melt, flowing water sorts and deposits eroded rock, gravel, and sand over large areas. 

Quaternary: in geology (the study of Earth and rocks), the Quaternary Period is the time period we live in now. It started about 2.6 million years ago. It is known for dramatic climate changes where massive sheets of ice repeatedly covered large parts of the Earth and then melted away.

Retreat / Recession: When a glacier shrinks and gets shorter because the weather is warm and the ice is melting faster than new snow can form.

Rock flour: Rock ground into a fine powder by the heavy moving ice of a glacier.

Sérac: A giant pillar or tower of jagged ice found in an icefall. They can be as big as a house and can fall over without warning.

Tarn: A small lake found in the mountains which fills a bowl or cirque. A glacier once carved out this hollow. When the glacier melts, water fills the bowl, creating a lake or tarn.

Terminus: Sometimes called ‘snout’; The very bottom end or "toe" of the glacier. This is where the glacier finally melts into a river.

Tidewater glacier: A glacier that originates on land but that flows out over the ocean, where it begins to float.

Till: Sediment that is deposited at the glacier sole. Typically comprises fine-grained detritus, sand, and gravel eroded, modified, and transported by the glacier.

Tributary glacier: A glacier that originates on land but flows out into the sea, where it begins to float. If the floating portion of the glacier combines with that of several other glaciers, it forms a floating ice shelf.

U-shaped valley: A valley carved out by a glacier. The ice erodes steep valley sides and a flat valley floor.

V-shaped valley: A valley created by river erosion. It is shaped like a V in cross-section.

Weather: The day-to-day, short-term state of the atmosphere at a specific time and place, such as wind, rain and temperature.