50 Fun Facts About Glacier

A glacier forms where the accumulation of snow exceeds what, over many years?

Ablation is the loss of ice by melting, evaporation and calving; the equilibrium line marks where gain equals loss.

Roughly what percentage of Earth's glacial ice is held in the polar ice sheets?

The rest is in mountain glaciers on every continent except mainland Australia.

Which country has more glacial ice than any other outside the polar regions?

It has more than 7,000 known glaciers.

Glaciers cover roughly what share of Earth's land surface?

Nearly all of that is the Antarctic ice sheet, which blankets about 98% of the continent to an average depth of 2,100 metres.

Glacial ice and ice sheets hold roughly what share of the world's fresh water?

That makes glaciers the largest reservoir of fresh water on the planet.

Why does glacier ice look blue?

Air bubbles make ordinary ice white; in a glacier they are squeezed out under pressure.

The word 'glacier' comes ultimately from a Latin word meaning what?

It arrived in English from French via Franco-Provencal and the Vulgar Latin glaciarium.

What is the study of glaciers called?

Glaciers are a key part of the cryosphere, the frozen portion of the Earth system.

Above what area is a body of glacial ice classed as an ice sheet rather than an ice cap?

Only two ice sheets exist today, covering most of Antarctica and Greenland.

If both the Antarctic and Greenland ice sheets melted, roughly how much would global sea level rise?

Meltwater from today's shrinking glaciers is already what the IPCC calls a 'slow onset' driver of sea level rise.

What are rocky peaks that poke up through an ice sheet called?

They barely erode at all, an estimated 5 metres per 1.2 million years.

Glaciers that end in the sea and calve icebergs are known as what?

They go through centuries-long cycles of advance and retreat that are far less tied to climate than other glaciers.

A glacier that is at melting point from surface to base all year round is called what?

Polar glaciers stay below freezing throughout; a warm-based glacier can slide on a film of meltwater at its bed.

What is the granular, partly compacted snow that is on its way to becoming glacial ice called?

Fresh snow becomes neve, then firn, and finally glacial ice as the air is squeezed out over years.

What is the armchair-shaped hollow, also called a corrie or cwm, where a glacier usually begins?

Snow collects and compresses there until the ice overflows the 'lip' and starts to move.

Roughly how thick must ice be before a glacier will even begin to flow?

Once it passes about 50 metres, the upper layers slide over the lower ones and the ice deforms as a plastic flow.

Who came up with the essentially correct explanation of glacier flow in the 1840s?

Rival ideas included regelation and the notion that refreezing meltwater made glaciers dilate; acceptance took decades.

What is the typical mean speed of a glacier?

Greenland's Jakobshavn Isbrae can manage 20 to 30 metres a day, and surging glaciers have hit 90.

What are the cracks called that open in the rigid upper 50 metres of a glacier?

They rarely exceed 46 metres deep, because below that the ice is plastic; hidden under snow bridges they make travel hazardous.

What is a moulin?

Streams then run through englacial or subglacial tunnels and sometimes pop out again at the surface.

Isolated pinnacles of ice left where the cracks in a glacier's surface intersect are called what?

They form in the rigid fracture zone, the top 50 metres of the ice.

The combined width of a glacier's dark and light ogive bands usually equals what?

They form below icefalls, where broken ice ablates faster in summer and collects more snow in winter.

Glaciers moving faster than about a kilometre a year can trigger what?

In Greenland they peak in July to September and roughly doubled between 2002 and 2005.

What are the two principal processes by which glaciers erode terrain?

Plucking lifts blocks of fractured bedrock; abrasion sandpapers the rock beneath into flour.

What is the pulverised sediment produced by glacial abrasion called?

Its grains are just 0.002 to 0.00625 mm across, and wind can carry them far away to form deep deposits.

Long scratches carved into bedrock by boulders in a moving glacier are called what?

Mapping their direction tells researchers which way the ice was flowing.

Large boulders carried far from their source and dropped by a glacier are called what?

They can be a completely different rock from what they sit on, and their patterns hint at past ice movements.

What is a moraine formed at the foot of a glacier called?

Lateral moraines run along the sides, and medial moraines form where two glaciers merge; the word was coined by French Alpine peasants.

What are the canoe-shaped glacial hills called, of which about 10,000 lie east of Rochester, NY?

Their steep side faces the direction the ice came from, and their formation is still not fully understood.

Glaciers turn V-shaped river valleys into valleys shaped like which letter?

Smaller tributary glaciers cut less deep, leaving 'hanging valleys' perched above the main trough.

What is a glacial valley called if it runs into a large body of water?

Fjords can be a kilometre deep because ice is steered into them and erodes fastest where it is thickest.

What is the narrow ridge called that is left when two back-to-back cirques erode their walls?

Several cirques around one mountain leave a pyramidal peak; the steepest are called horns.

A bedrock knoll smoothed on the up-glacier side and plucked steep on the down-glacier side is what?

The name means 'sheepback rock'; they range from under a metre to hundreds of metres long.

What are the small lakes called that form when buried blocks of ice melt in outwash plains?

Most are circular because the ice blocks rounded off as they melted; they range from 5 metres to 13 km across.

Long, sinuous ridges of sand and gravel left by streams under a glacier are called what?

They can top 100 metres in height and run for 100 km.

Wind-blown glacial dust builds up as which deposit, hundreds of metres deep in parts of China and the US Midwest?

Katabatic winds pouring off ice sheets are an important part of the process.

Glaciers around the world have retreated substantially since the end of which period, around 1850?

A slight cooling let many alpine glaciers advance between 1950 and 1985, but the retreat since has been almost universal.

Reference glaciers tracked by the World Glacier Monitoring Service have lost ice every year since when?

In 2023 alone, Switzerland lost 4% of its glacier volume.

The United Nations declared which year the International Year of Glaciers' Preservation?

Switzerland spends close to US$500 million a year on barriers, nets and drainage to protect Alpine settlements from glacial hazards.

Ice cores show that for at least the last million years global temperatures have tracked what?

Researchers analyse the gas in bubbles trapped in each layer to reconstruct the ancient atmosphere.

An ice sheet typically depresses Earth's crust by what fraction of its own thickness?

After the ice melts the crust slowly rebounds, as is happening measurably in Scandinavia and around the Great Lakes today.

Which is the southernmost glacial mass in Europe?

It lies at a latitude of about 41 degrees 46 minutes north.

In the 2020s, Africa's last glaciers sat on Mount Kenya, the Rwenzoris and which peak?

Between 35 degrees north and south, glaciers survive only in the Himalayas, Andes and a few high peaks in East Africa, Mexico, New Guinea and Iran.

Why can glaciers not form in the McMurdo Dry Valleys of Antarctica despite the bitter cold?

They are polar deserts; cold air simply cannot carry much water vapour.

On Mars, mid-latitude glaciers lose ice solely by which process?

The atmosphere is too thin for liquid water; radar has found ice hiding under rock in 'lobate debris aprons'.

New Horizons found glacial flows of which ice around the Sputnik Planitia basin on Pluto in 2015?

The basin surface is broken into polygons thought to be convection cells driven by Pluto's internal heat.

Which Greenland glacier can flow as fast as 20 to 30 m a day?

That is dozens of times the typical glacier pace of about a metre a day; in stagnant parts of Alaska, trees even grow on glacier surfaces.

During a surge, a glacier's speed can temporarily reach up to roughly how much per day?

Surges may be triggered when meltwater pools beneath the ice, lubricating the bed before the glacier settles back to normal.

In New Guinea, the last small glaciers clung to which peak into the 2020s?

Mainland Australia has no glaciers at all, though one sat on Mount Kosciuszko during the last glacial period.

What is the term for a tributary trough left stranded high above the main glacial trough?

Main glaciers deepen their valleys more than their tributaries do, so the side valleys end abruptly, often in waterfalls.