A glacier is a slowly moving mass or river of ice formed by the accumulation and compaction of snow on mountains or near the poles.
Glaciers require very specific climatic conditions.
Glaciers begin to form when snow remains in the same area year-round, where enough snow accumulates to transform into ice. Each year, new layers of snow bury and compress the previous layers. As more and more snow piles up over the years, the weight of the snow on top starts to compress the snow on the bottom. This compression turns the snow to ice. For most glaciers, this process takes more than a hundred years.
Glaciers form only on land and are distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water.
What makes glaciers unique is their ability to move. Due to sheer mass, glaciers flow like very slow rivers.
Some glaciers are as small as football fields, while others grow to be dozens or even hundreds of kilometers long.
Glaciers are usually divided into two groups – alpine glaciers, which form on mountain sides and more downward through valleys; and continental ice sheets, which spread out and cover large areas.
On Earth, 99% of glacial ice is contained within vast ice sheets in the polar regions. [Photo below: South Pole – Antarctica]
Continental glaciers cover nearly 13,000,000 square kilometers (5,019,328 square miles) or about 98% of Antarctica’s 13,200,000 square kilometers (5,096,548 sq mi), with an average thickness of 2,100 meters (7,000 feet). Greenland and Patagonia also have huge expanses of continental glaciers.
Mountainous regions on every continent except Australia also contain glaciers.
Glaciers are found in 47 countries.
Glaciers form the largest reservoir of fresh water on the planet. About 75% of Earth’s fresh water is stored in glaciers.
The largest glacier in the world is the Lambert-Fisher Glacier in Antarctica. At 400 kilometers (250 miles) long, and up to 100 kilometers (60 miles) wide, this ice stream alone drains about 8% of the Antarctic Ice Sheet.
Glaciers are so powerful they can change the shape of mountain valleys. As a glacier flows down a valley it wears away the rock and changes it from a typical V-shape, created by river erosion, to a U-shape. This characteristic U-shape makes it easy to spot ancient glacial valleys.
Glacial motion can be fast (up to 30 meters (98 feet) per day, observed on Jakobshavn Isbræ in Greenland) or slow (0.5 meter (1.6 feet) per year on small glaciers or in the center of ice sheets), but is typically around 1 meter (3.3 feet) per day.
In 1953 the Kutiah Glacier in Pakistan advanced more than 12 kilometers (7.4 miles) in three months, averaging some 112 meters (367 feet) per day – the fastest glacial surge.
Glacial ice is a different color from regular ice. It is so blue because the dense ice of the glacier absorbs every other color of the spectrum except blue – so blue is what we see!
Glaciers are made up of more than just ice and snow. They contain water, rocks and sediments. This can make the ice look very dirty.
Glacial ice can be hundreds of thousands of years old, making it valuable for climate research. By extracting and analysing the ice, scientists can learn about what the climate was like on Earth thousands of years ago!
From the 17th century to the late 19th century, the world experienced a “Little Ice Age,” when temperatures were consistently cool enough for glaciers to advance in many areas of the world.
The 1991 discovery of the 5,000 year-old “ice man,” preserved in a glacier in the Alps, fascinated the world. Tragically, this also means that this glacier is retreating farther now than it has in 5,000 years, and other glaciers are as well.
Because glacial mass is affected by long-term climatic changes, e.g., precipitation, mean temperature, and cloud cover, glacial mass changes are considered among the most sensitive indicators of climate change and are a major source of variations in sea level.
U.S. Geological Survey estimates that if all of the world’s glaciers melted, sea level would rise by more than 80 meters (260 feet).
During the maximum point of the last ice age, glaciers covered about 32% of the total land area.
The study of glaciers is glaciology.
Ice shelves form when glaciers reach the sea and begin to float.
When the ice comes off the glacier it’s called ‘calving’. When that chunk of ice floats in the water it is called an iceberg.
The word “glacier” comes from the French language and the name is derived from the Latin word glacies meaning “ice“.
Glacial ice is a lot different from the frozen water you get out of the freezer.
A single glacier ice crystal can grow to be as large as a baseball.