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Read all about glaciers

All you need to know about the glaciers

What is a glacier?

A glacier is made up of fallen snow that has over many years, often centuries, compressed into a thick and persistent body of dense ice. The ice is then constantly moving under its own weight. This causes the glacier to slowly deform and flow creating crevasses, seracs, and other distinguishing features. Glacier can only form on land and actually make up about 1/10 of the Earth’s dry land. Glaciers carry the most reservoir of fresh water supply in the world. They grow during winters but shrink during summers. Glaciers can have a tremendous effect on the land and habitats of the land as they carve valleys, scrape the earth beneath them, as well as pushing and shoving the earth’s soil around. But glaciers are also affected by climate as well as other natural factors. This is especially true for Iceland, where volcanic eruptions and earthquakes can shape and size the glaciers.

How are glaciers formed?


A glacier begins to form when snow remains in the same location year-round. Eventually the snow will transform into ice and each year a new layer of snow will cover and compress the older layer.
The compression then forces the snow to re-crystallize which will form grains. Those grains are similar in size of sugar grains. With time these grains will enlarge and the air pockets between them get smaller. This causes the snow to slowly compact and the density increases.

In about 2 years the snow has turned into, what is called firn. This is the state between snow and glacier ice. Firn is about two-thirds as dense as water. The density will then only continue to increase and over time the larger ice crystals become even more compresses causing the air pockets to get even smaller. If the glacier is very old the crystals can be only several inches in length. But this usually doesn’t happen until more than a hundred years into the process.

What types of glaciers are there?

Mountain glaciers
These are the kind of glaciers that develop in high mountain regions. They often flow out of ice fields that can span over several peaks or even a whole mountain range.
The largest mountain glaciers can be found in the Himalayas in Nepal, The Andes mountains region in S-America, in Arctic Canada and in Alaska, N-America.

Valley glaciers
Valley glaciers glide down valleys and are often quite long. They are often described tongue-like. The glacier often flows down beyond the snow line and sometimes even reach sea level. When a valley glacier flows far enough to reach sea it’s often called a Tidewater glacier. These are often the glaciers that icebergs at sea originate from.

Piedmont glaciers
Piedmont glaciers are the glaciers that spill into quite flat plains from steep valleys. They then often spread into bulb-like lobes.

Cirque glaciers
These glaciers are typically found high in mountainsides and tend to be quite wide rather than long. They take their name from their bowl-like hollows they occupy.

Ice Aprons
Ice Aprons are the glacier the hang to high mountainsides and are quite small. They are often wide rather than long. These glaciers types are common in areas like the Alps and New Zealand. They are also known to cause avalanches due to the steep incline they stand against.

Rock Glaciers
When glacial ice is covered by debris moves very slowly it sometimes forms what we call a Rock glacier. They are often formed in steep valleys where both rocks and soil can fall from the hills into the ice.

Ice sheets
This type is now only found in Greenland and Antarctica. They are gigantic continental masses of ice and snow that expand over 50,000 kilometers or 19,305 square miles. Ice sheets were once also found covering parts of Canada and Scandinavia but they have now disappeared leaving behind only a few ice caps and mountain glaciers.

Ice shelves
Are basically ice sheets that are now floating on water and they can range from a few hundred meters to over 1 km or 0.62 miles. Ice shelves found surrounding most of the Antarctic continent.

Ice caps
Ice caps are basically miniature ice sheets. They cover less than 50,000 square kilometers or 19,305 square miles. They mainly form in sub-polar and polar regions that have high elevation and are quite flat.

Ice fields
They are quite similar to before talked about Ice caps but the difference lies in the way they flow.
The flow of Ice fields is influenced by underlying topography. They are also usually smaller than ice caps. Langjökull, the second largest glacier in Iceland is for an example a Ice field.

Ice streams
Ice streams are enormous masses of flowing ice that are often quite sensitive to changes. This can be for example loss of ice shelves at their terminus or a changing amount of water that flows beneath them. Ice stream are very large and set within an ice sheet. They are for that reason surrounded ice that is flowing very slowly.

What about glaciers and climate change?

Glaciers are hugely impacted by climate changes, these magnificent crystalline forms are losing volume at a rate which is gaining acceleration. Since the first half of the 19th century more than two-thirds of the ice cover in the Pyrenees has melted, much of it after 1980.

Satellite imagery shows that the Helheim Glacier in Greenland did not alter between 1950 and the year 2000. However, by 2005 this glacier was retreating an astonishing 110 feet per day. Some glaciers have been declassified as such because they ceased to satisfy the defining criteria. Climate change scientists are predicting the disappearance of many more glaciers over the next twenty years.

Climate change in Iceland  

In 2014 the Icelandic glacier, Okjökull, could no longer be classified as a glacier, it had become too small to move under its own weight – something a glacier has to do!
Here you can clearly see how much Ok glacier has decreased in the last century. The red line is where the glacier stood in 1890, the green is from 1945 and the purle one from 2012.  Photo from Vísindavefurinn.

ok glacier in iceland  okjokull glacier iceland

The number of polar bears who swim ashore, or rather the lack of them in recent years is also a big indicator of Icelandic climate change. We only have to look to Landnámabók (The Book of Settlement), an Icelandic Saga, to see that polar bears have crossed the pack ice from Greenland and swum onto Icelandic shores since ancient times. During the big Frost winter, 1917-1918 21 beers were listed and one might guess that they must have been even more. Experts tell us that usually one to two bears made this journey each year.  Since 2000 the reduction in pack ice has changed things, now, most years there are no bears. In 2016 just one polar bear made her way ashore, she was the first visitor for several years.  

What do glaciers give to us?

When people are asked to think about the loss of glacial ice their first thoughts normally relate strongly to the destruction of pure, pristine and uniquely beautiful wild places. Hopefully, we would all agree that the preservation of some of the purest, great wilderness areas on earth is a matter of supreme importance.

There is far more at stake here than the loss of beauty. The glaciers and sea ice perform an important function when it comes to holding back the pace of climate change. Glaciers and sea ice reflect heat away from the earth, the reduction in ice will, therefore, actually accelerate global warming. Glacier and sea ice provide a mechanism which limits the pace of global warming, giving some protection to ecosystems. Glaciers give us far more than we realize!