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How Glaciers Are Formed

Margerie Glacier, a 21-mile long glacier, in Glacier Bay, Alaska.

Margerie Glacier, a 21-mile long glacier, in Glacier Bay, Alaska.

What is a Glacier?

A glacier is a large body of ice, created by the accumulation of snow, that persists over several years, often lasting centuries. Glaciers occur in the earth's polar regions as well as mountainous areas.

There are a number of phases that these massive chunks of ice go through which include their initial formation, continual growth, and flow. This process is called glaciation.

Glaciers are an important indication of climate change, so scientists often monitor and study them in an effort to better understand the effect humans have on the earth's climate. While not much is known in regards to why glaciers are disappearing, scientists do know how they are created.

Each summer, gravel is deposited on top of the Cavell Glacier. Each streak along this glacier represents one year.

Each summer, gravel is deposited on top of the Cavell Glacier. Each streak along this glacier represents one year.

How Glaciers Form

When snow does not melt, it accumulates and glaciers form when snow accumulates faster than it can melt or evaporate. The weight of the accumulating snow compacts the older, lower layers. This compression causes the snow to crystallize and become more dense, essentially turning sheets of snow into compacted ice.2

The process of glacier formation can happen in two ways:

  1. Alpine glaciers form in high mountain ranges where snow accumulates in a basin or cirque, and then flows down a valley as a stream of ice.
  2. Continental glaciers form when snow accumulates over a large area, such as a polar region, and forms a thick ice sheet.

The critical ingredient for glacier formation is long-term snowfall that exceeds the rate of melting and evaporation. This most commonly occurs in areas of high elevation or high latitude, where temperatures are low enough to allow snow to persist year-round.

It is worth noting that climate change and global warming have been affecting the formation of the glacier, reducing their size and causing some to disappear.

Compressed snow is called firn. New firn, found in the upper layers of a glacier, is made up of granules of ice, each about the size of a grain of sugar. As firn is further compressed by new snowfall, the granules fuse together creating even larger crystals of ice. As it further compresses, it becomes considerably more dense than the newer firn. After enough compression, it turns into what is called glacial ice.

How much weight and pressure is needed to cause firn to become glacial ice? Firn usually turns into glacial ice when it's around 150 feet deep. This is when the weight of the upper layers of the glacier puts so much pressure on the older firm that it's crystallized into solid ice.

A chunk of ice falls from the Perito Moreno Glacier in Argentina.

A chunk of ice falls from the Perito Moreno Glacier in Argentina.

Where glaciers can be found (in blue.)

Where glaciers can be found (in blue.)

Where Can Glaciers Be Found?

Glaciers only form in areas of colder temperatures where snow is unable to completely melt.1 Polar regions such as Antarctica or Greenland are known for having most of the world's glaciers. This is because these areas are so cold that any snow that accumulates doesn't melt away.

Glaciers can also be found in areas of high altitude, where the air is cold year-round. For example, a number of glaciers are located in the Himalayas, the Alps, and the Andes.

Since the creation of glaciers depends heavily on snowfall, they do not exist in cold deserts. While these areas often experience frigid weather, because it does not often snow, glaciers are unable to form.

A huge crack in Antarctica’s Pine Island Glacier

A huge crack in Antarctica’s Pine Island Glacier

Did you know?

If Antarctica's ice sheet completely melted, the oceans would rise about 210 feet!

The Movement & Anatomy of Glaciers

In mountainous regions, gravity and deformations in the ice cause the top layers of glaciers to flow downward to the valley below. This very slow process causes stress on various parts of a glacier which often causes deformities like crevasses and seracs.

The area where the glacier originates is called the glacier head, or the accumulation zone. As the ice flows away from the accumulation zone, it is replaced by new firn, which will eventually become a part of the glacier as well.

As glaciers move, glaciers often carve their way through soil and rock, creating unique landforms. They also sometimes pick up and carry large rocks and boulders, which are left behind when the glacier eventually melts.3 Because of this, huge boulders left by glaciers that occurred thousands of years ago can be found all over the world!

Glaciers melt as they move to warmer areas, and provide the land with fresh water, an invaluable resource. As you may have guessed, glaciers are major storehouses of water. In fact, they store about 69% of the world's freshwater!4

The "glacier foot" is where the glacier ends. The glacier can end in a valley where the foot may melt (creating "meltwater") or end in a large body of water, where chunks of ice often break off and float away as icebergs.

The Greenland Ice Sheet (Photo taken near Kangerlussuaq, Greenland)

The Greenland Ice Sheet (Photo taken near Kangerlussuaq, Greenland)


  1. "Where Glaciers Are Found." National Park Service.
  2. "How Are Glaciers Formed?" National Snow & Ice Data Center.
  3. "Glaciers." Northern Illinois University.
  4. "Glaciers and Icecaps: Storehouses of Freshwater." US Geological Survey, 9 March 2012.

© 2012 Melanie Palen


Suhail Zubaid aka Clark Kent from Mississauga, ON on January 06, 2013:

What a beautiful and informative hub!

I read a lot about glaciers, because the geographical features close to where I live, known as Niagara Escarpment, were also impacted by a glacier millions of years ago. Then also Baltoro Glacier in the Karakorums of Pakistan is the one that I hiked to back in the late 80s.

I read three books recently that familiarized me to the world of glaciers.

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Tristan Gooley's 'Natural Explorer' narrates some important features of glaciers, such as valleys formed by glaciers are 'u' shaped, as opposed to 'v' shaped valleys formed by rivers.

Kieran Mulvaney introduces readers to Polar Bears and to the world of arctic glaciers and ice in his book 'The Great White Bear'.

Tom Avery, in his book 'To the end of the Earth', takes his readers on a journey to the North Pole along with his team of 5 humans and 16 sled dogs and in the process them to the tough world of glaciers and exceptionally difficult trek across them.

Thank you Mel, for keeping my interest in glaciers alive.

Tammy from North Carolina on January 06, 2013:

These are so beautiful to look at, but I wouldn't want to climb one. This is an informative hub with wonderful photos!

Marcy Goodfleisch from Planet Earth on January 06, 2013:

I've always been fascinated by glaciers - and one of my goals is to do an Alaskan cruise, so this is a compelling hub for me! You always have great hubs about interesting topics, Mel!

Vin Chauhun from Durban on May 07, 2012:

great, interesting article.....i wonder if any of my long time extinct relatives are buried under any of those mammoth glaciers,,,,,

Melanie Palen (author) from Midwest, USA on April 09, 2012:

I had a blast writing on this topic, so I'm glad you guys enjoy it! It makes me want to go trekking in Patagonia or just take a trip up to Alaska to see Margerie Glacier!

TENKAY from Philippines on March 22, 2012:

I just hope all these glaciers won't melt because of global warming. It's going to wipe our country from the map.

This is an informative hub and I love the pictures.

Voted up and interesting.

Danette Watt from Illinois on March 21, 2012:

Great article on glaciers, which I've always found interesting anyway. They are so huge, massive, I can't imagine standing near one. I know there is concern in the scientific community about their melting. Who said climate change isn't a reality. Great photos too

James Kenny from Birmingham, England on March 21, 2012:

You're right Bob. I live in the Midlands, and if another ice age struck, then my house would be buried by a mile of ice. The rest of the UK will turn into Arctic tundra, so we'll have to learn how to hunt musk ox and dodge polar bears. We'll no longer walk dogs, instead we'll have them pushing sleighs in sub zero temperatures. Or, we could all just move to Spain, I wouldn't mind that.

diogenes from UK and Mexico on March 21, 2012:

Good explanation about glacier formation and life.

If we do get a new ice age in the UK and it follows previous patterns, it would cut off two thirds of the country.

That would be embarrasing for the Brits: they have 700 people per square mile now! But at least they's keep warm.


James Kenny from Birmingham, England on March 21, 2012:

Really interesting article, well laid out and presented. Interesting info about the Antarctic ice cap, 210 feet, my god. That would drown most of Britain, I'd retreat to the Scottish Highlands to continue my writing career. Although, I do remember reading that it would take 10,000 years of continuous warming to melt the ice cap completely, so hopefully we'll be fine. Voted up and shared.

Joseph De Cross from New York on March 20, 2012:

210 Feet? Oh My God! I live In NJ, and that would end my writing career. Pretty much well explained Melanie. I wonder if they will ever melt if our poles ever shift, which is likely to happen. Great hub!


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