A glacier is when ice or snow does not completely melt when the weather gets warmer and then as new snow falls on top of it, thick layers are formed and the pressure from the weight of the snow causes the snow to turn into glacial ice.


How Does a Glacier Move?

Even though a glacier looks like it would be heavy and that it looks like a very big piece of ice, it really moves very, very slow.  The only reason that the glacier moves is because the weight and pressure from the ice causes it to start to change forms and the water to flow.

Water that flows from the bottom of the glacier is called meltwater.  The meltwater causes the glacier to move over the land.

Aerial view of a glacier in Chugach State Park

A glacier only moves a few centimeters to a few meters each day.

When a glacier speeds up, it is called surging.  When a glacier is surging, it can go up to 10 meters to hundreds of meters each day.

What Are Parts of a Glacier?

The upper layers and the edges of the glacier are not under pressure like the bottom of the glacier is.  The areas that are not under pressure are more likely to crack than other parts of the glacier.  When these areas crack, it is called crevasses.

When the glacier runs into valleys or bumps into things, many of the crevasses are formed around the edges of the glacier.

The part of the glacier that is where the ice is beginning to melt is called the ablation.  The ablation is the part of the glacier that is melting and where evaporation is taking place.

The Aletsch Glacier, the largest glacier of the Alps

The area of the glacier where the snow falls and sticks are called the accumulation zone.  The accumulation zone is on top of the ablation.

When the snow of a glacier is pushed together between the ice and the new snow, this is the area of the glacier that is called the firn.

The end of the glacier is called the terminus or the glacier foot.

The beginning of the glacier or where the glacier starts is called the head.

Types of Glaciers

There are different types of glaciers such as Alpine glaciers and Continental glaciers.

  • Alpine glaciers-these type of glaciers happens high in the mountain areas.  They form glaciers that look like bowls and they are hollow.  These are called cirques.
  • Continental glaciers-these are glaciers that have many, many masses of ice.  The Continental glacier is a lot bigger than the Alpine glacier.
  • Calving glacier-A calving glacier stops when it reaches the lake or ocean.  This type of glacier is also called a Tidewater glacier because it breaks up by the waves of the water.
  • Cirque glacier-A cirque glacier is one that forms where the mountains slopes.  This is another name for an Alpine glacier.
  • Hanging glacier-A hanging glacier is one that form along the valley or mountain.  They are called hanging because they never get to the valley where the main part of the glacier is.
  • Ice cap-This is the area of a glacier that covers all the land.  Nothing shows above the ice cap, not even mountains.
  • Piedmont glacier-This is the type of glacier that is found at the edge of a mountain range.
  • Polar glacier-A polar glacier is formed in areas where the temperature is always freezing.
  • Temperate glacier-A temperate glacier is a glacier that is formed in water.
  • Valley glacier-A valley glacier is a glacier that fills the complete valley between two different mountain ranges.

Where Are Most Glaciers Found?

Most glaciers are found around the South Pole or the North Pole.  Some of the glaciers are found high in the mountains such as in the Himalaya Mountains or the Andes Mountains.

The whole world is about 10% covered with glacier ice.  Since it takes so long for snow to fall, some glaciers take years and years to get very big.

What Are Glaciers Made Up Of?

Even though we think of glaciers being made up of only ice and water, this is not true.  Most glaciers are made up of ice, water and different kinds of rocks and other sediments.

When we look at a glacier, it looks very dirty and not just like clean ice.  This is because of all the sediments and rocks that are picked up as the glacier moves.


When the bottom of the glacier starts to melt, it will refreeze into the rock that is surrounding it.  As the glacier begins to move, some of the rock is pushed into the glacier and it is carried on the glacier as it moves.  When there is rock and other debris that is around the glacier, it can also be carried at the bottom of the glacier.

When rocks fall from the mountains, they can also fall on the glacier and this will be carried as the glacier moves.

As the temperatures start to warm up, such as in the summer months, the snow and the ice that the glacier is made up of starts to melt.  When this happens, the meltwater will flow on top of the glacier and will form small streams on top of the glacier.  Then some of the meltwater will fall through cracks and small drainage areas on the glacier.  These small drainage areas are called moulins.

History of Glaciers

Some glaciers are Alpine glaciers, and these are glaciers that are formed on top of mountains.  These glaciers can be seen all over the world.

Some of the mountains have so much ice that they can form ice caps or ice fields.  Some of the biggest ones are found in Antarctica and Greenland.

Years ago, though, the Alpine glaciers that were in the mountains covered a large part of the different continents.  There were many areas in North America and Europe that had huge ice sheets.

When scientists study glaciers, they can tell how big these ice sheets were by the different landforms and by the different rocks and sediments that the ice sheets left behind as they moved.


Around 650 million years ago was the Neoproterozoic era.  During this time, most of the Earth was covered with ice and there was a theory called the “snowball theory.”  This “snowball theory” says that the Earth was covered in ice.

Then around 2.5 billion years ago, the Paleoproterozoic era happened, and this is when much of the continents were covered by ice sheets.  Some of the deposits that were found in Canada were deposits that had turned into solid rock.

Ice Shelves

When there are glaciers that float in the ocean or the sea, they form what are called ice shelves.

As the ice shelves flow, some of the ice can break off and go into the water.  When this happens, it is called calving.  Some of the calving can be super large, even more than 250 kilometers long.

When there are small ice bergs that break off then they are called bergy bits.

Sediment Till

When a glacier starts to melt, the sediments that the glacier was carrying get left behind.  Some of this includes:

  • Rock
  • Debris
  • Sand
  • Mud
  • Salt

All of these things that get left behind are called sediment till.  Then as the sediment is left behind, it sometimes gets put at the edges or the front of the glacier.  When sediment is left on the edges or the front of a glacier, this is called a moraine.

When winds blow, the dirt and rock that is in the glacier can blow and it can build up in different size layers.  These sediment layers of left behind glacier dirt is called loess.  Some loess’ are so big that people use them to build their homes in.

What Do Glaciers Make as They Move?

When glaciers move, they cause the land to change.  Some of the changes include:

  • Tarn-tarn is when the lakes fill up because of the water that has melted off of the glacier.
  • Moraine-This is when the till left behind by the glacier builds up.
  • Horn-This is a mountain that is pointy and is created when erosion happens on top of the same mountain.
  • Fjord-A fjord is a valley that is formed by glaciers.  This is usually a U-shaped valley.
  • Drumlin-A drumlin is when a hill is crated because of a glacier.  This hill is usually oval shaped and very long.
  • Cirque-A cirque is a glacier that is shaped like a bowl.
  • Arete-This is a ridge that is formed by two glaciers.  When the glaciers erode on the opposite sides of the ridge, a steep area is formed.  This steep area or ridge is called an arete.

Facts About Glaciers:

  • When a scientist studies glacier, they are called glaciologists.
  • Greenland is covered by an ice cap that can be over 2 miles thick.
  • When a glacier melts faster than it is forming more ice, it is called a retreating glacier.
  • A retreating glacier looks like it is moving backwards but it is just melting.
  • The Bering Glacier is the longest glacier in the United States.
  • The Bering Glacier is in Alaska and is 125 miles long.
  • Ice in Greenland and Antarctica make up 99% of the glaciers in the world.
  • The fastest surge glacier is the Kutiah Glacier.  This glacier is located in Pakistan and moved over 12 kilometers in a three months period.
  • Some glacial ice is over hundreds of thousands of years old.
  • Sometimes glaciers look blue because they are very dense.
  • Glaciers make up the largest freshwater on the whole Earth.  They have 75% of all of the freshwater in the whole world.

What Did You Learn?

  • What is a glacier?
    A glacier is an ice sheet that is formed by layers and layers of snow piling up on each other.  As the snow piles, it causes pressure and turns the snow into ice.
  • Do glaciers move fast?
    Most glaciers do not move fast but some glaciers, called surge glaciers move much faster.
  • What happens when a glacier moves through an area?
    When a glacier moves through an area it picks up rocks and debris with it.
  • Can glaciers form in the mountains?
    Many glaciers are found in the top of mountains.  These are called Alpine glaciers.
  • Are glaciers made up of saltwater or fresh water?
    Glaciers are made up of fresh water and form 75% of all the fresh water on the Earth.