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.
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.
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.
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 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.
There are different types of glaciers such as Alpine glaciers and Continental glaciers.
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.
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.
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.
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.
When a glacier starts to melt, the sediments that the glacier was carrying get left behind. Some of this includes:
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.
When glaciers move, they cause the land to change. Some of the changes include: