Glaciers
If you've ever seen the movie Titanic, you will know that the unsinkable ship sunk, because the Titanic had hit the side of an iceberg. Glaciers are very much similar to an iceberg, speaking the fact that they are both huge amounts of ice that you see on water. Over time, glaciers and icebergs form greatly.
A glacier is a large mass of ice that slowly moves over land. There are two different types of glaciers that you normally see in places that are cold, like Alaska or Antarctica. Those types are continental glaciers and valley glaciers.
Continental Glaciers
The first type of glacier that I had mentioned above are continental glaciers. A continental glacier is a glacier that covers much of a continent or large island. It is very possible that glaciers can spread out to even millions of square kilometers. Greenland and Antarctica are two places with very many glaciers. These continental glaciers can move from any direction. These continental glaciers are the type of glaciers you would see in the past where they had covered up most of Earth's surface. Those times were once known as ice ages. Just about 1/3 of Earth's land was covered with continental glaciers about 2.5 million years ago. 10,000 years ago they had finally melted away, and it took so long because they would always come right back.
Valley Glaciers
The second type is a valley glacier. A valley glacier is a long and narrow glacier that forms when snow and ice build up high in a mountain valley. The mountains underneath these glaciers are what keeps them pretty stable. Valleys that had already been cut by rivers are what glaciers usually slide down from. These glaciers are a lot smaller than continental glaciers, yet they can still be up to tens of kilometers long, possibly bigger.
How Glaciers Shape the Land
When a glacier moves, the land beneath it changes as well. They are major forces of erosion, even though glaciers move slowly. There are two types of erosion in which glaciers are capable of doing. These two types of erosion by glaciers are plucking and abrasion.
A glacier can sometimes pick up rocks while moving across the land in a process that people call plucking. This is because the weight of the glacier on land is able to break up rocks. Then, these rocks freeze to the bottom of the glacier, sticking to it. The rocks end up becoming stuck completely to the bottom of the glacier, so then those rocks are moving along with the glacier. As the glaciers drag the rocks across the land, it gouges and scratches the bedrock, and this is called abrasion.
Glacial Deposition
As a glacier erodes the land in its way, it gathers huge amounts of rock and soil. When a glacier melts, it deposits the sediment it eroded from the land, creating various landforms. After the glacier had melted, those landforms stay there for thousands of years. There is a mixture of sediments that a glacier deposits on the surface, which is called till. Till is a mixture of particles of different sizes. Clay, silt, sand, and also boulders are what can be included.
The till that is deposited right at the edge of a glacier and forms a ridge is called moraine. A terminal moraine is the ridge of a till of the absolute farthest point reached by the glacier. Although, retreating glaciers also create the features that are called kettles. A kettle is the small depression when a smaller piece of glacier is inside the till. The kettle stays as the ice melts away. The last ice age continental glacier had left remains, which were kettles. It is possible for kettles to have water inside of them, in which forms kettle lakes. Places that are covered in ice are where these are rather common.