What Landforms Come From A Continental Glacier

A glacier found on land is called a continental glacier.

During the Ice Ages that occurred in Earth’s history, ice and snow covered huge swaths of the land and ocean before retreating once more toward the poles. Sometimes this happened more than once in a lot of places. There are parts of the world, such as Greenland, that are still covered with glaciers. When they happen on land, they’re called continental glaciers. When they move, they produce depositional landforms such as moraines, eskers, kettle ponds, drumlins and outwash plains. They also produce erosional features.

Moraines

Moraines are the scientific term for all the rocks and debris left behind when a glacier has either moved on, or melted back. There are eight kinds, but only six of them remain once the glacier is gone to make up landforms. Those six are ground, lateral, medial, push, recessional and terminal. Ground moraine is simply where stuff gets washed out from under the ice, where it meets the ground. Lateral moraine is found at the sides of the glacier where it has broken up the earth as it has advanced or retreated, like a finger drawn in the sand. When two glaciers meet, they can sometimes get a dark stripe down the middle; this is called a medial moraine, and it’s caused by two laterals combining. If a glacier retreats and then advances again, that is the only way to get a push moraine, and you can usually tell by the way the rocks have been pushed up from being horizontal. Recessional moraines form at the very ends of the still-retreating glacier because it’s paused for long enough to let the debris pile up. The same method is used to produce a terminal moraine, but with this type, the glacier didn’t move again — it’s the furthest extent of the ice.

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Outwash Plains

The outwash plain is the usually flat land located beyond the terminal moraine. As the glacier melts, it produces a lot of water. This water flows across the ground between the ice and the earth, picking up debris as it goes along. Usually this debris is sand and silt, small stones, and the like. It gets washed out from beneath the glacier and across what is called the outwash plain. In many places where glaciers still exist, this sandy soil is used for specialized farming. One of the best places to see this type of formation in the U.S. is in Michigan.

Drumlins

Drumlin creation is still debated amongst geologists and geographers today, but several theories do exist. They all have to do with glaciers. A drumlin is a streamlined hill that can be found behind large moraine complexes, like an inverted spoon with the blunt end facing toward where the glacier has come from. There can be many of them, and they tend to form on slightly rounded or flat land, but not always. They are parallel to the direction the glacier is going, but perpendicular to the ice margin itself. The best place to see them is in Ireland; however, there are plenty of drumlins in Canada, New York and even North Dakota.

Eskers and Kettle Ponds

Eskers are ridges of gravel and sand that occur whenever a continental glacier melts away. Often, these glaciers have valleys or rivers running through them; however, instead of their bottoms and banks being the earth, they’re all ice. When the ice melts, it leaves behind the long ridges and piles of sediment. North Dakota has one of the best-known eskers in North America: the Dahlen Esker. Another formation is the kettle pond. If a large block or chunk of ice from the glacier happens to break off and bury itself in the sediments the ice has kicked up, it will later melt and leave a large hole. Usually, water will then fill it to create a small lake.

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Erosional Landforms

Not all landforms are depositional. Erosional landforms are created by the glacier’s process of erosion as it pushes on and scrapes across the earth. These can include striations, cirques, glacial horns, aretes, U-shaped valleys and hanging valleys. The cirque is the headwater of the glacier; where it begins. As the glacier moves, it cuts out striations, or scrapes, on the bedrock that can be seen today. If more than one glacier erodes the same mountain, it will create a horn, or pyramid-shaped peak. Aretes are related to horns in that two glaciers erode the same peak, only they give it a very steep-sided and sharp-edged ridge. If a glacier moves through where a river has already carved out a V-shaped trough, it will widen the bottom out to a U-shape, thus creating a U-shaped valley or glacial trough. Hanging valleys happen when a much larger glacier creates a deep valley (as the size of one determines how deep it can carve out stuff), but a smaller glacier joins it and can only create a smaller one higher up.