The correct answer is
B. drumlins.
Detailed Explanation
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Definition of Drumlins: Drumlins are smooth, oval-shaped hills that are formed by the movement of glacial ice. They are typically composed of boulders, sand, and gravel that have been deposited by the glacier as it advances and retreats. The shape of a drumlin is streamlined, with a steeper side facing the direction from which the glacier came and a gentler slope on the opposite side.
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Formation Process: Drumlins are formed under the ice of a glacier. As the glacier moves, it picks up and transports sediment. When the glacier retreats, it deposits this sediment in a streamlined hill shape. The specific conditions of the glacier's movement, including its speed and the amount of sediment it carries, influence the size and shape of the drumlin.
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Characteristics of Drumlins:
- Shape: They are elongated and oval, resembling the shape of a spoon or a teardrop.
- Composition: They are primarily made up of glacial till, which includes a mix of clay, silt, sand, gravel, and boulders.
- Orientation: The orientation of drumlins is typically aligned with the direction of glacial movement.
Why Other Options Are Incorrect
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A. Eskers: Eskers are long, winding ridges of stratified sand and gravel that were deposited by meltwater streams flowing beneath a glacier. They are not oval-shaped hills but rather elongated features that can stretch for several kilometers. Therefore, they do not fit the description of smooth oval hills.
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C. Moraines: Moraines are accumulations of debris (till) that have been pushed along by a glacier. They can take various forms, including lateral moraines (along the sides of glaciers), terminal moraines (at the end of glaciers), and ground moraines (beneath the glacier). Moraines are typically more irregular in shape and are not specifically smooth or oval.
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D. Aretes: Aretes are sharp ridges that form between two glacial valleys. They are characterized by their steep sides and jagged peaks, resulting from the erosion of glaciers on either side. Aretes are not smooth or oval-shaped and do not fit the description provided in the question.
Summary of Key Points
- Drumlins are smooth, oval hills formed by glacial activity, composed mainly of boulders, sand, and gravel.
- They are streamlined in shape, with a steep side facing the glacier's direction of movement.
- Other options (eskers, moraines, aretes) do not match the description of smooth oval hills and have distinct characteristics that differentiate them from drumlins.
Revision Summary
- Drumlins are oval-shaped hills formed by glacial deposits.
- They consist of boulders, sand, and gravel, shaped by glacial movement.
- Eskers, moraines, and aretes are different landforms with unique characteristics.
- Understanding the formation and features of these landforms is crucial for geography studies.