Transportation Mechanisms in Glaciers

Glaciers are extremely slow moving, but perfectly transport material from one area to another. They do this in several ways:

  • Freeze-thaw weathering causes large pieces of rock to break off and fall onto the glacier. Once there, these rocks are transported to different areas.
  • As glaciers move downhill, they can “pluck” rocks from their surroundings. These rocks then travel downhill along with the glacier, within the icy flow.
  • Debris in front of the glacier is pushed downhill by the force of the moving ice in a process called bulldozing. Imagine a bulldozer clearing a path, but in this case, it’s a glacier pushing material ahead of it.

Moraines

The materials that are moved and deposited by a glacier are called moraines. These are accumulations of debris deposited by glaciers. There are several types of moraines, including:

  • Terminal Moraine: This is a mound or ridge made of debris that marks the farthest point a glacier reaches. Think of it as a line that shows how far the glacier stretched. Terminal moraines typically have a crescent shape and you can find them at the end of a valley or basin.
  • Lateral Moraine: These are elongated mounds or hills of debris that form along the sides of a glacier. As the glacier moves, it gathers material like rocks and dirt along its edges, creating these moraines which run parallel to the glacier.
  • Medial Moraine: When two glaciers come together, the debris along their edges can merge to form a medial moraine. This looks like a dark stripe or line running down the middle of the new, larger glacier.
  • Ground Moraine: This is the layer of debris and sediment left behind by a retreating glacier. As the ice melts and pulls back, it deposits a layer of material over the land it once covered. Ground moraines typically have a blanket of debris covering the ground, creating a surface that is mostly flat or has gentle hills and dips.