Question

Describe the various kinds of glacial deposits. Be sure to note the materials from which the deposits are made and the landforms that result from deposition.

Short answer

Glacial deposits, or glacial drift, consist of two types: Till and Outwash. Till deposits are unsorted materials dropped directly by a melting glacier, leading to landforms like Moraines and Drumlins. Outwash deposits are sorted and stratified sand and gravel dropped by meltwater, forming landforms like Outwash Plains or Sandur. These deposits and landforms, made of rock, sand, and gravel, offer crucial insight into past glaciological events and glacier impacts on the landscape.

Step-by-step solution

Define Glacial Deposits

(Glacial deposits, also known as glacial drift, are sediments deposited by a glacier. They are typically composed of a mixture of materials, including rock, clay, sand, and gravel, which have been eroded from the landmass and transported by the movement of the glacier.)

Discuss Types of Glacial Deposits

(There are two types of glacial deposits: Till and Outwash. a. Till: These are unsorted deposits that a glacier drops directly onto the landscape as it melts. The materials causing till deposits include rock particles varying in size from clay to boulders, often mixed together without layering. b. Outwash: These glacial deposits are sorted and dropped out by water flowing from the melting ice of a glacier. The resulting deposit, often stratified sand and gravel, has been sorted and carried along by the water, ending up in river bends or forming outwash plains.)

Describe Landforms from Till Deposits

(There are two significant types of landforms that result from till deposits: Moraines and Drumlins. a. Moraines: These are accumulations of dirt and rocks that have fallen onto a glacier surface or have been pushed along by the glacier as it moves. Moraines are found in ridges along the edge of the glacier. b. Drumlin: These are elongated, tear-drop-shaped hills of till that aligned in the direction of ice movement. The tapered end points towards the direction from which the glacier came.)

Describe Landforms from Outwash Deposits

(The main landform resulting from outwash deposits is called an Outwash plain or Sandur. Outwash Plain/Sandur: This is a plain formed of glacial deposits deposited by meltwater outwash at the terminus of a glacier. As the water leaves a glacier, it sorts out sediments based on size; thus, an outwash plain may contain a variety of sediment sizes.)

Conclusion

(Glacial deposits are significant geological formations that provide evidence of past glaciological events. Through their study, we can comprehend the movement, size, and impact of glaciers on the landscape. They are primarily composed of rock, sand, and gravel, transported and deposited by glaciers, and form various landforms, including Moraines, Drumlins, and Outwash Plains.)

Key concepts

Till

Till is a fascinating type of glacial deposit that reveals much about a glacier's past journey. It consists of unsorted sediment directly dropped by a melting glacier. This mixture includes various sizes of materials such as clay, sand, gravel, and boulders.
As glaciers move, they pick up debris from the underlying ground, which becomes part of this unsorted mass. As the ice melts, all this material is left behind, providing a snapshot of the glacier's reach and activity.
What's interesting about till is its lack of strata, meaning there's no layering. This happens because the till is deposited all at once, without the sorting action of running water that you find with other types of deposits.

Outwash

Outwash deposits tell a different story from till. These occur when meltwater flows from a glacier, carrying along the finer sediments. Unlike till, outwash materials are sorted by the flowing water.
This sorting process means that sediments are often stratified - or layered - according to size. Outwash typically includes sand and gravel because the finer materials are carried further away from the glacier.
These deposits usually accumulate in flat areas and can sometimes make their way into river channels, forming the landforms known as outwash plains.

Moraines

Moraines are one of the most striking landforms created by till deposits. They are ridges of earth and debris that have been churned up by a moving glacier.
Moraines are significant because they mark the boundaries and movement paths of glaciers. When a glacier moves, it pushes the accumulated material along, forming ridges at its edges.
This process results in different types of moraines, such as terminal moraines, which form at the furthest point reached by a glacier. We also see lateral moraines along the glacier's sides and ground moraines beneath it.

Drumlins

Drumlins are another remarkable landform linked to glacial till. These are smooth, elongated hills that appear in clusters called drumlin fields.
One of the defining features of a drumlin is its shape: teardrop-like, with the tapered end pointing in the direction from where the glacier came. This shape provides clues about the ice flow's direction and dynamics.
Despite their streamlined appearance, drumlins contain all the varied materials found in till, emphasizing the force and pressure involved in their formation.

Outwash Plain

An outwash plain, also called a sandur, is a flat area formed by glacial sediments laid down by meltwater from a glacier. As these waters flow away from the glacier terminus, they sort the sediments by size.

• Outwash plains are typically stratified with layers of sand and gravel.
• They often border the edge of a glacier and can stretch over large areas.

Such landforms are important for understanding sediment transport processes and serve as evidence of historical glaciological events.
They provide valuable insights into the ways glaciers modified landscapes long after the ice itself has receded.