with glaciers producing lots of melting water, lighter colored sands are deposited on top of
the darker layers at the bottom of the lakes. These distinctive layers, calledvarveshave
paired dark/light layers, with each layer representing one year of deposits.
Loessis a very fine grained, wind transported deposit which forms in areas of stratified
drift glacial deposits. It is common in the middle of North America as well as the eastern
central portion of Europe. This fine sediment is produced as glaciers grind the underlying
rock producing a fine powder calledrock flour.
Lesson Summary
- The movement of ice in the form of glaciers has transformed our mountainous land
surfaces with its tremendous power of erosion. - U-shaped valleys, hanging valleys, cirques, horns and aretes are just a few of the
features sculpted by ice. - The eroded material is later deposited as large glacial erratics, in moraines, stratified
drift, outwash plains and drumlins. - Varves are a very useful yearly deposit that forms in glacial lakes.
Review Questions
- How much of the Earth’s land surface is covered by glaciers today? Was the Earth
ever covered by more ice than it is today? - What is the shape of a valley that has been eroded by glaciers? How did it get that
shape? - What are two different features that can form as smaller side glaciers join the central
main glacier? - Name and describe the two processes by which glaciers erode the surrounding rocks.
- Name the erosional feature that would form as several glaciers in a mountainous region
move downslope in different directions from a central peak. - Describe the different types of moraines formed by glaciers.
- Describe the difference between glacial till and stratified drift. Give an example of how
each type of deposit forms. - Name and describe the two asymmetrical hill shaped landforms created by glaciers.
Vocabulary
abrasion Scraping of the underlying bedrock, produced as ice flows against it.
arête Steep sided, sharp edged ridge that forms as two glaciers erode in opposite directions.