Geology Chapter 12 - Continental Glaciers

Questions and Answers

What are tills?

Liquid sediments

Unsorted compressed sediments (correct)

Compressed sediments

Sorted sediments

What is stratified till?

Well sorted sediments, often in layers

Which of the following is NOT a type of continental glacier landform?

Dunes (correct)

Terminal Moraines

Ground Moraines

Drumlins

What characterizes ground moraines?

Even blanket, normally 10s of meters thick Signup and view all the answers

What do terminal moraines indicate?

Location of ice fronts Signup and view all the answers

What are drumlins?

Composed of till under ice, indicating stream direction Signup and view all the answers

What are outwash points?

Large fluvial deposits from water and sediments down valley Signup and view all the answers

How is a kame formed?

When sediments are deposited on ice surfaces and lowered when melted Signup and view all the answers

What are eskers?

Channel bed deposits of a river running through glaciers Signup and view all the answers

What does glaciation refer to?

Advancing ice sheets Signup and view all the answers

What is deglaciation?

Retreating ice sheets Signup and view all the answers

What is an interglacial period?

Period between glaciation Signup and view all the answers

How many glaciations occurred in the last 2.6 million years?

12 glaciations Signup and view all the answers

What was the last major glaciation?

Wisconsinan glaciation Signup and view all the answers

What defines permafrost?

Material below ground that has remained constantly below 0 degrees Celsius Signup and view all the answers

What is continuous permafrost?

Permafrost everywhere underground Signup and view all the answers

What is discontinuous permafrost?

Permafrost is thinner and only in areas favorable to permafrost Signup and view all the answers

What characterizes dry permafrost?

Cold soil cemented together Signup and view all the answers

What does wet permafrost contain?

Abundant amount of water Signup and view all the answers

What is the active layer above permafrost?

Area that freezes and melts, inoculating the permafrost area Signup and view all the answers

What are ice wedges?

Vertically oriented wedge-shaped body of pure ice Signup and view all the answers

What are pingos?

Can be 60-70m high and form from the permafrost Signup and view all the answers

What is a talik?

Hole in permafrost beneath lake Signup and view all the answers

What is loess?

Region where windblown dust settles Signup and view all the answers

Study Notes

Tills and Stratified Till

Tills are unsorted, compressed sediments left behind by glaciers.
Stratified till consists of well-sorted sediments, often deposited in distinct layers.

Continental Glacier Landforms

Ground moraines are even, blanket-like deposits, typically tens of meters thick.
Terminal moraines mark the positions of glacier ice fronts.
Recessional moraines occur where glaciers halt temporarily during retreat.
Drumlins are streamlined hills formed from till beneath moving ice, indicating past ice flow direction.
Outwash plains are large fluvial deposits created by meltwater transporting sediments down glacier valleys.
Kames result from sediments deposited on ice surfaces that lower when the ice melts.
Eskers are long, winding ridges formed from river deposits within or under glacial ice.

Glacial Processes

Glaciation refers to the advancement of ice sheets across land.
Deglaciation indicates the retreat of ice sheets.
Interglacial periods are times between glaciation events.

Causes of Ice Ages

Ice ages are influenced by climate variations, notably the Milankovitch Cycle, which includes changes in Earth’s axial tilt and orbit.
Ice ages recur approximately every 100,000 years due to these cycles.

Recent Glaciation History

Over the last 2.6 million years, there have been 12 distinct glaciations.
The last major glaciation, known as the Wisconsinan glaciation, occurred around 25,000 years ago in North America and Canada, with global sea levels approximately 125 meters below current levels due to isostatic rebound.

Permafrost Characteristics

Permafrost consists of ground material that remains permanently below 0 degrees Celsius.
Continuous permafrost indicates a widespread, unbroken layer beneath the surface.
Discontinuous permafrost is found only in favorable areas and varies in thickness.
Dry permafrost is characterized by cold, cemented soil, while wet permafrost contains significant water content.
The active layer above permafrost thaws and freezes seasonally, affecting the underlying permafrost.

Ice Features

Ice wedges form as cold conditions cause shrinkage in ice, leading to polygonal cracking, which fills with meltwater and refreezes.
Pingos are dome-shaped mounds that can reach 60-70 meters in height, formed by water pressure freezing and expanding beneath permafrost layers.
Talik represents a zone of unfrozen ground located beneath a lake within permafrost.

Loess Deposits

Loess refers to thick blankets of windblown dust that settle in certain regions, promoting agricultural productivity and good infiltration. Sources include desert regions and areas affected by deglaciation.

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Description

This quiz focuses on important terms related to continental glaciers from Chapter 12. It covers definitions of key concepts such as till, stratified till, and various landforms created by glacial activity. Test your understanding and enhance your knowledge of glacial geology.