Chapter 15: Glaciers (Geology 1)

Note the glacier and its landforms in this image. They tell a story about what happened years ago, as well as what is happening now. Where are the following glacial zones and related depositional landscape features located? Drag the appropriate labels to their respective targets.

(From top of slope to bottom) -Zone of accumulation -Lateral moraine -Zone of wastage -End moraine

Look again at the Gigapan image, and note the main features in this landscape. Observe what type of glacier this is given the surrounding landscape. Compare the sizes and shapes of the various glacial zones, as well as the associated landscape features. Then, review the statements below and indicate which are correct for this particular glacier.

-It is easy to find till in this image. -This glacier appears to be retreating.

Which two regions currently contain the world's last remaining ice sheets?

Antarctica and Greenland

Why does the crust subside slightly on either side of a melting glacier?

Crust under the glacier rises as the ice melts. This allows mantle on either side of the glacier to move to areas under the glacier.

Look at the following series of thumbnails from the Gigapan image, and determine if erosion is occurring or if deposition has occurred in each of these locations. Drag the appropriate items into their respective bins.

Erosion of a glacier takes place where the glacier actually is and can actually pluck and abrade materials. Deposition of the material that has been eroded takes place either to the sides of the glacier or at the end of the glacier as the ice melts and recedes. Erosion= snow/ice images Deposition=Soil and rock images

Under what conditions will the front of a glacier remain stationary?

Glacial fronts remain stationary when melting and snow accumulation are equal.

How does a glacier lose ice through sublimation?

Ice changes from solid to gas.

Explain why post A has moved farther than posts B and C.

Ice in the center of a glacier has the least friction with the surrounding bedrock and can flow faster.

Why does the crust uplift slightly on either side of a growing glacier?

Mantle under the glacier is pushed aside by sinking crust. This mantle pushes up the crust on either side of the glacier.

Examine the diagram of the glacier movement experiment again. Can you identify the best reason why the rate of ice movement at the center of the glacier was larger than the rate of ice movement along its sides?

The center of the glacier is not in contact with the valley walls, and the edge of the glacier is.

What will happen to the crust as a glacier grows?

The crust under the glacier will sink into the mantle.

How would you expect the front of a glacier to move if it undergoes a period of net accumulation, followed by net wastage, and finally a period of net accumulation?

The glacier's front would move forward, backward, and then forward again.

What causes streams that emerge from glaciers to be milk-colored?

The presence of finely ground sediment called rock flour in the meltwater.

Why does glacial subsidence NOT occur at the exact moment that a glacier forms?

The rate of subsidence is controlled by the rate at which mantle can flow.

How would a snow line on a glacier move as a glacial front is advancing?

The snow line would move downslope.

What is the best way to describe the shape of a glacial valley?

U-shaped

What shape is a glacial trough?

U-shaped

What causes a crevasse to form?

When ice flows around a bend or over an obstacle, it is stretched and torn, causing large cracks to form.

Will plucking occur if a glacier is NOT advancing?

Yes, because glacial ice is still moving inside the glacier even if the glacier's front is not advancing.

Which part of a glacier will see the build-up of ice and snow over the course of a full year?

Zone of Accumulation

What is an end moraine?

a ridge of debris deposited at the end of a glacier

What glacial feature is circled in Figure 1? (Side of steep mountain to the right of the lake)

arête

Which type of glacial movement is circled in Figure 1? (Bottom Arrow)

basal sliding

Which way does ice flow in a glacier retreating uphill?

downslope

What glacial landform is visible in Figure 1?

drumlin

Which orbital effect describes how the shape of Earth's orbit around the Sun will change over time?

eccentricity

Which of the following scenarios will have the greatest chance of triggering an ice age?

eccentricity, obliquity, and precession overlapping to provide the least amount of solar radiation

What is the name for an isolated boulder of unexpected rock type that has been transported by a glacier and stranded after the ice melts?

erratic

During a glacial retreat, a glacier will flow _____ while the terminus moves _____.

forward; backward

What glacial feature is circled in Figure 2? (Peak of mountain behind everything)

horn

Where do glaciers form?

in places where more snow falls in the winter than melts away in the summer

Which type of glacial movement will be responsible for the greatest amount of glacial flow?

internal flow

Most modern glaciers are __________.

retreating

What feature is responsible for creating eskers?

streams that flowed below, in, or on the glacier

Which landform marks the furthest extent of an advancing glacier?

terminal moraine

What is the snowline?

the elevation above which snow persists throughout the year

Which is the best definition of glacial snow line?

the line dividing zones of accumulation and melting of ice at the surface of a glacier

What is the zone of wastage?

the part of a glacier where snow melting exceeds snow accumulation

What is isostasy?

the rising and sinking of Earth's crust relative to the mantle in response to the redistribution of mass on the surface

For how long will land rebound after a glacier melts?

thousands of years

What effect will an increased angle of tilt have on the Earth's climate?

warmer summers and colder winters

Examine the diagram of the glacier movement experiment again. What was the average daily rate of ice advance in the center of the glacier?

0.32 meter per day

Examine the diagram below, which shows the results of an 8-year-long classic experiment used to determine how glacial ice moves in a mountain valley. Refer to this image for the following questions. What was the average yearly rate of ice advance in the center of the glacier?

115 meters per year

When was the last time North America had major ice sheets?

18,000 years ago

How many years does one complete cycle of precession take?

26,000 years

Examine the diagram of the glacier movement experiment again. If the data was collected over an 8-year time period, what was the average rate at which the ice advanced along the sides of the glacier in meters per year?

40 meters per year

What is the critical latitude for incoming solar radiation, which could affect the formation of ice sheets?

65° N

Which of the following budget scenarios describes a glacial advance?

More ice and snow accumulates than melts each year.

__________ are defined as a chain of glacial lakes where each lake flows into the next.

Pater noster lakes

How does an end moraine form?

Pieces of rock are transported to the front of a glacier as ice within the glacier moves.