HW 05 - Ch 5: Glacial and Arid Landscapes

Determine which sentences are true about wind deposits and glacial deposits. Drag the appropriate items to their respective bins.

-Wind deposited materials are well sorted. -Ice deposited materials are poorly sorted. -Materials deposited by wind can contain extremely fine materials.

Select the statements that are true about wind erosion. Select the three that apply.

-Wind is most effective as an erosional agent in dry places. -An important erosion-related role of wind in a desert is abrasion of rock surfaces. -Sediment deposited by wind in deserts can mostly be found in the form of sand dunes and loses deposits.

How do glaciers move? Choose all that apply.

-ice mass sliding along the ground -plastic flow of ice

Where is the world's largest ice sheet located today?

Antarctica

What does saltating mean?

Sand grains are lifted by the wind, leap a short distance, and then fall back to the ground.

How is desert different from steppe?

Steppe is more humid than desert.

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.

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.

If accumulation exceeds ablation in a glacial budget, which of the following will happen?

The terminus will move downhill ("advance").

When desert pavement is produced in a desert, why do the larger particles accumulate on the surface?

The wind can move particles of only a very specific size and it takes away these small particles, concentrating the larger ones.

Which one of the following is NOT true of glaciers?

They exist only in the Northern Hemisphere.

Although infrequent, running water is responsible for most of the erosional work in deserts.

True

Bajadas develop when multiple alluvial fans grow and merge along the fronts of mountain ranges in arid lands.

True

Examine the photo. Is it true or false to say, "the dunes that deposited these cross beds were moving from the left to the right"?

True

Glaciers are part of the hydrologic cycle.

True

Till is unsorted sediment deposited directly from the melting glacial ice; stream action is not involved.

True

In the desert environment, how are ventifacts created?

Ventifacts are produced on the surface of a rock by the continued impact of very small particles carried by the wind.

Which of the following statements about deserts is true?

Water is the most significant agent of erosion in deserts.

Why do desert dunes migrate?

Wind erodes material on the back side of the dune and deposits it on the front side of the dune.

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

Zone of Accumulation

When alluvial fans enlarge and coalesce in the Basin and Range mountain desert environment, what feature do they form?

a bajada

Deflation may lead to ________.

all of the above

What is a playa commonly occupied by?

an ephemeral lake

What is the largest type of glacier?

an ice sheet

Ephemeral streams ________.

are a major agent of erosion in desert regions

In an area of alpine glaciation, sinuous, sharp-edged ridges called ________ and sharp, pyramid- like peaks called ________ are common features.

arêtes; horns

If ice accumulation equals the amount of ice lost, the glacier will ________.

become stationary

At what latitudes do the large-scale, convection cells bring dry air downward toward the Earth's surface?

between 20-30° north and south

If you were on a geology field trip in an area of glacial deposition, how would you distinguish between samples of till and stratified drift?

by comparing their grain size and sorting

Which way does ice flow in a glacier retreating uphill?

downslope

Which glacial feature indicates the maximum extent of a glacier?

end (terminal) moraine

Which of the following is a feature of a desert environment?.

ephemeral streams

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

forward; backward

What formed this valley's distinctive "U" shape?

glacial erosion

A landscape dominated by U-shaped valleys and pyramid-shaped mountains is most likely formed due to ________.

glaciation

Which one of the following is an evaporite mineral?

gypsum

Where are drumlins formed?

in areas of ground moraine

A rainshadow desert forms ________.

in places where mountain ranges act as barriers to the movement of water vapor

Where do crevasses form?

in the zone of fracture

What are cross beds?

inclined layers in sediment or sedimentary rocks that reveal the direction of wave or wind transport

A glacier's downstream end ________.

is in the zone of wastage

This cobble shows prominent scratches because ________.

it was scraped against other rocks in a glacier

The __________ of a dune is characterized by a decrease in energy and sand avalanches, which occur due to oversteepening.

leeward side

Desert regions occur __________, and always have a(n) __________ climate zone adjacent to them.

on every continent; steppe

Match the landscape feature with the material from which it is formed. esker

outwash

How do pieces of rock move under the influence of wind?

rolling, sliding, bouncing, suspension

What is the term for the rolling and bouncing of sand grains during transport?

saltation

When air __________, it is compressed and warmed.

sinks

What property of a piece of material will most directly determine how it is carried by wind?

size

Cross-bedded sandstone shows inclined beds in a downward direction. What part of the ancient dune do these features represent?

slip face

Cross-bedding consists of many preserved ________ resulting from moving sand dunes.

slip faces

Match the landscape feature with the material from which it is formed. cirque

solid rock

Match the landscape feature with the material from which it is formed. glacial erratic

solid rock

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 do cross beds represent?

the moving front of a ripple or dune

What is dust?

the particles carried in suspension by wind

Deserts that lie outside of the subtropics and mid-latitude belts are most likely the result of __________.

the presence of a rainshadow

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

Match the landscape feature with the material from which it is formed. drumlin

till

Most of the erosion that took place during the "Dust Bowl" years of the 1930s in the Great Plains of North America was the result of which of the following processes?

wind

Precipitation occurs on the __________ of the mountain range, while the __________ is dry.

windward side; leeward side

About what percentage of Earth's land surface is covered by deserts?

30%

What is the natural angle of repose for sand?

34 degrees

________ are erosional features produced by valley (alpine) glaciers.

Cirques

What is the relationship between water currents and cross beds?

Cross beds sit at an angle to current direction.

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.

________ are long, linear scratch marks carved onto bedrock by glacial abrasion.

Glacial striations

Which of the following is true about sand dunes?

Dunes move over time.

Which of the following statements characterizes ephemeral streams?

Ephemeral streams flow only at certain times of the year.

Arêtes, horns, and U-shaped valleys are depositional features made of till.

False

Hanging valleys are glacier-cut valleys that flooded as sea level rose in post-glacial times.

False

Loess consists mainly of sand-sized particles.

False

Melting and calving are two forms of accumulation.

False

Steppes are the driest of the true desert lands.

False

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.

What is cross bedding?

Layers deposited on a dune slip face that are inclined in the direction of wind transport.

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.

Which of the following budget scenarios describes a glacial advance?

More ice and snow accumulates than melts each year.