Science Chapter 9

How effective would a retaining wall made of fine wire mesh be against erosion?

A fine mesh wire will prevent only larger particles such as pebbles and boulders from eroding. Smaller sediments like sand, silt, and dust will fall through the mesh.

What type of wind erosion leaves pebbles and boulders behind? A) deflation B) loess C) abrasion D) sandblasting

A) deflation

Which characteristic is common to all agents of erosion? A) they carry sediments when they have enough energy of motion B) they are most likely to erode when sediments are moist C) they create deposits called dunes D) they erode large sediments before they erode small ones

A) they carry sediments when they have enough energy of motion

What characteristics do all types of mass movements have in common?

All happen on slopes; depend on gravity; occur more often after heavy rain; and result in the production of less steep slopes.

How do moraines form?

As a glacier melts, material drops out of the ice and builds up at the sides and front of the glacier.

Which of the following is the slowest type of mass movement? A) abrasion B) creep C) slump D) mudflow

B) creep

What term describes a mass of snow and ice in motion? A) loess deposit B) glacier C) outwash D) abrasion

B) glacier

What happens when glacial erosion occurs? A) Eskers form. B) Landforms such as arêtes and grooves are formed. C) Moraines are deposited. D) The climate gets warmer.

B) landforms such as arêtes and grooves are formed

What shape do glacier-created valleys have? A) V shaped B) L shaped C) U shaped D) S shaped

C) U shaped

The best vegetation to plant to reduce erosion has what kind of root system? A) taproot system B) striated root system C) fibrous root system D) sheet root system

C) fibrous root system

What does a valley glacier create at the point where it starts? A) esker B) moraine C) till D) cirque

D) cirque

Which term is an example of a structure created by deposition? A) cirque B) abrasion C) striation D) dune

D) dune

What is a ridge formed by deposition of till called? A) striation B) esker C) cirque D) moraine

D) moraine

Compare and contrast abrasion and deflation. How do they affect the surface of Earth?

Deflation occurs when wind picks up and transports small sediments, leaving behind heavier sediments such as pebbles and boulders. Abrasion is a natural form of sand blasting. Blowing sand grains strike and break off small fragments of rock. Both abrasion and deflation erode and change surface features.

Define erosion and name the agents that cause it.

Erosion wears away surface materials and moves them from one location to another. Agents include gravity, glaciers, wind, and water.

How does a glacier cause erosion?

Glaciers erode by scraping, scouring, pushing big rocks, and plucking.

If creep has occurred in an area, what evidence would you see?

Leaning trees, leaning fences, tilted telephone poles.

When people build houses and roads, they often pile up dirt or cut into the sides of hills. Predict how these activities affect sediments on a slope.

Piling up dirt and cutting into the hills create steep slopes. Steep slopes are unstable and prone to erosion.

Sand dunes often migrate. What can be done to prevent the migration of beach dunes?

Planting vegetation or erecting fences can reduce or prevent dune migration.

Explain the differences between dust storms and sandstorms. Describe how the energy of motion affects the deposition of sand and dust by these storms.

Sandstorms remain close to the ground. Sand grains travel along the ground and don't go far at one time. In dust storms, wind picks up dust and carries it great distances. Loess can be deposited far from its origin because the dust particles are so small. The greater the energy of motion, the greater the distance that both sand and dust are transported.

How can striations give information about the direction a glacier moved?

Striations are made by glacial debris embedded in the bottom or sides of the ice. The debris gouges the bedrock as the glacier moves. Striation are generally parallel to glacial movement.

Scientists have found evidence of movement of ice within a glacier. Explain how this could occur. (HINT: recall how putty-like ice forms at the base of a glacier.)

The mass of overlying snow and ice compresses underlying layers. This pressure can cause the ice to melt partially. The melting then causes movement at the bottom and within the glacier.

How does erosion change the surface of Earth?

The surface changes shape when sediments are transported from one location to another.

Rivers and lakes that receive water from glacial meltwater often appear milky blue in color. Explain why this occurs.

The water contains fine particles of eroded rock. These particles give it the milky look.

Explain how till and out wash are different.

Till is a mixture of boulders, sand, and silt deposited directly from glacial ice. Outwash sediment is deposited by glacial meltwater and is sorted by size. Large sediments are closer to the glacier; smaller ones are farther away. Outwash has layers.

The front end of a valley glacier is at a lower elevation than the tail end. How does this explain melting at its front end while snow is still accumulating at its tail end?

Warmer weather at lower elevation could cause the front end to melt and to appear to retreat. Colder temperatures at higher elevations would allow the snow and ice to accumulate and cause the glacial tail end to advance.

You notice that snow is piling up behind a fence outside your apartment building. Why?

When the wind strikes the fence, it loses some of its energy of motion and can carry the snow no farther.