Use the words below to fill in each blank.

1. The mixture of different-sized sediments left by a retreating glacier is called __________.

2. __________ are winding ridges of sand and gravel deposited by glacial melt water streams.

3. Cirques are created by 3. Cirques are created by __________ glaciers.glaciers.

4. Large striations are called 4. Large striations are called __________.

till

eskers

valley

grooves

Chapter 3 Section 3: Wind

You will learn about wind erosion.

Don’t copy the words in this color

Arizona 7/5/2011

Air differs from other erosional forces because it usually cannot pick

up heavy sediments.

Wind carries and deposits sediments over large areas.

Wind erodes Earth’s surface by deflation and

abrasion.

When wind erodes by

deflation, it blows across

loose sediment, removing small

particles such as silt and sand.

When windblown sediment strikes rock, the surface of the rock gets

scraped and worn away by a process called abrasion.

Wind acts like a sandblasting machine, bouncing and blowing sand

grains along.

These sand grains strike against rock and break off small fragments.

The rocks becomes pitted and are worn down gradually.

Deflation and abrasion happen to

all land surfaces but occur mostly in deserts, beaches, and plowed fields.

These areas have fewer plants to

hold the sediments in place.

When winds blow over them, they can be eroded

rapidly.

When the wind blows forcefully in the sandy parts of deserts, sand

grains bounce along and hit other sand grains, causing more and more

grains to rise into the air.

These windblown sand grains form a low cloud just above the ground.

Silt and clay particles are small and stick together.

A faster wind is needed to lift these fine particles of soil than is needed to lift

grains of sand.

However, after they are airborne, the wind can carry them long distances.

Where the land is dry, dust storms can cover hundreds of kilometers.

These storms blow topsoil from open fields, overgrazed

areas, and places where vegetation has disappeared.

1. Wind erodes Earth’s surface by __________ and __________.

2. Where the land is dry, __________ can cover hundreds of kilometers.

3. Dust storms blow __________ from open fields, overgrazed areas, and places where vegetation has disappeared.

Use the words below to fill in each blank.

1. When wind erodes by ________, it blows across loose sediment, removing small particles such as silt and sand.

2. When windblown sediment strikes rock, the surface of the rock gets scraped and worn away by a process called _________.

3. Explain the difference between sand storms and dust storms.

deflation

abrasion

One of the best ways to slow or stop

wind erosion is to plant vegetation.

For centuries, farmers have

planted trees along their fields to act as

windbreaks that prevent soil erosion.

As the wind hits the trees, its energy of motion is reduced.

It no longer is able to lift particles.

Plants with fibrous systems, such as

grasses, work best at stopping wind

erosion.

Grass roots are shallow and slender

with many fibers.

They twist and turn between particles in the soil and hold it in

place.

Wind deposits of fine-grained sediments are

known as loess.

Strong winds that blew

across glacial outwash areas

carried the sediments and

deposited them.

Once there, the particles packed

together, creating a thick,

unlayered, yellowish-brown-colored deposit.

Loess is as fine as talcum powder.

A dune is a mound of sediments drifted by the wind.

Dunes are common in

desert regions.

A sand dune has two sides.

The side facing the wind has a gentler

slope.

The side away from the wind is

steeper.

Most dunes move, or migrate away

from the direction of the wind.

As they lose sand on one side, they build it up on the

other.

The shape of a dune depends on the amount of sand or other sediment

available, the wind speed and direction, and the amount of

vegetation present.

One common dune shape is a crescent-shaped dune known as a

barchan dune.

This type of dune forms on hard surfaces where the sand supply is

limited.

Crescentic Dunes of Coastal

Peru

Crescentic Dunes Namibia

(country of southern Africa)

Another common type of dune, called a transverse dune, forms

where sand is abundant.

In regions where the wind changes, star dunes, form pointed structures.

When dunes and loess form, the

landscape changes.

Wind, like gravity, running water, and glaciers, shapes the

land.

New landforms created by these

agents of erosion are themselves being

eroded.

Erosion and deposition are part of a cycle of change that

constantly shapes and reshapes the

land.

Use the words below to fill in each blank. Keep in mind, you will not use all the words.

1. One of the best ways to slow or stop wind erosion is to plant .

2. Wind deposits of fine-grained sediments are known as .

3. is as fine as talcum powder.

vegetation loessdune(s) wind