Use the words below to fill in each blank. Do Now!!! 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 __________ glaciers. 4. Large striations are called __________. till eskers valley grooves

WIND

You will learn about wind erosion. Objective: Chapter 3 Section 3: Wind You will learn about wind erosion.

Don’t copy the words in this color

Arizona 7/5/2011

Wind carries and deposits sediments over large areas. 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.

Sand Blasting

These sand grains strike against rock and break off small fragments. The rocks becomes pitted and are worn down gradually.

These areas have fewer plants to hold the sediments in place. 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.

Sandstorms!!!

Sandstorm!!!

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

Let's Review!!! Wind erodes Earth’s surface by __________ and __________. 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. Do Now!!! 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

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

Grass roots are shallow and slender with many fibers. 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.

Loess is as fine as talcum powder. 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 Namibia (country of southern Africa) Crescentic Dunes of Coastal Peru

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.

Let's Review!!! 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 dune(s) loess wind