Forces That Shape Our Earth:

Erosion and Weathering

Why is this important?

1. Erosion and weathering are major forces that shape the world around us. Understanding these forces helps us to understand the way our land is shaped – from rivers to lakes to canyons and our shore lines. For example the Grand Canyon was formed through erosion by the Colorado River running through it!

Why is this important?

2. People play a part in the way and amount that our soil erodes around us. It is important for us to understand how erosion works and how effect on soil erosion since we depend on soil to grow our food and without it we would starve!

So what is erosion?

Erosion:

when earth’s

surface is

worn away.

Erosion is caused by moving water, oceans, wind, and the glaciers.

Soil Erosion

When we think about erosion we usually think about our soil being worn away and moving around. This is important to humans because we need soil to grow our food.

Plant roots help soil stay where it is supposed to and humans can make soil erosion worse by cutting down our trees.

Apple Demonstration (1) Cut a large apple into four equal parts. "Three parts represent the oceans

of the world. The fourth part represents the land area of the world."

(2) Cut the land section in half lengthwise. "One section represents land such as deserts, swamps, antarctic, arctic, and mountain regions. The other 1/8 represents land where man can live but may NOT grow food."

(3) Slice this 1/8 section crosswise into four equal parts. "Three of these 1/32 sections represent the areas of the world which are too rocky, too wet, too hot, or where soils are too poor for food production, as well as areas developed by man."

(4) Carefully peel the last 1/32 section. "This one small bit of peeling represents the soil of our earth on which mankind depends for food production."

Weathering

One type of erosion is when rocks are broken

down. We call this weathering.

So what is weathering?

Weathering: The breaking down of rocks into smaller pieces.

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Hulk Rock

Smash!

There are five types of weathering…

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Five types of weathering

WindWind breaks down rocks in two ways:

1. Wind can blow small pieces of rock off a large rock.

2. Wind blows sand, which grinds pieces of rock off a large rock.

Plant Roots

Plants roots can grow into cracks in the rock, slowing breaking them apart.

Freezing WaterIn your groups, hypothesize how the water

in this rock can cause weathering. (Hint: what happens to water when it freezes?)

Flowing WaterWater changes the landscape as it

flows, or moves, by moving rocks and soil as it goes.

Moving water is THE STRONGEST weathering force changes the land we see.

Chemical Weathering

This is when an acid that either occurs natural or because of pollution (acid rain) breaks down rocks.

One more thing we need to know….

Deposition

After the earth’s surface has eroded or the rocks are weathered, these materials move. When they stop moving and are “dropped off” we call this deposition.

Deposition: when soil and rocks are deposited, or left, somewhere different then where they started.

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Quiz on Monday!! Don’t forget to learn and study

your new (and old) vocabulary words!!