EROSION

BACKGROUND

Erosion can be caused by wind, ice or water. The amount of erosion that takes place depends on lots of things. Let's see how the shape of the land affects how much erosion occurs. We'll also look at the effect plants have on erosion.

WHAT YOU NEED

3 pans	1 pencil	1 tissue
1 small cup	1 large cup	1 ruler
water	moist sand

WHAT YOU DO

1. Put 1 large cup-full of sand into each pan. Shape two piles of sand into a "mountain". Smooth the other pile out flat so that it fills the whole pan to form a "plain".

2. Predict! You are going to cause rain to fall on your mountain and your plain. Which do you think will have more erosion and why?

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3. Use the pencil point to make a small hole in the bottom of the small cup.

4. Fill the large cup with water to have at your desk.

5. Put your finger over the hole in the cup and fill the cup half way with water. Hold it approximately 30 cm over the center of the plain and remove your finger. Watch and record what happens.

6. Now repeat this letting the half cup of water "rain" on the top of one of the mountains. Watch and record what happens.

TYPE OF LAND	OBSERVATIONS
Plain
Mountain
Mountain With Grass

7. Now pretend to grow grass all over your second mountain by covering it with the tissue. Pat the tissue down lightly so that it is touching the sand everywhere. Let it rain on the grass-covered mountain. What happens?

QUESTIONS

How is the amount of erosion affected by the shape of the land and what's growing there?

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_____________________________________________________________________________________ In some places, forests are being cut down off of hillsides to make fields for growing farm crops. What do you think might happen if no one plants crops right away?

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