Erosion: A Flowing River

This is a good one to do outside, if you can swing it.  If not, it can be done inside, you'll just need to work harder to contain the water.

Materials:

--Paper cup

--Drinking straw
--Clay
-- Cookie sheet
--Loose soil or sand
--Jug filled with water (or other water source)

Prep Work:

Poke a hole in the side of the paper cup, near the bottom. 

Cut the straw in half and place one half in the hole.

Seal the hole, around the straw, with the clay.

For the Demonstration:

Lay the cookie sheet upside down on the ground and raise one end about 2 inches, using scrap wood, a brick, a pile of soil, whatever's convenient. 

Cover the cookie sheet with a thin layer of soil or sand. Place the cup at the raised end of the cookie sheet.

Hold your finger over the straw as you fill the cup with water. Remove your finger and watch the way path of the water.

Raise the end of the cookie sheet to about 6 inches, recover the sheet with soil and repeat.

What differences did the slope make in the erosion?

Cover the cookie sheet with a layer of soil again.  This time, place a small rock  in the soil in front of the straw. 

Fill the cup and watch what happens to the water as it encounters the rock.  You can place additional rocks along the way to change the direction of the river.