1. Investigation 3 Go with the Flow

2. The Grand Canyon is one place where erosion has taken place on a grand scale. Geologists are still trying to figure out how the Colorado River could have carved such a deep canyon. They have come up with several ideas that might explain what happened. One idea is that the slope of the Colorado Plateau became steeper and caused the canyon to erode faster. Slope is the angle or slant of the stream channel or the land's surface.

3. Geologists think that the surface of the Colorado Plateau was slowly tipping while the Grand Canyon formed. Think about what effect the slope of the Colorado Plateau could have had in the formation of the Grand Canyon.

4. Key words: Slope: the angle or slant of a stream channel or land surface Alluvial Fan: fan-shaped landform deposited at the end of a steep canyon where the slope becomes flatter. What differences did you observe in the landforms when the slope increased? How did slope affect the time it took for landforms to appear?

5. Often great thunderstorms near the Grand Canyon send huge amounts of water down the side canyons. These events are called flash floods.

6. What do you think happens to flood waters when they reach another body of water like a lake? Where did you see that happen in your stream-table? What might happen in the Grand Canyon when there is a flash flood? What might make water flowing through a stream channel slow down? What would you expect to see where the slope changes?

7. Note: Most rivers in the U.S. and around the world travel less steep slopes than those in the desert areas like Death Valley. Some examples are the Mississippi River in the U.S., the Amazon in South America, and the Nile in Africa. These rivers flow faster near their mouths, even though their slopes decrease as they flow across the land.

8. How can you use what you know about flooding and increased volume of water to explain why rivers could flow more Quickly over a flatter slope as they approach their mouths? Work Bank: flood, flash flood Flood – a very heavy flow of water, which is greater than the normal flow of water and goes over the stream’s normal Channel. Flash Flood – rises and falls rapidly with little or no advance warning, usually as the result of very heavy rainfall Over a relatively small area.

9. Why would someone want to build a home next to or near a river? What kinds of problems might someone have who lives near a river?

10. Many rivers have been changed by people so that they can live close to them. What are some of the changes people make to rivers and streams? How could each of these changes to a river affect erosion and deposition?