Chapter 13 Notes

1. Chapter 13 Notes

2. Running water as an agent of erosion would include: • Drops of water moving down a hillside • The Mississippi River • Water flowing from a melting snowfield Limestone and marble are types of bedrock dissolved easily by running water. Materials carried in suspension by a river tend to make the water muddy.

3. The discharge of a stream is the volume of water flowing past a given point in a stream. Streams of mountain regions and high plateaus are likely to have V-shaped valleys, rapid water flows, rapids and waterfalls. In a relatively short period of time, a river has formed a V-shaped valley. The bedrock is most probably soft and the climate is wet.

4. The western divide for the Mississippi River system is in the Rocky Mountains. Headwood erosion is an important factor in the process of stream piracy. When a river flows into a lake the river is most likely to deposit all of its sediments. Fertile agricultural areas are characteristic of many of the world’s flood plains. Constructing spillways is a method of flood prevention using back swamps to contain the overflow.

5. Factors that directly affect the velocity of a stream are: • The steepness of the slope down which the stream travels. • The amount of water traveling downstream. • The number of meanders in the river. Potholes form due to cutting tools such as sand, pebbles, and small boulders moved by running water.

6. Most of the material a river carries in solution comes from the groundwater that seeps into it. A large increase in stream velocity is likely to increase the stream’s competence and capacity. Stream discharge and velocity increase when flooding occurs. An alluvial fan forms when a steep mountain stream meets dry, level land at the base of a mountain.

7. The process of undermining is described as the erosion of rock layers at the base of a waterfall. A curved body of water that forms when deposits separate a meander from its river is called an oxbow lake. Replanting vegetation at the headwater regions of a watershed is a flood prevention method best for reducing runoff.

8. What has happened at line Y over the years?

9. Most river deltas occur where a river flows into an enclosed or protected body of water. Describe the conditions necessary for a delta to form at the place where a river flows into an open ocean. The river must carry a lot of sediment. It must carry more sediment than can be eroded by the waves or ocean currents.

10. Describe why a river flowing near its base level is likely to have meanders. As a river nears its base level, less of its energy goes to eroding down into the channel. Instead, the river’s energy is deflected toward the sides of the channel. Over time, meanders develop as the river erodes away the outsides of river bends. The river deposits material on the inside of the river bend, and erodes the outside of the river bend.