Student Exploration.GIZMO Copy of KWAL 5 - River Erosion

GIZMO Copy of KWAL 5 - River Erosion.Vocabulary: cutbank, discharge, erosion, flood, floodplain, meander, meandering river, oxbow lake, point bar, river speed, sediments, slope, streambank, streambed, tributary, weathering Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. The image above shows a raging mountain river in full flood. What do you think is making the water brown in color? Dirt 2. What impact do you think the flooding river will have on the surrounding landscape? Erosion Gizmo Warm-up If you stand by the bank of a river, it may seem that very little is happening. But over thousands and even millions of years, rivers can have a profound effect on the landscape. In the River Erosion Gizmo, you will see how rivers move materials and how they affect landscapes. To begin, check that Mountain stream and Short-term erosion are selected. The Gizmo shows a typical stream that is moving through a hilly area. 1. The two movie cameras ( ) allow you to observe different parts of the stream up close. Click on the left movie camera. What do you see? I see fish swimming in the water & some rocks. 2. Sediments are small rock fragments such as sand or pebbles. What evidence do you see that sediments are being transported? How the water is flowing & the fish moving right. 3. Now select the right movie camera to see the bank of the mountain stream. What is happening to sediments on the bank? It eroded & then it fell into water. This study source was downloaded by from CourseH on :08:37 GMT -06:00 Activity A: Mountain streams Get the Gizmo ready: ● Check that Mountain stream and Short-term erosion are selected. ● If necessary, click outside the circle to close the zoomed-in view. Introduction: Erosion occurs when sediments and other materials are moved from one place to another. Along with weathering, which is the breakdown of large rocks into smaller sediments, erosion can have a profound impact on the landscape. Question: How does river erosion affect landscapes in the mountains? 1. Label: First, get to know some of the different parts of a mountain stream. Turn on Show labels. Label the image to the right, then fill in the word that goes with each description. A small stream that flows into a larger stream: Tributary A place along a stream where water drops straight down: Waterfall A letter that describes the shape of a typical mountain valley: V_shaped valley The side of a stream: Streambank The bottom of a stream: Streambed 2. Observe: Turn off Show labels. Next to “Release barrel,” click Play ( ). Observe how fast the barrel moves as it floats down the stream. What happens when the barrel goes over the waterfall? The barrel speeds up when falling down the waterfall. 3. Calculate: The two red flags are 100 meters apart. The time at which the barrel passes the flag is shown. Remember, there are 60 seconds in a minute. A. How many seconds did it take for the barrel to go 100 meters? 91 seconds B. To find the barrel’s speed, use a calculator to divide the distance traveled (100 m) by the time it took the barrel to float 100 m. The units are meters per second (m/s). What is the speed of the barrel? 1.1 m/s V-shaped valley Waterfall Tributary Streambed Streambank This study source was downloaded by from CourseH on :08:37 GMT -06:00 4. Record: Click Reset ( ). Turn on Show data. A. The slope of the channel is how steep it is, or how many meters the streambed drops for every horizontal kilometer. What is the slope of the stream? 22.0 m/km B. River speed is a measure of how fast water flows. What is the river speed? 1.1 m/s C. How does the river speed compare to the speed of the barrel you calculated on the previous page? There the same D. Discharge is the water volume that flows past a given point every second, measured in cubic meters per second (m3 /s). What is the stream’s discharge? 2.3 ㎥/s E. What types of sediments are transported by this stream? Sand, silt, & clay. Sediments are classified by size. The smallest sediments are clay particles, followed by silt, sand, and pebbles. Larger sediments include cobbles and boulders. 5. Observe: Turn off Show data. Next to River flow, select Flood. Look at the landscape, and then click on the movie cameras to see zoomed-in views. Describe what you notice. The water level rose, it moved faster, the water got darker, the amount of sediments increased, the erosion on banks of river increased. 6. Calculate: Click Play to release the barrel. How many seconds does it take the barrel to get from one flag to the other? What is the speed of the barrel? Time: 31 seconds Speed: 3.2 m/s 7. Compare: Turn on Show data. During a flood, how do the river speed, discharge, and transported sediments compare to normal flow conditions? The river speed got aster, the discharge increased, & the transported larger sediments (pebbles). This study source was downloaded by from CourseH on :08:37 GMT -06:00 Activity B: Meandering rivers Get the Gizmo ready: ● Select Meandering river. ● Select Short-term erosion, Low vegetation, and Normal river flow. Turn off Show data. Introduction: Meandering rivers are found in flatter areas. Unlike the V-shaped mountain valleys, the valleys of meandering rivers have wide, flat bottoms called floodplains. Question: How does river erosion affect landscapes in hilly or flat areas? 1. Label: Turn on Show labels. Label the image to the right, then fill in the word that goes with each description. A large S-shaped bend in a river: Meander A flat area next to the river: Floodplain A steep stream bank on the outside of a bend in the river: Cutbank A gently sloping deposit of sediments on the inside of a bend in the river: Point Bar 2. Observe: Turn off Show labels. Click Play to release the barrel. Observe the path of the barrel as it floats down the river. (The flags are 100 meters apart.) A. How many seconds did it take for the barrel to go 100 meters? (Remember, there are 60 seconds in a minute.) 125 seconds B. What is the speed of the barrel? 0.8 meters per seconds C. Turn on Show path. Did the barrel stay in the center of the river or go from side to side? Side to side D. As the barrel went around each meander, did it stay closer to the point bars or the cutbanks? Cutbanks In a meandering river, the water flows faster on the outside of a meander, near the cutbank, and moves more slowly near the point bar on the inside of the meander. The current carries the barrel toward the cutbanks and away from the point bars. 3. Compare: Click Reset. Turn on Show data. List the slope, speed, discharge, and transported sediments of the meandering river. Then select Mountain stream and fill in the remainder of the table. Change back to the Meandering river and compare the values. Foodplain Cutbank Meander Point bar This study source was downloaded by from CourseH on :08:37 GMT -06:00 Meandering river Mountain stream Slope 1.0 m/km 22.0 m/km Speed 0.8 m/s 1.1 m/s Discharge 187 m3/s 2.3 m3/s Transported sediments silt & clay sand, silt, & clay In what ways is a meandering river different from a mountain stream? The meandering river is that the slope is less than the mountain stream. The speed is slower. The discharge greater. The meandering river doesn´t have any sand. 4. Observe: Turn off Show data. Click the right movie camera to see the cutbank. Look at the sediments just above the water. What do you see? I noticed that the sediments are sinking into the river. Now select the left movie camera to see the point bar. Look at the sediments in the water. What do you notice? I noticed that the sediments are falling onto the point bar. Erosion occurs at the cutbank, where water is moving faster. As a result, cutbanks are steep and often overhanging. Sediments are deposited in the slow-moving water near point bars. 5. Compare: Click in the simulation area to turn off the movie camera. Select Flood. A. The flat area surrounding the river is called a floodplain. Why do you think it has this name? I think this is the name because the water floods over the plain. B. Why might it be a bad idea to build a house in a floodplain? It might be a bad idea to build a house in a floodplain because the house is surrounded by a body of water & it could flood. C. Turn on Show data. How do flood conditions differ from normal conditions? Flood conditions differ from normal conditions because the river speed goes faster, the discharge was greater, the sediments transported are much larger. D. Look at the two close-up views. What do you notice? I noticed that there were more sediments, sediments are no longer deposited along the point bar, the flood also carries sticks. This study source was downloaded by from CourseH on :08:37 GMT -06:00 Activity C: Long-term erosion Get the Gizmo ready: ● Select Mountain stream. ● Select Long-term erosion and Low vegetation.