River Erosion Gizmo

Student Exploration: River Erosion Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes. 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 a streambed which is rocky. There are small substances that are being carried by the stream current. 2. Sediments are small rock fragments such as sand or pebbles. What evidence do you see that sediments are being transported? The sediments are moving from left to right. 3. Now select the right movie camera to see the bank of the mountain stream. What is happening to sediments on the bank? The sediments are falling into the stream. 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. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

1. Label: First, get to know some of the different parts of a mountain stream. Turn on Show labels . Fill in the word that goes with each description. A small stream that flows into a larger stream: Waterfall A place along a stream where water drops straight down: Tributary A letter that describes the shape of a typical mountain valley: V 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 ? It goes over first, then flows along with the stream of the river. The speed of the barrel increase from the flag checkpoint. 3. 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 below. I notice that the color of the water is different. (It is in a brownish color); the water seems to be flowing much slower and water level is higher based on the visual. 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 . Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

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 see that they are falling/sliding from the rock to the river. Now select the left movie camera to see the point bar. Look at the sediments in the water. What do you notice? The sediments in the water are different colors and they are headed toward the bottom of the ocean. 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? It has this type of name as when water accumulates more in the stream. B. Why might it be a bad idea to build a house in a floodplain? The house may accumulate water and could cause damage to the house. C. Turn on Show data . How do flood conditions differ from normal conditions? The river discharge is way higher than normal. D. Look at the two close-up views. What do you notice? there is more discolored sediment. lots of something like dead plant pieces. Activity C: Long-term erosion Get the Gizmo ready: ● Select Mountain stream . ● Select Long-term erosion and Low vegetation. Introduction : Both in the mountains and in flatter areas, river erosion can cause large changes to the landscape over time. In this activity, you will observe some of these changes. 1. Predict: How do you think the mountain valley will change over time? Prediction: I think that the mountain valley will widen and the river will also widen. 2. Observe: Click Play . Observe the valley for 200,000 simulated years. What do you notice? I notice that the mountains have eroded significantly and they have become smaller. The stream/river hasn’t changed much. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

3. Analyze: Click Reset . Turn on Show data . Record the slope, speed, and discharge of the stream. Click Play , wait until the end of the simulation, and record the same data. Year Channel slope River speed Discharge 0 22.0 m/km 1.1 m/s 2.3 m^3 200,000 14 m/km 0.8 m/2 2.8 m^3 How does the stream data change over time? The channel slope decreases, the river speed decreases, and the water discharge increases. 4. Observe: Click Reset . Click the movie camera to see a side view of the valley. Click Play . Over time, does the valley erode downward or side to side? The valley erodes downward. 5. Compare: Click Reset . Next to Vegetation , select High . Click Play . Compare the end result of 200,000 years of erosion with high vegetation to erosion with low vegetation. Which landscape eroded more, and why do you think this is so? The landscape that eroded more was the one with vegetation. 6. Predict: Click Reset . Select Meandering river and Low vegetation. How do you think the meandering river valley will change over time? There will be meandering on different parts of the river and some of the water on the river stream will runoff to the land 7. Observe: Click Play . Observe the valley for 2,000 simulated years. (The time frame is much shorter for the meandering river valley because changes occur faster there.) A. What do you notice? The shape of the river changes. This is more meandering. B. Over time, do the meanders grow wider or narrower? They kinda grow narrower. C. How does the width of the floodplain change over time? The width of the floodplain decreases. D. Turn on Show labels . What feature is formed when the river breaks through the narrowest part of the meander? oxbow lake Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved