Weathering, Erosion and Deposition
The next time you are outside, take a good look around. Really examine the lay of the land, the soil and the vegetation. Keep in mind that the many different landforms we see around us are forever changing. New ones appear while others are altered or totally disappear. What causes some of these changes to happen? Weathering, erosion and deposition are 3 of the forces that work together to change the Earth’s surface. They can be both constructive and destructive.
You and your partner will be learning more about these earth changing forces and how they alter our earth through videos and interactives. You will help each other have a good understanding of these processes as you work through the following activities and discuss them with each other. Start by looking at the images below. Talk about what forces of nature you think created these. Are these constructive or destructive?
Weathering
Just what is weathering? How many different kinds of weathering processes are there? What are the differences between chemical and mechanical/physical weathering? How does weathering change the surface of the earth? Find answers to these by watching this BrainPop video. You will need to log in. When you finish watching it, take the Review Quiz. How did you do?
Weathering and Climate Interactive
Click the image to the left. It will take you to an online activity that will help you understand more about mechanical/physical weathering and chemical weathering. Take turns reading the information given and working through the activities. Explain the difference between the 2 types of weathering to each other.
Erosion
You now know that weathering happens when rocks are broken or worn into smaller pieces called sediment, sand, pebbles or silt. So, what is erosion? How can erosion change the earth's surface? How might a change in the Earth’s surface increase erosion? What are some examples of erosion you may have seen in nature? Watch this BrainPop video and look for answers to these questions. When you finish, take the Review Quiz. How did you do?
Erosion Interactive
Click the image to the left. You will be completing a virtual lab measuring the amount of sediment collected from water runoff to compare the effect of 3 variables on water erosion. Begin by reading the information together. When you are finished with the activity, explain to each other how certain factors affect the erosion of soil by water.
Deposition
Deposition is the process by which rocks, sand, and sediments are deposited or laid down after being transported by the forces of water, wind, ice or gravity. Think about the different factors that affect when and where deposition will occur once the rock and sediment have been eroded. The speed of wind or water is important because as it slows, heavier and often larger rock is deposited first while smaller particles continue to flow downward. The shape of the sediments and the slope of the land also play a role.
Watch the stream table demonstrations to see this in action. The second is a time lapse video compressing 35 minutes of erosion and depostion into 3. Discuss with each other the types of changes you see happening.
Study the diagrams below to see how erosion and deposition work together.
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Many of the landforms we have come from the process of deposition. Rockslides on hills and mountains are created as gravity erodes and deposits rocks. Deltas are created by streams when they deposit sand and sediment at their mouths where the water flows to meet the ocean. Blowing winds create sand dunes in the desert. Beaches are created by sand being deposited over time by the waves and tides rushing in and out. When glaciers melt, they drop the rocks and other sediments they are carrying onto the landscape. As glaciers move over the landscape, they collect the rocks into piles called glacial moraines. Can you think of others? Some depositional landforms change frequently while others have taken place over thousands of years. What caused these landform changes below?
What are some effects of erosion?
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Soil erosion by water, wind and farming affects both agriculture and the natural environment. Soil loss and its impacts is one of the most important (yet probably the least well-known) of today's environmental problems. It can be a slow process that continues relatively unnoticed or can occur at an alarming rate, creating serious loss of topsoil. Other causes of soil erosion include deforestation, clearing land for roads and construction, and the rise in sea level. Talk about what you see happening in the video.
Erosion normally breaks down the landscape a tiny piece at a time, but sometimes rocks and soil move downhill in large volumes. These movements which include landslides, mudflows, and rock falls are called mass movements. They happen when rock, debris, or soil on a slope becomes unstable and can no longer resist the downward force of gravity. Watch how the steepness of a slope makes a difference on the amount of erosion. What might prevent this?
Did you see that slope stability is based on the way driving forces and resisting forces work together? Driving forces promote downslope movement of material, whereas resisting forces deter movement. So, when driving forces like wind, water, temperature, gravity and chemical weathering overcome resisting forces, the slope becomes unstable. The steeper the slope, the greater the end result will be. Some examples of catastrophic slope instability are landslides, mudslides and avalanches. Discuss the forces you see in action here.
What are ways to prevent weathering and erosion?
You should now have a good understanding of the causes and effects of weathering and erosion. You have seen some of the beauty that comes from these forces, but you have also witnessed some of the destruction. Brainstorm with each other ways that man has helped add to the devastation and at least 6 ways that we can help control it. When you have finished, click on the picture to see how you did. know a little more about you.