Erosion: Washing Away the Earth
OverviewErosion can be a major issue. It is caused by a number of factors, both manmade and natural. The effects of erosion are very evident on Arctic coastal villages that are experiencing storm surges and no longer have the added protection of longer lasting sea ice. Research indicates that both the storm surges and lost of sea ice are the result of climate change.
Students will be able to describe erosion. They will also be able to list at least three causes of erosion.
Start the lesson by asking students to tell you what erosion is. Erosion is the displacement of solids (soil, mud, rock and other particles) by the agents of wind, water, ice, or living organisms, or by down-slope movement in response to gravity. (New World Encyclopedia)
Show students the short video of an Alaskan coastal area eroding at: http://dotearth.blogs.nytimes.com/2008/09/25/video-alaskas-eroding-arctic-coast/. Ask them what is happening and why.
If time permits, take the students to the library or computer lab to research different causes of erosion and to find images of Alaskan coastal villages that have been affected by erosion. You may want to assign different topics to different students (groups) and then have them share (present) they findings to the rest of the class.
Emphasize to them that erosion is the wearing away of a substance. It can happen over a long period of time or it can be quick. The soil around a river is susceptible to gradual erosion. When it storms or blows, then erosion may happen in a quicker fashion. Highlight the fact that erosion can be caused by wind, rain, water, ice and sea. Tell them that today they are going to perform an experiment to evaluate how much the Earth can erode.
- Two large disposable aluminum lasagna pans
- Natural soil from outside
- A watering can or bucket of water
- A magnifying glass
- Two or three books or wooden boards about 1/2-inch thick each
- A pair of pointy scissors or the needle of a drawing compass
- A small portable desk fan
- A small scale to measure how much dirt has eroded
- A small shovel or garden trowel to scoop the dirt
- The Last Days of Shishmaref Video
- Break the students up into small groups (3-5 people). Make sure each person has a writing utensil and paper to record observations.
- Pour the dirt into one of the pans so that it makes a layer on the bottom 2 to 3 inches deep. Smooth the soil out so that it is as even as possible on the top.
- TELL the students to: Examine the soil closely with the magnifier. Touch it and run it through your fingers. ASK - What is the soil made of? Does it all feel the same? How do you think the different soil parts would react if water was poured on them?
- Write down your observations or record the observations on the board for all to see.
- Use the scissors or compass needle to punch 6 small holes in one end of the tray.
- Place the second pan under the end of the dirt-filled pan where the holes are. (The second pan will catch the water as it leaves the top pan.)
- Slip 2 or 3 books under the other end of the dirt-filled pan so that it is propped up about 2 inches higher than the end with the holes punched in it.
The Effect of Wind
- Start with the pan on a slight slope. Plug in the fan and blow it down towards the dirt for 1-2 minutes. Stop the fan.
- Using the garden trowel, carefully collect the top layer of dirt that was blown into the bottom of the pan. Weigh it and record your measurements.
- Replace the dirt into the first pan by spreading it around evenly when done.
The Effect of Water
- Take the bucket of water and pour it into the high end of the pan. Repeat your measurement as you did in Step 9.
- (You may want to compare sprinkling water to simulate a steady rain fall to dumping the water that might occur during a storm surge.
Ask the students if they can think of other conditions that could affect the rate of erosion. You may test other variables such as the slope of the pan, different speeds of wind (fan), and dry versus wet soil.
Have the students answer the following questions on their observation sheets:
- How does rain shape the Earth?
- How does wind shape the Earth?
- Do all of the soil particles get pushed equally by the water?
- Under what conditions do you think soil is most likely to erode?
- Review erosion. Have the students define it.
- Have the students list the different kinds of erosion.
- Have the students list various causes of erosion and how it negatively affects their lives.
- Conclude by having the student's list things that they can do to help combat erosion.