Grade Levels

2 - 9

Objectives

    Students will investigate equilibrium in erosion and deposition by:

• predicting   effects of moving water on soil;
• modeling    an erosion simulation;
• observing    results of a test;
• inferring    causes and effects;
• planning    for personal action to save soil;
• hypothesizing    about erosion variables.

Standards of Learning

Science:

• Grade Two: 2.1, 2.6, 2.7
• Three: 3.1, 3.6, 3.7
• Four: 4.1, 4.8
• Five: 5.1, 5.7
• Six : 6.1, 6.2
• Life Science: LS.1, LS.12
• Earth Science: ES.1, ES.2, ES.8, ES.10

History and Social Science:

• Grade Three: 3.6

Background

    Although erosion is a naturally occurring process, it is often accelerated by human activities on the land. Some practices that expose or loosen soil include construction and other development for housing and roads, conventional tillage for crops, allowing livestock to trample stream-banks, and improper lawn care. Any loosened or exposed soil is prone to being washed away.

    To slow erosion, these activities must be controlled. Plants help to hold soil in place and to trap soil eroding from other places. Wetland plants are especially valuable in filtering soil before it reaches the waterways. On shoreline properties, people often build structures for erosion control. A bulkhead is a wall built to keep waves from carving away the shoreline. Another method is the placement of rocks (called "rip rap") along the shore, which dissipate wave energy while holding the existing shoreline. Planting or maintaining trees and other plants on shoreline as well as upland areas is always a good way to slow the erosion process.

Materials

• 5 clear jars of similar size

  Per group:
  

• two shallow, nonbreakable baking-type pans
• sand or soil
• one watering can with sprinkling spout or cup with holes in the bottom
• three clear containers or jars
• assorted sticks, stones, small pieces of sod, popsicle sticks, spoons, pieces of plastic, etc.
• hand lenses

Resources:

Chase, V. 1989.

"The Forcer of Moving Water" The changing Chesapeake. National Aquarium in Baltimore, MD.

Slattery, B. 1989.

"Our Chesapeake Bay;" "Pathway to the Bay."Bay B C's.   U.S. Fish and Wildlife Service, Baltimore, MD.

Procedure

Before the Trip:

1. Read the directions, assemble materials, and do a trial run. The amount of water needed to get results will vary depending on tray size, amount and type of soil or sand.

2. Set up stations for students to demonstrate weathering and erosion. Divide the class into groups of four. Each group will do both demonstrations, then will discuss the results as a class.

3. Demonstrations: Tilt It and Spill it. Start with several shallow pans with soil or sand covering the bottom and a sprinkling can of water (or large paper cup with holes in the bottom). Predict what will happen when the water is sprinkled onto the soil. Restate predictions as a testable hypothesis. Test the hypothesis and record observations.
   • What do you think will happen if you try this again in another pan, this time tilting one end of the pan up 10" or so?
   • Sprinkle the water on again and record the results.
   • How were the results different?
   • What landforms can you name that resemble the flat pan and the sloped pen? (flat = lawn, playing field, etc.; sloped = bank of a stream or river, hillside, etc.)
   • What is this process called when it happens in nature? (Erosion).
   • Why are farmers concerned about erosion?

      Spread the soil evenly again in the pans. Ask the class to develop hypotheses about erosion control mechanisms. Provide the class with materials that might be useful in preventing erosion. Give them 5 minutes to devise and construct a way to slow erosion. After 5 minutes, make it rain again and observe how the erosion control devices work.

4. Demonstration: Soil and Pebble Shakers. Fill a jar with soil, sand, pebbles, and water; shake well. While shaking the jar, predict which particles will settle to the bottom fastest and which will settle last. Why? Set the jar on a flat surface and allow the particles to settle over-night. Observe the order of the deposition of layers. Draw and label the layers. Use a hand lens to compare the sizes of the particles in the different layers.
   • Is the water completely clear?
   • If not, why not?
   • If these particles were eroding from a stream or river bank, which would cloud the water the most?
   • Which would travel farthest? Why?
   • Which size particle would naturally erode faster? Why?

At the Park:

1. Lead the class to a lawn or field area to play the following game simulating how plants function as sediment traps. Divide the class into two teams:
   Team 1 will be "plants growing along a shoreline," and Team 2 will be "soil particles."
   • The plants form an irregular line at one end of the field, spaced so their outstretched arms do not touch.
   • The area behind the plants is designated the waterway.
   • The soil particles line up facing the plants and, on a signal, must make their way to the waterway without being touched by a plant. Slow the soil particles by requiring them to drag one foot.
   • The plants may bend stretch, and stoop, but may not move their feet (*"roots") in order to tag the soil particles. Soil particles may not go around the end of the plant line.
   • When a soil particle is tagged, he or she becomes a plant at that exact spot.
   • The game continues until all the particles at the start of the game are caught or escape to the waterway.

2. Repeat the game several times, using student suggestions for modifying the plant spacing to change the results. Keep count of the number of rounds required to complete each game with the modified spacing. Give each student a chance to play both roles.

3. After the game, discuss the roles played and relate the results of the rounds to what actually happens when it rains.
   • Were the plants able to trap more particles in areas where they grew close together?
   • What happened when there were gaps or bare spots in the line of plants? Relate this to the formation of gullies.
   • Why are shoreline or wetland plants important to the water that they border?
   
      Ask students to suggest some solutions to problems of erosion, based upon the game.

4. Ask students to name some signs of erosion. Take them on a walk to look for these signs. Look for: muddy water in puddles, creeks, streams, or rivers; water running or dripping onto bare ground bare slopes with paths that seem to have been carved by water; gullies; soil washing away from construction sites or other areas where the ground and plants have been disturbed.

5. At each sign located, ask:
   • Can you tell where the soil went?
   • Can you find any structures built by man to control erosion?
   • Do these devices appear to work? Find natural materials or situations that help to control erosion.
   • How do these help to slow erosion?

Where in the Parks?

Follow-up:

1. Students identify at least five-sites on the school grounds where they might collect runoff after a rain shower.
2. Students predict the relative amounts of sediment that will be suspended in the runoff from each site by ranking the sites.
3. Label jars of similar dimensions with the site names and keep them ready for a rainy day.
4. When it rains, fill the jars with runoff from each site.
5. Students observe and rank the jars according to the clarity of the water, after shaking them.
6. Students compare the results with their predictions and discuss:
   • Does any sediment settle out?
   • Are all the samples the same?
   • Is it possible to determine the source of this sediment?
   • What are some ways to control the erosion or keep the sediment out of the nearest waterway?
7. Students do an erosion inspection around their homes. Discuss options for improving problem areas.

When

At the Park:

Allow 20-30 min. for the game, and up to an hour to take the walk.

Time of Year:

Any time of year.

Credits:

Adapted with permission from:
Ranger Rick's NatureScope; Geology, The Active Earth. 1987
"Shaping the Landscape," and
The Class Project. 1982    © National Wildlife Federation, 1400 16th St., N.W., Washington, D.C. 20036-2266.

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