Investigation Sequence

Title

Erosion

Written by:

Unknown ?                 Date

 

Focus Questions

What is erosion?
What causes erosion?

Concepts

Content: Earth, Physical, & Life

Erosion – a continuous process of the wearing away of the surface of the earth
Weathering – gradual physical and chemical wearing away of rocks

Cross cutting concepts

 

Science Practice

 

Personal, Social, Technology, Nature of Science, History

 

Background information

Water plays an important role in erosion by carrying away material that has been weathered and broken down. When an area receives more water (in the form of rain, melting snow, or ice) than the ground can absorb, the excess water flows to the lowest level, carrying loose material with it.
Glaciers are important agents of erosion. Although a glacier moves slowly, it gradually removes all the loose material from the surface over which it travels, leaving bare rock surfaces when the ice melts. Besides removing loose material, glaciers actively erode the solid rock over which they travel. Rock fragments that become embedded in the bottom and sides of the moving ice mass act as an abrasive, grinding and scouring the bedrock which forms the walls and floors of mountain valleys.
Wind blowing across bare land lifts particles of sand and silt but leaves behind larger pebbles and cobbles. Eventually, a surface layer of closely packed stones, called a desert pavement, is formed as the sand and silt is removed.

Activity Sequence

1. Chemical Erosion
2. Water Erosion
3. Wind Erosion
4. Glacier Erosion
5. Temperature Erosion
6. Mountain Building

Activity Descriptions

Activity 1
Chemical Erosion
Materials:
Glass tray, plastic tray, chalk, diluted hydrochloric acid (safety demonstration), vinegar, science journal
Procedure:
1. Place a piece of flat limestone into a glass tray. Then get students, who are gathered around the experiment table, to guess out loud what they think will happen when drops of an unknown liquid (dilute hydrochloric acid) are added to the limestone.
2. Add drops from time to time for several minutes, asking students to describe what they observe (fizzing, discovering that a hole is slowly forming).
3. Ask students how chemicals might affect rocks.
4. Divide the students into groups. Direct students by writing on the board the following: 1. Place a piece of limestone into the plastic container. 2. Slowly add drops of vinegar using the eyedropper. 3. Record your observations. 4. As a group, discuss why you think such a reaction occurred.
5. Some specific questions: What do you think the unknown liquid might be? What do you think the liquid is doing to the limestone? What happened when you dropped the vinegar on the chalk? Why do you think this happened? What materials do you think would react the same way as the chalk and limestone? What type of reaction do you think occurred in these two experiments?
6. After asking the above, discuss the term chemical reaction.
7. Can show them pictorial examples of chemical erosion (Mammoth Cave in Kentucky, the Carlsbad Caverns in New Mexico, and results of acid rain) be able to explain to students why these are examples of chemical erosion.

Activity 2
Water Erosion
Materials:
Nonoily clay (not modeling clay), tray or pan, outdoors water hose, pebbles, coins, plastic chips, science journal
Procedure:
1. Before class form a mound of nonoily clay into a level mass about 5-10 centimeters across and place it into a tray or large pan.
2. Pebbles, coins, and plastic chips will be pressed into the top surface of clay.
3. Have the class follow you outside where you will lightly spray the clay from above.
4. Students should note in their science journals how the spray washes away the clay while the pebbles, coins, and plastic chips cause pinnacles to form. They should be able to infer that the harder surfaces are more durable in the face of water erosion.
5. Questions: What caused the clay to run off? Why did the pinnacles form? What other materials might have protected the clay? Can you think of any examples of such pinnacle formations in nature? What other examples of water erosion can you think of?
6. May want to show pictures of Grand Canyon, Grand Tetons National Park, and Monuments National Park.

Activity 3
Wind Erosion
Materials:
Cardboard box with top and one side removed, sand, water, plastic chips, pebbles, coins, science journal
Procedure:
1. Warning-require students to wear goggles. Every group should be given a box with its top and one side removed. A pile of sand will then be formed in the center of the box bottom.
2. Instruct students to blow over the sand using a straw from the open side of the box.
3. Students will then record their results.
4. Ask them to reform their sand piles and give them a choice of materials (water, plastic chips, pebbles, coins) to choose from to try and prevent the sand from moving.
5. Students will again blow and will record their results.
6. Questions: What happened to the sand as you blew? Could you make the whole pile move if you blew long enough? What materials did you choose to add to your reformed piles and why did you choose these materials? Can you think of any examples of wind erosion in nature?
7. Pictures of the sand dunes from the Sahara and Kalahari Deserts in Africa. The Dust Bowl of the 1930’s could be a topic to discuss.

Activity 4
Glacier Erosion
Materials:
Ice cubes, sand, modeling clay, paper towel, science journal
Procedure:
1. Press an ice cube against the flat surface of modeling clay and move it back and forth several times and record observations.
2. Then place a small pile of sand on the clay. The ice cube should be placed on top of the sand left for one minute.
3. Then pick up the ice cube and observe the surface of the cube that was touching the sand and record their observations.
4. The same side of the ice cube should then be placed on the sandy part of the clay and moved back and forth several times.
5. When ice cube is melted, the sand should be wiped away form the surface of the clay, and the clay’s surface texture should be recorded.
6. Questions: What happened to the clay the first time you wiped the cube against it? What happened to the ice cube after it sat on the sand? What did the surface of the clay look like after you rubbed the cube against it the second time? Does glacial erosion still occur today or is it just an ice age phenomenon? Can you give any examples of Glacier erosion?
7. Pictures of Hubbard Glacier in Alaska and a picture of the Matterhorn in Switzerland, a geographical anomaly produced by glaciers should be shown.

Activity 5
Temperature Erosion
Materials:
1 pot boiling water, marbles, cups of ice, cups of water, nonmetal tongs, goggles, science journal
Procedure:
1. Review safety rules thoroughly.
2. The teacher should have one container of boiling water with marbles for the children in it.
3. Students should go to the teacher to get a hot marble. The teacher will place the marble directly from the boiling water into the student’s glass of water.
4. Students should then put the marble into the jar full of ice.
5. Questions: What happened to the marbles? What do you think caused the marbles to crack? Can you give me examples of temperature erosion? How might we prevent erosion due to temperature?
6. As a class go outside and observe the sidewalk and driveway, noting that the cracks are perhaps due to temperature erosion. Also draw their attention to the grooves in the sidewalk to prevent temperature erosion.

Activity 6
Mountain Building
Materials:
Dish pans, potting soil, rocks, plastic chips, ice cubes, sand, water, and watering can, science journal
Procedure:
1. Place the students into approximately five groups.
2. Students will be asked to build a mountain, which they believe will best hold up a watering can full of water being poured over their structure.
3. One group will be assigned to build their mountain out of sand, one group will use rocks and a small amount of sand, one group will use soil, and two groups will be able to use any combination. All groups will have access to a certain number of plastic chips, pebbles, ice cubes.
4. The groups must devise a building plan writing down all suggestions. The groups must also write down what their final building plan consists of and why they think this is the best structure to withstand water.
5. Students will be allowed to observe all groups’ completed structures and make predictions. (May want to record predictions on board.)
6. The students should then build their mountains.
7. Then empty the watering can of water on them.
8. Students should record the results and explain why they think such an outcome occurred. The students must suggest improvements to their structure and explain why they think such improvements will be beneficial.
9. Have a class discussion.

Dr. Robert Sweetland's notes