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Volcanic cones
June 25, 2001
Web posted at: 6:17 PM EDT (2217 GMT)
Lesson Plans by month
Lesson Plans by subject
A cinder cone is formed by material thrown out during an explosive volcanic eruption. A shield volcano is made up of layers of lava that have flowed out during a quieter eruption. You can demonstrate that the very different shapes of these cones are the result of the different materials from which they are made.
Materials
plaster of Paris, measuring cup, water, mixing spoon, metric ruler, paper plates, protractor, dry cereal or potato flakes and a graduated cylinder
Procedure
1. Pour 1/2 cup of plaster of Paris into the measuring cup. Gently tap the cup so that the plaster settles to the 1/2 cup level.
2. Use the graduated cylinder to measure out 60 mL of water, and add it to the dry plaster in the measuring cup. Use a mixing spoon to blend the mixture until it is smooth and uniform.
3. Hold the measuring cup about 2 cm over a paper plate. Pour the contents slowly and steadily onto the center of the plate.
4. When the cone has hardened (15-20 min.), remove it from the plate. Measure the average slope angle with a protractor.
5. Pour dry cereal or potato flakes slowly onto the center of a clean paper plate until the mound is approximately 5 cm high.
6. Without disturbing the mound, measure its slope with a protractor.
Analysis and conclusions
1. Which cone that you formed represents a cinder cone? a shield volcano? How do the angles formed by these cones compare?
2. How would the slope be affected if the cereal were rounder? thicker?
3. Suppose you formed a cone by pouring alternating layers of wet plaster of Paris and dry cereal. How would the shape and overall size of this cone differ from the two cones you have already formed? Which type of volcano would such a cone look like?
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