SCIENCE ITALIAN STYLE: Eruption!
In 1991, computer technology and brute strength diverted lava from Mt. Etna 300 yards before it reached the nearest town. Millions of people living in the shadow of Mt. Vesuvius may not be as lucky. Computer models predict that a 2000 degree F avalanche of gas and rock would reach the nearest town in less than five minutes. Scientists demonstrate ways to prepare for a future eruption, but will residents heed their advice, or end up entombed like the victims of Pompeii in 79 A.D.?
Activity: Through Thick and Thin
land forms, volcanoes
ACTIVITY: THROUGH THICK AND THIN
The activity in this file is adapted from the Volcano! module of the Event-Based Science (EBS) Project, an exciting new series of innovative middle school science units. Funded in part by NSF, EBS modules feature television news coverage of real earth science events --earthquakes, oil spills, volcanoes and hurricanes.
In each module, real-world tasks create the need to know more about earth science and allow students to apply their newly acquired science knowledge as they create their own television shows, reports, newspapers and recommendations for action.
In the Volcano! task, students form a media production company to produce a television program about volcanoes for middle school students, as part of a public information campaign to inform citizens of Washington State about Mount Rainier. Some of the topics in the module include: volcanic formation and classification, lava flows, predictions and volcanoes in history.
The following activity is adapted with permission from the Event-Based Science (EBS) Project, published by Innovative Learning Publications, a division of Addison-Wesley Publishing Co., and produced by Montgomery Public Schools, Rockville, Maryland. For information about EBS modules - Oil Spill!, Earthquake!, Hurricane!, Asteroid!, Toxic Leak!, Flood!, Volcano!, Gold Rush! and Tornado! - call 1 800 552 2259.
In this activity, you are part of a research team working to find out more about volcanoes. Your assignment is to gather information about magma and present it as part of a television program to educate students in middle schools. Your goal is to create a demonstration that will show how the composition of a liquid affects its viscosity.
While conducting your research, you have discovered some interesting information about magma. When it flows from the ground and over the earth's surface, it becomes lava (extrusive igneous rock). By observing the behavior of lava, scientists have learned much about the compositions, temperatures and liquid properties of different types of magmas. They have learned that not all lava flows at the same speed. Some of the speedy lava at Mauna Loa in Hawaii has reached speeds of 16 kilometers an hour, but most lava flow rates are measured in meters per hour or per day.
Viscosity is a property of liquids used to describe resistance to flow. During your research, you have learned that the viscosity of a magma depends on temperature and composition. Lava flows at different rates of speed, depending on chemical composition and temperature. By performing this activity, you can demonstrate the relationship of viscosity to lava flow.
- various liquids, such as heavy corn syrup, glycerine, cooking oil,
- 10mL graduated cylinders
- small plastic beads
- warm, soapy water and towels for cleanup
- Begin the demonstration with a comparison of how long it takes a plastic bead to fall through two different substances. After you conduct trials, mix together different volumes of liquids to determine how various ratios of each affect the settling rate of a plastic bead.
- Keep accurate records of volumes (in mL) and time (in seconds). You should also calculate and keep a record of the concentrations of the solutions you test. For example, a solution made with 20mL of corn syrup and 60mL of water would have a concentration of 25 percent. The formula for calculating this concentration is:
CONCENTRATION (percentage) = volume of corn syrup, divided by total volume of solution; multiplied by 100
- After you have tested various concentrations of syrup, water and alcohol, test concentrations of some of the other liquids. How do you think changing the temperature of the solutions you test would affect their viscosity? Test your ideas if possible.
- After completing your experiments, prepare graphs that will make it easy for people to compare the viscosities of the solutions you tested.
- Write a conclusion based on your research.
- In "Through Thick and Thin," students design and perform experiments to test how different concentrations and temperature affect viscosity. Tests are conducted by timing how long it takes plastic beads to fall through graduated cylinders containing the solutions. Students should record data in tables and graph results for comparisons.
- Because of the different densities of the liquids, mix solutions thoroughly before putting them in the graduates. The number of concentrations and liquids tested (syrup, glycerine, cooking oil, etc.) will depend on the amount of time available, but students should test at least two liquids.
- Make sure students clean graduates between trials of different solutions.
- Direct students to use a water bath to heat solutions instead of heating the graduates directly over a burner.
- Test different beads before having students use them. Students may experience problems when trying to sink the plastic beads in viscous liquids. The beads must be denser than the most viscous liquid (corn syrup). The drop rate in corn syrup is quite slow. At first the beads appear to be stuck, but they do move, so patience is necessary. Students may poke the bead gently to get it moving.
- Compare the eruptions of Kilauea, Stromboli, Vesuvius, Etna and other volcanoes.
- Have students identify the three types of volcanoes and find examples of each.
- Why does so much volcanic activity occur in the Mediterranean region?
- The key component that determines the viscosity of magma is quartz. The more quartz crystals contained in a magma, the greater is its viscosity. How could you make up a lab to demonstrate this phenomenon, using corn starch and water?
Magma is thickened by the addition of silica. You can demonstrate this in the following mini-lab by boiling corn starch and water; cornstarch represents molten quartz (silica).
- Mix 2 tablespoons of corn starch in 1/4 cup of water; stir well.
- Boil 1 cup of water in a saucepan and slowly add the corn starch/water mixture to the boiling water.
- Boil for about two minutes. Remove the pan from the stove and let cool.
- Volcanic eruptions may produce viscous lava (Mt. Etna) or an explosive combination of gas and particles (Mt. Vesuvius). These pyroclastic eruptions are far more lethal.
- Computer models estimate that volcanic material would flow from Mt. Vesuvius at 200 miles per hour. Calculate that speed in kilometers per hour.
- In 79 A.D., the eruption of Mt. Vesuvius buried the towns of Pompeii and nearby Herculaneum within hours. Volcanic ash and gas decimated Pompeii; a layer of hot mud 15 to 20 meters thick buried Herculaneum. This blast from the past left perfect time capsules; archaeologists found bread in bakery ovens and half-eaten meals on tables.
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