Grade 5- 8
Students learn how scientists determine how dangerous an active volcano might be.
Tell students that many mountains in countries like Japan are actually active volcanoes. Scientists in Japan study many aspects of their volcanoes, including lava viscosity. Viscosity is the internal friction of a liqud, or its ability to run fast or slow. Water is a liquid with low viscosity, and so it runs freely. Liquids such as honey and maple syrup both have high viscosity, making them thick and slow moving. By studying the viscosity of lava, scientists can determine how dangerous an active volcano might be. It is the amount of silica in the lava that determines its viscosity. A volcano with small amounts of silica has a low viscosity. It is swift moving and able to destroy surrounding areas quickly without much time for evacuation. The more silica in the lava, the thicker and slower it flows.<br />
By studying the lava viscosity, scientists can also determine the type of volcano that will be formed. For example, the lava from Mount St. Helens is highly viscous, and so the slow-moving lava created a steep-sided volcano. On the other hand, the lava found in the Hawaiian Islands is thin and swift moving, creating flat volcanoes.<br />
Have students try the following experiment:<br />
Gather four clear household liquids with a variety of viscosity.<br />
Pour the same amount of each liquid into four tall, clear beakers or graduated cylinders. Label the beakers A, B, C, and D. Imagine the four cylinders are lava taken from four different volcanoes in Japan. It is your job as the scientist to test the lava viscosity and report to the public the dangers posed by each volcano.<br />
Use a stopwatch and four marbles to test the viscosity of the lave and record your findings on the activity sheet. Begin with sample A. Describe the liquid and then time how long it takes for a marble to drop through the liquid to the bottom of the container. Record your findings on the chart. Based on the speed of the marble, predict the amount of silica in this lava sample and record your prediction on the chart by placing an X along the scale and drawing a picture of the volcano that would be formed.<br />
Continue this procedure with the three other lava samples. Then make a report to the people living in the areas around each of the volcanoes. What kind of warning would each receive?
<li>Volcanic Unrest activity sheet</li>
<li>four clear household liquids such as cooking oil, vinegar, shampoo, liquid soap, corn syrup, molasses, honey, baby oil, etc.</li>
<li>four tall clear beakers or graduated cylinders</li>