Melt Down: Can Solid Rock Melt? (page 2)

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Author: Janice VanCleave

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  1. Magma is a thick liquid. Thick liquids are said to have a high viscosity (the property of a liquid that makes it resistant to flow). Liquids such as water, honey, and shampoo can be used to represent magma of various viscosities. Test the viscosity of each liquid by placing 1 drop of each liquid about 2 inches (5 cm) apart on a metal baking pan. Then slowly raise the end of the pan until one of the drops starts to move down the pan. The slower the movement of the drop of liquid, the more viscous (resistant to flow)the liquid is.
  2. Demonstrate the effect of temperature on the viscosity of magma by repeating the previous experiment twice. The first time, raise the temperature of the samples before performing the experiment. To do this, place 1 tablespoon (15 ml) of each sample in separate baby food jars. Set the jars in a bowl. Pour warm water into the bowl to a height greater than that of the liquids in the jars. Wait 3 minutes, stir the liquids, then perform the experiment. The second time, begin by lowering the temperature of the samples. Place the jars containing the remaining unused samples in the refrigerator for about 30 minutes, then perform the experiment. Use diagrams and the results of each experiment as part of a project display.

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The three principal kinds of magma are andesitic, basaltic, and rhyolitic. Find out more about the characteristics of these magma types. What is their chemical composition? How does the viscosity of each differ? For more information about magma, see "Up and Down" on pages 16–19 in Janice VanCleave's Volcanoes (New York: Wiley, 1994).

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