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# Magma Flow: How Does Temperature Affect the Movement of Magma?

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Author: Janice VanCleave

### PROBLEM

How does temperature affect the movement of magma?

### Materials

• Teaspoon (5-ml spoon)
• Soft margarine
• Small baby-food jar
• Cereal bowl
• Warm tap water

### Procedure

1. Fill the teaspoon (5-ml spoon) with margarine.
2. Using your finger, push the margarine out of the spoon and into the babyfood jar so that the glob of margarine is centered in the bottom of the jar.
3. Hold the jar in your hand and turn it on its side.
4. Observe any movement of the margarine.
5. Fill the bowl halfway with warm (slightly hotter than room temperature) tap water.
6. Set the baby-food jar in the warm water.
7. After three minutes, pick up the jar and turn it on its side.
8. Again, observe any movement made by the glob of margarine.

### Results

At first the margarine inside the tilted jar does not move much, but heating the margarine causes it to move more freely.

### Why?

As the temperature of the margarine increased, it became thinner and moved more easily. Molecules in colder materials have less energy, are closer together, and move more slowly than warmer molecules with more energy. These warm, energized molecules move away from each other, causing solids to melt and liquids to thin. Just as the temperature of the margarine affected the way it moved across the surface of the jar, the temperature of magma affects the way it moves up the volcano's vent (the channel of a volcano that connects the source of magma to the volcano's opening). Hot magma is thin and moves easily and quickly up the vent, while cooler magma is thick and sluggish.

### LET'S EXPLORE

1. Would a different heating time affect the results? Repeat the experiment, checking the movement of the margarine every minute for six minutes. Use a thermometer to keep the temperature of the water as constant as possible, and replace the warm water each time you make an observation. Quickly replace the jar in the warm water after each testing.
2. Does the composition of the material being heated affect the results? Repeat the original experiment using other solids such as butter or chocolate candy with and without nuts.

### SHOW TIME!

1. Thick liquids are said to have a high viscosity (the measurement of a liquid's ability to flow). Viscous liquids flow slowly, and particles dropped into the liquid fall slowly as well. Liquids such as water, honey, and shampoo can be used to simulate magma of various viscosities. Test the viscosity of each liquid by dropping a marble into a tall, slender glass filled with the liquid at room temperature. The slower the marble falls, the more viscous the liquid is.
2. Demonstrate the effect of temperature on the viscosity of the liquids by repeating the experiment above twice. First, raise the temperature of the samples by standing each glass in a jar of warm water. After three minutes, stir the liquids and use a thermometer to determine the temperature of each. Second, lower the temperature of the samples to about 50° Fahrenheit (10°C) by inserting a thermometer in each liquid sample and placing them in a refrigerator. Diagrams and the results of each experiment can be used as part of a project display.

### CHECK IT OUT!

The three distinct types of magma—andesitic, basaltic, and rhyolitic—harden into different kinds of rock. Find out more about the characteristics of these magma types. What is their chemical composition? Where are they formed? How does the temperature of each differ? Which is the most common? For information about magma see pages 74-79 in The Dynamic Earth, Second Edition (New York: Wiley, 1992), by Brian J. Skinner and Stephen C. Porter.