Linda F. Malanson
(figure available in print form)
Volcanoes are a source of fascination and fear. Cultures from around the world have created stories to explain the causes of volcanic eruptions. The word “volcano” comes from Vulcano, an island near Sicily that was thought to be the home of Vulcan, the ancient Roman god of fire.
Magma is a mass of melted rock that originated in the Earth’s lower crust and upper mantle where temperatures may reach more than 700 degrees Centigrade. The magma tends to rise because it is less dense than the surrounding rock. Basaltic magma forms at about 1200 degrees Centigrade.
The magma, which is under a great deal of pressure, escapes through the weakest area in the surface. These weak areas could be places where the crust is thin or cracked or along boundaries of Earth’s plates. Magma that has reached Earth’s surface is called “lava”.
A “volcano” is an opening in the Earth’s crust through which hot molten rock, gases, solid rock fragments, ashes, etc. from inside the Earth make their way to the surface. A volcano can take on different forms, but the one we usually think of is that of a mountain in the shape of a cone.
There are about 500 active volcanoes on Earth. Volcanoes are often located over areas where crustal plates meet, separate, or subduct (one plate is forced beneath another). Volcanoes that erupt where the plates are separating tend to be much gentler than those where the plates collide and these are all under water. As the plates pull apart, magma wells up to seal the gap between the plates.
There are or have been volcanoes in almost every part of the world. Although volcanoes may seem quite destructive, they are also considered quite beneficial. Volcanic ash is full of nutrients that enrich the soil. In many parts of the world, people risk living near volcanoes so they can tend farms on the fertile volcanic slopes. Steam and hot water from volcanoes are used for heating houses and for generating electricity in many parts of the world.
EXPERIMENT: VOLCANO MODEL
(figure available in print form)
Before attempting this experiment collect newspapers to cover the work area. Put the baking soda in a small jar. (If desired, add small pieces of styrofoam to represent rocks.)
Mix the vinegar, soap, and food coloring in a jar. Make a cardboard tube (or use a toilet paper roll) and fit it around the jar. Cut holes in the tube for drinking straws or small plastic tubing which represents vents.
The reaction of vinegar and baking soda is used in the simulation of a volcanic eruption. When vinegar and soda are mixed together, a chemical reaction will occur. This chemical reaction will produce carbon dioxide gas bubbles. These bubbles will rise to the top of the volcano and spill over the sides. The soap is added for a more frothy volcano.
MATERIALS NEEDED:
1. dirt
2. sand
3. water
4. straws
5. baking soda
6. vinegar
7. food coloring
8. cardboard
9. small jar
10. pan
DIRECTIONS:
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1. Put sand in a pan or small box.
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2. Make a cardboard tube and fit it around the top of a small jar.
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3. Cut 2 or 3 holes in the tube. Put plastic straws or small tubes in the holes.
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4. Mix sand, dirt and water. Mold it around the jar on the tube to make a mountain.
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5. Put baking soda in the jar. Mix vinegar, food coloring and dishwashing liquid in a cup.
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6. Eruption Time! Pour the vinegar mixture into the jar and tube. Stand back and observe.
WHAT HAPPENED?