A DYNAMIC MODEL OF VOLCANIC ERUPTION

By Tyler Jennison, Fifth Grade Braly School Sunnyvale, California

Volcanic eruption theory can be tested in the lab and show that molten rock can be moved to the surface overcoming both gravity and the earth's solid rock crust.

There are several kinds of volcanoes. The one thing that they all have in common is that material from the interior of the earth is forced upward and breaks through the crust to the surface. This experiment examines how and why this happens.

Geologists believe that volcanoes erupt when the earth's crust breaks under the pressure of molten magma charged with gas. Molten basalt, which has a density of 2.2 grams per cubic centimeter, rises through solid basalt, which has a density of 2.5 grams per cubic centimeter. This means that magma rises though miles of solid rock by "floating" to the surface. Eruptions occur when the gas which is dissolved in the molten lava begins to expand from the reduced pressure as it gets to the surface of the earth. The expanding gas pushed the magma out of the ground and forms the lava, ash and escaping gases. This experiment tries to reproduce this affect under conditions that can be managed in a laboratory.

Gelatin was used in the experiment because it is near room temperature in both it's solid and liquid states. The density of gelatin at 30 degrees C is 1.005 and at 20 degrees C is 1.006. Therefore, the density of gelatin and basalt are similiar because they are both denser when cooler. Gelatin is similar to basalt.

Carbon dioxide gas was used because it was available and because it makes up 14% of the gases during Hawaiian volcanic eruptions.

Glass tank Plastic tubing Couplings Hose clamp Seltzer bottle CO2 gas cartridge Pure gelatin Red food coloring Distilled water Stove Refrigerator Pan - two quart Measuring cup Thermometer Scale Video Camera

1. A glass tank with an opening in the bottom was connected to the nozzle of the seltzer bottle with several hoses of different sizes.
2. Two identical batches of pure gelatin were made according to the directions on the package. Uncolored gelatin was placed in glass tank.
3. One batch was colored with red food dye.
4. Both batches were cooled to a firm state overnight in the refrigerator.
5. Just prior to the experiment the red colored gelatin was melted to 30 degrees C.
6. Red liquid gelatin was poured into the seltzer bottle.
7. Camera was set up to record the experiment.
8. Experiment began when the seltzer button was activated.

TRIAL ONE:

There was an apparatus failure when a hose was blown off when the button on the seltzer bottle was pushed. I noticed that the spout was closed on the glass tank when this happened. The red gelatin escaped out of the hose and sprayed all over the kitchen.

TRIAL TWO:

The apparatus was reassembled adding a hose clamp. I opened the spout vent the glass tank and the button was reactivated. This resulted in a successful eruption. The red colored liquid gelatin moved across the width of the tank hitting the side and formed two rifts. The main channel of liquid gelatin rose immediately to the surface breaking through the top of the uncolored gelatin. The red gelatin that moved to the top of the glass tank was mixed with gas which caused it to foam. On the surface it immediately started to separate and red liquid appeared where the original channels had formed.

• For images of trial 2 click here.

The experiment seems to show that the geologists theory is correct, and it proves my hypothesis. Molten rock like the red liquid gelatin can move through denser material and overcome the force of gravity. Eruptions take place because molten rock is forced through solid rock by gases and lower density. An unexpected result was the formation of multiple channels and sideways rift vents.

   To VolcanoWorld           To Volcano Models