Sunday, July 22, 2012

Experiment 12: Erupting Volcano

Experiment 12: Erupting Volcano

I know, most of us have done this a million times, but it is soooo much fun! My kids love erupting volcanos so much that we finally made a permanent volcano so they can erupt it over and over!

Supplies: (most of these measurements are rough)
6 cups flour
2 cups salt
4 tbs cooking oil
2 cups water
Empty soda bottle (16 oz)
Warm water
Red food coloring
6 drops dish detergent
2 tbs baking soda
Vinegar about 1 Tbs
Baking dish
Large bowl

  1. Stand bottle up in the baking dish
  2. In large bowl, mix flour and salt. 
  3. Add the water (from the 2 cups) at cup at a time. More might be needed. Mix until you result in a smooth & firm mixture.
  4. Use mixture to make the sides of the volcano, smoothing from the neck out and down to the baking dish, trying to make the sides sloping and smooth.Be careful not to cover the opening or drop dough into it!
  5. Let your volcano dry, you could even paint it if you want!
  6. Fill the bottle about 3/4 of the way with warm water.
  7. Add a few drops of red food coloring to the water
  8. Add the few drops of dish detergent.
  9. Add baking soda to water
  10. Slowly add the vinegar and watch the eruption!

What's Happening?
Chemistry (for older kids).
In this experiment you have several chemical reactions that happen in rapid succession. First, the acidic acid in vinegar (the stuff that makes it sour) reacts to the Sodium Bicarbonate in the baking soda, the result is Carbonic acid. But carbonic acid is very unstable, and it rapidly decomposes (an immediate reaction) into carbon dioxide and water. The bubbles in this experiment are from the carbon dioxide. The bubbles flow down the sides of e 'volcano' because carbon dioxide is heavier than oxygen. In this experiment you get even more bubbles because of the dish soap.

Why do volcanoes erupt? There are several different types of volcanoes and therefore there are several different types of volcano eruptions. In this experiment we are simulating a Strato-Volcano - this is the type of volcano that has steep sides reaching up toward the sky. The eruption of these volcanos usually occurs in stages. These stages can happen in rapid succession or each stage can last days, months, even years! 

The inside of a volcano is like a bowl with a bunch of straws sticking out of it. Most of the straws go off in different directions. The 'bowl' is the magma chamber. Magma is liquified rock from deep within the earth. There are cracks, or weak spots in e crust that allow the magma to travel closer to the surface. These tunnels (like the straws in the above analogy) are vents. Usually there is one main vent, and many secondary vents.

Did you know it's called Magma when it's underground, but Lava when it's above ground?

The closer the magma gets to the surface, the more ground water is boiled into water vapor. If the vents are open, there might be a constant stream of steam that escapes the vent. This stage usually lasts the longest. Water vapor below ground build pressure. If the vent is open enough, it could release this pressure enough to prevent an eruption from happening for years!

But, if the vent isn't open enough, then the pressure with build and build. This is like shaking a closed soda bottle. Eventually the volcano will blow apart in a violent release of pressure. The first part of this kind of volcanic eruption is made up of rock and super heated gas, the rock and dust is usually what remained of the part of the volcano above the blocked vent. (look at videos of Mt St Helen's erupting, where 1/3 of the volcano was blown away!) this bstage of the eruption is called the Pyroclastic Flow - believe it or not, this type of eruption is more deadly than any other stage. Because it is so explosive, it can happen with little to no warning. And the super heated gases and rocks can be thousands of degrees in temp and travel hundreds of miles an hour! This doesn't give people much time to get out of the way. The next stage of the explosion is the ash cloud. When the volcano violently erupts, the stuff too heavy to fly flows down the side of the volcano in the Pyroclastic flow, but dust and ash is very light, most often it is made up of pumice which is very light, and this ash can be blown miles into the atmosphere, but eventually it will come back to earth. Feet upon feet of ash can fall for days, eve, weeks, after the initial eruption.

If this initial explosion destroys enough of the volcano the magma can leak out. In the final stage of an eruption. This stage isn't very often. Most often the pressure is released in the early stages. But if the magma chamber is high enough, or if enough of the vent is blown open, then the magma will spill outward, flowing downhill, much like water. As soon as this super heated rock touches surface air it immediately cools back into solid rock. Eventually this rock will again plug the hole in the end of the vent, and the process begins all over again.

To Make a More Permanent Volvano:

1 Empty Toilet Paper Roll
10 lengths of string about 18-24 inches in length each
1 large paper plate
Plaster of Paris
2-4 Roll of Gause
Warm Water
1 mini plastic bowl (I used a washed out cup from the cinnamon rolls, the one the frosting comes in) < br/> Spray Sealant (optional)


  1. Cut 4 small slits on the bottom of the tp roll, very small ones, then bend the pieces out until you have 4 'feet'
  2. Tape these feet to the middle of your paper plate
  3. Cut about 12 evenly spaced tiny cuts along the top edge of the tp roll.
  4. Tape one end of one piece of string to the bottom edge of the plate, wrap the middle of the string between 2 slits on the top of the roll, then tape the other end under the edge of the plate. Try to make the string go to a slight diagonal.
  5.  Repeat step 4 until you have a nice structure for a Strato-volcano. (you'll use all if not most of your string.
  6. Cut a roll of Gause into roughly 8 inch strips.
  7. Mix some of your plaster with water. I do this in small sections because plaster dries crazy fast, and you need to move fairly quickly.
  8. Dip a section of Gause into the plaster and lay it over your structure, making sure not to seal off the top hole, until the whole thing (even bottom edge) is covered in a nice thick layer.
  9.  Allow it to dry completely. You can do a couple of layers until you have a solid volcano
  10.  Allow it to dry, then paint as desired
  11. You can chose to seal it with a spray sealer if you think the kids will want to cause repeated eruptions (sealer will prevent the sides from getting sticky once the 'lava' starts flowing).
  12. Fit tiny cup into the top of your volcano, this is where you'll put your chemical mixture.

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