Volcano Eruptions What do shaking a can of soda and a volcanic eruption have in common? email to friend
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What do shaking a can of soda and a volcanic eruption have in common? Yes, both make a mess but there’s more. Scientists are keeping a watchful eye on Mount St. Helens as plumes of steam and ash continue to spew from the awakened volcano. Steve Spangler uses some simple experiments with soda and Alka-Seltzer to better explain the underground science.

Experiment
Video

Volcanoes form when chambers of magma, or hot molten rock, boil to the surface. These magma chambers often remain sealed for hundreds of years between eruptions, until the pressure builds sufficiently to break through a vent, which is a crack or weak spot in the rock above. A considerable amount of gas is also mixed in with the molten rock which accounts for the build-up in pressure. Think of the magma as the soda inside a 2-liter plastic bottle (the magma chamber). Give the bottle a few shakes and then twist open the cap. It’s no surprise that soda spews everywhere. The same holds true for a volcano. The built-up pressure in the magma chamber breaks through a crack or weak spot and the gases force the molten rock out of the chamber.

In order to understand the build-up of pressure caused by the gases in the magma, try the following experiments:

Alka-Seltzer Rocket

Mentos Eruption

The blast creates a crater, where lava and ash spill out, forming the cone. On some volcanoes, the magma chamber collapses after a violent eruption and a caldera forms, which is just a large, bowl-shaped crater.