What causes Volcanic Eruption to be so explosive?
Some lava is more viscous (gooey) than other lava. these lavas can also contain a lot of volatiles, substances like water, CO2, and H2S that normally exist as gas. All lava contains some of these gases in small amounts; it turns out that the more gooey lavas can hold more of these gases in solution (for various chemical reasons). When the lava cools, the gases bubble out. This is all fine and good if the lava is fairly runny and the bubbles can migrate up to the surface and pop. But with a gooey lava, the bubbles cannot escape fast enough and the gas wants out but cannot get out. This causes pressure to build until suddenly, Kabooom!, the gas pressure is high enough to blow the lava wide open. Sometimes the problem is that the solid rock at the surface is what is preventing the gas from escaping, and the same result happens; the gas builds up pressure until it is stronger than the stuff that is preventing its escape and then Kaboom!, a really big explosion. Mount st helens is a good ex
