by Christyl Rivers

Created on: October 14, 2010

Living on an active volcano is about as serene as anyone could imagine.  That is because, Hualalai, the volcano upon which I sit as I type, has been relatively quiet for decades.

However, on the other side of our island of Hawaii, Kilauea is not so serene.  Nor is it threatening, either.  Although belching fire and brimstone for almost thirty years now, one intrepid enough to brave the jungle and heat, can approach the 2,500  degree Fahrenheit molten lava and, upon a twig, toast a marshmallow over it.  Kilauea, like all Hawaiian hot spot volcanoes, is a shield volcano.  Moving a few meters per hour, only the forest cannot outrun lava here.  Yes, they consume everything in their path, including homes, but it must be remembered it is the volcanoes that gave us this land, and while the death part is momentary and destructive, the life-maintaining portion lasts many human generations in geologic time.

Having been in both locations, I have to admit that living in the Pacific Northwest, as a child, Mt. St. Helens, a composite volcano, (as are all the Cascade Mountains), was much more entertaining, and explosive.  Composite volcanoes, also known as stratovolvanoes, and sometimes andesitic volcanoes, are the more unpredictable ones.  They have the classic mountain shape with steep sides and often near perfect pointed cones.  Mt. St. Helens was almost Fuji like on May 17, 1980, but the next morning, Ka-boom. My sister in Spokane got to see St. Helen’s several hours after the rest of us, because it came (the top part of it) to her in a shower of ash.

Why do some volcanoes blow in massive bursts, and others, as though living in slow, paradise, island time, slowly flow out their glowing rivers?  It would be great to say that this is just the way we do things in the islands, slow and leisurely.  The real reason is because of the composition, pressurized gases and water, and mass of the mountains.  Mt. St. Helen’s, and most of the Cascade cones all along the west coast of the Pacific along the eastern side of the ring of fire, have much more pressure built up.  They are not casually flowing basalt, allowing it to puddle into ropy pahoehoe lava, the way we do things here on Hawaii, and also in Iceland.

Although they do let off some steam, Composite volcanoes usually always have a several thousand year old plug right in their central core which allows a lot of pressure to build up. Composed of

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