(Courtesy of Trinity University Press)
Living on Earth continues its series exploring features of the American landscape. It’s based on the book “Home Ground: Language for an American Landscape,” edited by Barry Lopez and Debra Gwartney. This week, John Daniel explains the term “stratovolcano.”
Among the earth’s geothermal sweet spots are areas where volcanic activity is high. They’re not places people ordinarily live - but awe-inspiring features of our planet - also featured in the book, “Home Ground, Language for an American Landscape.” It’s a compilation of geological terms edited by Barry Lopez and Debra Gwartney, and an occasional series on Living on Earth. Today, John Daniel’s definition of “Stratovolcano.”
DANIEL: Stratovolcano. Stratovolcanoes, also called composite or cone volcanoes, are known for their stature as mountains and for their variety of utterance. Venting at times pyroclastic – “fire-broken” – particulates, as Mount St. Helens did in 1980, and at other times exuding lava, a stratovolcano develops a layered composition as it grows. The steeply bedded ash and cinders of its pyroclastic explosions tend to give it a conical form, while its gentler expressions of lava provide structural stability. All the major Pacific Rim volcanoes are stratovolcanoes. By present measurements, it takes anywhere from roughly 20,000 years (St. Helens) to more than half a million years (Hood and Rainier) to build a stratovolcano of respectable size. Some erupt so exuberantly that they self-destruct. Mount Mazama, a 12,000-foot peak in the southern Oregon Cascades composed of several overlapping volcanoes, emptied its magma chamber and blew off its upper four thousand feet - 12 cubic miles of rock - in a single day some 6,800 years ago, collapsing into a caldera we call Crater Lake.
GELLERMAN: John Daniel lives and writes in the hills just outside of Eugene, Oregon. His definition of stratovolcano comes from the book "Home Ground: Language for an American Landscape," edited by Barry Lopez and Debra Gwartney.
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