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Rhyolitic volcanoes pack a much bigger punch

Posted by feww on October 11, 2009

Quote of the Day:

“The largest eruptions on the planet have been rhyolitic …  you might have fewer of these volcanoes, but they pack a way bigger punch.”

—Jonathan Castro of the Institut des Sciences de la Terre in Orléans, France.

30410914-072_med
Flow banding in rhyolite lava from Mono-Inyo Craters volcanic chain, California (black bands composed of obsidian). Source: USGS

Large rhyolitic volcanoes include

  • Yellowstone, Wyoming (hotspot track near the Idaho-Oregon border)
  • Long Valley, California
  • Valles, New Mexico
  • Chaiténvolcano, Chile
  • Japanese Volcanoes
  • Taupo Volcanic Zone,  New Zealand
  • Ethiopian hotspot in northeastern Africa

Chaiten - UPI
After 9,000 years of slumber, Chile’s Chaiténvolcano erupted spewing lava and ejecting ash up to 20 km into into the atmosphere, with lightning added for extra dramatic effect. (Photograph by Carlos Gutierrez/UPI,  dated May 3, 2008) . Image may be subject to copyright.

Rhyolite often erupts explosively because its high silica content results in extremely high viscosity (resistance to flow), which hinders degassing. When bubbles form, they can cause the magma to explode, fragmenting the rock into pumice and tiny particles of volcanic ash.

Rhyolite:

Rhyolite which is erupted at temperatures of 700 to 850° C, is a light-colored rock consisting of

  • Silica (SiO 2 ) content greater than about 68 percent (by weight )
  • Sodium and potassium oxides up to  about 5 percent.
  • Common mineral types include biotite, feldspar and quartz (found in a glassy matrix)

Related Links:

FEWW Volcanic Activity Forecast

Recent Posts on Chaitén:

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