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Posts Tagged ‘Chaitén Activity’

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.

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 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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Chaitén Still Awake!

Posted by feww on September 29, 2009

Chaitén: A New Phase of Activity?

On June 29, 2009, after a magnitude 5.3 quake struck off coast of Isen, Chile, at a depth of 10km, the Moderators forecast:

FEWW believes that the quake could be followed by more shocks, a number of which could be larger in magnitude, along the Chile Ridge, near the coast of Chile and about the subducting Nazca Plate. Additional seismic activity in the region could result in a new, more intense phase of activity in Chaitén, or prime other regional volcanoes for eruption.

Well, Chaitén is still awake, doing what volcanoes do best: Spewing ash, steam, sulfur…

Ash and Steam Plume from Chaitén

The Advanced Land Imager (ALI) aboard the NASA/USGS Earth Observing-1 (EO-1) satellite acquired this natural color image of Chaitén on September 27, 2009, at roughly 10:30 am local time.  According to a report, there was an ash plume extending 56 km (35 miles) northwest of the summit at the time the image was taken.
NASA image by Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Caption by Robert Simmon. [Edited by FEWW]

Related Links:

Posted in Chaiten, Chaiten volcano, obduction, oceanic tectonic plate, orogeny. Tagged: block rotation, Plate Tectonics | Tagged: , , , , , , | Leave a Comment »