I learned about the relationship of explosiveness when it comes to a magma's silica content. You have listed an explosive scale, is this too based on the volcano's silica/viscosity ?

rocky Candy Copeland

Dear Candy,

The Volcanic Explosivity Index (VEI) is not based on the volcano's silicic content, but considers the general description (non-explosive to very large), the volume of tephra, cloud column height, qualitative description (gentle to cataclysmic), and eruption type (Hawaiian to Ultra-Plinian. The VEI was developed by Chris Newhall and Steve Self in 1982. The index ranges from 0 to 8. Typical eruptions in Hawaii are at the low end of the scale (0-1). Most eruptions are in the range of 0-2.

Only four eruptions have been assigned a VEI of 7: Tambora in 1815, Baitoushan ca. 1050, Kikai ca. 4,350 BC, and Crater Lake ca. 4,895 BC. In the last 10,000 years there have been no VEI 8 eruptions.

You might share your new knowledge with your teacher and classmates.

Steve Mattox, University of North Dakota 

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