Hello, I am Dwight Williams, a nuclear scientist working with the Center for Monitoring Research in Arlington, Virginia.
I appreciate the service you all are presently offering to the public, and I hope that you are able to benefit from your efforts in some way as you are benefitting the public.
I would like to know what typical radionuclides (radioactive compounds and isotopes) are emitted from a volcanic eruption of ash (specifically, the recent eruption in Iceland).
Also, I was recently informed of the Volcanic Explosivity Index (VEI). I would like for you to provide for me some sort of quantification for each of the VEI numerical rankings
(e.g., "1" is nearly unnoticeable; "4" is very lage -- about the size of Mt. St. Helen; "10" is so large that the earth would be permanantly disfigured; etc.)
Finally, I would like to know the approximate frequency of the various numerical VEI scale rankings during the past year and over the past 5 years.

Thank you.

rocky Dwight Williams

Dear Dwight,

The answer to your question is best found at:

http://volcano.und.edu/vwdocs/frequent_questions/grp10/question810.html

As for the radioactivity, I know that back in the 1950's (of course) geologists wondered about radioactivity in volcanic eruptions. At least during the big 1950 eruption of Mauna Loa, measurements were made of the lava flows with geiger counters. They found no radioactivity other than what you would expect from basalt (not much). For that reason I kind of doubt that there is much radioactivity in the Iceland material either. Certainly volcanoes that erupt in continental regions will tend to have slightly higher contents of radioactive materials due to continental-crustal contamination, but I still don't think there is anything to worry about.

Scott Rowland, University of Hawaii

Dwight -
Here is some more info in response to your question to VolcanoWorld about radioactivity associated with volcanic eruptions. I can't find any references relating to the topic. I think Scott's answer is right; early testing showed none and there has been little reason to doubt those results so no more recent research. As for the VEI and the frequencey of activity at each level: check out the following pages:
http://volcano.und.edu/vwdocs/eruption_scale.html

http://volcano.und.edu/vwdocs/vw_hyperexchange/largest_erups.html

There has only been one VEI 7 (bigger than collossal) in the last 500 years, and four VEI 6s.
Chuck Wood, University of North Dakota 

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