Has there been, in the last twenty years, a trend of increase in volcanic activity and/or a trend of increase in volcanic induced production of greenhouse gases or ozone depleting atmospheric chemicals?

Tom

Since scientists have gained access to all the remote regions of the Earth (in the 1960s) and catalogued the number of active volcanoes the number has been about 55-60 active volcanoes per year. So, there is no trend for an increase in volcanic activity. There has been a BIG growth in public awareness of volcanic activity thanks to the media, the web, and even Hollywood. Volcanic emissions come from small nearly continuous eruptions, dozens of small-moderate eruptions, and rare big eruptions (like Pinatubo or El Chichon). I have not seen any papers that report trends in these types of volcanic gases. Have a look at Volcanic emissions and global change (http://vulcan.wr.usgs.gov/Projects/Emissions/framework.html).

Sincerely,
Steve Mattox

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