Russian doctor tells how to destroy the USA.
http://finance.yahoo.com/news/russian-doctor-military-sciences-says-181400470.html
http://finance.yahoo.com/news/russian-doctor-military-sciences-says-181400470.html
Perhaps you are either thinking of 'Deep Winter' by T. C. Sherry or one of the stories by Jerry Young?
I think both of those revolve around a Yellowstone type of eruption...
Can't remember the name of the Jerry D Young one though...