Just for everybody's information . . .
The VEI, or Volcanic Explosivity Index, is the measurement of the scale of a volcanic eruption. It is not perfect, since it only measures the amount of solid matter, from ash to boulders, ejected by an eruption, and the height to which it is ejected, so a simple flow of hot lava that covers 1000 square kilometers and obliterates all plant and animal life in that area would be labeled a VEI 0 or 1 and the actual damage done to the landscape considerably underestimated.
MegaColossal, by the way, is the title given to a VEI 8 eruption, one which ejects over 1000 cubic kilometers of matter and throws some of it up to 20 kilometers high - into the stratosphere. The last such eruption occured about 27,000 years ago, so its appearance in the game is a little problematic: as far as we can tell, that size (the highest measured) eruption comes around about once in every 50,000 years.
Lesser eruptions, though, can still do a lot of damage: the eruption of Vesuvius that obliterated two Roman towns in 79 CE was a VEI 5 ("Cataclysmic") eruption that ejected about 1 cubic kilometer of matter, as was the Mount St Helens eruption in 1980 CE that, mercifully, took place in a felatively uninhabited region but spread airborne ash across half the North American continent. Tamboura in 1815 CE, that caused a "Year without summer" in Europe a year later because of the effects of its ash cloud, was a VEI 7 ("Super Colossal") eruption that ejected an estimated 150 cubic kilometers of matter, so one of the largest eruptions in known human history, and with world-wide effects - quite large enough for my game, thank you!
