Read many years ago that in some of the eruptions that formed the pacific northwestern US there were lava flows that deposited as much as 1000' deep of new land. Geez Louise!

I dunno about the one GAK mentioned but after many years of study geologists have revised their estimate of the Yellowstone caldera to actually be much larger than was once thought at a whopping 90 miles across.

It's almost incomprehensible to imagine an area of that size erupting and spewing rock and ash into the stratosphere for even an hour, much less weeks or months at a time.

Seems the best hope the world in general has is that the earths core and the proximity of the magma chamber beneath Yellowstone has shifted enough over time, relative to the surface, that it may have significantly enough sealed off the vents which would allow another such eruption.

'Course that's all speculation and there's plenty enough voices in the seismic community that say one day it will still happen, so who knows. I do know that if the geologic timeline of previous eruptions were an absolute figure we're already right at or overdue for an eruption, which is a scary thought