Volcanic activity is VERY comparable to 40 days and 40 nights worth of torrential rainfall apparently, at least according to this card which was, again, taken from the Open Air stall in early August.
Hit the jump for the back
The root problem with Creationism is having to explain away the piles upon piles of evidence that the world is in fact billions of years old and everything on it can be explained by natural phenomena. This results in really pitiful attempts to lie about science to explain how everything can be caused by God creating the universe 6000 years ago and/or flooding the earth 4000 years ago. In this case, the implication is that Noah's Flood caused the Grand Canyon, and that the canyons on Mount St Helens are proof.
The Grand Canyon and the canyons on Mount St Helens are not comparable phenomena. For a start, by "smaller" they mean smaller on a 1:500,000 scale. Furthermore, the sediments cut through were just unconsolidated volcanic ash, which is pretty easy to cut through compared with say.... the consolidated materials that the Grand Canyon is made of.
Source: Talkorigins http://www.talkorigins.org/indexcc/CH/CH581_1.html