Ever see the video of Mt. St. Helens and the crap that came down the rivers and stacked up? And how fast it was? There are humans buried in that mud that haven't been dug out. We even know their names.
That seems like a valid mechanism.
/johnny
Read the book and then get back to me, you can’t compare Mt St Helens with a world-wide catastrophe. I only quoted one of a great number of examples.
Space constraints.
That’s why books are written.