Interesting. Thanks.
And, I think the "run-out" of liquid and gaseous flows might be different in measurable ways.
On St. Helens, the mud and rocks ran-out a long, long ways, and climbed partway up a hill.
Don't think liquid could have done that.
AND, don't pay any attention to me, I just sort of get off on thinking about it.
I enjoyed your web site a lot, and will enjoy it more tomorrow.