From the site you offered (without any comment I might add) so I don't know what you are trying to refer to.
quote:
there’s one rock layer that’s 30 feet thick — and it was formed in less than one day — in fact in one afternoon
(this is in reference to Mt St Helen's)
You have chosen as a reference a site that can't tell the difference between unconsolidated ash and very solid stone. I'm afraid as a geological reference it's credibility isn't as solid as the ash.
(am I allowed to say it? --they're trying to make an ash out of you? :-) )