“and the Mt. St. Helen’s sedimentary depositions that bring the whole presuppositions of history of geology, as taught, into disrepute.)”
—I’m guessing that the layers that the site is discussing are these (at least, it’s the only photos of layers that I can find):
The problem is that any geologist undergrad should be able to quickly discern that the layers are volcanic ash that consolidated, and probably formed very quickly from a single volcanic eruption.
Here’s another well known example:
That’s Cathedral Rock - also from a single eruption, with subsequent erosion exposing the layers.
Here’s a description of how such layers are formed:
“During some volcanic eruptions a layer of ashes several feet in thickness is deposited over a considerable district, but such beds thin out rapidly as the distance from the crater increases, and ash deposits covering many square miles are usually very thin. The showers of ashes often follow one another after longer or shorter intervals, and hence thick masses of tuff, whether of subaerial or of marine origin, have mostly a stratified character. The coarsest materials or agglomerates show this least distinctly; in the fine beds it is often developed in great perfection.”