[humblegunner]

Sedimentary layers hundreds of feet thick formed within hours during the eruption itself, and then hardened into rock soon after the water drained from them.

No.

Could other layered sedimentary rocks in Earth’s crust have formed rapidly?

Probably not.

[knarf]

Being a born again Christian, I believe in a young earth

This;

"The mountain also provided a clear reason to distrust radioisotope dating. Geologist Steve Austin sampled new rock from atop the mountain that formed in 1986. If the K-Ar radioisotope method really works, then it should have revealed the rock’s true age of only ten years. Instead, three rock “ages” ranged from 340,000 to 2,800,000 years.1 What other rocks from around the world have been dated incorrectly by following those same questionable age-dating protocols?"

.. is an interesting paragraph

I think Mt St Helens was God's last message to the earth daters regarding how it came to be.