Come on now. We all know it wasn't solid rock that was eroded at Mount St. Helens, but unconsolidated material in the form of landslides, lahars, tephra deposits, ash, etc.
The bottom line is that 4,000 year old eye witness testimony is the ONLY line of evidence that supports the flood myth. Eye witness testimony isn't even all that great when it's a month old... or even days or hours. Ask any crime investigator. What IS solid evidence is the physical remnants of events/occurrences.
So please, let's not start that "if you weren't there, then you can't say for certain" rubbish.
As others have stated, even if some ark was found, it doesn't prove the flood. You're still left with the wrong geology.