OP, I followed the linked thread to your posting, and I noticed something on the graphic you posted. Something I found a while back.

Look at Washington state, and how the volcanoes are placed. Do you see any patterns...

Mount Adams, Mount St Helens, and Mount Rainier. Look at these three, and tell me if this is a pattern worth any more conversations.

I have a theory, but want for you to make your own assessment before I disclose this information. Thank you in advance.

Note: The graphic that showed the coast of Washington and the magma chamber near the surface of the ocean floor.