Watching a show about America's Volcanos, and just heard the following two things:
the grinding as one tectonic plate subducts beneath another melts the rock and causes volcanos, and
subduction volcanos create the deadliest kind of eruption, the pyroclastic flow.
Well, gee I thought it was the one plate being forced down to the earth's interior, where it's supposed to be kind of hot, that melted the new rock and other stuff. And I guess that since the most violent volcanos tend to be along subduction zones you could say that subduction causes pyroclastic flows, but...
I've noticed that in political matters you have to watch what comes out in some Discover and History channel shows, but damn.