As a follow up, could slab window volcanism be responsible for the volcanoes in southern and eastern California such as Long Valley since it is too far south to be driven by the Cascade Subduction zone?

Earth science: What happens when a divergent plate boundary, such as a mid-ocean ridge, gets subducted beneath a continental plate?

I believe this has happened in the past with the Farallon plate undergoing subduction with the North American plate, with the Juan de Fuca plate being all that remains of the Farallon.

How does this affect subduction based volcanism related to the subduction zone?