Interesting. also a nice pic of a coastal tuff cone.

There is a possibility of a bow shock in the asthenosphere from the approaching South American plate. This however would imply overrun of the subduction zone and forcing of the mantle away from South America.

May have a lot do do with the Andes mountain range.

Other possibility is that the mantle is near static & the hotspot is moving.

3rd possibility is that the hotspot & mantle are unmoving & the hotspot deviates toward the Galapagos rift as it approaches the deep crust. This scenario puts shield volcanoes on the Nazca plate as in rivets on a raft, with a lot of the magma from the Galapagos hotspot being erupted in the Galapagos rift having passed under the Galapagos chain and heading further north.

Have a nice day: Ag