Why is the Nazca plate along the East Pacific Rise a divergent boundary rather than a convergent one?

Answer 1

Because this is a mid-ocean ridge where new crust is being created. The Nazca plate is subducting under the South American plate, and as it sinks the weight of the plate pulls the entire plate away from the east-pacific rise. Also, convection currents in the mantle/asthenosphere are pulling hotter rock from inside the earth up to the surface at the east-pacific rise pushing the Nazca plate to the east and pushing the Pacific plate west.

A convergent boundry would be on the far east side of the Nazca plate where it is pushing east and the South American plate is pushing west - causing the more dense Nazca plate to subduct under the less dense South American plate.