what type of plate is plate a

Plate A is an oceanic plate in the most commonly referenced school and homework diagrams that ask “What type of plate is Plate A? What about Plate B?”

In those standard convergence diagrams:

• Plate A lies under the ocean and is shown as denser crust that sinks or is subducted. This is characteristic of an oceanic tectonic plate.

• Plate B, by contrast, is drawn as the thicker, more buoyant landmass overriding Plate A, so Plate B is a continental plate.

So, for that widely used diagram, Plate A = oceanic plate, Plate B = continental plate, identified by their position (under the ocean vs. forming the landmass) and by the subduction/overriding behavior at the convergent boundary.