Which process is responsible for causing rock to rise in a convection current?

Seafloor spreading.

Explanation:

Seafloor spreading is a  process that is responsible for causing rock to rise in a convection current. Convection currents moves the Earth's rigid tectonic plates in the planet's fluid molten mantle. Seafloor spreading is a process in which tectonic plates split apart from each other. As the movement of tectonic plates from each other occurs, heat released from the mantle's convection currents makes the crust more plastic and less dense.

answer; in the united states the plains include the great plains of the west and the tail grass prairie to the south of the great lakes extending east to the appalachian plateau