Answer:
Divergent margins
Explanation:
The process most likely causing the Pacific Plate to expand is divergent margins. Along a divergent margin, the lithosphere splits and begins to move apart. In a convergent margin, plates are pulling together relative to each other. At a divergent margin, the plates are pulled apart. This leads to the formation of new crusts and it is usually described as a constructive margin. The mantle below is the driving force of the movement of the divergent plates.
