Thus,while the upper surface of an oceanic plate is a crystalline solid ,the underside exhibits a gradual phase change,from solid to plastic to viscous liquid as the temperatures and pressures increase with depth.

• 因此，虽然一个洋壳的上部是晶体，下面却显示了逐步的变化，即当温度和压力随深度增加时，便从固体到可塑体再到粘滞的液体。