Complex sentence: In contrast to the relative permanence of continental crust, the size, shape, and number of continents are constantly changing; different tracts rift apart, collide and recoalesce as part of a grand supercontinent cycle.
Split into simpler sentences: In contrast to the persistence of continental crust, the size, shape, and number of continents are constantly changing. Different tracts rift apart, collide and recoalesce as part of a grand supercontinent cycle.