If there were substantially less water the Earth would be covered with lakes and puddles. If there were substantially more water the land would be completely submerged . This apparent coincidence may have grand implications for the development of complex life on Earth . The mountain chains seem to prefer the centers of oceans and edges of continents. Mountain chains and boundaries between continents and basins are associated with earthquakes and volcanoes.
Continental outlines fit together like a jigsaw puzzle.
The Earth's crust is thin and fragile. The Earth's interior is still warm and active. Motions in the Earth's interior crumple and break apart the thin crust and permit fresh molten material to reach the surface. These plates grind against one another, split, and collide producing many of the geological features we see on the Earth's surface today. Old crust is destroyed where plates collide as it subducts back into the Earth's interior.