The Earth has oceans and continents: how weird is that? For a planetary surface to boast extensive areas of both land and water, a delicate balance must be struck between the volume of water it retains, and the depth and height of its valleys and mountains. With too much water, sea levels will be above the highest point on the planet. But if a planet doesn't have enough water, it will be quasi-desert. Data: Thursday, 16 March, 2017 Read more about The Earth has oceans and continents: how weird is that?