Where did the ground we walk on come from? As humans, we tend to take land for granted, despite the fact that, even today, it covers only about a third of the Earth’s surface. What’s more, land is largely two-dimensional. With the exception of tiny burrowing beasts, most of our activity takes place on the surface. The ocean, on the other hand, has a vast third dimension, hosting various kinds of creatures all the way through. “How inappropriate to call this planet Earth”, the science-fiction novelist Arthur C. Clarke once wrote, “when it should quite clearly be called Ocean”.
Be that as it may, we do have our land. And we take it for granted that this land always existed on Earth, albeit in a different form, with a different climate and inhabited by different creatures.