Geography

Question

how come there is so much land on the earth?

Answer

Kara, Actually, the Earth is only about 30% land -- even less when there are no icecaps at the poles and sea level rises. We believe the Earth started out as a molten ball 4.5 million years ago, and for a while, as the Earth cooled, the densest materials like iron settled to the core while the less dense materials floated to the top. The least dense materials formed the early continents. Some continents are very old -- Australia may be 3 million years old. These great continental plates have moved around over the eons but retained their character, although occasionally breaking in two. As these plates float around, they open and close gaps which are the oceans. Thus the land at the bottom of the ocean is very young, nothing older than a few hundred million years. Luckily, there isn't so much water that even the continents are under water! That might happen on some planets and they would be true Waterworlds.