Earth, the largest and densest rocky planet, was created about 4.5 billion years ago. The earth's interior is composed mostly of iron and oxygen. It is divided into four layers which is typical of rocky planets. The core can reach temperatures as great as 9000 F. The surface is unique from the other planets because it is the only one which has liquid water in such large quantities. Mountains, earthquakes, rivers, volcanoes, and deserts are all examples of surface features on the earth, however there are many more due to the complexity of our planet.
