Cool Planet:
And what a long story it is. Earth is 4.5 billion years old! At first, it was just a big blob of melted rock. Slowly, the planet cooled. The heaveiest things such as iron sank down. Lighter materials rose up. Over hudreds of millions of year, the materials formed three main layers. No one has drilled to the Earth's deepest layers, Not yet at least. but scientists know what the layers are like. By studying earthquakes, they know some layer are made of liquid metal. Other layers are made of hard rock.

Signing off,
Blogger