How Can the Earth Create the Earth?

My son was on his chamber pot, as we've chosen to call it recently, and when he finished he told me, "While I was in there I was thinking, how does the earth create the earth? Air is easy, but the rest of the earth couldn't be easy to create. How does Earth do it, I was wondering." This while he was pooping. Who needs a magazine by the pooper when you think this big?