What happens when a coin is split?
Each fragment starts it's own chain.

Edit: I randomly selected a transaction for you to see.  Try this link: http://blockchain.info/tree/7514743 and click on the yellow circles.

Edit2:: Actually, this one is more interesting: http://blockchain.info/tree/50429084  In the former, the payments mostly returned in part to the original address.  That's odd.  The usual way of doing things is sending to one address and returning to yourself at yet another address.