terminology - What's the name of this 2D cellular automaton?

Does this 2D cellular automaton have a known name and history?

• n colors (numbered 1 to n), assigned randomly at the start.


• For each generation, every cell that has at least one neighbour cell with a color that is one higher changes its color to that "next higher" color. Additionally, the "lowest" color is considered "next higher" to the highest one.


• Emergent behaviour shows up best around n=16, disappears for much higher or much lower n

I have it implemented on my website so you can see it in action.

I saw this ages ago and always remembered it as a great example of emergent behaviour, but can't remember what it was called, and couldn't find it on Wikipedia or Wolfram Mathworld.