SimEarth

If you've read my last two posts, you've probably figured out why no simple plate tectonics algorithms are known. It's a complicated process, one that doesn't lend itself to simple code. That, however, hasn't stopped people from trying.

SimEarth has a very simple, highly unrealistic algorithm for continental drift. The world, which is cylindrical (i.e. wraps around horizontally but not vertically), is divided into a grid of cells, each of which is assigned one of the 8 compass directions or "not moving". Occasional random "earthquakes" assign the same direction to a circular area (a "plate"). Occasional random "volcanos" produce land. Land in a particular cell moves by one cell in the direction indicated every time unit, and if no land enters a cell it is set to ocean.

This algorithm captures the concept of moving land, and not much else. Faults are completely ignored, so that no island chains or mountain ranges are generated, just islands with single large peaks in the center.

On the other hand, SimEarth had to be computationally inexpensive enough to run quickly on a desktop computer in 1988, with a lot more than just continental drift being simulated. It's still a great simulation toy (like SimCity, only on the grandest scale), and it runs fine on WinXP.