Summary: How Many Plates?
By Don L. Anderson
California Institute of Technology
Pasadena, CA 91125
Word Count: 4,124
18 July, 2001
GEOLOGY, July 2001 Page 2 of 21
The questions I address are: how many plates are there, and how many should there be?
Is there a pattern in the plate mosaic? Related issues have to do with the optimal sizes and
shapes of plates and spacings of ridges, trenches and transform faults. Similar questions arise in
studies of foams, bubble rafts, buckyballs, mudcracks, columnar jointing, in the tessellation of
spheres and the planforms of convection. In sphere covering problems, and in dynamic
problems, pentagons replace the familiar hexagons. The "ground" state of plate tectonics on a
homogeneous planet may involve about twelve plates with five nearest and five next-nearest