Various (100) wafer etch rate diagrams:

This figure shows some calculated 2d etch rate diagrams for (100) wafers 
using different parameters. The basis model was used to obtain these diagrams.

The upper left hand diagram is approximately isotropic while the lower right 
hand diagram is highly anisotropic. The numbers above each diagram give the 
relative values of the (111), (100), (110), and (311) rates respectively.

The outer contours in each diagram represent the rate at the surface 
(the 2D rate) while the inner contours give the rate deeper in the crystal.