a little closer look at the eastern inselberg: The monzogranite developed a system of rectangular joints. One set, oriented roughly horizontally, resulted from the removal -- by erosion -- of the miles of overlying rock, called gneiss (pronounced "nice"). Another set of joints is oriented vertically, roughly paralleling the contact of the monzogranite with its surrounding rocks.

The third set is also vertical but cuts the second set at high angles. The resulting system of joints tended to develop rectangular blocks.