(b) Steep-sided tower-like fonts; (c) conical font.
afforded by the limestone blocks but rather to the increased turbulence and diversion of waves by
the blocks. In this way, the sandstone on which a block rests facing the sea is preferentially
scoured, forming a low cliff and the beginnings of a plinth. Similarly, waves diverted around the
sides of the block erode the platform there, again leaving the base on which the blocks rest in
relief, as a plinth ( Fig. 12.21a).
Many rock basins (overwhelmingly of the hemispherical or pit type - see Chapter 9) are pot-holes
due to abrasion by cobbles and small boulders swirled around by waves. They have their congeners
in granitic stream channels though the basins of terrestrial granite outcrops are due predominantly