A most curious observation is the way triangles are a recurring theme of the sedimentary rocks on the shore at Kimmeridge Bay in Dorset. The photographs in this Post show how entire boulders have this shape as well as naturally-occurring cracks, crevices and fissures in the bedrock layers of the ledges and platforms. Most of the triangles are found in the harder dolomitic limestone.
Why should triangular fractures be so common? I think that they may be related to the phenomenon that has created the so-called expansion megapolygons in the bedrock here but would appreciate a simple explanation, if anyone could help me, of what exactly that is.
Triangular beach boulder.
Triangular fissure outlines in rock pavement.
More triangle-shaped cracks in a dolomite rock platform.
How many triangles can you see here and below? Spotting and counting triangles could be fun activity for kids on the Kimmeridge shore.
For more information about Kimmeridge Bay see the Purbeck Marine Wildlife Reserve Web Site.
Jessica's Nature Blog 
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