Monday, July 19, 2010

The Geometry of Stress and the Lack of Rain

Contraction of rock and soil causes cracking perpendicular to the stress direction with fractures widening based on the rate of cooling, or in our case, drying. The fractures form a V shape until the stress has subsided, whatever distance that may be below the surface. However, since the medium contracts from all directions, interlocked polygons are seen from above. From my observations, the rock forms are generally hexagonal while soil, at least our clay, tends to fracture in pentagonal shapes. The most beautiful examples of this are volcanic and refer to Satan down below. Devil's Tower and Devil's Postpile are probably the best sites to view these columnar polygonal patterns in the United States.
Other examples exist on the northern end of the Mid Atlantic Ridge on a small country known as Iceland. The most horrific examples are the dried up lakes, river beds, and yes, even garden soil. So as I'm standing there, hose in hand, watering the plants that have been stressed by this extreme weather, I can see clearly below the toasted green leaves to the geometric shapes that scream at you like red graffiti on a new white concrete wall, we need rain!

1 comment:

nathan said...

my mashed potatoes looked strangely similar to that last night at dinner