Arroyo Walls

[I originally wrote this in October 2011, but never posted this series on the local geology. The pictures are still worth seeing.]

Appearances are deceiving.

When you walk through the far arroyo, the walls on the one side are tall and furrowed like the sandstone you see in pictures of Egypt’s Valley of the Kings. On the other side are low, sloping banks.

You assume the first are more substantial than the second. Don’t bet your climbing knees on it.

The surface here is the ungainly named Santa Fe Conglomerate, a lamination of sand, clay, and gravel. If you paw at the sand-clay layers they crumble in your finders. If you claw at the gravel it stays put until you increase your pressure.

The sculptured surfaces of the tall walls must be the result of constant wind action. When it falls, the rain pocks the skin, leaving small depressions. This year, soot from the Las Conchas fire collected on the ridges between.

The slovenly surfaces of the other result from rain which forms a glaze that resists the wind. When it washes out, however, it disintegrates faster than the clay it lay with. And, apparently when its surfaces can’t produce an adhesive, it leaches and, eventually, brings the clay down with it.