Chalk Up Another Win for Geology

In my line of work, it would not do to be afraid of heights, and I'm not.  But it is actually an advantage to freak out when seeing mining shafts or strange holes in the ground.  A pleasant walk along a new arroyo can suddenly get a little dramatic when encountering a strange hole.

 We were walking downstream when this hole came along.  I was so glad my little cutie was on a leash.  At first the hole seemed like it was part of an old mine, but after all, it was in the middle of the "water channel."

What would it look like from the opposite side, the downstream side?

OK, so it was a strange-shaped hole made by water.  Whenever you see something like this, you wonder what was so unusual about the rocks that caused such a strange shape.

In general, reading an article on Wikipedia is no help.  The geology articles are just jargon and memorization.  I want to understand processes, and how the geology shaped the landscape -- that is, things I can see and walk on.

The arroyo was not done with surprises.  Was this whitish sedimentary layer chalk or mudstone?

I poked it with the walking stick and it crumbled, like chalk.  But when the idea of chalk comes into the mind, you always thing of the white, chalk cliffs at Dover England.  In an arroyo in Arizona?

The last delightful surprise was a human-sized version of the famous Vasquez Rocks, used for shooting the opening of the old TV western "Laramie."  (and many other shows and commercials.)  My photo was a dud so I'm not showing it.  But who knows, I might have been fluttering my eyelashes by then and was imagining things that weren't really there.