One of the most remarkable characteristics of the Earth is that the rates of its interior (tectonic) and exterior (climatic) processes are approximately balanced. Erosion can dismantle mountain belts nearly as fast as they grow. …No mountain is exempt from erosion, and the steepest slopes are subject to the fiercest attacks.
- Marcia Bjornerud, Reading the Rocks: The Autobiography of the Earth
We are once again in the Dos Cabezas Mountains -- right in our backyard, so to speak, “we” being Therese and I and our dogs, Yogi and Sunny. Therese has explored part of this territory before, long ago, but it’s completely new for the dogs and me. The open-looking ground in the lower left-hand corner above is, once again, what remains of a former mining road, and our hike will take us back into the picture, past that big tree on the left and eventually deep into a canyon we can’t see at all yet. What looks like a road high above on the right, below the rocky summit, is an old mining scar, but we’re not going there. We will take what remains of the old road paralleling a rocky wash, descend into the wash where rains have washed away sections of road, and explore the canyon not yet visible – because while the land looks quite open in this initial photograph, most of what we will encounter on the ground is still hidden from view, only gradually revealed as we penetrate farther into the picture.
These massive, towering promontories, for instance, so close at hand! Did you see them coming?
The light, bright green plant in the foreground here is Mormon tea, Ephedra viridis. Early Mormon settlers to this region followed the Native American practice of making tea from the dried plant stems, for use not only as a beverage but also to treat colds. Commercial cold remedies are made from an Asian species of Ephedra; the Arizona species does not contain ephedrine, its effect derived instead from tannins.
Going is not fast or easy in a boulder-filled wash. Great forces were necessary to bring the boulders down in the first place, and yet not all monsoon floods were strong enough to keep pushing them. Sometimes the water had to go around the rocks instead, crumbling and eroding and bringing down soil from the banks of what was temporarily a stream to fill the bed with sediment and widen the whole course – except where the bed is bedrock rather than soil, and then the way remains narrow and rockbound.
We humans with our short lifespans and human-centric views of nature usually tend to think of erosion in negative terms, and yet structural geologist Marcia Bjornerud explains it as part of a constantly repeating cycle, the growth and erosion of mountain belts “keeping [the] planet on an even keel,” unlike other planets where volcanoes spew forth unchecked lava flows, growing and growing. “On earth,” she writes, “there are limits to growth, imposed largely by running water.” Bjornerud’s explanations and descriptions take her beneath the ocean, where sediments collect on continental shelves, but I’m sticking to the neighborhood at hand: mountains, rains, and periodically flooded washes.
Sunny and Yogi’s interests are even more locally focused than mine. A bone! They have found a bone! Trust those dogs always to find something thrilling – and better a bone than partially decayed rabbit carcasses or bloody deer legs left behind by coyotes!
I wish you could see how this boulder really looked. It sparkled in the sunlight, but my phone photo does not capture the sparkles.
Our course has altered by about 90 degrees now, and we are getting into the canyon we wanted to explore today. These views are looking back the way we came, through that sunlight into the background and into deep shade.
It was exciting to come upon a pool of water.
Later at home, examining topo maps, I decided we had probably been in Walnut Canyon, and had we gone farther up we might have come to Walnut Spring. Maybe. (We saw no walnuts.) Whatever the name of this rocky slot canyon, it is not anywhere you would want to be during a summer monsoon. As our way narrowed, with massive rock walls on either side, the cowpath and/or game trail became more and more what I would call a precarious goat path. But the rocks were beautiful! --If only I knew their names! That will be in my next life, when I begin in girlhood to prepare for a career as a horseback field geologist….
Our way came out into the sun again eventually, but boulders lay thicker than ever ahead, and we agreed to turn back and call it a morning.
One main theme I have taken so far from Reading the Rocks is that the history of the earth, like the history of the universe, is a story of alternate mixing and sorting. (That, in fact, is the title of one of the author’s chapters.) Stars explode, and eventually planets and their satellites settle out of the chaos. Volcanoes erupt and jumble things again, but in time the boulders and rocks and stones sort themselves out. Tectonic plates collide and give us a new reconfiguration of land and sea. Maybe we need periodic upsets in our brief, small personal lives, unwelcome as they often are, to give us reason to reassess and re-sort, finding a new (though always temporary) equilibrium. What do you think?
Be that as it may, another satisfying mountain expedition has whetted my enthusiasm for further adventures off the beaten path and provided food for thought to accompany my reading.