In the dead center of a dry, desiccated, and somewhat desolate winter there is always one thing we can rely upon to pique the naturalist in each of us – rocks! With wildlife populations diminished by drought and our local flora seeming little more than a motley collection of half-alive trees and shrubs, we can take true solace in our unique Sky Islands geology.
Through the vast expanses of geologic time, what is now Southeast Arizona has been variously: inundated by a shallow sea, blasted by violent vulcanism, uplifted and sunk by major faulting, seriously eroded by a wetter/colder Pleistocene ice age climate, and even rocked by devastating earthquakes. Collectively, these and other natural forces have rendered our Sky Islands one of the most geologically diverse regions in North America, if not the world. Here, I shall profile some of the star players in our local and distinct geologic theatre.
It is perhaps fitting to begin with our nearby mountain ranges, as they visually and ecologically dominate our landscapes. Have you ever pondered the truly bewildering variety of shapes and profiles presented by our mountains? They run the gamut – from bold spires (think Baboquivari Peak and the Dos Cabezas) to super-sized rock walls (e.g. the Atascosas) to gentle domes (e.g. the Pinalenos and Chiricahuas) and even bizarre hybrid landscapes (e.g. the Catalinas). By comparison, other mountainous regions of the world often present more uniform and thematic mountain shapes and profiles.
Delving for a moment into one of our ranges, the town of Patagonia is on the precipice of its namesake range, which generally harbors more gentle profiles with a few triangular peaks. Herein lies a vast armada of assorted rocks and minerals, which a casual walk up the dry bed of Harshaw Creek readily reveals. The array of colors, shapes, and textures is best appreciated by picking up and handling each rock that catches your eye.
As you allow yourself to delve deeper into the nuance of a particular stone, realize that almost assuredly you are handling an ex-mountain! One maxim of geology is: “gravity never sleeps.” In other words, what goes up (i.e. mountains, via vulcanism and faulting) must come down (i.e. via erosion). The journey that each rock takes until it becomes mere particles must truly be epic.
Going back to the more macro scale, contemplate the astonishing variety of canyons found within a 100-mile radius of Patagonia. Some, like Madera Canyon are major defiles, while others are measured in mere dozens of vertical feet. Be they grand or minute, canyons literally funnel water and its attendant erosive forces, as well as life itself into their depths. More water equates to more flora and fauna, while the looming cliffs and caves so prevalent in some chasms – think Cave Creek Canyon in the Chiricahuas – provide breeding sites for raptors, ringtails, and other rock-loving species. Canyons provide the perfect landscapes to explore, while experiencing the intimate connection between geology and biodiversity.
Speaking of caves, they too present a broad spectrum of exploration opportunities. Our best-known major cave system is Kartchner Caverns in the limestone-dominated Whetstone Mountains. Here you’ll find a deep, “living” cave environment, where ongoing action by water creates stalagmites, stalactites, ribbons, and other distinctive cave features. A tour through the caverns is a local geologic “must.” Other caves may be mere grottos, visible in their entirety at a glance. Yet these too bear exploration, as many an ancient artifact and/or wildlife sign (scat, feathers, etc.) have been found in such locales.
Fossils – those mineralized portions of dead plants and animals – can be found here and there throughout the Sky Islands. On numerous occasions I have marveled at finding sea fossils, such as crinoids and brachiopods, high in remote mountain ranges. These harken back to our long-gone shallow seas and to the fact that what we are witnessing today is indeed a mere geologic snapshot. Here today, gone “tomorrow” (i.e. within a few million years or so).
We end with a few landscape features that dazzle and bewilder. Tinajas are natural rock basins eroded out of the bedrock in an often otherwise dry creek bed. Given the vagaries of local precipitation – feast or famine – these temporary pools of water often provide the only respite for thirty wildlife or hydrophilic flora. A well-timed visit to a tinaja might reveal not only wildlife sign, but even frogs, toads, and perhaps fairy shrimp breeding in the pools. Instant magic in a sere landscape.
Hoodoos are eroded rock spires that can occur here and there in most mountain ranges, yet which locally are most renowned in Chiricahua National Monument. There you can witness the results of an approximately 27-million-year-old volcanic eruption with its attendant deposition of materials, and the subsequent profound erosion of solid rock into awe-inspiring and otherworldly shapes.
So when you want to sing those mid-winter, humdrum blues just head for the rocks!
Vincent Pinto and his wife, Claudia, run RAVENS-WAY WILD JOURNEYS LLC, their Nature Adventure & Conservation organization devoted to protecting and promoting the unique biodiversity of the Sky Islands region. RWWJ offers private birding & biodiversity tours. Visit: www.ravensnatureschool.org