It was a crisp autumn day, and I had just crossed over a narrow divide into a broad empty canyon in the White Tank Mountains, just west of town. Until then, that morning, it had all been mostly uphill, and I could finally just “coast” now for a while, even though I was only about halfway through my hike.

  Still mildly sweating, and with slow, steady breath returning, I stood there in the glaring sun, just gazing into the desolate solitude ahead of me. It was empty, and silent. I just had to get out my camera, and take a photo of the lonely magnificence. There was something about that perspective, indeed the very presence within those barren rocks, that could not be denied.

  Look at my picture here. You might ask yourself, “so what’s there here to see?” “It’s just some hills and lots of cactus. There’s nothing there!”

  Precisely. It was one of those “you had to be there” moments, and yet, it was intimately tied to that place, too (and still is). There is an appeal to such views, and it doesn’t happen everywhere. It has to do with the lay of the land, the look of the rocks, in fact their very makeup.

  I’ve talked about this kind of thing before. I mentioned that in Western thought (and science) we give little or no importance to subtleties and feelings. Most other geologists I know would see in that hollow only metamorphic rocks, classified as Precambrian age (around 1.7 billion year old), and a much younger granite, judged to be about 70 million years old (both of these rock formations really are what is there). They would also see nothing of economic value, hence making the place “worthless”.

  But mix a little Zen into the Earth Sciences, and you have a different way of classifying things. According to Oriental wisdom, “every stone has a face.” Every rock looks best when viewed in a certain way, from a specific angle. I would have to agree, and on a large scale it is what makes particular mountains look so appealing, and gives them character.

  I think of that valley and the impression it created in me often. I look at its picture sometimes just to remind myself of how I felt then, how momentarily unburdened of all the clutter in my mind I had been. When I first saw the panorama, the instantaneous perception of that scene was like walking into a dark room, pushing the light switch to “On”, only to have the light instantly “pop” with the flash of a bulb just burning out.

  Think back — you’ve had that experience. Remember how you can visualize the room for a few moments, before the image fades from your brain (and before you run to replace the light bulb)? In the instant the view unfolds, you have the briefest chance to experience the scene without thinking about it. And then you may see aspects you would otherwise never notice.

  There is a Japanese art form known as Suiseki (literally “water stone”), in which natural rocks or stones, in this case small enough to be easily carried around, are valued for their aesthetic appeal. The characteristics that make them so desirable are a combination of suggestiveness, subdued color, balance, and four other aesthetic qualities for which we in the Western world have no precise words: wabi, sabi, shibui, and yugen. These words connote a mental state, felt by the observer.

  “Wabi” translates roughly as a mood of melancholy, loneliness, desolation, stillness, and unpretentiousness. The object evokes a subjective feeling. “Sabi” means ancient, mellowed, seasoned, or mature. “Shibui” connotes quiet, elegant, under-statedness, even refined. And “yugen” can imply obscurity, mystery, the profound, and the subtle, much in the way the moon shines out from behind a pattern of clouds, or a mountainside shows through a layer of thin fog.

  It is not without merit to say that rock formations, hills and valleys, even mountains can display equivalent indescribable characteristics. You may have noticed such feelings yourself somewhere in the great outdoors. You’ve just never thought about them later. You see such feelings expressed in the works of certain landscape painters, especially impressionist artists.

  Walk through some galleries in Scottsdale and take a close look at what various artists are trying to convey. I often wish that I was a painter, and fancy that if I could only master the strokes of brushes and thick oils on canvas, I would go back to the White Tanks, or seek out other such spots, and spend my time trying to capture the essence of landscape.

  The nature of that landscape is in the rocks as much as in anything else out there — maybe more so. Their age, their presence, is something that controls one’s mind and sets one’s mood.

  As with meeting someone new, it’s all in the first impression.
 

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  For more on this subject, go to my website at www.gemland.com, click on “GeoArt”, and visit the Japanese Friendship Garden in downtown Phoenix. The whole park is constructed with these concepts in mind.

  Also visit the “GeoScenery” section, by going to the map called
“The Rocks of the Valley of the Sun”, and look at the sequence of views in the White Tank Mountains. If you want to shift back to Western sensibilities you can do that, too, and indulge yourself with geologic explanations galore.

  And then, even better, go visit the Japanese Friendship Garden in person!

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  Rocks arouse feelings. All we have to consider are gemstones to realize that. Though they are small, the power they exert on the wearer, or even the bestower, is legendary. You can make the case that a stone’s power is constructed by advertising, using diamond as an example. Or you can look at an ancient stone like turquoise, for instance, and mull over the probable connections the ancient Hohokam people in our Valley made between it and the sky, water, or coolness.

  Big rocks elicit feelings, too, I think, and I mean big rocks that form things like cliffs, hills, and mountains. One of my favorites is the rock known as basalt.

  Not long ago, I was trying to “get a feel” myself for what basalt evokes. I was driving around Moon Hill (pictured, from Shaw Butte), that little ridge that lies just north of Thunderbird Road, on the east side of I-17 and 19th Avenue. My attempts to go up onto it were to no avail, however, as every road was gated. I probably could have waited at a gate, and slipped through behind someone else’s car. But then if asked, how would I explain what I was doing there? “Yes, sir. Who? Me? Oh, I’m just here feeling the rocks.”

  “Rrrright,” would undoubtedly be going through the mind of my inquisitor.

  Melancholy, mild foreboding, and loneliness are some of the feelings I’ve seen in myself around basalt in other places. I had really wanted to go door to door on Moon Hill, from home to home (and I could see some nice ones up on top), and ask people what they feel living there.

  Maybe someday I will get that chance. It has got to be different from what people living on Camelback Mountain (mostly granite) feel, for example, or from what people around Squaw Peak (mostly schist) sense. That feeling would have nothing to do with the view, or the facing direction.

  This kind of thinking is, by the way, off the scale for most geologists. But not all. There are those of us of a scientific bent that are open to the subtleties of nature. As one old saying goes, “the devil is in the details.” So are the good spirits, I think, and much of the beauty. Illustrating this view of nature, the Japanese have ways of classifying rocks that are unheard of in our Western culture, and I have pursued this subject in other writings (see “First Impressions”).

  Basalt (say buh-SALT, not BAY-salt) is a very dark, heavy rock. When molten, it flows easily. It covers many of the hills along what we call the Black Canyon Freeway (I-17) between Phoenix and Black Canyon City. Along the road you can see black rock, sort of “dripping” off the edges of the hills.

  That look is simply the result of the basalt breaking up into chunks and fragments that roll and slide downslope because of erosion. The solid rock itself forms very resistant flat caps or layers on much of the higher ground north of the metro area, creating scenic backdrops such as New River Mesa and Skull Mesa (mesa means “table” in Spanish).

  Around fifteen million years ago, deep fractures opened the crust of the Earth in the area north of Phoenix, and from within erupted the fiery liquid that then cooled and now covers Moon Hill. The basalt flows in central Arizona are some of the youngest rocks around us. I know, fifteen million years sounds like a long time ago, but it is not, really. Earth is 4.6 billion years old. Fifteen million years represents just a third of one percent of its history!

  I was curious as to the origins of the rock’s name, which was not an easy subject to track down. Apparently the Romans took the name basaltes from the Greeks, who in turn got it from the Egyptians, and it seems to have meant “touchstone”. Another source I saw attributed the word to unknown African sources. But then, Egypt is in Africa.

  The Hawaiian Islands (not an easy place to feel melancholic, I admit) are made mostly of basalt, as are the plains of eastern Washington State (an easier place to be depressed), the Snake River Plain that runs across southern Idaho, and the dark splotches that we see on our moon overhead.

  It covers the seafloors, and if you drive north from Flagstaff towards Page, you can see great long tongues of basalt, now mostly covered by brush, emanating northwards from the San Francisco Peaks, running for miles along Highway 89. In the back-country on the way to Puerto Peñasco (Rocky Point), in Mexico, are some of the most amazingly picturesque basalt flows I have ever seen.

  Next time you see some, get out of your car, approach it, spend some time, and see what you think. Or more importantly, what you feel.

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  The first time I walked up the trail on Shaw Butte, I didn’t even notice them.

  It took another trip, and a little exploring, and then I found what I had been looking for: a set of ancient ruins, and some people think, a prehistoric solar observatory. Actually, there is a sign there, posted by the City of Phoenix, asking visitors to respect these antiquities. Just behind a bush, it’s not easily noticeable from the trail, almost as if it had been planned that way. Like, “now that you’ve found this secret spot, please don’t damage it!”

  Just having read my opening lines here, you might already think you know where I am going with this article—another description of some of the Hohokam ruins for which the Phoenix area is famous.

  There is more than that, however, to this saga. These ruins are just part of a bigger picture that I want to present to you. Geology is not just something we study. Geology is something we are. By that, I mean that humans are inextricably connected to planet Earth and are part of its organic evolution.

  Those who think that nature is here for us to use, that it is at our disposal, have it all wrong. We are part of it. We are all one thing.

  For those of you not familiar with which of the peaks around Phoenix is Shaw Butte, you do know it. When traveling down I-17 from the north, it is the mountain on your left as you drive into the Valley of the Sun, just before you get to what we call Central Phoenix. The butte has a grove of tall metallic towers on its summit, and sort of a looming shape that to me has always suggested, “Welcome to Phoenix.” If you drive north on Fifteenth Avenue from, let’s say, Northern Avenue, you will run right into it.

  If you go around to the north side of the mountain, which some would call the “back” side, and look up, you will see a lot of black, rubbly-looking rock. Much of the north side of Shaw Butte is covered with this rock, known as basalt, or here, officially, the “Moon Hill Basalt”. It flowed up and out of volcanic vents around 20 to 15 million years ago. That sounds like a long time back, but actually these are some of the youngest rocks around the Phoenix area. You can see other areas of basalt around the Valley, too, and along the freeway to Flagstaff.

  When you look up at the Moon, the dark areas you see that form the “Man in the Moon” are basalt. Maybe that’s where the name of nearby “Moon Hill” came from.

  Those of you that have studied geology — even just the basics — know the three types of rocks: Igneous, Sedimentary, and Metamorphic. The above-mentioned basalt is an igneous rock, once molten.

  “New thinking” scientists now name a fourth rock-type —”Anthropic” rocks — rocks made, modified, or moved by humans. This new classificatory scheme now takes into account what should have been obvious all along.

  Think about how much of the Earth is covered with asphalt, concrete, bricks, shaped stones, and stones transported long distances (like maybe the counter tops in your kitchen). Even little gemstones are rocks which have been cut and modified by humans.

  We are transforming the surface of our planet in ways that other natural processes have never done, and in record speed! Like coral colonies in the sea which build colossal reefs, humans on their own scale add their signature to the world.

  I sat down in the musty dirt, in the middle of what is left of an 800 or 900 year old Hohokam room to ponder this concept, snacking from a bag of “Corn Nuts”, one of my favorite hiking foods. (Not that I’m really into “going native”, but these are very similar to what the Hohokam actually ate back then — roasted corn. How appropriate.)

  It had rained a few days before, and the desert still had that pungent, “wet-bushes” smell to it. The brittlebush all around glowed yellow in the low sunlight. I was all alone, and it was quiet except for the very dull roar of the suburban city stretching off below — traffic noise, occasional dogs barking, a yelled voice here or there, telling the dogs to shut up. I could see far into the distance, miles of human construction laid out everywhere.

  Black boulders surrounded me. They had been piled up to form walls, and pathways, and some sort of arrangement to guide the learned as to when to plant crops, when to get ready for the colder days of the year, when to celebrate whatever. Spiral petroglyphs had been etched into some surfaces. We will never know the exact purposes of this structure.

  Anthropic rocks. Shapes amidst geology, caused and formed by humans.   Unfortunately, I didn’t have a lot of time to linger there. It was an afternoon hike, just a break from work, and I had much more to do that day. I picked up my pack and walked on, past the summit, through who-knows-what-kind-of-radiation blasting out from the gigantic antennas above me.

  Then I found some more ruins, and an even better view.

*********

  It was when I walked up into another set of crumbling walls, down through an old staircase, and out onto a weathered concrete floor that the concept of Anthropic rocks — rocks made, modified, or moved by humans — really sank in.

  The view of Phoenix was grand. I was standing on a semicircular deck, looking out onto a valley below, filled with roadways and houses, and tall buildings in the distance. It was like an immense green carpet laid out there, the look of a garden amongst the barren rocky peaks.

  I had come across the ridge from the Hohokam ruins I had found earlier, and discovered this!

  I tried for a moment to put myself into the mindset of some Hohokam hiker, out for a day’s stroll from the solar observatory I had just visited. You know, like one of those old “Twilight Zone” episodes, where some lonely traveler rounds a bend in a remote road, only to find himself in some future setting, filled with strange structures, the purposes of which are unknown.

  As such, I tried to let my mind just view the scene, without judging it. In the distance, long silvery objects with wings were lifting up, out, and away from near the middle of the sprawl, while others glided down into it.

  My “Hohokam mind” wondered what had happened to the valley I knew, with its low adobe buildings, vast green fields, and long sinuous canals, rippling with life-giving water. My memories recalled how small columns of smoke rose here and there from the flats — signs of cooking, and warmth. There was no roar.

  It had been replaced by this! So similar, yet, so different in its look. There were long straight streets, the patches of greenery laid out in neat square blocks, and I could still see a canal or two. The fields? They were mostly gone, and gleaming buildings of all kinds were everywhere. There were what seemed like thousands and thousands of metallic objects rolling along on the roadways. I could hear distant sounds from them like I had never heard before, like the buzz of insects, but stronger and lower in tone.

  I snapped back to reality. I had once heard of this site where I stood — it was called Cloud Nine. I was standing on the floor of a classy old restaurant which had been named “Cloud Nine”, and it must have been quite a place before it burned down in 1964. A narrow, difficult road had once brought its guests up to this point high on Shaw Butte, where they could gaze out over Phoenix in style.

  You can see this spot today from I-17, as you drive by the mountain. Standing between what are left of its walls, I tried to imagine being there in days gone by, with maybe Sinatra or Sarah Vaughn on the jukebox, the lights of the city just coming on. At one table sat two businessmen talking up a deal; at another, in a dimly lit corner, a couple plotting infidelity over a couple of drinks. I could almost hear the plates rattling, the clink of glasses, and the sizzle of grilling steaks. They smelled delicious.

  Now, all that is left are these decrepit walls and flooring. If it weren’t for the City of Phoenix Park System, these would be gone, too. But here they have been preserved, not out of choice I presume, but because they are too difficult (i.e., expensive) to get at and remove, the land not being open for commercial development. What a great set of ruins!

  I hope the City leaves them alone forever. They have as much character as the older Hohokam ones, with every bit as much right to stay on the mountain. You just need to look at them with new eyes, that’s all.

  Though not with the original artwork, of course, the remaining walls are intricately decorated — some actually completely covered — with all colors of spray-painted symbols, slogans, and initials left by those intent on leaving their mark in the world. In their own way, those would-be artists came here on pilgrimages, whether to celebrate some event in their lives, to make some statement, or just to take in the magnificent view. I thought again about the petroglyphs I had just seen, on the boulders, over on the other side of the mountain.

  And here is where it all “clicked” for me — the subject of Anthropic rocks, I mean. I have always been very wary of “development”. I have always looked at the continual encroachment of human structures onto the natural world as a negative thing. And many times it is, to be sure. But here I realized that it is also a natural thing — a part of nature.

  As I said above, we are part of geology. Humans are modifying the surface of the Earth in drastic ways, and in big fashion. Cities, dams, highway systems, and canals are just a few examples. We are changing the nature of planet Earth faster than any other force. Whether in the form of Hohokam observatories or Cloud Nine ruins; whether in the form of ancient Hohokam cities or our modern-day metropolis, we are geology.

  What the Hohokam called their “city” we will never know. It was a human-made work of geology, situated in the Salt River Valley — a patch of structure on Earth’s surface. We call its new incarnation (appropriately) Phoenix — it too, a work of geological change, much more massive. What further will grow here in the future we can only guess about, and I have a feeling our vision will be way off.

  It’s hard to imagine 80 years into the future, let alone another 800.

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  Author’s note: If you manage to find these ruins on your own, please take care to preserve their nature, and don’t take anything but pictures!

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  “What did you say you’re here for, again?” The woman at the desk looked up at me over her reading glasses, and added, “Why are you here?”

  I was standing in the Headquarters of the San Carlos Apache Reservation. A faded photo of the famed Apache shaman Geronimo hung above her on the wall behind. His fierce eyes stared down at me, and it was not a friendly look. I showed her the official-looking letter I carried with me, a letter from the Tribal Chairman. It had given me permission to visit the mines on nearby Peridot Mesa, on Apache land.

  Her look conveyed “we’ve never heard of you”, but that didn’t stop me from explaining that I had driven all the way there, for hours, to be there at a pre-appointed time, secured by a recent phone call to the same headquarters, just to visit the diggings. Nobody else in the room seemed too accommodating, either. I thought I was going to be abruptly shown the door. But I was wrong.

  “OK,” she smiled and said. “Wait right here.” Shortly, I was introduced to another quiet, but friendly Apache woman, who had seemingly on-the-spot volunteered to drive me to the mining area on the mesa. I was reminded of actor / director Woody Allen’s (no relation to me) comment: “Eighty percent of success is showing up.” In this case, the percentage was even higher. I was “in the zone”, so to speak.

  She had one of those big, old cars from the 60’s, but skillfully maneuvered it up the dusty, dirt road winding out of town. On the way, she told me all about her claims, and a few miles later, there we were, looking at a series of cliff-faces, excavations, and piles of stone.

  The ground all around us looked green and sparkley, like green sand. And it was, too, for it was all mounds of small crystals of Peridot, for which the mesa is named. The bigger crystals, the objects of the quest, were the ones still lodged in the rock, soon to be dug out by her nephews.

  Many Arizonans are surprised to learn that their state hosts one of the largest jewel treasures in the world. More surprisingly, these gems are not often seen in local jewelry stores. In varied colors of green, not prohibitively expensive, and possessing a rich history, they are now enjoying greater awareness, and jewelry designers everywhere are realizing that such stones and soothing colors add extra appeal to their work.

  Peridot, chrysolite, olivine these are the names given to our gemstone depending on which part of the world you live in. We call it Peridot. There is even a small town named after it, just off Highway 70, between Globe and Safford. (The gem is pronounced pear’-ih-dough; the town pear’-ih-dawt.)

  The Apache Indians now rule the land on which the Peridot lies, and their story is one which rivals any of the other jewelry lore and legends of the world. Geronimo, who was not a Chief, but a medicine man (and therein lay his strength), and his Chiricahua band were subdued and moved to what is now the San Carlos Apache Reservation during the turmoil that raged in the Southwest in the late 1800’s.

  His relatives’ descendants are among those that mine the Peridot. Only within the past few decades have any serious attempts been made to acquaint the American public with what should be a well-known symbol of our country’s riches.

  Peridot’s use as a gemstone is one of the oldest known. Called the “gem of the sun” (fittingly enough for Arizona) by the ancients, it was originally mined in biblical times on an island in the Red Sea. Burma has also been a major producer of Peridot in historical times. Recent discoveries in China and the Himalaya Mountains of Pakistan have added to the world’s inventory, and gem-sized stones are found occasionally in the lava flows of the Hawaiian Islands.

  Peridot is even found in certain meteorites making for truly “heavenly” jewels. When sliced and polished, these meteorites (known as pallasites) present an enticing look of shiny, silvery metal inlaid with green, transparent gems.

  Gemstones are, by definition, rare, and fine quality Peridot is no exception. But strangely enough, and differently from other gems, the same mineral, in its non-gem mode of formation (always known as olivine), is one of the major constituents of our earth. Between the earth’s crust and its core lies a zone some 1800 miles thick, known to geologists as the mantle, and much of it consists of the mineral olivine.

  Arizona’s large deposit of Peridot is found where deeply-formed molten rock has blasted its way to the surface, and then cooled in layers. Large “blobs” within the lava flows now contain the bright green crystals which help make Arizona America’s leading gemstone-producing state.

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  I moved to Phoenix about thirteen years ago, and as I drove around a bit back then and started learning my way around town, I took note of the various landforms surrounding us. I couldn’t quite put my finger on why, but South Mountain looked distinct to me — different from and more rounded than the other mountains that stick out of the relentless grid of asphalt and concrete that stretches on and on through the Valley of the Sun.

  I started looking into the reason, and one of the things I soon found out is that the rugged barrier at the south end of Central Avenue is correctly called the South Mountains (note the “s”). Where all the TV towers stand, and what most people refer to as “South Mountain”, is more properly named the Main Ridge. Looking south from the downtown area of Phoenix, you can also see a separate, smaller high point on the west end (right) of that rise. Its correct name is the Alta Ridge. Much lower, in front of it, and just next to the small town of Laveen, is the North Ridge.

  Speaking of names, the Pima Indian (Akimel O’odham) name for this set of peaks is “Muhadag Du’ag”, or “Greasy Mountain” — a take-off on the dark sheen of the rocks there, caused by a surface coloration known as “desert varnish”. If we really wanted to honor Native Americans, especially those who actually lived in the Valley, we would return its name to what they called it. We could have applied this line of thinking to certain other mountains around Phoenix as well, but I’ll save that discussion for another time.

  More often than not, like everyone else in town, I also call this aggregate of lumps South Mountain. The big point here is the way it looks -a long, low dome-shaped rampart. There is one simple reason for that: the rocks of South Mountain were pushed up, basically through the crust of the Earth. Most of the other ranges around us traverse central Arizona for the opposite reason: the landscape is being pulled apart on a massive scale. They are left standing as evidence of that strain as the valleys between them, like our own, drop away slowly, surely over time. Gravity never sleeps.

  South Mountain is what is called in geology-speak a Metamorphic Core Complex, and I’ll spare you some of the technical details. That term, which from now on in this article I’ll refer to as “MCC”, is a great name to throw around at cocktail parties, and one to remember if you are ever to be on one of those TV “Question & Answer” shows with big prize money. There is a whole, albeit small, subset of humanity out there that seems to be fascinated by them, and they’re not just geologists.

  Don’t ask me why, but one time, on a whim, I typed the term into a music-sharing website, and was amazed that a song actually came up with that name. Somebody (artist unknown) had in fact named a song to honor one! I downloaded it immediately, of course, certain the musician would not have minded. It is a spacey-sounding instrumental (naturally, and gladly) — I am not sure what kind of lyrics you could put to the subject of plate tectonics.

  There is “belt” of MCC’s across western North America, running from British Columbia down into Mexico. They run right through central Arizona, and South Mountain is one of the best of them. They are thought to represent an early phase of the “pulling apart” of North America. Around 25 million years ago, the crust started to stretch in a northeast to southwest direction. As it did so, it thinned out, and lighter rocks, which were once more deeply situated, basically “bobbed up” (the pushing-up I mentioned above) as sort of dome-shaped wrinkles — the South Mountains are one such dome.

  Then, millions of years later, the crust actually started to fracture and break apart. As you might expect, the resulting cracks — called faults — run perpendicular to the orientation of the stretching. This force, then, gave us the big valleys we inhabit, and left in-between massive blocks of rock standing — these are the mountains (Camelback Mountain and Squaw / Piestewa Peak, for example) around that have weathered into jagged summits with a character unlike that of South Mountain.

  I am continually perplexed by the number of Phoenicians who have told me they’ve never been up onto the South Mountains! There is no better view of the Valley than what you can get from Dobbins Lookout (the most popular spot). When you go that viewpoint, look just to the east, at the canyon wall just below you. There you will see the rocks all stretched out, horizontally, with very gentle curves from side to side — visible testimony of the doming forces that created the South Mountains MCC (see photo). Once you see that evidence, you will notice the same rock fabric everywhere around in those peaks.

  For more on MCC’s, go to my website, and look at a string of six photos beginning with a view of Central Phoenix from South Mountain. The fifth view in the sequence is a view from the Space Shuttle Atlantis, looking directly down onto the subject of someone’s favorite song.

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  Dominating the skyline east of Phoenix and Scottsdale, Four Peaks is one of the most recognizable of central Arizona’s mountains. Locals consider it to be one mountain, so I won’t say “Four Peaks are …”. It’s one of Arizona’s landmarks for which little pondering is required as to how it got it’s name! (In the photo above, Four Peaks is in the distance behind the closer Goldfield Mountains.)

  Geologically, it is a piece of landscape art, and the way it formed is almost counterintuitive. You might think that the four summits we see so easily are big piles of rock that were molded into shape on top of the older, lower slopes. But that would be wrong! The rocks of those four summits were there first. Then the granite below was added.

  How, you might ask, could that be? Well, the makeup of the Earth’s crust is a complicated thing, and is not always what it seems. Geologic time, and the forces that have moved things around throughout the history of the world, always seem to combine to give us an interesting story.

  If you drive out the Beeline Highway (SR87), by the time you are about 15 miles from Fountain Hills you will be near Milepost 200, and you will be looking at Four Peaks on your right (east). Even better, go to near Milepost 204 and turn onto the gravel road marked “Four Peaks”, and you can get a few miles closer. You’ll be able to see that the mountain is basically made of two rock formations. One is a continuation of the bedrock you may be standing on: granite. The other forms all four of the peaks. The dividing line between these rocks is more or less where the slope breaks, just below the notches between the peaks.

  About 1700 million years ago, during what we now call Precambrian time, our area lay on the edge of an old continent — an area probably much like today’s Gulf Coast near New Orleans. All of the sand and muck that came down the big rivers from the interior got dumped into a big basin, like the present-day Gulf of Mexico. There it piled up, got buried, eventually hardened, and was baked into thick, resistant layer or slab — very hard rock we call quartzite.

  Several hundred million years later (not really a long time in geologic terms) the immense forces that constantly reshape the Earth’s surface crumpled the land and its many rock formations from side to side, pushing up great mountain ranges that actually extended all the way over to where today’s Great Lakes are. Geologists give this little event a nicely sensual name — the Mazatzal Orogeny.

  During all of that pushing and shoving a lot of the rock below was very hot. Molten granite, in fact, and here’s where the art work comes in. For whatever reason, in the area of the future Verde River Valley, the underside of the above-mentioned quartzite slab was very unevenly shaped. Maybe it started out that way; maybe it got shaped by the pushing action of the molten rock, pulsing up from below. The result, in any case, was that monstrous chunks of the quartzite now hung down into the granite. Four of them.

  Granite erodes away more easily than quartzite. It breaks down into crumbly rock grains, some of which those of us who hate mowing lawns use for landscaping around Phoenix. So the granite around the four big masses of rock slowly wore away, down, down, into rolling hills and slopes and surrealistically shaped boulders that make the Beeline such a scenic drive.

  The four big peaks towering above the trip to Payson even have a geologically technical name: roof pendants — remnants of a much more vast layer of quartzite; a layer of one-time mud and beach sands and sea-side days gone by.

  These big pendants give rise to little pendants — sparkling, beautiful little pendants in the form of the vivid purple gemstones we call Amethyst, mounted into jewelry (yes, not only pendants, but ring stones, earrings, and all other wearable forms).

  You see, up there on southernmost of those peaks, is one of Arizona’s (and America’s) treasures: the Four Peaks Amethyst Mine. Deep inside the quartzite, and way in the past, networks of fractures formed where quartz-rich solutions grew beautiful quartz crystals.

  Quartz is a mineral composed of silicon and oxygen, and the purple variety is called Amethyst. The crystals are now mined and cut into gems, which in this case are considered to be within the world’s finest grade of amethyst.

  You can even wear one — a little pendant cut from a very big one!

 Author’s note: Besides being very inaccessible, the Four Peaks Amethyst Mine is on private property and is completely closed to the public.

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  It looks more like a dessert, than a desert, in northern Arizona.

  Picture this: you are working for a Hollywood director. The film on which he is working is a science-fiction feature, and your job is to find a filming location that is other-worldly. He wants it to be an extraordinary scene – the countryside of a planet devoid of life, with a forlorn and desolate feel, and with colors like nowhere familiar. Where would you send him and the film crew?

  I know just the site. Every time I drive through it I imagine for a moment that I am there, on that other world, and it wouldn’t surprise me at all to see some Martian-like creatures topping one of the rolling hills, coming to check me out, for good or for worse.

  Where is this spot? You might have guessed already. It is Arizona’s Painted Desert, and it is one of the strangest landscapes anywhere. It’s almost as barren as a place can be, and it looks like it was spray-painted with a variety of hues – colors which have come to symbolize the Southwest. The gently smoothed hills even have a fractal sense to them, as they scale down into smaller, similar forms of themselves. Unless there is something familiar standing next to one, it is difficult to tell a hill’s size from a distance.

  How did our famous scenic desert get that way? The “paint” was volcanic ash; the “canvas” was the coastal plain of earliest North America. And the “brush”? A series of massive eruptions, which blanketed the area with layer after layer of fine-grained dust.

  The Chinle Formation is the name geologists give to the group of these particularly colorful layers of soft, crumbly rock. During Triassic time, around 200 million years ago, vast amounts of ash spewed forth from volcanic ranges far to the west. Carried by the winds, that ash fell in what is now northern Arizona, which was then a lowland area of mud flats and gentle plains.

  Sluggish rivers also carried fine sediments into the basins there, and these mixed with the various ash falls. Varying amounts of organic debris accumulated, and added to the mixture of color. The name of the formation is taken from the nearby town of Chinle, farther east in the Navajo Nation.

  The Triassic Period is responsible for some of the best of the red-rock scenery of the Southwest, as its rocks contain a high proportion of iron compounds. Those minerals have oxidized – basically rusted – giving the land its signature color-scheme. It is the first period of the Mesozoic (“middle life”) Era, the huge span of time that is also commonly called the “Age of Dinosaurs”.

  You would have had mainly reptilian neighbors back then, but may have noticed an occasional little critter scurrying about that looked a bit mammalian. The forests around would have contained stands of cycads, conifers, and ferns. Not many flowers, though, as true flowering plants evolved later.

  And if you had listened intently, you would have noted the missing chirping and singing of birds, as they had yet to make their appearance on the world stage. (You can see what is left of some of the occupants of those prehistoric woods in the eastern end of the Painted Desert, at Petrified Forest National Park.)

  Over time, in that alien panorama, the strata built up, eventually giving way to the great deserts of the Jurassic Period, some 50 million years later. The layers of fine powder that fell from the sky weathered and altered into clay minerals, which are very delicate, and when wet, behave plastically and can even be molded. Geologists call the type of clay found in the Painted Desert bentonite, and the nature of that mineral contributes to the “badlands” found there.

  Bentonite swells when wet, and shrinks when the wet clay dries out. That varying consistency makes it hard for plants to take root, and additionally, since the clay erodes rather quickly when it rains and during windstorms, it makes it difficult for them to stay rooted.

  The impurities within different layers make for the variety of hues and tones in the tinted landscape. Combine those with the easily eroded shapes of the soft rock, and the resulting deposits of slaked-off soil, and you have a first class work of art – one that covers a good deal of northern Arizona. It is perhaps the best place I can think of in which to grasp one of the least appreciated agents of geologic deposition: the air around us.

  Go see for yourself! One of the best viewpoints from which to see a vast expanse of the colorful Chinle Formation is at Painted Desert County Park, just off SR87, about 15 miles north of Winslow, and about 50 miles east-northeast of Flagstaff.

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  It was late afternoon, with the sun orange and low in the southwestern sky — one of those late December days when the air around Phoenix has sort of a drab look — somewhat dusty, layered, and gray. But it was also the Holiday Season, and I felt a bit like celebrating. I had been looking forward to my drive to this part of the Valley all day, as I hadn’t visited it before.

  Had the main reason for my anticipation been that it was another chance to get out and look at the landscape and rock formations? No, I have to confess. It was the thought of having an ice cold Martini, in the laid-back lounge of the Carefree area’s most elegant resort, that had gotten me going.

  I had just moved to Arizona, and I had read that this particular resort was a place not to be missed. That certainly proved out to be true. Rocks did get in the way that day, however, as they do so frequently in my life. Luckily for me, those interludes always make it interesting. They have a tendency to put things in perspective for me — they separate the little things of everyday life from the things of eternity, or at least the bigger picture, and the longer view.

  I was passing Black Mountain, on its south side. I rolled down the window and tried to get a scent of the cool desert air, but there was none. Being new to Arizona, I only guessed that it must take heat to bring out the smell. The peak loomed high to the left; houses and various structures clinging to its barren slopes, interlaced by tiny roadways that snaked up through stands of tall Saguaro cacti, Palo Verde trees, and Jojoba bushes.

  Not cheap real estate, I figured. It would take a few more dollars in the old savings account before I could put something down on one of those. But the monetary “bottom line” separating me from a life of leisure and afternoons on a deck patio up there somewhere, was not what intrigued me. You guessed it — it was the rocks — and more precisely, a line through the rocks.

  From the south, Black Mountain looks neatly divided in half. The western half is all dark, fragmented rock, and the Saguaros must like it, because there is a thin forest of them there. The other side of the mountain, or its eastern flank, looks like a giant pile of beige rubble. There are fewer of the tall, exotic cacti. Granite boulders abound, and the tan rock is all broken and rounded into picturesque shapes and crags.

  I mentally noted that hiking up that side of the mountain would be a real chore. Making my way on down the road, the division through the rocks stuck with me. I knew right then that I would “get into” the geology behind that granite, which rises above the resort’s lodge, too.

  And that the adventure that afternoon would pay off in more ways than one.

  Why the stark division in those rocks? Why the strong contrast between the two sides of Black Mountain? I knew the hotel’s bar would be the perfect place to ponder those very questions. It did end up taking a little more research, and eventually even a hike up to the summit, to fully grasp it all.

  In other GeoStories™, I have discussed the great antiquity of many of the rock formations around the Valley of the Sun. I’ve also related how the Valley’s mountains themselves, which include Black Mountain, are mostly young — meaning only about 15 or 20 million years old (yes, that’s right, that’s geologically young). They are composed of older rock in much the same way as bricks from old buildings have been recycled and used to create new structures.

  In my GeoStory™, “Missing Time”, I discussed Camelback Mountain, where you can see two formations in contact with each other, the line between them representing a vanished past. In this case, however, on Black Mountain, the line running so neatly up and over its divided summit is a forced contact between two ancient rock types—one literally having intruded into the other.

  On the surface of the world about 1.7 billion years ago, where the places known as Cave Creek and Carefree now lie, sat thick formations of rocks laid down as sediments by vast, ancient river systems. Layers of rock, spewed out of nearby volcanoes, occasionally alternated throughout these. It was the landscape of a continent so old we can only speculate about its outlines. We know, though, that it was moving about the Earth’s surface, as all the continental rocks have done throughout history (and still are doing).

  Along with the movement, and its associated heat and pressure, the rock layers changed their nature a bit (this is called metamorphism). We know them now as slates and phyllites — the geologic names of the rocks of the western part of Black Mountain.

  Throughout the next few hundred million years, with this continental crust literally floating on the more dense, moving, plastic layers below, great crumpling forces caused the Earth to convulse and pulse. The energy drove its crust into long “belts” of distorted rock, that in this case actually stretched over a thousand miles to the northeast.

  This particular period of deformation is called the Mazatzal Orogeny (sounds sexy, doesn’t it?), and during its final throes an extremely hot, fluid body of rock, now described as 1.4 billion year old granite, pushed up and intruded into higher reaches of the older rocks. We see part of that intrusion today, the eastern side of the mountain, on the other side of the line dividing Black Mountain. The two rock formations, and the division between them, exist in other places in the Phoenix area, too, but they’re a little harder to see. They have all been exposed, for us to view now, by recent millions of years of weathering and erosion.

  How nice of those rocks, I thought, for they had once again made my day. That diversion was just what I had needed, and oh, by the way, the Martini was perfect.

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  If you look through some of the various articles I’ve written (for example, “Time Travel and other Everyday Things”), you might think I’ve got a slight obsession with time.

  And you’re right.

  I do! Sometimes I think the reason I love geology so much does not have to do with rocks per se. It has to do with time — the concept of deep time. It’s something akin to looking into the night sky high overhead and being enthralled by the great distances to the stars — the depth of space.

  They are so, so far away that even with our best technology today, just getting to the nearest (not counting our sun) star, Proxima Centauri, only a little over 4 light-years distant, would take over 120,000 years!

  The depth of time has that same kind of fascination for me, and, for sure, lots of other geologists. “Deep time” is another name (and, I think, a more appealing one), for “geologic time” — those time-spans of millions and billions of years that are so incomprehensible to all of us.

  I’ve mentioned in previous stories that many of the rock formations encircling Phoenix are very, very old, like those around Squaw Peak aka Piestewa Peak (nearly 1700 million years old). And I’ve talked about others that are quite young — the basalt on Moon Hill, for example (some 15 million years old). So where are the ones that are in-between? What is their story?

  It’s simple. Around the Phoenix area, they just don’t exist anymore. This was something I didn’t really grasp when I first moved here, until I hiked up Camelback Mountain. There are places there where you can walk up and put your finger on a thin line which has replaced those missing rock formations — a line representing essentially all the deep time that elapsed during the time they were deposited, and then eroded away.

  You don’t have to take that heart-pounding jaunt up the Echo Canyon Trail, though, to see that line. Just drive around the west end of the mountain a bit. Or you can even see it from Camelback Road, anywhere from 44th Street to say, 56th Street.

  The west end of the mountain, what some people see as the head and neck of the reclining camel (it must have been the heat that got to him!), is formed of reddish sandstone (and conglomerate — a rock made of mixed sand, gravel, and boulders) layers. They are tilted gently towards the west, and they lie on top of coarse-grained granite, which further to the east of there forms the highest part of the mountain.

  The granite also looks reddish here, but that’s because of a thin coating of rust-colored sand grains, loosened from the rocks above, now covering it.

  The place where the two different rocks contact each other is called an “unconformity” in geology-speak. In other words, there was no direct transition from the formation of the lower rock to the other one above it. In this case, that line of contact represents over a billion and a half years of time — time in which many thousands of feet (probably) of younger rocks were deposited by wind and water over the older granite, and then subsequently eroded away back down to the granite.

  Then, on top of the granite, the younger red sandstone formations we see now were laid down by more wind, water, and maybe some really destructive landslides. These layers of stone are approximately 25 million years old. In my photo, taken along the Echo Canyon Trail on the north side of Camelback Mountain, you can see where the line separates the two rock types.

  It runs from near the center of the picture towards the lower left corner. The sandstone is seen in the vertical face. The lumpy-looking rock below the line, or unconformity, is the very old granite. Here, confusingly, as I mentioned above, both look reddish-orange, due to the dusty coating. Far in the background and across the valley, you can see the McDowell Mountains.

  Any of you who have traveled to our spectacular Grand Canyon may have seen another and famous (but unrelated) unconformity. Down by the river, the flat-lying rock formations that make up all those colorful layers visible in the canyon walls are sitting directly on much, much older rock.

  There, that contact is called the “Great Unconformity”, and it is a classic, textbook example, well-known to generations of geology students from, where else, their textbooks, where it is always prominently discussed.

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  You’ve all heard it before. You know, the line about how tough things are, the line about an impossible situation, about being “between a rock and a hard place”.

  It was a warm spring day, and I had just about had it with the climb up a steep, brushy, wooded slope, if you want to call it that. It was more like a tangled obstacle course, except that it seemed nearly vertical, and the loose soil beneath my feet made getting up through it even more frustrating, as it was two steps forward, slide back one.

  Annoying little bugs swarmed around my face and ears, but they kept me company and gave me something to yell at. They were the only creatures, I’m sure, that would have thought my sweat- soaked shirt and hat smelled nice. I was beginning to wonder if it was worth it, if all this work made any sense. It would be easier to turn around, and go back to the car, now miles down the deep canyon. My heart was pounding. I was trying to find some ruins.

  I was well into the rugged Sierra Ancha (in Spanish, “wide mountains”), about 75 miles northeast of Phoenix. This remote range is one of the least explored archaeological areas in Arizona, and it is not hard to understand why. Deeply-incised canyons cut through massive layers of rock, and these in turn are coated with all kinds of thick vegetation – tall pine woods at the summit, right on down to the cactus-strewn canyon floors.

  Rattlesnakes abound, and who knows what other dangers, too – maybe the emotional ghosts of those who lived here and built my goal about 700 years ago. Whatever caused people to live in such a place must have been an intensely emotional thing, and I imagine that that emotion was fear.

  And then I saw them. Right above me was one of the most spectacular sets of cliff-dwellings I had ever seen, there literally clinging to the massive rock cliffs above. They looked like they had just grown there, right out of the stone. My mind flashed on the connection between life and rocks, and here was another example. Only here it was humans that grew this place in the rocks, and I knew there were more such spots around that area, too. The rocks offered protection.

  The Sierra Ancha are so rough and craggy because most of the rock there is very hard and tough, and consequently very resistant to erosion. In the area of these Anchan Culture cliff-dwellings, quartzite and limestone are the order of the day.

  Quartzite is a metamorphic rock, meaning that the original stone has been changed by heat and pressure, in this case altering an old sandstone formation (left-over beach sands, possibly) into a much more durable rock unit.

  Limestone is a rock, also very unyielding, precipitated out of oceanic waters, and forms vertical cliffs in a lot of places where it occurs.

  Both of these rocks point to a time when this part of what we now call Arizona lay along the shores of ancient seas lying to the west and south. It was not North America then, and what we now see as our landscape would then have been around a billion years into the future.

  These rocks are collectively known to geologists as the Apache Group. Higher up in their section, you can also see layers of dark basalt, a volcanic rock that erupted way back then in various places, as the old setting went through some convulsive times.

  Equivalent rock formations are found in and below the bottom of the Grand Canyon, and there they are approximately 5000 feet lower in elevation than they are here, there near the Colorado River itself. Therefore, the rocks above that point, most all of those colorful layers now seen in the walls of the Grand Canyon, were once on top of the Sierra Ancha as well.

  Because of massive uplift of the region, the younger rocks are now gone, and the innards are exposed.

  You can see these same rocks when you wind your way up State Route 288 (also known as the Young Road) from the valley floor, near the Salt River and Roosevelt Lake, to the upper reaches of the Sierra Ancha, near Aztec Peak, on the way to the small town of Young. In this stretch, you are going up through time.

  My distress at the sweaty work-out turned to delight; my desperation turned to awe. Tough places, tough rocks, I mused. The Apache Group is still there because it is so hard to get at, and in turn, the dwellings of the ancients remain tucked within its depths, mostly untouched, for the same reason.

  That the inhabitants of these ruins chose to live, and die, between the difficulties of the nearly impassible terrain below and the sheer walls of stone, demonstrates the incredibly fine line of life to which they clung, and the tenacity of nature itself.

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