Posts Tagged ‘Arizona’


Thursday, September 8th, 2011

Basaltic Moon Hill, as seen from Shaw Butte, looking northwest, in Phoenix, Arizona.

  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.

Recent basalt flows cover the desert north of Rocky Point, Mexico.

  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.

Colors in the Sun

Friday, August 12th, 2011

Bright blue pebbles catch my eye. Is it turquoise?

  I was sitting low in the hot tub the other day, my mind wandering and drifting about like the palm fronds in the gentle breeze above me. It is where I get some of my best thinking done. No pressure, no distracting phone calls, no emails beckoning me from the cathode ray tube that is usually in my face.

  As is usual on weekday afternoons, there was no one else around. The sun was intense, the dry desert air invigorating, lightly scented as it was with the warm pungency of chlorine. The bubbling of the Jacuzzi added to the stimulation, and its gentle massage coaxed me to just relax, and let the thoughts flow.

  I am lucky enough to live in a place with a very attractive swimming area and spa. Sometimes when I walk over to the pool, with its tiles colored like turquoise and lapis lazuli, I am taken aback by its soothing effect – the cool blue somehow so easily mitigates the fierceness of central Phoenix in the summertime. Once in a while, when I’m in the tub, someone will walk by me there and remark “how can you stand being in that thing when it’s 114 degrees out?” I point out that it is cooler there than the air, and that usually shuts them up. A small observance, yes, but significant.

  So it was in that vein when I looked over my shoulder and noticed a little gathering of rocks that someone had left sitting just by the edge of the bath. There they had placed a handful of pebbles, all reddish-brown, but tinged with bright blue coatings, and they glowed intensely against the glaring ivory colored background of the pool deck. They hadn’t been there long – some were still wet – and I guessed that some child had gathered them from nearby, had been playing with them in the pool, and then, as children do so easily, simply became distracted and forgot them there before leaving.

  I wondered why they had not registered more in my own mind when I had arrived. After all, I had to have literally stepped over them to get into the tub. “That just goes to show you,” I thought to myself, “so busy thinking, mind all cluttered up, I didn’t even notice.” Sitting in the bubbling waters had changed that. And then I had another thought: here is a metaphor right in front of me (or actually behind me, in this case) of the beginnings of jewelry, the very business I am in!

  No one knows when humans first started using stones for decorative purposes, but we do know it was a long time ago. Drawings on cave walls showing humans with body ornamentation are believed to be at least 20,000 years old. People used a variety of things to decorate themselves: feathers, seeds, insect wings, and stones.

  Far, far back into human history, someone somewhere was walking up a streambed or dry wash (most likely), and saw some pretty rock lying in the gravel at his or her feet. They reached down, picked up the attractive rock, and from that moment on, it was special to them. Maybe they took it home and set it on a shelf next to the hearth. Maybe they decided to drill a little hole in it, put a string through it and wear it, or maybe they just set it aside there near where it originally lay, as if to proclaim, “this is special – I’ll give it its own spot.”

  The tradition goes on today. Kids (and lots of adults) all over the world pick up pretty rocks, for whatever reason – the main one being that that stone is special to them. The stone has just received a little dose of power – a power of influence on that person’s life (and maybe others).

  You see the same thing now in jewelry all around us, in whatever form. Some people wear crystals or carved stone amulets to ward off perceived evil or gain good fortune. Some people wear gemstones as a symbol of home, or history (think: grandma’s diamond ring). Lots of people wear them as a symbol of wealth and prestige (all you have to do is watch the Academy Awards on TV, with glamorous actresses decked out in diamonds galore remind yourself of that!). Even more wear them as a symbol of eternity. De Beers has been very skillful at cementing together diamonds, love, and forever.

  Gemstones and their uses so surround us, and are so common in all their forms, that people tend to forget that they come from the Earth. They are creations of nature (except for those nowadays that are altered, dyed, treated, repaired, irradiated, or synthesized!).

  I have actually seen people look surprised when I remind them that the diamond they are looking to purchase may not exist, or at least may not be easily found in the marketplace. Want to buy a three carat, natural, blue sapphire from Montana’s Yogo Mine? Good luck. There are only a few in existence. Don’t blame the jewelry trade. Blame Mother Nature and the volcanic rocks of central Montana for being so stingy.

  “Uh, oh,” I thought. I was starting to feel “well-done.” Time to get out of the water. All these realizations had totally absorbed my attention, and time had passed by quickly. The sky-blue and celadon-green stones assembled there in the sun were not turquoise, I knew, unfortunately.

  I had had my hopes high for a moment, but knew too much about the geology around Phoenix for that to be the case. Chrysocolla is the name of the look-alike. It’s a copper mineral, too, but this stuff is too soft and thin to use for jewelry. The landscaping company gets its rock from formations around the valley where slight copper mineralization occurs. Look in your backyard – maybe you have some of the same.

  I climbed out, toweling myself off, and glanced at the gravel beds from which the palms around the pool grew, and there, sure enough, were other turquoise-hued fragments calling out from the reddish, chipped landscaping pebbles. As many times as I had been to the spa, I hadn’t noticed them before. Hot tubs work wonders.

On Cloud 9

Sunday, July 3rd, 2011

Ancient petroglyphs on a basalt boulder in Phoenix, Arizona.

  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.

Downtown Phoenix, Arizona, from the ruins of Cloud Nine.

  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.

The now-deserted deck of Cloud Nine, in the Phoenix Mountains Preserve.

  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.

What’s the Angle?

Wednesday, June 15th, 2011

Tilted rocks in Papago Park, in Phoenix, Arizona.

  Weirdly-shaped rocks. I’ve heard that phrase over and over again, mostly from tourists. Wondering why the rocks look like they do, those visiting the Valley of the Sun notice them immediately, as those formations are almost right next to the airport where the visitors have just arrived.

  The pinnacles stuck in my mind, too, on my first visit to Phoenix, many years ago. Brightly orange in the setting sunlight, there was something about their curvy, pointed look, all filled with voids and cavities: they seemed like frozen flames rising from the flat desert floor.

  The Papago Buttes, we call them. They are the centerpiece of Papago Park, one of the City’s thoughtfully planned expanses of preservation in what otherwise surely would be yet more endlessly repetitive housing tracts, strip malls, and asphalt checkerboard development.

  What people first notice about the buttes are the caves and the holes in the rock. In geology-speak, those are called “tifoni”. I looked up that word, and it means “typhoons” in Italian. I’m not sure why or how those storms made it into the lexicon of geology, let alone in Italian, but maybe that’s a subject for another day.

  As for the openings themselves, they are caused by differential weathering and breaking-down of the host sandstone and conglomerate (which is a rock composed of different-sized stones and particles, sometimes called “puddingstone”).

  But there is more here of which to speak. The structure of the buttes, or the way in which they connect to the rocks underneath, is one of the more interesting facets of the geology here.

  In other writings, I’ve previously described to you the nature of the rock surface underlying our valley — an amazingly deep, rugged trench in the Earth’s crust. The buttes are just the tips of some craggy peaks that are almost completely buried by the sand, gravel, and salt beds that fill the valley and give its floor such a flat appearance. They poke through the surface in Papago Park just enough to make a great backdrop for the Phoenix Zoo, and the Desert Botanical Garden.

  Drive along Galvin Parkway near the Zoo, or better yet, take a walk around the Hole-in-the-Rock area in Papago Park and look over at the prominent tall butte, just to the northwest. You will notice there, I hope, that the reddish sandstone and conglomerate is layered, and that the layers are slanted steeply to the southwest.

  Recall also, that I told you about the South Mountain Metamorphic Core Complex (I just love that phrase — it’s got such an academically-sounding, yet melodic, ring to it.) in my previous essay, “Name That Tune”.

  I explained there how the broad, arching dome of South Mountain was pushed up from the heated, plastic rock of our planet’s crust around 25 million years ago. Though the rock was hot and soft down deep, it had to push through higher layers that were cool and rigid. Some of those layers are the orange rocks that make up the Papago Buttes.

  Rigid rocks don’t bend, of course. They break. And when they broke, in this case, they had to “get out of the way” of the emerging dome, part of which we see now as South Mountain. In making way for that uprising mass, they couldn’t just simply slide out sideways, as they were confined by other rocks in the same layer, and rocks behind, above, and below those.

  You might be thinking that South Mountain is quite a distance from Papago Park, so why the problem? Geologically, of course, it is not. And at depth, down there below the fill material in the valley, their rocks are physically connected. When the rock layers broke from the pressure below, they could only break up into fragmentary pieces or slabs, looking something like how a deck of playing cards looks when it is unevenly pushed from the side, splaying the cards into a skewed stack.

The Papago Buttes, with Camelback Mountain in the background, highlight the Phoenix Zoo's Lake, in this view.

  Now imagine those cards as the rock slabs, first breaking into pieces, then standing up, while tilting back and away from the imposing mass coming up from below. That’s what you see at the Papago Buttes, and in my accompanying picture. The tilt can even be seen at Tempe Butte, next to Sun Devil Stadium, even though that is a different type of rock. All of the rock layers are tilting away from South Mountain.

  Theoretically, other rock layers hidden beneath us also tilt away from South Mountain, making it the center of a giant bullseye, of sorts. Those inclined layers strangely reveal one more chapter of the ongoing story written in the rocks all around us.

Geology Upside Down

Monday, May 9th, 2011

Four Peaks,on the skyline east of Phoenix, Arizona.

  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.

4 Peaks Amethyst gemstone  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.

Jewel Box

Wednesday, April 27th, 2011

A pegmatite in the Sierra Estrella, southwest of Phoenix, Arizona.

  Cutting the sky southwest of Phoenix is the jagged, long ridge of the Sierra Estrella — it dominates the Valley of the Sun. Yet, it is less well known to locals than many smaller, less imposing ranges here, and I will bet that most Phoenicians couldn’t even name its more prominent peaks.

  I had just set forth up its southwest-facing side — the side opposite from town — and had just barely started along the trail when I was greeted by fields of glitter along the ground’s surface. Multitudes of bright flashes caught my eyes, making a rich scintillation amidst the chollas, saguaros, and ocotillos growing in profusion along those lower slopes.

  Up to that point, the only thing on my mind had been one thought: what a workout this was going to be. A look up at the high summits above me, one of which was my destination, had convinced me that it was going to be a long, long, sweaty day. Although I was on my way up to one of the less conspicuous points along the sawtooth-like crest, I had heard that this trail was one of the more spectacular hikes in the Estrella Mountains — one not to be missed.

  Reaching down to grab one of the sparkles, I saw right away that it was a flat, shiny leaf — but not a leaf of vegetation. Rather it was a thin leaf of stone — a piece of a mineral known as mica — that was beaming back at me. Its lustrous surface had captured the strong light of the desert sun, throwing it right back into my face.

  And I was delighted with that, as I knew that this mineral, and the way it lay strewn all over there in numerous fragments, meant that somewhere up above me, on those steep, rocky cliffs of the Estrellas, was a pegmatite, an example of a rock formation sometimes known as “Nature’s Jewel Box”.

  Right up my alley, I remember thinking. A hike through gemstone country! A treasure hunt, even. Well, not quite, it turned out, but it was close. All that was missing were the gems and jewels (saleable ones, at least).

  By the time I saw it, I was dripping wet and breathing heavily. I was not sure which smelled more strongly: me (probably), or the pungent, desert brush all around, baked dry by the hot, unforgiving sun. There before me, crowning the mountain, was a great outcrop of quartz, white and glassy, looking like a chunky snow-bank, gleaming with the same sheets of mica that I had seen down in the valley.

  If you want to go gem hunting, finding a pegmatite is a good way to start, for pegmatites are rock formations where gem minerals are frequently found. There are other places in and around the Valley where such rock structures also occur. “Swarms” of them are to be found in the Hieroglyphic Mountains, and even Mummy Mountain plays host to some mineralogically-rich ones.

  Imagine a gigantic body of molten rock, granite in this case, deep in the Earth’s crust. As it intrudes into the rock surrounding it, it forces fractures to run through the enclosing hard stone. Into these fractures flows more molten rock, composed of minerals which are more mobile and volatile — distilled, so-to-speak, off the parent mass.

  This “liquor” of fluid rock then cools slowly into a solid, dike-like pattern of large crystals — a pegmatite. Later, when it gets exposed by erosion, its concentration of sharp, angular forms reveals the mixture of segregated minerals within — in this case, quartz and mica.

  It was these large mica plates, weathered and washed out of the formation, that I was seeing along my route. They make excellent reflectors. But no emeralds or sapphires here. (I had kind of figured that.) Otherwise, there would have been a mine here, probably a very old mine, as pegmatites have been known since ancient times as good places to find large crystals of beautiful and rare gemstones.

  I struggled to the very top of the rocks, where the view was breathtaking. In the distance was the metropolis of Phoenix. I could see its downtown skyscrapers, and several snake-like freeways winding through the Valley’s maze of crisscrossed streets and avenues.

  I recognized Camelback Mountain, readily distinguished by its reddish profile, and beyond I could even see the McDowells and the far-off Mazatzal Mountains. Once more grateful that I’d achieved my goal — this time with the added bonus of some unexpected beauty along the way — I sat there on the immense white, dazzling, hard exposure of almost pure silica, and had the quick thought that it was a wonderful place to get a good, all-around suntan, too.

  A little closer to the sun, and heaven, you know….

Rock and Roll

Monday, March 28th, 2011

Granite boulder in sandstone on Camelback Mountain (note the one-foot long scale), in Phoenix, Arizona.

  The sound of a muffled shriek, coming from the seat behind, made me look ahead.

  I corrected the vehicle’s path instantly, putting it back between the yellow lines, so to speak. Fortunately, we had been going only about five miles an hour. What had happened? Well, it was a quick but typical instance of geologist’s “Road-Cut Attention Deficit Disorder”.

  RCADD is little known among the general population, but well known among geologists.

  It is the tendency to be distracted by the rocks in a road-cut or on nearby cliffs, let’s say, while driving past them. (What are those rocks? Where did they come from? What does their structure mean?)

  It is not the kind of thing you want to have kick in while you are speeding along the edge of a precipice, or on a busy freeway — especially if the geologist is the driver, and you are the passenger.

  In this case, I had been driving some tourists from out-of-town down one of the pretty little residential roads high up on the south side of Camelback Mountain.

  We had been looking at marvelous views of the valley, peering through people’s back yards and over rooftops, at South Mountain in the distance, the Sierra Estrella, and the groves of downtown skyscrapers sprouting out of the layer of brown murk that was no doubt at that very moment causing the eyes of the down-towners to itch and burn.

  We had rounded a bend, and that is where I saw it. There, just behind a Palo Verde tree, at eye level and only about 15 feet away, was a giant boulder of very old granite about three feet across, rounded along most of its edges, suspended in the midst of the red sandstone that make up the cliffs that tower above the glamorous homes of the neighborhood we had been invading. That was when RCADD had hit me.

  To the non-geologists next to me, and in the back seat, the puzzle hadn’t registered. After I had adjusted our trajectory, and everyone had breathed a sigh of relief, I explained why I had become so distracted.

  Here was a classic geologic anomaly. How is it, that this big rock could have been deposited right down into the depth of the fine sand? Think about it. Sand like this is usually laid down by relatively slow moving water, or maybe even wind, as in sand dunes.

  How did the heavy boulder get carried into this setting, and just dropped off, before being buried by even more sand? And keep in mind that whatever happened here happened about 25 million years ago — it’s not just evidence of an accident yesterday by one of the construction crews finishing off someone’s million-dollar back patio!

  That one boulder is to me the most curious example of a type of strange geology you can see in several places around Phoenix. The west end of Camelback Mountain, and the buttes in Papago Park are the best places to see these rocks whose formation stretches my imagination, as well as that of other geologists.

  One current theory ascribes their genesis to “long runout landslides”, also known as “sturzstroms”. Maybe in an instant, on a nice summer morning much like today, by a process not yet well understood, a monstrous amount of sand and rock collapsed from the steep slopes of mountains that stood just east of the present- day metro area.

  A vast mixture of rock, sand, and debris rolled out over the flats, at first glance possibly looking much like one of the big dust storms we see during the monsoon season here in Phoenix, but devastating beyond comprehension.

  The landslide flowed for many miles, basically along a layer of air, and then it just stopped dead in its tracks. The theorized mechanism behind such a phenomenon is given the name “acoustic fluidization”.

  Hard to believe? Yes. I kind of want to see one before I can really buy into this theory. There are some modern-day cases of smaller events, however, that seem similar. One happened during the large 1959 earthquake near West Yellowstone, Montana.

  There, at a place just below Hebgen Lake, a mountainside collapsed, flowed instantly down and across the small valley, even running part-way up another mountain on the other side of the river. That landslide obliterated a campground, at once killing 28 people, who in their sleep never knew what hit them.

  You can see some such unusual rocks just by looking out the window as you drive along McDowell Road between the Papago Buttes. You will see large (and small) chunks of granite caught up in reddish sandstone, like dried-out, jagged bleached plums in rusty, desiccated pudding.

  If you spend more than a few seconds looking, watch out! You, too, have RCADD.


  You can see other scenes of rocks, and discover more of our area’s fascinating geologic story by going to a map called “The Rocks of the Valley of the Sun”, where you can click on “Camelback Mountain” to begin a series of pictures.

First Impressions

Saturday, February 12th, 2011

Desolate hills like these give you room to think, or NOT to think.

  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.


  For more on this subject, go to, 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!


Tuesday, January 18th, 2011

Surrealistically shaped ancient granite looks

  “How did these boulders get stacked up this way?”

  The tourist who fired off that question to me was impatient, but in a friendly way. We had just started up a trail that wandered over and through a small mountain of weirdly-shaped rocks. Below us lay lush carpets of green, lazy golf courses winding through even more rounded, but smaller, boulders.

  The look from above was that of a carefully tended garden, with tall cacti, Palo Verde trees, and ocotillo everywhere. Bushes surrounding us filled the air with the pungent, sweet, tarry smell of creosote. The warm autumn sun created shadows on the rocks that only accented their beguiling nature.

  Those with me were wearing shorts, tennis shoes, and polo shirts, casually outfitted for the little hike we were on, all eager to learn something about the place to which they had come to escape for a short while the brutal weather back home. Down by the resort, we could see some men that appeared to have just stepped out of a Wall Street office building, looking very smart in their $3000 suits. New arrivals, we all knew. That manner of dress wouldn’t last long. Behind the lobby area there were others wearing not much at all: beautiful people lounging around the pool, margaritas in hand. There were several girls that were …..

  Oh, yes! Back to the rocks.

  The lady was anxious for an answer. She had been pondering an explanation since she had first arrived at the resort several days earlier and had seen the magnificent display of rocks looming above the luxurious lodge. “We don’t have anything like that back home,” she said hurriedly, and then started spewing out what she thought might be possible answers to her own question. “Glaciers did it!” “No?” “Floods?”

  I get asked that question a lot, even from people that live in the Phoenix area, who have grown up around the picturesque granite boulders which provide the exotic backdrop in places like Carefree, Troon, and Reata Pass.

  People’s fascination with them might have something to do with scenes of landscapes remembered from childhood — like maybe from those western movies where outlaws hid amongst such rocks before ambushing the stagecoach. Apaches disappeared into such settings with the cavalry in hot pursuit, and they appear even in scenes from other planets, like the Star Trek episode where Captain Kirk and Spock do battle with an ugly space monster deep within a wilderness of granite shapes and spires. There is something about them that suggests an alien quality.

  But they are not so alien. In fact, in some ways they are the very core of our landscape. Once, I read about an exhibition in New York City, a display of Chinese carvings and garden art in which stone is the central theme. In that show, rocks were called the “Bones of Earth”, and I can think of no more apt name for them here. As we all can see, the landscape of Phoenix is one which has been scoured and eroded by the desert climate right down to the stone within.

  The granite so exposed around here is very old — about 1400 million years old. It intruded into ancient mountain ranges back then, as a molten mass rising from below, squeezed and reshaped by forces on a continental scale. It never made it to the surface, but cooled slowly, slowly. The evidence of this is seen in the large crystals that can be seen just by breaking a piece of it open.

  Later, over the more than one billion years that followed, it became laid bare at the surface. Changes of tension in that process led to fracturing of the rock in many different places and orientations. If you study an outcrop from a short distance, say near The Boulders Resort in Carefree, or the Four Seasons Resort near Pinnacle Peak, you can see that many of the large cracks running through the granite are somewhat parallel to each other. Some run almost horizontally, some run almost vertically, some are diagonal to those.

  The important thing is that they intersect in various places, and when they do, they isolate off chunks of stone, many of which are house-size pieces. As weathering works its toll, the cracks widen out, and sharp corners tend to round out.

  It’s what causes that “stacked” look. They are not piled up at all, like they appear. No glaciers, no floods. It is the way solid rock is breaking down into pieces. Granted, some do eventually roll down-slope, and probably every few thousand years one makes a pretty good “thud”.

  They make for some of the most striking scenery in the world — a setting for which those visitors from Wall Street don’t mind paying to experience.


  You can see other scenes of these formations, and discover more of our area’s fascinating geologic story by going to a map called “The Rocks of the Valley of the Sun”, where you can click on “Black Mountain”, or “Pinnacle Peak”, to begin a series of pictures.

Time is on my Side

Wednesday, November 3rd, 2010

Ferruginous quartzite (dark rocks) in Phoenix Mountains, Phoenix, Arizona.

  When I was young, growing up on the brown, flat Cretaceous rocks of central Montana, I used to fantasize about dinosaurs. It’s what got me into geology in the beginning, I guess. I was taken by the idea that where they roamed was right there, in the same physical space I was in at the time. Just about eighty million years earlier is all. Maybe a Tyrannosaurus Rex had actually walked across the ground occupied by my bedroom!

  People tend to visualize scenes from the distant past as though they were necessarily somewhere else. In space, I mean. But there were alien landscapes right here, just not now. This idea is conveyed in H.G. Wells‘ classic novel “The Time Machine”, now recently made (actually remade) into a movie.

  The movie does horrible justice to the original story, but you get the idea by watching the Time Traveler in his machine, sitting in one spot, with the “hours-days-years” odometer rolling on in a blur. He starts the machine and his journey through time in his laboratory in London. At one point (in the book) he “lands” in a rhododendron garden looking over the River Thames, surrounded by alien structures; in another scene he is on a barren beach in the distant future, watching a dying red sun setting into a future ocean of dead, spent waters. All those scenes occur in the same place.

  Back to Phoenix and now, in which the landscape is far different from way back then, let’s say, in Precambrian time, for example. Take a drive on SR 51, the Piestewa Freeway, where it cuts through the Phoenix Mountains, just to the northwest of Squaw Peak, and you will see what I mean.

  If you are going north, look off to the west (left) just after you have passed the Northern Avenue Exit; if you are going south start looking west (right) about the time you get to the Exit ramp. If you like to walk, you can park in the Dreamy Draw area, and approach this area from one of the trails in the Phoenix Mountains Preserve, a city park.

  About half a mile away, up on the east slopes of those rugged rocky peaks you will see dark brown, almost black areas of broken up rocks and rubble. Some of this rock forms a pointed outcrop just at the south end of that set of hills, and is also visible elsewhere in the Park. There are a few houses (with great views of the Valley, to be sure) to the north of these rocks, near a saddle.

  What you are looking at are the remains of ancient, submarine hot springs — very ancient, and very submarine, from the bottom of an ancient ocean. These rocks have the wonderfully technical name of “ferruginous quartzites” and the hot springs that formed them erupted, seethed, and bubbled about 1700 million years ago, at the bottom of a vast sea whose only occupants were life forms so primitive that you would have needed a microscope to get their names. The hot springs were rich in iron, and those iron minerals give the rocks their current color.

  The Phoenix Mountains are made of a section of the earlier crust of Earth where the rocks were formed in an environment somewhat like that off the coast of present day Japan. If you were to walk from the freeway in Dreamy Draw over to Shaw Butte (about 4 miles), you would be going right down through rock section (now standing on end, basically), that shows the whole evolution of that environment. If you were going to strap yourself into Wells’ Time Machine, and dial up, say, April 10, 1,700,000,000 BC, you had better already be wearing your deep-diving equipment!

  Our planet’s crust is in constant motion. The shapes of the land masses we know today are as ephemeral as the shapes of clouds in the sky. The continents move about relentlessly, literally floating on top of more dense fluid rock below. Heat from deep within the Earth sets huge convection currents into motion, causing continental rocks above to glide about, sometimes crashing and fusing together, sometimes splitting into new shapes, all of it happening all of the time, just in too slow of a fashion for us to grasp easily.

  Our journey through time would take us to the edge of one of these land masses, where heat from the gargantuan convection cell below has broken through, boiling the waters, and creating a primordial soup in which early life prospers.