Posts Tagged ‘Psychogeography’

Pressure Cooker

Wednesday, July 17th, 2013

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  Pictured above is the inner north wall of Cerro Colorado. This structure is about one kilometer (3300 feet) in diameter, and about 110 meters (360 feet) deep. You can just barely make out our vehicles in this image. They are the small white dots, across the crater, along its rim. A dark lava flow can be seen in the distance.
 

  Just across Arizona’s southern border, on the way to the Gulf of California, lies one of the Sonoran Desert’s most spectacular geologic features – the Pinacate Volcanic Field. Few of the many thousands of tourists that each year visit the party-place we call Rocky Point (Puerto Peñasco to the Mexicans) even know that it is there. That’s a good thing, too, for part of its beauty is its desolation. It is one of the most similar places to the surface of the Moon that you will find anywhere on Earth. Not because of its loneliness, though.

  From the highway to the coast, you cannot see that out there in that barrenness lie a number of impressive craters. Get up in the air, however, and it looks much like what you see through a telescope focused on the lunar landscape. Massive, ring-shaped, and deep, those craters show that the now-quiet countryside was once a pretty violent place.

  Previously, I’ve written about the explosive San Francisco Peak(s) of northern Arizona, towering above Flagstaff, and not hard to miss at all. But the craters of the Sierra Pinacate region of Sonora are not readily apparent until you are right there.

  This area lies within a Mexican National Park – the Parque Natural del Gran Desierto del Pinacate – which also features a sea of sand dunes, lava flows, and a number of volcanic cinder cones. It is not the kind of place you want to venture into light-heartedly, with your passenger car and beach clothes. Take a lot of water – that is some good advice, too.

Basalt lava flows cover valley floors within the Gran Desierto del Pinacate.

  To me, the craters are the most interesting things to see, and these are some really good ones. They are different from craters on the Moon, though, because the lunar ones were formed by impact – asteroid, meteoric. Same with Meteor Crater, near Flagstaff.

  The Pinacate craters were created by relatively shallow explosions in the crust of the Earth. They are a type different even from the volcanic craters and cones of northern Arizona, like Sunset Crater. In “geology-speak”, they are called maars, and these happen to be some especially young ones.

  The Gran Desierto (Grand Desert) is a dry, dry place. Yet, deep underneath the sparse desert scrub that does exist there, is groundwater, or very recently was, apparently. That water occupied layers of rock, in turn overlying lower rock units that become hotter with depth.

  Remember, and I’ve written about this in many other articles as well, that this part of North America is very active, geologically. Earth’s crust is and has been breaking up in this zone, and the fractures run deep. Molten rock can move upwards along those fractures, eventually making its way to the surface, hence the cinder cones and lava flows.

Crater Elegante is too wide<br />
to fit into one picture.

  In the past, here in the Pinacate Field, some of that molten rock moved upwards, and encountered groundwater deposits (known as aquifers). When it did, it converted the water instantaneously to steam – massive amounts of it – and the ground literally exploded outward, creating maars.

  Then, at least in some of the cases in the Parque Natural, those exploded chambers collapsed back into themselves, expanding them additionally into structures known as calderas – gaping holes in the ground. There are at least ten of these maar / calderas in the Volcanic Field.

  It is possible that humans witnessed some of the eruptions. Hohokam relics have been found along some of the erosion surfaces in the area. Studies show that the blasts occurred within the last few million years, and some only within the last few thousand years. Very jagged, black, and barren, the basalt lava formations that you drive by between the craters look like they flowed yesterday.

  As you can see, the starkness of the vista adds much to the otherworldly look of this place, so if you can’t make it to the Moon (and most of us won’t have that chance), you can at least get an idea of the lunar scenery by visiting the Pinacates.

  Breathing is easier there, too.

Undercoat

Friday, September 28th, 2012

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  That the native inhabitants of the Americas had a different way of relating to the landscape is without much question. Their sacred sites and temples were placed in special geographic places.

  But what led to such a view? Could it be because that within their culture, they value fitting in with nature, not trying to change it? Seeing yourself as part of something is, to be sure, not the same as seeing yourself as separate from something.

  What we are all part of is a vast web of life that covers our planet. So far, based on the current state of scientific knowledge, it is that web which makes Earth distinct and unlike any other place we know of in the Universe.

  That “coating” of life includes plants, of course, and animals, fungi, and microbes of many kinds. Life lives in the air, in the water, and on the land. And, now it turns out, inside the planet, too. It thrives even in the rocks.

  In last month’s GeoStory™ (“Top Coat” — also in gemland.net), I talked about life on the surface of rocks. However, that layer pales in comparison with what is underneath.

  Geologists and other scientists are beginning to realize that in what we once thought was barren, lifeless stone, is, in many cases, teeming with microorganisms. Some of those microscopic life-forms are strange indeed, and can feed from the rocks, without needing air or light.

  Sedimentary rocks (which are deposited by water or wind) usually have small pore spaces within. These pores can and many times do, contain water, oil, or gases. It is from this porosity that we pump groundwater, petroleum, or natural gas.

  Other kinds of rocks, by nature of the way they formed, have no pores per se. But they frequently contain fractures of all sizes, and water or hydrocarbons can occupy those cracks, too. Living things – microbes – can occupy them all.

  Various experiments over the past few decades have shown that certain bacteria can flourish in such environments. No sunshine. No fresh air. Sometimes stiflingly hot temperatures. Yet, there they grow and multiply. The only thing that seems to be required in all cases for life to exist is the presence of water. We have lots of that, and we know now that our neighbor planet Mars probably does (or at least once did), too.

  No wonder that space scientists look with intense interest upon such organisms. If they can exist in the rocks here, then maybe they can exist in the rocks of Mars, or other worlds, too. And for earth scientists, such “deep life”, is leading to a new level of understanding of how the world works.

  Based on data derived from deep-drilling projects, the late, brilliant, and controversial Cornell University astronomer Thomas Gold did some calculating. His reasonable estimates indicate that the top five kilometers (about three miles) of the Earth’s crust could contain as much as 200 trillion metric tons of live bacteria. This would be like covering the entire planet with a layer of bacterial organisms one and a half meters (approximately five feet) deep!

  This is more than a hundred times as much living mass (called biomass) as all of the other life-forms (including us) of the world put together! If aliens from another world were studying our planet, they would easily conclude that the rocks are the most alive part of it.

  There are, of course, visible remnants of past subsurface life: coal beds, fossils, tar sands and other petroleum formations. There are metallic mineral deposits which seem to have been “helped along” in their genesis by organic life.

  Professor Gold has even suggested that diamonds come from deep-seated organic materials, and we know today that diamonds must form in an environment at least 75 miles down. If hydrocarbon compounds can exist that far below us, and the rocks are alive, so to speak, then the Earth we all know and love is a very unusual place.

  Perhaps, though I can’t prove it, life gravitates towards other life, and I don’t mean just to eat it, either. Maybe it’s a stretch, but think about it the next time you pull into an almost-empty parking lot, and you park right next to another person’s lonely vehicle.

  The Indians (and to be fair, many other ancient cultures) may have subliminally recognized the existence of places where life was, in effect, somehow concentrated nearby, though not apparent on the surface. Some of those places became special to them.

  Ponder that the next time you are out in the great outdoors somewhere, and “feel alive”. Look around and see what makes that so, and then look down, too.

  It may all be underneath you.

Time After Time

Friday, June 22nd, 2012

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  If you look through some of the various articles I’ve written, 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.

Exhilaration & Loathing

Tuesday, April 17th, 2012

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  Organic. That’s the word I gravitate towards when I think of the landscape of southern Utah. A myriad of canyons, incised into bands of vermilion, mauve, ivory, ochre and chocolate — rocks from the depths of time in living color.

  It’s a fractal place, if there ever was one. Big gorges branch into smaller gorges. They, in turn, divide into even smaller canyons, subdividing and subdividing, right down to the seemingly microscopic level. Life forms of all sizes cling to those tributaries, however big or small, as those very furrows are the arteries of water, the lifeblood of this high desert plateau. The panorama is rumpled, folded, and convoluted like some kind of living tissue, like a dissected brain of gigantic proportion.

  Just recently, I drove north along one such magnificent artery: White Canyon. There the road skims over surrealistically-shaped Permian sandstone ledges, and I was just beginning a long awaited August vacation. I looked from my speeding vehicle down into the winding chasm I was paralleling, hoping to catch sight of some ancient Anasazi ruin, that (of course) no one had ever noticed before.

  That highway, which runs between the “middle-of-nowhere” towns of Blanding and Hanksville, is among the most inspiring drives I have ever seen. That I could spot some prehistoric cliff structure was not impossible. There are plenty in those canyons. There used to be a lot more.

  I crossed several bridges, looking down into overgrown streams below. Even there, the rich smell of murky stream water in the hot sun reminded me of the life-giving power barely flowing beneath the steel girders. A cobalt sky overhead only accented the scene. Now the road wound up and up, away from the water, through immense vertical cuts in the rock strata, blasted and carved away to oblige the road — as if to enforce upon us all the fact that humans can do anything once they put their minds to it.

  High above the Colorado River, the biggest artery in the plateau, is one of the most expansive viewpoints anywhere. I got out of my car, as I always do at that spot, ready to bask in the vista for a few moments. I walked over to the edge, and looked down.

  Unprepared for what I saw, I gasped (it was only a short one), and then a big, wide smile started to break across my face. I almost started to jump up and down with delight. There you go, boys. Try water-skiing on that. What goes around, comes around.

  Far below, where wakes from motorboats and “personal watercraft” once crisscrossed Lake Powell, lay mudflats. Miles and miles of mud, baking in the sun. I couldn’t believe it. In all my years of driving back and forth across the American West, I had never seen anything like that. I thought again of that idea of “humans being able to engineer anything”. Now, really?

  Do we really think we can just remake Earth’s surface without consequences?

  There is probably no greater symbol of the defacement of the American West than “Lake” Powell — actually a reservoir. It is formed behind Glen Canyon Dam, the concrete wall that stands further downstream in the way of the once relentless Colorado.

  And there is probably no greater insult to a true nineteenth-century American legend, the first explorer of Glen Canyon, than to have his name affixed to what he surely would abhor. John Wesley Powell must be rolling over in his grave, smiling, too, at the cubic miles of mud and silt accumulating in Glen Canyon, and he would probably say to us now, “I told you so”. At least he got to see its splendor. So the symbol is not a mark of progress, after all. It is a symbol of hubris, indeed, even death.

  In my picture, you can see what looks like a long, sloping runway above the mudflats, below the cliff. That is the huge boat launching ramp of the now-closed Hite Marina. Or was the ramp, I should say. The reservoir is almost 100 feet below “full pool”, and therefore lies hundreds of feet from the bottom of that ramp.

  A result of drought in the West, this situation will almost certainly get worse, for the foreseeable future anyway. Combine that with the fact that when you block a river as muddy as the Colorado, lots of silt drops out of suspension, and it starts to build up. All of that grayish sludge you can see now is covering a lost world.

  These realities will render Glen Canyon Dam useless — for either storing water, or for generating electric power. Somehow, people just don’t get it — how fast it is happening here. Those motivated by politics would have us all believe that dismantling the dam is some wacko idea, selfishly promoted by those awful environmentalists. That the aforementioned are so skilled at calculated nuance and misinformation does little to dismiss the facts.

  The Colorado River averages a sediment load of about 100 million tons a year. That’s about 30,000 dump truck loads every day. And as of the time of this writing, the reservoir is dropping about one foot every nine days! The drying-up of the reservoir, coupled with the filling-in by silt, means that it is losing on both fronts: from the top down, and from the bottom up. If you don’t believe me, drive there and look for yourself.

  Beneath that mud and what’s left of the water, are countless archaeological ruins, and the remains of the most intricately beautiful canyon on Earth. By most estimates, present climatic conditions will actually worsen, causing an increase in the rate of the water level’s decline.

  Eventually, the silt accumulation will start to block the dam’s outtake portals, making operation of the power generators unsafe. And by then, even more irreplaceable canyon beauty will be lost to the muck.

  In recent publications, I have written about the modification of Earth’s geology by humans, and how it can be either good or bad. This modification (Glen Canyon Reservoir began filling in 1963), will go down as one of the most calamitous and short-sighted ever.

  If for no other reason, Glen Canyon Dam should be demolished, and what’s left of its reservoir drained, as an admission of our arrogance and conceit in living with nature. Let life return to the landscape.

  If we had real vision, and cared at all about people yet to come into this world, we would leave them something of magnificence and meaning, not the entrenched wasteland that is inevitable under current policy.

A Hard Place

Saturday, March 17th, 2012

These ancient ruins cling to resistant vertical cliffs, either avoiding something, or in hope of something.

  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.

Massive quartzite in the Sierra Ancha.

  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.

The Sierra Ancha, along the left skyline, appear deceptively gentle. Roosevelt Lake is in the foreground.

  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.

Name that Tune

Thursday, February 9th, 2012

  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, 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.

LandMark

Monday, November 14th, 2011

Camelback Mountain, in Phoenix, Arizona.

  Ask yourself which natural rock formation has come to symbolize Phoenix? Which one actually represents our city?

  Most people would say Camelback Mountain. Everyone here knows Camelback. Tourists from afar know of Camelback. And even those who have never been to Phoenix have somewhere heard that name, or read it.

  Rising almost out of the middle of the metropolitan area, it gives personality to our city. Like an actor who works best when able to “play off” of a certain other character, Phoenix has that statuesque mountain. More than just a prop, it is, many would say, the centerpiece of our stage in the world.

  If you are new to the Valley, or have just never noticed, when viewed from the south, the mountain’s profile does bear a resemblance to a reclining camel. You can see the head and neck on the west end, and the higher “hump” of the camel is the eastern part of the peak.

  Now since we are in the American Southwest, a camel would seem to be a figure unlikely envisioned in anything local. But there were camels in Arizona in the 1850’s—they were imported by the US Army, and used briefly for transport. That experiment didn’t work out very well, but since a camel’s association with the desert is almost a primeval thing, a sort of camel’s “essence” remains here.

  Few other cities in the world have such prominent, singular, natural monuments within easy reach. Rio de Janeiro, with its Sugarloaf, is one contender; or Capetown, South Africa, with its captivating Table Mountain. The Rock of Gibraltar certainly comes to mind, but it sits at the gate of the Mediterranean Sea, and is not really in a large city. And Ayers Rock, Australia? Well, it’s out in the middle of nowhere.

  Identity is a key factor in one’s psyche, and identification with landscape goes way back to when humans were just figuring out the world. For ancient Native Americans, the association with landscape was a given—for most of us in the modern-day world it is just a distant memory. But it is lodged deep in our minds somewhere, and without it we might as well live in underground bunkers, or windowless, modular structures without end.

  I feel sorry for space-station colonizers of the future, for they will never know the wonder of gazing up at a big, beautiful rock that can be seen for miles and miles, knowing that it is right in their own backyard, and that they can walk right on up it if they like.

  Although many don’t know it as such, Camelback Mountain is just one of the peaks in what are called the Phoenix Mountains. They cut our city roughly in half, and run from Moon Hill, on the northwest end (near I-17), to Camelback itself on the southeast end. North Mountain, Shaw Butte, Squaw Peak, and Mummy Mountain are some of the other well known prominences in the series.

  The whole group is what is known as a fault-block range. The Valley of the Sun owes most of its general appearance to a particular episode of geologic activity called the Basin and Range Disturbance, which ran from around 15 million years to about 8 million years ago.

  That span of time is a very recent part of Earth’s history, and so our setting is really one of geologic youth. The rocks which make up many of the mountains and features around us are very, very old, but they have just been recycled into the shapes we see now, that’s all.

  During that episode, the crust of our planet here stretched out and broke into pieces which run for miles and miles in more or less parallel orientations. With that activity, and because of gravity, some of those slabs started to settle down, alternating in a fashion with blocks left standing in between— the Phoenix Mountains are one such block. Millions of years of erosion then sculpted that high ground into the picturesque shapes we see now, one of which looks like a very tired camel.

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  The Valley’s “look” is very much due to “fault-block” mountains, like the Phoenix Mountains. The McDowell Mountains and the Sierra Estrella are also such ranges. But, there is another significant piece of the story of our setting, though, and that has to do with why our Valley floors appear to be so flat. In this case, I will also use Camelback Mountain to illustrate the point.

Camelback Mountain, from the summit of Squaw Peak, in Phoenix, AZ.

  The second picture here was taken from the near the summit of Squaw Peak, looking to the southeast. In it, Camelback Mountain has a shape very different from that in the first photo, where the “reclining camel” can be seen. In the forefront of this image is a ridge of the ancient metamorphic rocks of the Phoenix Mountains, on Squaw Peak.

  But behind it, you can see a small, level valley filled with the growth of civilization—a patchwork of cross streets lined with houses, buildings, landscaping, light poles and wires, and other signatures of humanity. On a mammoth scale, it looks here so much how like a colony of mold might appear in an old, forgotten bowl of Jell-O still open in your refrigerator, a dish with an uneaten piece of fruit left sticking out of the dessert’s firm surface. The mold relentlessly multiplies against the chunk’s base, ever struggling to breed its way up the sides of the lump.

  Similarly, Camelback rises out of that swale—its profile now a rugged, majestic pyramid— accenting the flatness all around it. The vast Sonoran Desert stretches out in back, for many, many miles.

  This view of Camelback Mountain alone, in my mind, makes the “workout” trek up Squaw Peak worth it. Just drive to the Phoenix Mountains Preserve, north of Lincoln Drive, park in the massive parking lot, and start up. For most, it will be slow going, but you will have lots of company. I have read that this hiking route is the busiest trail in North America, and it will indeed seem that way as you make your way up and down along with hundreds of other people, some young, some old; a few running, most walking, taking in the view.

  So why then, given that Earth’s crust is so broken up by the faults that delineated the Phoenix Mountains, is the surrounding landscape so flat? Shouldn’t we see a wilderness of canyons and gorges, and not the gentle valley floor that so readily harbors life and our comfortable, enviable world of greenery and strip malls?

  It’s that old, never ending story of “what is up, must come down”. Over the past ten or fifteen million years that our friend Camelback has been looming above the down-dropped blocks of rock once attached to its flanks, its slopes have also been eroding on a less exaggerated scale—a little bit here, a little bit there, day by day.

  All that sand, gravel, and clay has had to go somewhere, and where it ended up is simply down-slope in the deep basins surrounding Camelback Mountain, the Phoenix Mountains, and all the other ranges in our scenic part of the world.

  Over those millions of years, all of that eroded material—which geologists loosely call alluvium—has accumulated greatly in the Valley of the Sun and many other valleys of southern Arizona. Between all of the mountain ranges around here are deep, deep trenches. The actual bedrock surfaces of many of these basins are way below sea level, and many are thousands of feet below the surrounding landscape.

  That is why the land, out of which rises Camelback Mountain and the other peaks of the Phoenix area, is so flat. It is like a calm ocean of sand and gravel, barely rippling against the ranges, not revealing what lies beneath. What we see above it are simply the very tips of the mountains, in the same way that icebergs only show a small part of their true mass above the water’s surface, belying the real nature of what is unseen.

  In the case of our Camelback, it looks in my picture like it is separated from the rest of the Phoenix Mountains by the flat area, but “below the deck”, it is not. Down there, and here not too far down, underneath those houses, roadways, and trees, is the bedrock that connects all of the Phoenix Range together. Off to its south, and to its north, the fill material is much, much deeper.

  Thankfully, there is lots and lots of that alluvial fill, and those filled-in basins are wide and voluminous, for they hold vast amounts of groundwater—enough to keep that “growth” of civilization going for decades to come.

*******

  There is yet one more part of Camelback’s story—one missed by even the many hundreds of hikers who ascend its slopes daily: that of its role as an ancient sacred spot, where for centuries humans came to connect with their surroundings, or perhaps disconnect from them.

The Grotto in Camelback Mountain.

  Tucked low into the northern side of the rugged and strangely-shaped rocks of its western end, is a large cavity—a shady, cool cave that looks like it might have been designed as a band shell—a prehistoric amphitheater which even way back then was recognized as prime real estate.

  From inside it, the view to the north expands to include the Phoenix Mountains and Squaw Peak. Yet, there is a sense of enclosure, security, and especially of harmony. It’s not just because you are mostly surrounded by solid rock, offering safe haven from any attacker that might want to sneak up on you. No, it’s the feel of the setting that you notice. It feels rejuvenating.

  Many people are under the impression that primitive peoples thought of caves like this one simply as shelter. I would argue the opposite. The Hohokam people who lived in our valley up until around 1450 CE (current era) didn’t need shelter. They already had well-developed pueblos all over the area, as well as vast farm fields, extensive trade routes, and an elaborate culture. Indeed, they had other uses for such special places—what some would call magical places.

  The Camelback Grotto is one such spot. While standing in it, with the rocky, orange-brown, half-dome shaped ceiling some forty or fifty feet overhead, I couldn’t help but notice a close ridge of similar reddish sandstone and conglomerate a hundred yards or so out in front of the opening.

  The more distant mountains are off to the left—the ridge itself interrupts that background range as a natural sculpture of rounded and cave-riddled rock that looks organic, like a growth blooming up from the flat valley floor just below. That arrangement of rock not only adds to the feeling of the place—it is integral to it.

  The Grotto in the rocks of Camelback Mountain was formed by weathering and erosion. Those relatively soft sedimentary layers on Camelback’s west end have all been shaped by the same processes that also formed the scenic redrock buttes in nearby Papago Park, and in fact, they are part of the same geological formation.

  (The first photograph above was taken from the Papago Park area, near McDowell Road, looking north towards Camelback Mountain. The red rocks and buttes of Papago Park also stick out of the Valley’s alluvial fill—only they are lower in elevation and therefore less imposing. When such smaller formations poke up through the surrounding alluvium, they are called inselbergs.)

  It is possible that some of the opening’s shape has been modified by humans, but if so, not in noticeable fashion. As elsewhere on the mountain, the conglomerate unit contains small to massive chunks of much older, angular granite—evidence that these rocks resulted from very violent forces some twentyfive or thirty million years ago. It is serendipitous that such chaotic stone has evolved into the serene site it is.

  Why above do I say “connect”? Because that means changing a state-of-mind. Why do I say “disconnect”? Same thing: that means changing state-of-mind. It’s the change of mind that counts. The alteration of state-of-mind creates a sense of just being there, being absorbed in the present.

  Ancient Indian peoples looked at the landscape as part of their being, not just as something to utilize economically. It was not outside of them—it was part of them. Landscape exerted force on their daily lives, and influenced them in ways most of us just do not get or understand. Some places had the ability to amplify or modify those forces and influences, and the Grotto is one of those sites.

  The Camelback Mountain Grotto has been known to Phoenicians since around the time our city was established. People then visiting the cavern found and noted artifacts such as decorated, short, cane reeds. There were also lumps of salt, shell beads, small bones, arrowheads, and skyblue turquoise.

  But the reeds were particularly intriguing. They appear to have been ceremonial or ritual objects containing plant material, and were embellished with inked-in figures or marks. Wrapped around the outside of many of them was cloth fabric, and they were often found in bundles of four. Incense? Cigarettes? Who knows? Besides being a spiritual setting, maybe the Grotto was a party place, too.

  More than just a landmark, Camelback Mountain has been a special place for at least a thousand years.

  We are fortunate that it still is.
 

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.

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.