Journeys in the Back of Beyond: Simply Driving to the Bottom of the Grand Canyon (!?)

Running a geology field studies course is nothing if not stressful. Right on the heels of the most intense storm I've experienced on one of these trips, it was morning and we were on the road to the next thing. A simple thing really, just driving down to the bottom of the Grand Canyon. But I had no way of knowing it would happen, given the storms of the previous night. Had the storm affected the road into the canyon?

 
The Grand Canyon is one of the great spectacles of the Earth. Millions of people every year stand on the edge of the abyss and peer in, taking in the vivid colors and hidden depths. Tens of thousands venture down some of the few trails that reach into the incredible gorge, and several thousand raft the river. But how many drive the canyon? Did you even know you could?
And no, I'm not talking about visiting the canyon "Thelma and Louise" style...

For more than two hundred river miles, no road crosses the Grand Canyon (plus another hundred miles along the shores of Lake Mead). Navajo Bridge near Lee's Ferry is at one end, and Pat Tilman Bridge near Hoover Dam is at the other. In between in the depths of Grand Canyon there is a single road that reaches the river. It's called Diamond Creek Road, and it starts on Hualapai Nation land at Peach Springs, Arizona. It's a marvelous adventure.

The "diamond" that gives the road its name: Diamond Peak

Without even considering the philosophical objections to building roads through the wilderness world of the Grand Canyon (objections I completely agree with), there are staggering engineering barriers. There are a series of formations, including the Redwall Limestone and the Coconino Sandstone that form sheer cliffs. The locations of trails in the Grand Canyon are controlled almost entirely by the few locations where they can surmount the cliffs of these two layers.

At Diamond Creek, the Hurricane Fault has offset the formations in just such a way that the cliffs can be avoided entirely. For the entire twenty mile length of the road, there is nary a cliff to worry about, as the road follows the bottoms of desert arroyos and washes. The biggest worry is flash floods and mudflows, which can easily shut down the road in July and August during the monsoons (and badly inconvenience river rafters who plan to take out at Diamond Creek). Unfortunately, our storm had all the hallmarks of an intense monsoon storm, and for all we knew, the road would be closed, and the whole endeavor moot. We were running late anyway, and I couldn't know the status of the road until we reached the Peach Springs office of the Game and Fish Service of the Hualapai Nation. We got there, and the sign on the door told me the worst...

All my plans dashed. But what can you do but barge your way into the office and see if the road was really closed? And it turned out that their closure was cautionary, the sign left from earlier in the day when no one had checked the road conditions. The road was okay, and I was given the permit to take our group into the canyon (the form interestingly was a permit to trespass on Hualapai land). It was the only permit given that day, and we would have the Grand Canyon to ourselves! We started down the gravel road, the Colorado River twenty miles away.

One can certainly debate the idea that it's "cheating" to drive to the bottom of the canyon, and there is a certain validity that scenery that hasn't been "earned" by completing a stiff hike might end up being less appreciated. But many people can't handle the very strenuous hiking and many simply don't have the time. Driving down into the canyon is a unique opportunity to study the oldest rocks of the canyon, the ones that are the very hardest to access in any other situation.

Diamond Creek cuts through to the Granite Gorge Metamorphic Suite, which is the oldest group of rocks found in the American Southwest, dating to as early as 1.8 billion years ago. At roadside there are marvelous exposures of schist, gneiss, and pegmatite granite with bright shiny crystals of muscovite mica and quartz.

Outcrops of schist intruded by pink pegmatite granite

A bit farther up the canyon one can see the layers of the Tonto Group, a series of three formations called the Tapeats Sandstone, the Bright Angel Shale, and the Muav Limestone. The three layers formed as the Pacific Ocean transgressed and covered much of the western North American continent in Cambrian time, just over 500 million years ago. The Tapeats Sandstone sits atop the rocks of the Granite Gorge Metamorphic Suite.

The Great Unconformity: the vertically oriented rocks in the lower half of the photo are the ancient metamorphic schist and gneiss. Above the metamorphic rocks are horizontal layers of the Tonto Group.

That last sentence needs a bit more explanation. The boundary between the Tapeats and the Granite Gorge rocks is a profound unconformity representing a gap of more than a billion years. This unconformity is actually called the "Great Unconformity", and is an erosional surface that was witness to not one, but two major mountain-building events. The metamorphic rocks were once the core of a vast mountain range that formed 1.7 billion years ago when the North American continent collided with a set of two exotic terranes, the Yavapai block and the Mazatzal block. Imagine an island the size of California or New Zealand grinding into the edge of a continent along a subduction zone and you will get the picture. This massive mountain range eroded to a flat low-relief surface over the next few hundred million years.

The Great Unconformity up close. Dark brown conglomerate of the Tonto Group rests unconformably atop the ancient metamorphic rocks.

Later on, about a billion years ago, the continent stretched and broke apart, forming a series of fault-block mountain ranges that reached heights similar to the mountains in and around Death Valley National Park today. The rocks of these mountains are exposed in the easternmost part of the Grand Canyon, but they too were eventually eroded down to a low-relief surface as well, although small  ridges a few hundred feet high persisted. Along the lower reaches of Diamond Creek Road, you can lay your hand on a boundary between two rock sequences with a gap of more than a billion years between them. The unconformity can be seen in the photo above where a conglomerate rests on contorted metamorphic rocks in the bit of shadowed ledge. The "Diamond" of Diamond Creek is the uniquely shaped peak on the left side of the photograph. It is actually a sliver of rock caught between two branches of the Hurricane fault system.

Another layer that is prominently exposed along Diamond Creek Road is the Devonian-aged Temple Butte Limestone. Most park visitors never see it because in the eastern section of Grand Canyon National Park the Temple Butte is a discontinuous thin layer that is pretty well invisible from the rim. In western Grand Canyon it is more than 700 feet thick. It formed as a tidal estuary and tidal flats along the edge of the continent about 385 million years ago.

Temple Butte cliffs in Diamond Creek

We reached the end of the road where Diamond Creek flows into the Colorado River, the watercourse responsible for carving the Grand Canyon. It was a moment for the students to cavort in the river for a few minutes, and to wonder at the work the river has done. This spot is where many of those who've rafted the river through the Grand Canyon take out, a usually raucous process, but no one was about on this particular day.

The most "mysterious" aspect of Diamond Creek and Peach Springs Canyon is that the tributary canyons to this creek follow illogical pathways, and are actually older than the Grand Canyon itself! It's an odd problem. Along the upper reaches of Peach Springs Canyon, there are a series of Paleocene to Miocene-aged rocks clinging to the canyon walls. They once filled the canyon, meaning the canyon was carved prior to sixty million years ago, and the rivers that carved it flowed northeast, opposite of the Colorado River today. Apparently the land subsided so that the canyons were filled with sediment, and then they were exhumed when the modern Grand Canyon was carved, most likely within the last four or five million years. There has been more than one Grand Canyon carved through the Colorado Plateau!

Peach Springs Canyon  (red) and the odd channels (blue) that were carved millions of years prior to the Grand Canyon itself (they were buried and exhumed when the modern canyon was carved).

Near the bottom of the road we happened upon a Bighorn Sheep. They were once more common and figured prominently in the Ancestral Pueblo petroglyphs found throughout the region. 

Diamond Creek is a fascinating excursion. It is entirely on Hualapai lands, and they charge a fee of around $17 per person for permission to drive the road. I never mind paying the fee, because the tribe doesn't have many sources of income or all that many jobs on the reservation. The town of Peach Springs where the road starts has a very nice motel and restaurant (and not much else), and if you are a train lover, you'll be able to listen to them all night long. The rails are amongst the busiest you'll ever see. The town is on one of the last remaining stretches of the original Route 66.

Our crew was ready to get to camp, so we drove an hour or so to my brother's cabin where we would spend the next three nights.

Wait a minute. Showers, kitchen, hot tub? You call this roughing it?

Exploring the Depths of the Grand Canyon...By Car?

The Grand Canyon is one of the great spectacles of the Earth. Millions of people every year stand on the edge of the abyss and peer in, taking in the vivid colors and hidden depths. Tens of thousands venture down some of the few trails that reach into the incredible gorge, and several thousand raft the river. But how many drive the canyon? Did you even know you could?

And no, I'm not talking about visiting the canyon "Thelma and Louise" style...

For more than two hundred river miles, no road crosses the Grand Canyon (plus another hundred miles to Lake Mead). Navajo Bridge near Lee's Ferry is at one end, and Pat Tilman Bridge near Lake Mead is at the other. In between in the depths of Grand Canyon there is a single road that reaches the river. It's called Diamond Creek Road, and it starts on Hualapai Nation lands at Peach Springs. It's a marvelous adventure.

Without even considering the philosophical objections to building roads through the wilderness world of the Grand Canyon (objections I completely agree with), there are staggering engineering barriers. There are a series of formations, including the Redwall Limestone and the Coconino Sandstone that form sheer cliffs. The locations of trails in the Grand Canyon are controlled almost entirely by the few locations where they can surmount the cliffs of these two layers.

At Diamond Creek, the Hurricane Fault has offset the formations in just such a way that the cliffs can be avoided entirely. For the entire twenty mile length of the road, there is nary a cliff to worry about, as the road follows the bottoms of desert arroyos and washes. The biggest worry is flash floods and mudflows, which can easily shut down the road in July and August during the monsoons (and badly inconvenience river rafters who plan to take out at Diamond Creek).

One can certainly discuss the idea that it's "cheating" to drive to the bottom of the canyon, and there is a certain validity that scenery that hasn't been "earned" by completing a stiff hike might end up being less appreciated. But many people can't handle the very strenuous hiking and many simply don't have the time. Driving down into the canyon is a unique opportunity to study the oldest rocks of the canyon, the ones that are the very hardest to access in any other situation.

Diamond Creek cuts through to the Granite Gorge Metamorphic Suite, which is the oldest group of rocks found in the American Southwest, dating to as early as 1.8 billion years ago. At roadside there are marvelous exposures of schist, gneiss, and pegmatite granite with bright shiny crystals of muscovite mica and quartz.

A bit farther up the canyon one can see the layers of the Tonto Group, a series of three formations called the Tapeats Sandstone, the Bright Angel Shale, and the Muav Limestone. The three layers formed as the Pacific Ocean transgressed and covered much of the western North American continent in Cambrian time, just over 500 million years ago. The Tapeats Sandstone sits atop the rocks of the Granite Gorge Metamorphic Suite.

That last sentence needs a bit more explanation. The boundary between the Tapeats and the Granite Gorge rocks is a profound unconformity representing a gap of more than a billion years. This unconformity is actually called the "Great Unconformity", and is an erosional surface that was witness to not one, but two major mountain-building events. The metamorphic rocks were once the core of a vast mountain range that formed 1.7 billion years ago when the North American continent collided with a set of two exotic terranes, the Yavapai block and the Mazatzal block. Imagine an island the size of California or New Zealand grinding into the edge of a continent along a subduction zone and you will get the picture. This massive mountain range eroded to a flat low-relief surface over the next few hundred million years.

Later on, about a billion years ago, the continent stretched and broke apart, forming a series of fault-block mountain ranges that reached heights similar to the mountains in and around Death Valley National Park today. The rocks of these mountains are exposed in the easternmost part of the Grand Canyon, but they too were eventually eroded down to a low-relief surface as well, although small  ridges a few hundred feet high persisted. Along the lower reaches of Diamond Creek Road, you can lay your hand on a boundary between two rock sequences with a gap of more than a billion years between them. The unconformity can be seen in the photo above where a conglomerate rests on contorted metamorphic rocks in the bit of shadowed ledge. The "Diamond" of Diamond Creek is the uniquely shaped peak on the left side of the photograph. It is actually a sliver of rock caught between two branches of the Hurricane fault system.

Another layer that is prominently exposed along Diamond Creek Road is Devonian-aged Temple Butte Limestone. Most park visitors never see it because in the eastern section of Grand Canyon National Park the Temple Butte is a discontinuous thin layer that is pretty well invisible from the rim. In western Grand Canyon it is more than 700 feet thick. It formed as a tidal estuary and tidal flats along the edge of the continent about 385 million years ago.

The most "mysterious" aspect of Diamond Creek and Peach Springs Canyon is that the tributary canyons to this creek are older than the Grand Canyon itself. It's an odd problem. Along the upper reaches of Peach Springs Canyon, there are a series of Paleocene to Miocene-aged rocks clinging to the canyon walls. They once filled the canyon, meaning the canyon was carved prior to sixty million years ago, and the rivers that carved it flowed northeast, opposite of the Colorado River today. Apparently the land subsided so that the canyons were filled with sediment, and then they were exhumed when the modern Grand Canyon was carved, most likely within the last four or five million years.

Photo by Mrs. Geotripper

Diamond Creek is a fascinating excursion. It is entirely on Hualapai lands, and they charge a fee of around $25 per person for permission to drive the road. I never mind paying the fee, because the tribe doesn't have many sources of income or all that many jobs on the reservation. The town of Peach Springs where the road starts has a very nice motel and restaurant (and not much else), and if you are a train lover, you'll be able to listen to them all night long. The rails are amongst the busiest you'll ever see.The town is on one of the last remaining stretches of the original Route 66.

Into the Great Unknown: The Last Day...An Elegy for a Journey, and for a River

Elegy (from the Greek word for "lament") is a mournful, melancholic or plaintive poem, especially a funeral song or a lament for the dead.

How many ways can I describe the last day of our trip? The word "elegy" came to mind. It was the end of a long but incredible rafting trip down the Colorado River, and I was feeling sad. Sure, I was anxious to hear the news from the family and the outside world, but it was also the ending of one of the greatest experiences of my life. It was the ending of a personal journey, which ventured sometimes into terrifying darkness, but mostly it was a world of sublime beauty, even glory. And... the story was about the abuse and destruction of a river.

We packed at a leisurely pace. We only had a few miles to go, and the Hualapai Nation requested that no take-outs happen before 10 AM.

We set out down the river. We turned a corner and I saw something I hadn't seen in more than a week: a familiar sight. I've been down Diamond Creek several times, and Diamond Peak has an unmistakeable shape, even from the opposite side. To offer a sense of scale, Diamond Peak is only about 200 feet higher than the beach at the beginning of our trip in Lee's Ferry. It stands out in part because it is a fault block that has risen between two fault zones. Erosion along these faults has led to the trick of the topography that allowed a road to be constructed down to the river.

At mile 224 we passed the final rapid, a little riffle that didn't even merit a name. But it was the last one...

And then we entered the last mile or so of river, and it nearly broke my heart. It was perfect. In that moment I wanted to simply float on and on into eternity. Pete stopped rowing and we simply drifted. The river was quiet. A swallowtail butterfly landed briefly on my hand, confused by the bright colors of our clothing and luggage. Pete pulled out his harmonica and played a few tunes.

I wrote in my journal...

I was suddenly wistful, wishing to float down a serene river, at peace, but knowing that it is never truly serene. There are those perfect moments that make everything worthwhile but around the bend there can be excitement, action, and even terror. But peace returns, and we recover our sense of well being.

Such beauty in such a savage land. Without the river, life would be barely possible for a person. Too far between water sources when it is so god-awful hot. The hike yesterday across the Tapeats ledges could have been unbearable without soaking in the cold water first.

But along the string of life-giving water, the beauty is overwhelming. Every side canyon would be worthy of a national park all its own. I found myself thinking 30 Yosemite Valleys strung in a line would equal the Grand Canyon.

I don't know that I will be back. I faced the big waters twice and made it through, one time in terror, and the other less so. But I enjoyed the rapids a bit less afterwards...

...but nothing can take the place of drifting down the placid parts of the river; seeing the herons and bighorns, and I'll never forget the sounds of the canyon wrens. I would do it for that...those parts will always live on in my memories.

The cliffs would glow red in the pre-morning hours after the stars disappear. The red fades into shadow, and then the sun lights up the cliffs in blazing orange. The river was always brown but in the shadows of evening and morning, it reflected the lights of the cliffs above...wonderful moments.

I took one last video as we drifted...

 

And then, a strange sight, a big orange ball and a cable strung across the river. It was the gaging station at Diamond Creek. It was a reminder that this was a heavily utilized river that had to be measured and controlled. There was a feeling on the entire trip that the river we were traveling on was not "right". It was far too cold for a desert summer, and it ran too high for any snow-fed river in August. The disappearing beaches demonstrated that the river rarely flooded anymore.

It's hard to imagine the difference between this river and the river that was experienced by John Wesley Powell and his courageous men. And it was almost entirely due to the construction in 1963 of the monstrosity that flooded a precious gorge called Glen Canyon. And the sewage lagoon that formed behind the dam was named for Powell. I don't think he would have been pleased. He recognized sooner than most the problems that would lie ahead for the millions who would come to depend on an inherently undependable river. The lake that bears Powell's name may never again fill if the predictions of the climate scientists come to pass.

The river will return. And it probably won't take as long as it did when lava flows temporarily stopped the flows of the river. The dam is built in unstable porous rock, and it almost failed catastrophically in 1983, due in part to the arrogance of the dam engineers. It ultimately must fail, probably within a few years of being abandoned by the society that maintains it. Ultimately the river will return to something of its former self. Time is all it needs.

The gaging station also meant that our time was almost up...

A beach came into view, with trucks and giant pontoon boats. We waited until the other boats left on their journey to Lake Mead and pulled off the river for the last time.

Rigging the boats at the beginning of our trip took parts of two days. The de-rigging took an hour or less. No one wanted to hang out on the river in the growing heat of the day.

All of the material we began the trip with came off the river, although some of it had been, um, "transformed". A few items, most notably my hat, gloves and a guidebook were still in the river somewhere. Oh and a tent that blew away several days earlier.

I finally had a look at the unadorned raft that had been my home for the last two weeks. We developed a luggage line and got all our gear onto the truck; we would unscramble it in much more comfortable weather in Flagstaff at an elevation of 7,000 feet. We piled into the truck and a van and set out on the bumpy 20 mile drive to Peach Springs where we would rediscover ice cream and flush toilets. A 90 mile drive to Flagstaff followed...

...our trip was over.

I hope you have enjoyed following our journey. Thanks to all those who traveled with me, and especially my brother and his family who invited me to come along. Thanks to Pete, who was a wonderful boatman and traveling companion. They were wonderful people to travel with! Thanks to Barry, Bev and Jeff, who pulled me from the river, sometimes more than once.  And thanks to all the river runners who have clearly worked to keep the river clean and wild.

Look for one more post in this series, a compilation of all the posts on the journey, and maybe a few final thoughts.

Is it the Journey or the Destination? Part 2: I now know how my students feel...

I've seen the beginning...

I'm no adrenaline junkie. When I've been at Disneyland, Splash Mountain and the Pirates of the Caribbean is about my limit. I was dragged kicking and screaming into Space Mountain, and came out also screaming, with rubbery legs. Roller coasters unhinge me. So what the hell am I doing, and why?
 
A few weeks ago I wrote about whether it is the journey or the destination that is important. And it is indeed the journey that is important. I've been to the starting point...

And I've been to the ending point...twice (below). But in-between those two points are 220 miles of wild river. I'm about to go down the Colorado River through the Grand Canyon for the first time in my life, spending 16 days to get from Lees Ferry to Diamond Creek. It's both a life-long dream, and just a bit mysterious and scary. The rapids are legendary. There are rumors of stunning beauty and spiritual discovery. There are groovers (don't ask). And I've come to realize that I am (re)learning just what it is like to be one of my students going on a long field studies trip for the first time, being shaken out of the every-day grind and opening up to the possibility of new and incredible experiences.

I am a rank amateur at rafting, so I've been trying to learn everything I can about trips down the Grand Canyon. I have the questions. Am I in good enough shape? Am I going to embarrass myself on the first rapid? What's it like to get dumped into the river? One thing I do know, though. I'm going to live every moment on the river. The sights, the smells, the sounds. So many of my travels have been wrapped up in organizing the logistics, dealing with student problems, keeping schedules and appointments, and making sure that everything goes somehow smoothly for everyone. On Sunday, I become a student once again, both in learning, and in responsibility. I won't be the one leading, I'll be the follower (and the chore-doer; no more of that managerial supervising crap!).

Like I said, I'm not an adrenaline junkie. I'm not too sure how I feel about running the legendary rapids like Crystal, Hance or Lava Falls. But it's the only way to see the heart of the Grand Canyon. I've been all over the rims, and I've been down (and up) four different trails to the river. But I've never been able to explore the river itself, or any of the side canyons that make such river trips so memorable. I'm looking forward to exploring as much as I can.

I am, I admit, an internet junkie, and tech addict. I'm wondering how I will survive 16 days out of contact with the cyber-world. Without my smartphone. Without my laptop. Then again, I hear there is this stuff called paper, and things called pencils and chalk. I'm told I can preserve memories and experiences on beaten wood pulp, so I may give that a try. When I return, I'll see about transferring the paper data to a digital format, and let you know how things turned out.

I won't be totally bereft of technology. I've got two nearly worn-out digital cameras that I'll be taking along. I figure at least one might survive the journey.

It's all the in-between I don't know so much about...

But maybe most of all, I'm looking forward to the time I'm going to have with my brother, my sister-in-law, and my two nephews. Their hard effort navigating the whole permit and organizational maze made this adventure possible, and they invited me along to share in it. I don't know if I can ever repay the kindness. It's going to be a grand adventure!

I might get a few more posts up before I leave, but then Geotripper goes dark for three weeks.

Where They Almost Damned the Grand Canyon...

 Is there a limit to the destruction that humans can do? Yesterday's post concerned our desire to control the natural world around us, which in the case of the Colorado River meant the building of mega-dams, giant piles of concrete that pretend to hold back the floods, and dole out the riches of gravitationally produced electricity. Unfortunately such mega-dams were built with a priority of utility over beauty.

Of course, hardly anyone can profit from beauty, and if only a few people know of a place or have ever seen it, it can be easy to subvert a place to the profit of a few. After visiting one of the mega-dams, we explored a little-known road that actually reaches the bottom of the Grand Canyon. It follows Peach Springs Canyon and Diamond Creek to the Colorado River in about 20 bumpy dirt road miles. It is well known to river-runners, as the road serves as a take out point for river trips.

As we cooled our feet in the water, we had to contemplate that sixty years ago, this place was slated to become the next big dam on the river. The reservoir would have inundated miles of national park land upstream. It was unthinkable, and in the fashion of the thinking of the time, the dam was built instead in a place that only a few hundred people had ever seen: Glen Canyon.

It's hard to contemplate what was lost.  And only slightly a relief to know that at least one place was saved.

The Abandoned Lands...A Journey Through the Colorado Plateau: Where the Rivers Changed Direction

...it's gone away in yesterday
Now I find myself on the mountainside
Where the rivers change direction
Across the Great Divide...

from Kate Wolf (a folksinger sorely missed...)

Abandonment as a theme for my current blog series about the Colorado Plateau doesn't always involve people and cultures. It can include rivers and other natural features as well.

Peach Springs Canyon and Diamond Creek provide the only vehicular access to the Colorado River in the entire length of Grand Canyon. As noted in a previous post, it is a spectacular introduction to the geology of the Paleozoic and Proterozoic rocks of the region. The route also reveals a neat little riddle.

Peach Springs Canyon is a very deep gorge, one of the larger tributaries of the Grand Canyon. Peach Springs Creek is a dry wash most of the time, but it would be understandable that it could have been carved by huge flash floods over the years. But what gets interesting is that Peach Springs Canyon also has tributaries, and they are also huge. But they also have practically no drainage area that could efficiently collect cloudburst runoff. How did these tributaries get carved?

It gets better...check out the GoogleEarth image below (click it for a larger image). Why do the winding canyons bend away from the linear fault-line creek bed, and then bend back? And notice how they don't drain in one direction, but instead each canyon has a drainage divide, with water flowing two directions from a high point within each gorge. Shouldn't a drainage in a single canyon segment be one way?

Before I point out the third strange item, understand that the Grand Canyon and the Colorado River as we see them today didn't exist prior to six million years ago. The present course of the Colorado River was not even possible until the Gulf of California (Sea of Cortez) formed around 5 millon years ago. And deposits along the Grand Wash Cliffs where the Grand Canyon ends at Pierce Ferry show that no large river existed there 17 million years ago. Why is this a problem?

As one starts down the road into Peach Springs Canyon, the rolling hills reveal sediments that are filling some of these odd tributary canyons. and they are old sediments; some are as old as Paleocene, the earliest part of the Cenozoic era which began 65 million years ago. These abandoned channels were carved in latest Cretaceous time. These tributaries are older than the present day Grand Canyon! Much older...they've been exhumed by the carving of the present day Colorado River. But these valleys may once have been inhabited by the dinosaurs!

Today, the Peach Springs area lies near the western edge of the Colorado Plateau. The Basin and Range province lies to the west and south, a much lower area on average, providing an avenue for the Colorado River to reach the sea. 65 million years ago, the region was much different. What are today the low areas of the Basin and Range were once a high mountainous region that we call the Mogollon Highlands. Rivers drained from these highlands through the Peach Springs region, carving the channels and canyons towards the northeast, pretty much the opposite direction that the Colorado Plateau flows today. At some point in the last few tens of millions of years, the rivers changed direction through a combination of headward erosion and stream piracy, and ultimately the "old" Colorado River of Colorado and Utah was diverted west and the Grand Canyon was the happy result.

What an incredible adventure of the mind! The history of the Colorado River and the carving of the Grand Canyon have been complex problems that have kept some of the very best field geologists busy for decades, and the full story of how the grandest canyon on the planet came to be is still only partially complete. For more information, check out

Colorado River Origin and Evolution (free ebook at http://www.grandcanyon.org/booksmore/booksmore_epublications.asp)

and Richard Youngs recent work in Peach Spring Canyon at:
http://repository.azgs.az.gov/sites/default/files/dlio/files/nid1362/cr-11-o_peach_springs_quad_0.pdf

The Abandoned Lands...A Journey Through the Colorado Plateau: And not a single sentient being ever laid eyes on the mountains

What an incredible story can by told by rocks that are not there! Seriously, the Grand Canyon is full of rocks, but some of the most important parts of the geological story emerge when we realize just how much rock is missing. In the picture above, erosion has scooped out a small alcove on the right side. The rocks forming the roof of the alcove are crossbedded sandstones that formed on a beach around 500 million years ago. The rocks underneath are composed of schist and granite pegmatite (an extremely course-grained type of the plutonic rock) that date to between 1.4 and 1.8 billion years. The picture below shows a typical intrusion of the pegmatite between the layers of schist. What's missing? Just a billion years or so of geologic history!

Imagine: An ocean in the tropics...but no palm trees, no coconuts. No visible life at all except for a hint of green in the water; single-celled microorganisms rule the ecosystem. The air is unbreathable, as there is only a fraction of the oxygen we find in our atmosphere today. Our own world would be a foreign place to visit; we would need spacesuits to survive.

On one horizon, a landmass...it is large, more than a thousand miles across, the core of the North American continent.  It has existed already for most of a billion years. In the other direction, an island is visible in the distance. It is also large, hundreds of miles long. The two lands are on a collision course. It is not an overly fast collision, as they approach at the stunning speed of three or four inches a year. But over millions of years, they collide, first disturbing and folding the sediments on the seafloor between them, and then a vast mountain range grows as one land mass is pushed up and over the other. And within a few tens of millions of years, a second island collides, pushing the mountains even higher. A vast range now extends across the edge of the continent, from what is now the southeastern United States to California, and an unknown distance westward.

It was a mountain range that no eyes ever saw. Eyes would not develop in this world for another billion years. No trees ever graced its slopes, not a blade of grass, no terrestrial life at all. The mountain was composed of barren rock, and was touched only by snow and flowing water. But no life. The mountain range was pushed to great heights, and erosion tore away at its flanks. Over several hundred million years the mountain range was eroded away until it was a low plain, interrupted here and there by low hills no more than a few hundred feet high. The rocks that now lie exposed were once buried 12 miles deep in the crust. They have been changed by the extreme heat and pressure into schist and gneiss.

It is that surface that my students are exploring in the picture above. They are laying their hands on the core of a mountain range that no eyes ever saw, but whose existence is indicated by the rocks and by the erosion surface. 500 million years ago, a rising sea covered this region, leaving behind a sequence of sandstone (the Tapeats), shale (the Bright Angel), and limestone (the Muav). John Wesley Powell, the leader of the first team of people to navigate the Colorado River through the Grand Canyon, called the surface the Great Unconformity.

The Great Unconformity was one of our objectives while traveling down the Peach Springs Road into the Grand Canyon on our trip last month. In 21 miles we drove 4,000 feet into the canyon to the Colorado River at Diamond Creek. I'm not superstitious or anything, but in May we only got to the 17 mile mark before our car broke down, so this time our vans made the trip to the river without stopping, except for the rather incredible distraction of a herd of Bighorn Sheep grazing by the road.

 Yeah, we get sidetracked by furry mammals every time...

Back on the road, we made it to the river at the head of Diamond Creek rapids. I had not been this close to the Colorado River in the Grand Canyon in many years, and had forgotten what power the river exudes, even as her water is processed through dams and reservoirs. The river ran fast and surprisingly cold. It was a relief in the 113 degree temperature.

After cooling off in the water, we started back up the road, with several stops to visit the Great Unconformity and to have a look at the formations that are the most difficult to see and access from the rim of Grand Canyon. We were able to see the sandstones of the Cambrian beach, lying over the unconformity.

A few hundred feet higher, and we were able to check out the former muds of the Bright Angel Shale. We could see the trails of worms, trilobites and other creatures that squirmed and disturbed sediments for the first time in three billion years of Earth history. Ripplemarks can be seen in the picture below, on the left.

The Bright Angel Shale yields under pressure, and if not buttressed from below, it slides readily. A huge slide block was visible in the canyon wall on the west side of the Hurricane fault. The exposure of Bright Angel in the picture below is tilted about 45 degrees despite being sandwiched between horizontal layers.

Up close, the deformation of the greenish shale and siltstone is obvious....

The road to the bottom of the Grand Canyon, the only road to the river, is a fascinating journey. It is all gravel, it's bumpy in places, and the entrance fee is pretty steep. I didn't mind paying it, as tourism is essentially the only income for the Hualapai people who own this part of the Grand Canyon. But it provides unparalleled exposures of the Proterozoic rocks of the Grand Canyon Metamorphic Suite, the Paleozoic Tonto Group (the Tapeats, Bright Angel, and Muav formations), and the Devonian Temple Butte Limestone, a layer that is almost impossible to see from the rim of the Grand Canyon in the national park.

We made it back to Peach Springs without incident, and headed to our campsite on the south rim of Grand Canyon. Between our exploration of Hole in the Wall and the trip down to the river, it had been a full day! And it was only our second day out in the field...

PS: I forgot...there were more furry distractions on the way out of the canyon. I don't know how wild they were, given the rope on one of them, but there they were on the open range....

Here is the explanation of my "abandonment" theme for this series: http://geotripper.blogspot.com/2012/06/abandoned-landsa-journey-through.html