Thursday, July 28, 2011

A Colorado River Rafting Trip Through Horsethief, Ruby, and Westater Canyons

In mid-July I got to raft the Colorado River where it transitions to the red rock country of the Colorado Plateau. Horsethief, Ruby, and Westwater canyons are the first red rock canyons that the river flows through and we completed a 54 mile trip through them. Surprisingly (for this time of year), the river was running quite high flowing at just over 20,000 cfs (cubic feet per second). This volume contained the last of the spring snow melt from the high Rockies as well as recent inputs from monsoon rain.

The trip begins just downstream from the confluence of the Colorado and Gunnison rivers, near the town of Loma, Colorado. A canopy of cottonwood trees lines the river here and once away from shore, I took a picture in the upstream direction. The rocks in the far distance are rather young lake deposits about 60 million years old.
A mature bald eagle stood sentinel at the entrance to Horsethief Canyon.

Unlike the central portion of the Colorado Plateau, the Navajo Sandstone has either pinched out or changed facies in westernmost Colorado. Behind the far cottonwood trees you can see a bit of the Wingate Sandstone. The darker layered beds above it belong to the Kayenta Formation. But even though it looks similar to the Navajo Ss., that is the Entrada Sandstone forming the high cliff. The reason for the absence of the Navajo and Carmel Fm. here is that this was the flank of the Ancestral Rocky Mts. and it was not part of the depositional basin at that time (about 190 to 170 million years ago). Can be confusing at first but it has been worked out by stratigraphers.

The Kayenta Formation at River level capped by the Entrada Sandstone in Horsethief Canyon.

This is a view downstream of the Rattlesnake monocline, where the strata were compressed and upturned during the Laramide orogeny.

On day 2 I took this picture at sunrise of our rafts in Mee Corner camp. The river was whistling by at about 6 mph and became quite muddy from runoff overnight. Huge logs were seen drifting by.

We had time to hike up to the top of the cliff behind camp.

About 250 feet above the river lies a deposit of Colorado River cobbles. The suggestion is that the river has incised its channel 250 feet after these were laid down and they have become perched above the modern channel. Cobbles like these are the actual cutting agents that help rivers deepen their canyons.

A old juniper tree leans out over the mighty river. Prior to 1921, this stretch of it was known as the Grand River (thus the names that remain in the area - Grand Junction, Grand County, Grand Mesa, etc.). But in that year, the Colorado State Legislature, in an attempt to secure more water rights for the state, petitioned a federal commission to have the name changed. Prior to that change, the Green and the Grand flowed together downstream to create the Colorado River. See more about this name change here.

Every morning while in Ruby Canyon, the Amtrak Zephyr would come by about 10:30 AM. This rail line only saw about 5 trains in a 24 hour period. In Flagstaff, we get that many in an hour.

Another beautiful fold in the strata in Ruby Canyon.

As we approached our second nights camp we entered a shallow gorge cut into Precambrian age granite. These rocks are the same age and general composition of the Vishnu Schist in the bottom of the Grand Canyon. But take a look at the deposit that overlies it - that is the Chinle Formation. In the Grand Canyon, the schist is mostly overlain by the much older Tapeats Sandstone and 4,000 feet of other strata. That means that here in Ruby and Westwater canyons, the great unconformity is even greater than in the Grand Canyon! it is 1,500 million years duration here; in Grand Canyon it's only 1,200 million years. The reason? Again, it is the former presence of the Ancestral Rocky Mountains, which had all of their Paleozoic strata stripped off of them before the Chinle Formation finally buried this part of the ancient range.

Here is a close-up of the rock from behind our camp. The rectangular flecks are potassium feldspar crystals that grew in the magma as it slowly cooled.

Here two dikes cross one another with the granite. Can you see which dike occurred first? Since the dike in the lower left corner is offset slightly by the other one (look where the two cross each other), it must be the older dike - how else could it have been cut if it wasn't already there.

Steamy morning after a night of rain in Ruby Canyon.

A beautiful grove of cottonwood tress lines the Grand River (sorry - I think the name change is something that should be reversed - now that the water allotment has been determined). A cliff of Entrada Sandstone is capped by the Morrison Formation behind the trees.

Same thing here with a tilt in the strata. This marks the entrance into Westwater Canyon.

The Precambrian/Triassic unconformity rises again from beneath the depths. The rocks here are composed of high grade metamorphic types. At this point I put the camera away for about 7 miles. This is the whitewater stretch of the trip and I wasn't willing to take a chance. The rapids were mostly washed out at this water level but it still was a bit tense as we rode one long rapid where normally there are 8 or 9.

When we exited the whitewater stretch, the Precambrian gorge was almost 100 feet deep.

Once we landed at our third camp (Bighorn), we saw that the grade (or intensity) of metamorphism was much less here than it was back upstream. Visible here is evidence for the original rock types prior to metamorphism. The more massive, light colored rocks below the persons finger used to be sandstone until it was cooked and pressurized into a quartzite. The darker rocks above that used to be a shale or mudstone before they were changed into a pelite.

A the exit to Westwater Canyon, the Precmbrian rocks go beneath the surface and do not return back to river level until a place below Hance Rapid in the Grand Canyon! That means they are still buried in the subsurface beneath Moab, Canyonlands National Park, and all of Lake Powell and Marble Canyon - almost 400 miles.

A typical landform on the Colorado Plateau.

Whenever the river emerges from one of these wilderness canyons, the hum of humanity cycles loud. Whether it is an alfafa farmer plowing her field or a giant mower cutting down exotic vegetation, it seemed like something was always going on. Here a giant mower chews up tamarisk trees along the bank of the river.

The Morrison Formation is beautifully colored in this part of the world. The trip was led by Michael Smith and Tamsin McCormick, who direct Plateau Restoration, an organization dedicated to education and restoration of native habitats on the Colorado Plateau. They invited many old timers from the 1970's and '80's who worked at the Grand Canyon and this was a great trip!

Saturday, July 09, 2011


Time is likely the single most important idea in geology. The very basis of geology involves a survey of planet earth, and geologists think about time in much different ways than other professions. Time is important to us and makes us joyful when we witness its passage.

This idea became quite clear to me last year when I celebrated my 20,000 day of life. I invited a few friends over for a celebration but a few of them became perplexed when they learned the reason for the celebration. Most people I've met will encourage anyone to celebrate the years they've been alive, but I've discovered that if you attempt to measure your life in other units of time it perplexes people. I guess it's okay to measure years but counting the days, weeks, minutes or seconds you've been alive seems to perplex some people. Last year, you would have thought I was celebrating the death of a cherished pet the way some people reacted to my 20,000 day.

Nonetheless, I will be commemorating three important milestones on July 14. On that day I will turn 500,000 hours old. A little later in the day, I will turn 30 million minutes old and 1.8 billion seconds! I'm just so happy to have spent many of those hours, minutes, and seconds alive in the wild outdoors, the only true reality show that is actually based in reality. By the way, if you must know, those units of measure mean I've been alive just a little over 57 years.

If you are asking yourself how I will celebrate, it won't be with others who don't appreciate a good milestone. I'll probably take a walk through a northern Arizona forest in what is unequivocally the best time of year here. There may be a short but intense rain storm but the sun will never be far away. The clouds will be huge and billowy. The smells will be of green pine trees and fresh air. The temperature will be about 82 degrees and the humidity about 30%. It will be ideal. And I'll note the passing of time. I may not be aware of the exact second it happens or the exact hour but the whole week for me will be filled with reflections on time.

The most amazing thing to me about these milestones is the realization that I've only been here on earth a mere half a million hours. That seems so short a time, especially since I've been sleeping for at least 170,000 of those 500,000 hours! So few hours, yet so much that has been done.

Why note the 1.8 billionth second you ask? Well, that's the age (in years) of the oldest rocks in the bottom of the Grand Canyon. I will have been alive for as many seconds as the Vishnu Schist has been around in years! I will then be about 1/31,500,000 as old as the Vishnu Schist. That's a milestone worth noting.

If you'd like to chart your own time, use the Paul Sadowski web site that I use. You can mark your own disambiguous moments in life and watch as other people become perplexed at your hyper-awareness of time.

Have a great time, whatever you do next week!

Wednesday, July 06, 2011

To the Top of Arizona's Highest Peak - San Francisco Mountain

San Francisco Mountain is the highest point in Arizona, rising 12,633 feet into the sky. However, this strato-volcano has a collapsed top and if the former height of it were restored on the landscape today, the cone would top out at about 15,300 feet. This means that Arizona's San Francisco volcano might once have been the tallest mountain in the lower 48 states.

Back in the 1970's I started a tradition of hiking to the top of the San Francisco Peaks on my birthday. This past July 1 I did it again with my wife Helen.

The trail begins at an elevation of 9,200 feet and climbs through aspen and eventually the spruce-fir forest. The trail is quite shady on a summer morning but steadily climbs uphill.

Much of the geology is hidden beneath this veneer of vegetation but occasionally a block of andesite pokes through the green carpet and exposes vesicles, that formed when gas escaped as the lava hardened into rock.

We finally reached the saddle on the trial after only 2.5 hours. The elevation is about 11,900 feet. This is a view to the north and the summit area on Mt. Humphreys.

To the east is the Inner Basin of the Peaks and in the foreground you may notice a curved pile of talus rock. This is likely debris pushed into a ridge or moraine, when  Ice Age glaciers filled the Inner Basin and flowed to the east.

Does this bristlecone pine reveal the dominant wind direction. Agassiz Peak is seen in the distance, the second highest peak in the state.

We saw more flowers in the alpine zone than we did down below. Here small blue flowers frame the crest of this giant volcano.

Helen making her way up towards the summit. At this elevation, one must take a breath every few steps along the way.

There are numerous false summits on towards the top but here we can clearly see the crest.

This is the finally climb to the top! One last rubble strewn slope.

On top we found a small group of Boy Scouts from Gilbert enjoying the view.

For many years now, this stone wall has served as a wind protector. Surprisingly, there was no wind on top this day!

Helen taking a break on top of the mountain.

There is plenty of evidence of lightning strikes that have struck the top of the Peaks. Here is an example of a fulgarite where the rock was melted from the intense heat.

My official birthday shot for 2011.

Far off in the distance is the Grand Canyon and with my binoculars I saw Deva, Brahma and Zoroaster temples inside the canyon.

A view to the northwest and Kendrick Park (right) and Kendrick Peak (left).

This photo doesn't look like much but in the far distance (and perhaps too small in this photograph to appreciate) is a curious linear feature out on the grasslands. This is likely a fault and it is directed right towards the top of the San Francisco Peaks. I wondered, "Could this be a zone of weakness in the crust that these lava's took advantage of?"

Looking west to Kendrick Mountain (right), Sitgreaves Peak (center), and Bill Williams Mountain (left distance). These three lava dome volcano's were erupted along a fracture that is outlined by the position of the volcano's.

One last look from above the saddle before we headed down the slope.