Into the Great Unknown: Heat...and All Things Beautiful

It was our last full day on the Colorado River through the Grand Canyon, the Great Unknown as John Wesley Powell called it in 1869. One full day, and one more night on the life-giving stream of water through one of the spectacular canyons on Earth. We had eighteen miles to go, from our camp at Mile 202 to 220 Mile Camp (it was clear that the geographers were running out of names for the features in the canyon; it's that big).

It was a day full of the best things the canyon could offer. But it was also hot. Blazing oven hot. Merciless sun beating down hot. In other words, a normal summer day in the Inner Canyon. The thing is, we had already experienced a few hot days on the trip, but not quite the kind of 115 degree days that we were warned about in the training materials. I don't actually know how hot it got, but in my memory, it was the hottest day of the trip.

They said a few things in the training videos for rafting the river. To drink before you get thirsty. To drink a gallon a day. To always wear a hat. Seek out shade when possible, and don't hike between 10 and 4. They said it takes a human body about two weeks to acclimate to extreme hot temperatures, meaning a river trip was not long enough to do so.

We were seeing all kinds of adaptations to the heat as we explored the area around our camp during the relatively cool morning hours. We had dropped nearly 2,000 feet during our two weeks on the river, and the desert vegetation was characteristic of the Lower Sonoran Life Zone (or whatever the biologists are calling it these days). Cacti had been rare in the upper reaches of the river, but now they were common.

There were a few shrubs with their characteristic waxy leaves taking advantage of the recent storms by putting out a few flowers.

Best of all were the ocotillos that we had been seeing for the last two or three days. They too had taken advantage of the recent storms, and had put out thin leaves along their green branches (most of their food production happens in the branches rather than the leaves). There were none of the beautiful  red flowers (we'd need to be here in May for that).

We took advantage of the relative cool of the morning to search out some pictographs that were said to be up in 202 Mile Canyon. It took a while (which is why I had given up and photographed the plants instead), but eventually we found them. It was a small measure of the rate of geologic change that some of the blocks of rocks containing the rock paintings had tumbled down from the ledge.

Once the sun reached our boats, we set off down the river. We continued to see remnants of the lava flows that had once produced high dams, and which had continued downstream for many tens of miles (above).

We also saw another gigantic landslide that had involved the entire canyon wall (above). Lava flows aren't the only things that have produced dams on the river. As noted in an earlier post, landslides have altered the course of the river a number of times.

We saw more evidence of human occupation in the canyon. We discovered roasting pits in several of the debris fans at the mouths of some of the tributary streams. Along with the cracked and shattered rocks we found bit and pieces of pottery.

A short hot hike up Indian Canyon offered a fine view up the river. But it was hot and there was no shade. I shiver to thick how quickly I would have been in trouble here had I not been carrying a quart of water at all times. I was drinking at least a gallon and a half of water on days like this, and when it got too uncomfortable, I could splash in the river water to cool off. Despite being 200+ miles downstream from Glen Canyon Dam, the water was still in the mid-to-upper fifty degree range.

The scenery continued on a grand scale, with high cliffs at every turn. We saw another bighorn along the riverbank. It was as if the river was giving us reminders of why the canyon was precious. And that was the way I was feeling. This was the last full day, and while I was wanting to see the people I was missing in the outside world, I was also feeling like I wanted to hold onto these incredible experiences that I felt were enriching and transforming my life.

We crossed the Hurricane Fault again, and the ancient Vishnu Schist was exposed at river level once more.

 In the intense sunshine, the polished surfaces of mica, quartz and feldspar reflected brightly.

 It's amazing what the silt-filled water can accomplish!

 As we searched for (unsuccessfully) for a shady lunch stop, we encountered an unusual looking ledge of Tapeats Sandstone on the left bank.

The top of the ledge had been scoured and eroded by river currents, and it looked recent, yet the bench was 15 or 20 feet high. It looked extremely fresh.

 At the lower end, there was a strange orange-colored edifice called Pumpkin Spring. It was a warm spring deposit that was redepositing travertine that had been dissolved from the overlying limestone formations. The heat probably came from nearby active fault zones. The water was green and uninviting. The river guide suggested not drinking it because of high concentrations of arsenic (is that a poison or something?).

 We set up a canopy and crowded underneath it to eat lunch. There was a hot breeze blowing so the shade barely helped. Unfortunately the wind was trying to destroy the umbrellas that most of the boats had, so there was really no place to retreat from the sun. For pretty much the first time voluntarily, I spent most of the time soaking in the river as long as I could stand it (cold!), then getting out and warming up until I was dry and hot, and then getting back in the river!

Despite the heat, we wanted to check out the unusual terrace in the Tapeats Sandstone that we had just floated by. We grabbed some water and headed back up the canyon. The edge was pockmarked with huge potholes, many of which had carved right through the rock, forming little tunnels and caves. Many of the potholes still had the pebbles and cobbles that had carved them.

It turns out the terrace has been flooded by river water in historic time during the big spring floods, but only rarely since the floodgates of Glen Canyon Dam shut in 1963. The dam is still altering the river, even 200 miles downstream.

 We made one more stop that afternoon, at Three Springs Canyon. Like so many tributaries, it had a small stream of clear water that we could use for drinking. Some of the crew pumped the water filters while others hauled the five-gallon buckets down the trail to the boats.

 Yours truly found he could make a human dam across the trickling creek and have a nice bath.

It was the hottest part of a very hot day, and a hot breeze was blowing up-canyon. No one felt like rowing against the wind, not in the hot sun without the umbrellas. We holed up in the shade behind a ledge at Three Springs Canyon for quite awhile, letting the afternoon shadows extend across the canyon a bit.

 We arrived at our site for the night at 220 Mile Camp. As if to make some kind of point so late in our trip, it was one of the most beautiful camps of the trip. There was an island of Vishnu Schist in the river decorated with a few wispy tamarisk saplings. Our camp was in the shade (relief!), but the sun was shining brilliantly on the cliffs across the way, reflecting on the river.

The view upstream was gorgeous as well. At this late point in the day, no one else was on the river; the feeling of isolated wilderness was complete. It was strange to think that only six miles away a road reached river level, and that we would be driving out of the canyon in the morning.

We drank the last of the beers and the sodas, ate most of the remaining food, and sat in the warm air watching the sunlight drain away from the cliffs as night fell. After a while, a cool breeze wafted off the surface of the water.

The moon was a touch higher in the sky than the previous evening (it always happens that way), but it soon dipped below the cliffs. It was the 11th of August and the Perseids Meteor Shower was scheduled to debut in the night sky. It did not disappoint; as we talked and sang and played the guitar, I counted maybe a hundred shooting stars, some of them blazing a trail all the way across the sky. I had been turning in early on many nights of the trip, but on this night I was still awake staring at the show in the sky until well past midnight. I'll not forget it any time soon. I didn't want the night to end, and yet I did.

Tomorrow we would be back into civilization, and I would be starting the journey home...

Into the Great Unknown: Crossing the Great Unconformity Again; But Which One?

Every day is new. Every day the Canyon is different...

I look back over the notes of my journey down into the Great Unknown, the Colorado River through the Grand Canyon, and I am struck by the number of times I mention change. By mile 80 we had passed through essentially all the major rock units of the Grand Canyon, and one can be forgiven for thinking that things might get repetitious, but it just never happened. I was now fifty miles farther downstream, and every morning, every day produced new revelations. I knew by now on Day 11 that I was having one of the most incredible experiences I would ever have in my life, and still five days remained.

The day began as a sort of "passages" kind of journey. We needed to make 15 miles or so, and there was just one excursion up a side canyon in the plan. But there were also some big rapids to worry about, including Specter, Bedrock, and Deubendorff, as well as seven smaller ones. I could tell I was still a bit spooked after my swim down Crystal Rapid a few days earlier.

Enfilade Camp was on a sandy beach below a large terrace that promised a decent view. My nephew had hiked up the previous evening and had come face to face with a bighorn ram, so I was a bit curious to see what would be around in the morning. I found a nice view upstream and downstream, and a lot of sheep tracks and droppings, but none of them were visible (of course, given their excellent camouflage, they were probably there watching me).

We started the day in the Bright Angel Shale of Cambrian age, but before long we entered into the Granite Gorge again. It's interesting how we refer to the "Granite Gorge" when so much of it is actually composed of black schist. I was just stunned by the polished surfaces that looked all the world like obsidian, even on slopes dozens of feet above the river.

 The canyon walls closed in once again, and the schist cliffs rose high above us.

In eleven days we had dropped 1,200 feet or more, and the flora was picking up a definite Mojave-Sonoran flavor. Barrel cacti were common on the slopes above the river. Within a day or so we would be seeing ocotillo.

We reached Bedrock Rapid (6-8) and stopped to scout. It was appropriately named, as a big chunk of granite and schist split the river. If a boat went to the left, it would be caught in a too-small current and impossible eddy. But the river right tried to dash the boats against the rock outcrops. It took some hard rowing, but the boatmen got us through just fine. We bounced off a boulder, but it was done quickly and we were okay.

The river at Bedrock Rapid tries to mash my brother and sister-in-law against a cliff. I give them credit for carefully observing the geology.

Below the rapid I saw one of those extraordinary sights that seem to occur with continuing regularity. I've mentioned the Great Unconformity, and we saw a wonderful exposure in Blacktail Canyon, described in the previous post. The ancient erosion surface separates 500 million year old sediments from 1.7 billion year old metamorphic rocks.  It is marvelous to be able to lay one's hands on 1.2 billion years of missing history.

But the canyon hides secrets, and one of them is that rocks exist that fill that void. There are in fact lots of rocks, in layers about 12,000 feet thick. We had visited them earlier in the trip, in the area between Nankoweap and Hance Rapid. They too rest on a "great unconformity" spanning 500 million years. They in turn are overlain by the Tapeats Sandstone. Because the Supergroup has been tilted, they contact the rocks above at an angle, so this contact is known as an angular unconformity.

Above Bedrock Rapids, both unconformities could be seen in the same outcrop! The sun was at a difficult angle, so if you can't see it, take a look at the labeled version below. I've drawn this kind of rock relationship on chalkboards many, many times, but I haven't seen as many of them in the real world.

Downstream we encountered Deubendorff Rapid (5-8). As we bulled our way through, we caught the edge of a hole and lost an oar. Pete worked with the remaining oar, but got us through okay, if not a bit soaked.

Drifting along the river below, we encountered the second extraordinary sight of the day. Dikes and sills are the result of molten material forcing its way through solid rock. Dikes cut across the previously existing rock, while sills squeeze their way between layers. You can see examples of dikes, but few sills on my Geotripper Images website, and that's the thing: I don't have many pictures of sills.
As we came around the bend of the river, a black cliff came into view, a layer that ran parallel to the enclosing layers of Bass Limestone and Hotauta Conglomerate (these form the base of the Grand Canyon Supergroup). It was a basaltic sill of huge proportions. The precise name of the rock is diabase, which was a shallow intrusion that was neither extrusive in texture (fine-grained) or intrusive (coarse-grained). It's a grain-size in-betweener.

It was one more stunning sight in a canyon with many of them.

Soon after, the river re-entered exposures of the Granite Gorge Intrusive Suite, and the canyon narrowed. A lot. The walls of schist rose straight out of the river and soared for hundreds of feet. Just past Mile 135 we traveled through the narrowest gorge in the entire Grand Canyon, the Granite Narrows. It was only 76 feet wide. The river was over 100 feet deep!

It had been an incredible day, but the best part was just ahead. More on that in the next post!

Into the Great Unknown: Exploring the Heart of a Long-Gone Mountain Range (and words from home!)

 We were really out of touch. In the eight days we had been gone on the Colorado River (the Great Unknown), I sent one text from camp the first night (surprise, cellular coverage at mile 6!), and on the second or third night I had a two-minute conversation on the emergency satellite phone (we couldn't download a waiting message on the phone so we each checked on our loved ones; it turned out to be a "Welcome to Verizon" message or whatever satellite company it was). I had seen not a single sign of any sort since we left Lee's Ferry aside from some number markers on the Unkar Ruins trail. So the beginning of our day was a real culture shock. Less than a quarter mile from our camp at Cremation, a bridge came into view!

And what a bridge! For something like 400 miles, from Lee's Ferry to Pat Tilman Bridge and Hoover Dam not a single bridge crosses the Colorado River. How many rivers in the world in this day and age have that kind of a record? In any case, it was not a bridge for cars, but for hikers and mule trains. We had reached Grand Central Station of the Grand Canyon: Phantom Ranch.

Just how urbanized is Phantom Ranch? It has signs for one, like this one that greets boaters fresh off the river. And there are water spigots with treated water just 100 yards from the boat beach (our fresh water stores were becoming slim). And there were two dozen or more things called permanent "buildings", which apparently are used by other human beings for cooking, sleeping, showering, and even eliminating human waste! With flushing water! One of the most amazing contraptions I saw was a "pay telephone", an instrument I was able to use to contact the outside world for news. I was relieved to find that there had been no zombie apocalypse, and that life was more or less normal beyond the rim of the canyon.

And...there is green stuff all over the place, in spite of the 100+ degree temperatures that last all through the summer season. Cottonwood trees and grass and stuff. It turns out that Phantom Ranch was located along Bright Angel Creek, one of the larger tributary streams flowing into the Grand Canyon. Bright Angel Creek begins in earnest at Roaring Springs around 10 miles upstream. The water bursts out of the rock at the base of the Muav Limestone as an instant river. There is so much water that pumping stations were built so that the springs supply the water needs of the developments at both the North Rim and South Rim of Grand Canyon National Park: all the hotels, the campgrounds, the visitor centers, and the restrooms. And there is enough left over that the creek flows all year at the Ranch and supports a robust population of fish (eight native species originally and two introduced trout species that are being removed).

After talking on the phone, mailing postcards, and consuming both the most expensive and most refreshing iced lemonade I've ever had, we got back on the rafts and began the second half of our journey. A short distance downstream, just below the second footbridge, we met the new members of our party, and had lunch (salmon salad pitas).

We were deep within the Granite Gorge and not a whole lot of granite was to be seen. The cliffs were mostly composed of dark schist or gneiss. There were thin dikes and stringers of red and pink granite  and pegmatite here and there. But still, looking at the sheer walls coming straight down to the water, I could understand the apprehension of John Wesley Powell and his men as they ventured through this canyon in 1869. They were getting used to rapids by this point, but they had almost always been able to portage the boats around the worst rapids, or let them down the raging river by rope. Both of these methods were difficult at best, but with the sheer walls they were forced to run some rapids that they would have rather avoided.

 We were approaching our first class 9 rapid at Horn Creek. As we went in, I experienced one of the really big holes with a huge standing wave. We kind of shot right through it, meaning I was thoroughly and completely drenched.

It took awhile to dry off enough that I felt I could retrieve my camera from the dry bag, so my picture looking back at Horn Creek Rapid makes it look a great deal smaller than it actually is (below).

 Perhaps the comic I drew that night can provide some perspective...

We moved on downstream. It was a short day on the river, only five miles total, so we drifted with the current for awhile, passing gigantic towers of schist and granite. The peak in the picture below reminded me of Sentinel Rock in Yosemite Valley.

We passed an intriguing little island just before camp, with a tamarisk tree surviving somehow on a solid mass of schist and granite. This rock and the tree must surely be inundated during high water, and soil must be washed away on a continual basis. Then again, as of 1963 the flows of the river have been tightly controlled, with only a few floods (planned and unplanned) since then.

With the leisurely day, I had a chance to take some close up shots of the metamorphic rocks.

The forms are fascinating. As we noted in yesterday's post, these rocks are the deep crust remnants of a 1.7 billion year old mountain range that once extended from at least California (Death Valley area) to Mexico and perhaps Oklahoma and Arkansas. The mountains were pushed up as a result of the collisions between a series of island terranes and the core of the North American continent.

These rocks used to be mud and silt on the ocean floor, or volcanic rock like one sees in Japan or the Aleutian Islands. The rocks were crushed, buried, and heated nearly to the melting point, but not quite (different minerals melt at different temperatures, so part of the rock could have been molten, but not all of it). The rocks were twisted and folded like saltwater taffy, and later on they were intruded by hot masses of granitic magma, forming the pink rock in these pictures.

The granite has huge crystals of potassium feldspar (the pink/orange mineral), clear quartz, and plates or sheets of shiny muscovite mica. Such rocks are called pegmatites. Other beautiful minerals can sometimes be seen, including black biotite mica, and reddish brown garnet.

I was walking in a small unnamed canyon just upstream of Salt Creek (our camp was very creatively called "Above Salt Creek"). There was a small trickle of water.

The little bit of erosion has attacked the boundary between the schist and the granite, highlighting a fold in the schist.

My ankles were bothering me again, so there was no way I was going try to climb the jumble of boulders at the head of the canyon, but before I got there my attention was drawn to one of the strangest rocks I had seen in awhile. It was bright red.

Most of the time, geologists are pretty loose with their definition of the color red, using it to describe a lot of brown and reddish brown rocks and sediments. But this stuff was really red. It was essentially fine-grained, but may have had small phenocrysts (small crystals) of a white mineral, maybe feldspar. I couldn't tell, and to my shame I was caught in the wild without my handlens! It was fairly easy to weather, as you can see from the mineral veins that stand out in relief (this is material, probably calcium carbonate, that filled cracks and fissures in the rock much later).

I'm guessing it might have been some kind of metavolcanic rock, but really as a non-petrologist, I am not at all sure. Any ideas out there, gang?

The shadows grew longer in the dark canyon as the boatmen checked their rigs. Tomorrow was promising to be the most challenging day of the trip, with at least ten major rapids, including Granite (8), Hermit (8), and Crystal (9-10).

We were treated to a wonderful sunset. Once again I hit the sack early, just moments after sunset.