Wednesday, February 20, 2019

Grand Canyon's 100th Anniversary Podcast by the Pew Charitable Trusts

In honor of the 100th Anniversary of the establishment of Grand Canyon National Park next week, the Pew Charitable Trusts asked me to be a contributor to their 15 minute podcast that pays tribute to this world-class landscape. The actual anniversary will be next Tuesday February 26. Please have a listen to the podcast here. The site also includes five of my photographs of the Grand Canyon.

I will be at Grand Canyon the rest of the week and presenting a paper at the 5th Grand Canyon History Symposium. My paper is entitled, Geology for the Proletariate: The Writing of Carving Grand Canyon and Ancient Landscapes of the Colorao Plateau. I am honored to take part in the celebration of Grand Canyon National Parks 100th Anniversary. It is mind-boggling to think that when I first saw the National Park it was only 54 years old.

Happy Anniversary Grand Canyon National Park!

Monday, February 04, 2019

Department of the Interior Web Site About Water Management and the Ongoing Drought Along the Colorado River

The Department of the Interior has established an interactive web site that allows users to better understand the seriousness of the current drought (since 1999) along the Colorado River drainage basin. Eleven distinct panels are expertly rendered and take viewers on a tour of the drainage basin and the stakeholders that increasingly "tug" on its water resources. You can access the web site here.

This graphic from panel #5 shows how the water supply in the river varies over time. Using your cursor, you can hover over the graphic for individual year values. In this screen-capture, I hovered over the low water year of 1977 to show that the river only carried 5.36 million acre feet (maf), compared to a 10-year running average of 13.57 maf.

In this graphic from panel #8, water supply is contrasted against the ever-increasing consumptive use. In this screen-capture, I chose the very first year that use outstripped supply - 1954. Water use in that year was 10.7 maf, but the river only carried 9.6 maf. Note how the red line is on a steady upward trajectory while water supply is highly variable.

Although the interactive graphs are the highlight of this site, it is also wonderfully designed with beautiful photographs. More importantly, it is an attempt by managers from the Department of the Interior and the Federal Government to begin to instill an awareness in all stakeholders about the current drought conditions. In addition, they hope that meaningful conversations about where we are headed as a society can begin and solutions can be addressed. Check it out!

Saturday, January 12, 2019

Hike Into A World of Navajo Sandstone

Of all the colorful layers of strata found on the Colorado Plateau, none is as well-known perhaps as the Navajo Sandstone. As one field report described it in exposures found in southeast Utah, the Navajo Sandstone "...usually crops out in a wide belt of rounded cliffs and picturesque domes." So many nature preserves in the Southwest were designated because of the tendency of this sandstone to erode into beautiful and wondrous shapes. Zion National Park comes to mind, as well as Capitol Reef, Canyonlands, Grand Staircase-Escalante, and more.

In December, I joined two friends who also love to explore this exposures in this layer of rock. We were in a little known part of the Navajo Indian Reservation.

We began our hike climbing through other layers of rock on our way to the Navajo Sandstone, barely seen in the background at the top of the photo. Here the claystones of the Chinle Formation (right) are overlain by the Moenave and Kayenta formations. All three are fluvial deposits from between 215 and 200 Ma (million years ago).

In the lowermost Moenave Formation, we observed some root casts, that radiate out from a likely trunk of a small tree. The casts are composed of limestone which replaced the organic matter in the roots.

As we climbed higher, we obtained a great view to the north and saw that all of the strata were tilted down to the east along a monocline. These features formed on the Colorado Plateau during the Laramide orogeny or mountain building event (the same event that caused the initial uplift of the modern Rockies and the partial uplift of the Colorado Plateau). As the shallow-dipping, eastward-moving Farallon plate tugged on the bottom of the crust here, friction between the two caused these kinks in the strata. It's important to remember that when the tilting was ongoing, the rocks shown here were still buried under about one to on-an-a-half miles of overlying rocks that are now eroded.

Once the top of the cliff was achieved, we could see the dipping of the strata dying out to the east.

In the far distance was the profile of eastern Grand Canyon with the South Rim seen as the flat plateau on the left and the North Rim on the right.

Scott and Tony begin heading into the outcrops.

Finally, we arrived on some outcrops of the Navajo Sandstone. This rock unit is interpreted as being deposited in giant sand dunes that were shaped by the wind. The cross-bedding here shows that the dunes were migrating (in this view) from left to right.

Once the sand grains have been lithified into rock and eroded, they take on fantastic shapes.

Note that the cross-bedding does not "disappear" upon becoming lithified - the original texture of the dune is preserved, although it may become a bit compacted. Loose sand has a maximum angle of reps of about 33 degrees but the maximum angle typically found in lithified sandstone is between 25 to 29 degrees due to compaction.

In an overhang, we encountered a crude petroglyph of a Navajo horseman.

Note how each distinct set of cross-beds are all oriented in the same direction. This documents the regional wind pattern at the time of deposition - about 190 Ma. Today this direction is south or southeast but in the Early Jurassic, it might have been a bit different since the North American continent was slightly askew from its present position.

As we ventured farther "inland" the shapes became more pronounced as pinnacles and spires.

Note Tony walking on the cross-beds for scale.

Large water pockets were seen and in the early morning there was a thin sheet of ice on them.

Scott admires a gigantic set of cross-beds.

The small-scale structures within the outcrops reveals many intimate details about the accumulation of sand here. First, note that there are two sets of cross-beds separated by a semi-horizontal line. The cross-beds below are older and were planed off before the second set can in and buried them. The horizontal break is called a bounding surface and may represent the former position of the water table within the dune.

A closer view reveals even more detail. Note the two especially dark wedge-shaped sand beds. These contain larger grain sizes and are interpreted to be where sand avalanched down from the crest. If you've ever played on modern sand dunes, you will recall that avalanching is a common occurrence on sand dunes. Note that the avalanche beds pinch out as they approach the horizontal. For these reasons, these structures are called sand flow toes. The lighter colored beds separating these are where gentle winds deposited finer-grained sand and are called climbing translatent strata. Amazing preservation of detail here!

A much closer look at gravity deposited sand flow toes (dark) and wind deposited climbing translucent strata. Please have a look at this web site with descriptions of eolian terminology and fantastic animations of the processes that create them.

Another fantastic find was the concentration of iron-cemented sandstone clasts in dry water pockets.

Before the Navajo Sandstone was exposed to erosion here, fluids moved through the sandstone and mobilized iron in solutions. Certain chemical environments in these fluids would cause them to place the iron into solution. As the iron-rich fluids flowed elsewhere, a change in the chemistry would cause the iron to fall out of solution to concentrate within discrete beds. Then, upon erosion, the iron-rich sandstone weather into clasts and due to its increased weight cannot migrate too far and become concentrated in these "pools."

More water pockets in the sandstone.

The seasonal light was perfect for accentuating the cross-bedding. In the summer, this would just be flat-looking, without low angle shadows.

"Waves" of cloud crashing across the sky to the south.

"Waves" of cross-bedding crashing within a small gorge.

There was one tricky part getting out of here. One can become "rimrocked" in this kind of terrane very easily. I was glad to had Scott and Tony as my guide in here.

More evidence that we were not the first ones here, although there are very few people who come into this unknown place.

Afternoon light and clouds. What a day! What a place!

Monday, December 31, 2018

A Six-Day Mule Trip to the World Heritage Cave Paintings in the Sierra San Francisco, Baja California, Mexico - Day 6

What a trip! This phrase can be used in many different ways and when I typed it, I meant to speak to the excursion to the cave paintings we were about to complete. But after I typed "What a trip," I thought of that other usage as in what an unreal, unbelievable experience! What a trip! We signed on for a trip to the World Heritage Baja cave paintings that was mule supported. But what we got was a mule adventure that, oh yeah, visited some cave paintings as well.

Leaving the canyon involved riding in the bed of Arroyo Santa Teresa. Again, how the mules were able to maintain their footing in such a place was astounding.

Along the way, the boulders became even larger. There was a trail of sorts where they had trod before but once a big flood comes down and rearranges the bed, then it is destroyed.

Near the Rancho Santa Teresa, we entered an area that looked like it might have previously been a parasitic cone during an earlier phase of volcano construction. This area was rich in red pyroclastic cinders and dikes also permeated to rock walls as seen here. The overlying ash flows did not appear deformed (background) so my field interpretation is that before those flows were emplaced, a flank volcano off to the side of the central vent was located here. This flank volcano then became engulfed by the ash flows at a later time. More recent incision into the volcanic pile has reexposed the old parasitic cone. Dynamic geology at its best.

Rancho Santa Teresa is, like many of the ranchos here, a goat farm and we saw the rancheras milking the goats, as they do every morning.  We also sampled the delicious goat cheese that they trade for other needed goods.

A Side Trip Down Memory Lane

I was very keen to visit Rancho Santa Teresa because of a memorable incident that occurred here on my 1992 trip. While hiking down those 27 years ago, my friend Norm, the camp chef, and myself became separated from the group and the burros in the late afternoon. As the daylight quickly faded, we missed the trail and with only our daypacks we were forced to bivouac without food or camping gear. I had remembered the rancho a mile back further up in the canyon and in the dark we made our way there. In my poor Spanish at the time, I was able to relay our predicament to the rancheras. They guided us to an out-building where there were two rawhide supported beds with blankets. An anonymous arm placed a bowl of oranges and a pitcher of water on a nearby table. We spent the night here much as the Californio's have been doing for the last 320 years. In the morning, after leaving some peso's for their kind acceptance of these crazy gringos, we found our way downstream to our group. They barely noticed we were missing.

I had told this story to Fernando and he relayed it to it vaqueros on our current trip. They all thought it was worthy enough to ask the rancheras if they remembered such an incident 27 years prior. As they were busy milking goats, they barely looked at our group. Finally, one of the older ladies looked at up and replied, "No." That was it - my most memorable event from the 1992 trip hadn't registered at all with the locals. Although I did wonder after we left if their idea to develop a campsite at the rancho came about after our memorable night there. I could imagine them saying, "You know that's the fourth time some gringo's have gotten lost and asked to stay here. Maybe we should "invite" them to stay here." We did also learn however, that this family is especially private, with two twin relatives living farther up in a side canyon in a cave with little outside contact. Oh the stories that could be told down here!

Back to the Ride Out

The climb out was steep with another area requiring dismounting. But the scenery became grand.

This is the view back down to the Rancho Santa Teresa, located along the main drainage just out of view on the left. The canyon is very wide here and I suspect this is so because once the stream began to incise into the remnants of the parasitic cone, these rocks were softer than the others and began to crumble away more rapidly. This field interpretation is at least plausible.

Riding out toward Rancho Guadalupe.

All throughout the trip I had been recharging my iPhone camera with a Mophie device. Orlando also had a Mophie and had brought a solar charger. As the trip wore on, we all realized that we were advancing toward an"electron deficit." I was shooting with my last electrons as we neared the top. Note: I did not bring my larger camera because of the concerns in riding a mule. It turns out that I might have been able to make this work but changes lenses while underway would have been impossible. In the end, I think my iPhone did okay and at least I did not drop it to be stomped on my the hoof of a mule! But that exact fear was never far from my mind.

My last photo as we topped out! We enjoyed our last trail lunch right here on the rim of the canyon.

After getting a small electrical charge in our return vehicle, I turned back and snapped a shot of the central vent area of the San Francisco volcano. Even after 25 million years, it still retains much of its original shape, albeit with some very large canyons carved into its flanks.

When I returned home, I scanned this photo I took on December 31, 1991 as we approached the mountain back then. Back then, it was a dirt road into the range - now it is paved to within four miles of San Francisco de la Sierra.

Back in San Ignacio, a wonderful, quiet oasis in the desert.

The mission here was established in 1728 and is lovely in the ring light.

Mission fa├žade at sunrise.

Adjacent to the church is a museum that has reproductions of the cave paintings. One might imagine that they were this brightly colored when rendered.

Yes, a Happy Trip and thank you for your visit. The state line monument in the background at latitude 28 degrees north. Thank you for reading.

A Six-Day Mule Trip to the World Heritage Cave Paintings in the Sierra San Francisco, Baja California, Mexico - Days 4 and 5

After a good nights rest, we were at it again by 8 AM. Every morning Fernando our guide would give the call for coffee at 6:30. Then at 7:00 was breakfast and by 8:00 we would be in the saddle. I opted to take the morning trip but then stayed in camp when the afternoon trip went to Cueva San Julio. I had previously been in Arroyo Santa Teresa in early 1992 and had seen San Julio. And as this was a trip with very little down time, I wanted to have some time to myself. But in the morning...

We rode the mules back into a side canyon but when the going got too steep, we were required finish the climb on foot. One of the vaqueros had to cut vegetation away from the tail with his machete. This signaled to us that this next alcove was not regularly visited. Overnight or two-night trips into Arroyo Santa Teresa are not all that uncommon these days but that gives only enough time to see a few of the alcoves. Our trip allowed for more thorough investigations.

Orlando is a professional botanist of some note in Alta California and the smile on his face gives away the delight he had in seeing the fecundity of the super bloom from hurricanes Rosa and Sergio, just three weeks and five weeks before our arrival. It truly was an amazing display that might only experienced every decade or so.

We finally arrived at Cacariso, tucked into a side canyon off of Arroyo Santa Teresa. The slope that we descended on mules the previous day can be sen on the far left.

At little-known and little-visited Cacariso alcoves viewed a a very nice set of rock art elements.

Note the "pallet" upon which the rock art is placed - a course-grained ignimbrite. You can read about ignimbrite here but generally these are fiery hot ash flows with suspended particles of any size that flow away from a volcanic eruption at very high rates of speed, in events known as pyroclastic flows. The two included links with this photo will give the reader much information about how the rocks of the Sierra San Francisco were formed.

At nearly all of the rock art sites, some elements seemed to have been placed purposely at angles in the rock with part of the image on a roof and part on a wall. This photo gives a good example of this tendency. Most researchers think this holds meaning, but what it might be remains elusive.

Our next destination was to the only known petroglyph site in the range. This was only "discovered" about four years ago when a local vaquero was looking for goats.

This boulder is found on the floor of a small alcove and is of a much different rock type than the walls of the alcove. Therefore, the boulder likely originated as a clast within the finer-grained ash deposits here, but weathered out and fell to the floor of the alcove. The cave painters then chiseled numerous elements into it.

There are numerous geometric elements on the rock but curiously no animalmorphs, except for maybe the parallel lines on the right which may represent a turkey vulture (see the following descriptions below at Cueva Pintada). Our guide told us that the circles with lines through them (seen most readily on the left) might signify feminine vulvas, representing the creators desire for successful fertility within the group. Similar elements in the American Southwest are thought to represent the finger holes on an atlatl or spear throwing stick.

The beautiful Mexican blue palm growing on the floor of Santa Teresa Canyon near our camp. This ended our fourth day in the Sierra.

Day 5 saw us visiting some of the most important road arty sites in all of the Sierra. On our way, a young strangler fig (Ficus palmeri) is seen taking advantage of a bedding plane within the rocks. Note the small alcove behind the tree forming along the same bedding plane. The alcoves in this range have formed almost exclusively along such planes where groundwater finds easy access to the surface. As the water flows out, it weakens and erodes the upper layer and through time, the alcoves become larger.

This alcove-forming process is no better illustrated than in this wide-angle view of Cueva Pintada, thought to contain the largest collection of cave paintings in the entire range. Note the bedding plane that runs along the floor of the alcove and the arch-like erosion to create the alcove in the cliff above.

When I visited this area in 1992, there was no infrastructure whatsoever in these caves. But the following year, 1993, UNESCO (the United National Educational, Scientific and Cultural Organization) declared the area to be a World Heritage Site. Due to the increased awareness and visitation that followed, and the desire to protect the paintings, suspended walkways were installed in the following year, 1994. Here you see Fernando leading us into Cueva Pintada on such a walkway. Day 5 was a non-mule day.

What a sight to behold! An obvious black deer looks to be placed on top of a less obvious deer that is facing in the opposite direction. Just above Orlando's head are depictions of birds, likely turkey vultures or eagles that still soar above the canyons. Faint anthromomorphs can also be identified.

A closer view of the same panel. The obvious hole in the face of the rock was certainly present when the art was being made, as some of the paint can be seen coating the edges of the depression.

A closer view of the bird forms on the rock face.

Numerous fainter forms can be seen as well.

This is an interesting set of elements. Perhaps most obvious is the deer with its large ears near the top. Superimposed over it (or is it under it?) a land tortoise with its four limbs and digits clearly visible. It body is depicted as concentric circles over the body of the deer. The following elements have been identified at the more than 400 cave sites within the protected area: rabbit, puma, lynx, deer, Bighorn sheep, whale, turtle, tuna, sardine, octopus, eagle, turkey vulture and pelican.

By now we had become familiar with the major motifs displayed in the Sierra San Francisco. If you have the time, please read the citation recommending the inclusion of this area as a UNESCO World Heritage Site. I can also recommend watching this three-minute video created  by UNESCO of the features of the area here.

A last look at remarkable anthropomorphs in Cueva Pintada.

Our Mexican vaqueros and guides take a break while we visit Cueva Pintada.

Across the arroyo, is another alcove named La Flecha. We will visit there in the afternoon.

But first, we need to scale a cliff to access Cueva La Soledad. There were good hand and toe holds so it was no problem for those in our group. But we could tell that not all of the clients these guides take on this excursion were as nimble.

This is Arroyo Soledad. If you have been reading these postings from the start, you may recall that on day 1 we looked into this gorge from above as we made our way from right to left toward San Gregorio. Note that the floor of this canyon is filled with the Mexican blue palm.

Approaching the alcove through the ocotillo and elephant trees.

I've only included one image from this cave but there were many worth photographing. Here a deer seems to be pierced with an arrow or spear.

Another view of Soledad Canyon.

At the junction with Santa Teresa Canyon are numerous large and deep pools of clear water.

Another pool, another temptation.

This is the small spring where our guides obtained our drinking water for three nights and eleven people. The spring is located about 1/3 of mile upstream from our camp and once a day a vaquero would hike up here and fill a 30 liter can with fresh water. A reed has been split in half to provide an easy funnel system.

Beautiful Arroyo Santa Teresa and its palm trees.

Cueva La Flecha (Arrow Cave).

 An elegant Bighorn sheep is superimposed over anthropomorphs in La Flecha.

Note the head dress on these anthropomorphs.

These are some of the best anthropomorphs and deer seen on the whole trip. This ended day 5 on our trip. We went back to camp and prepared for our exit the next day.