Airliner Chronicles: Stuck on a Plane with a Proselytizer...

And really, I felt sorry for the poor guy who was stuck sitting with me on the plane flight from St. Louis to LAX. Oh, I wasn't trying to convert the poor guy into some religion. No, he got the full-court press from me about the importance of understanding what was going on 35,000 feet below us on the ground. He was being proselytized into the world of geology.

People who fly a lot for whatever region may be forgiven for not paying attention to the grand panorama unfolding below them, but to a geologist, the extra dimension is pure gold. Seeing a large swath of the Earth's surface grants a whole new perspective to understanding geological processes.

I didn't have a working GPS on the flight, so I had to guess our location for the first two hours of the flight, somewhere over Missouri, Oklahoma, or Texas. But it was unmistakable that we were over oil and gas country. The drilling rigs and their connecting roads could not be missed. Some politicians once described the "footprint" of oil and gas drilling on a landscape as just a few acres being torn up. Seeing the scene from above suggests that the footprint is "small" in the sense that a spider web is a few strings of dragline silk.

I was lost until the mesas and plateaus appeared. I knew at that point that we were in New Mexico, and I correctly figured out that we passed Sante Fe and Las Vegas, New Mexico. My seatmate, a Pittsburgh resident, got a bit confused about the Las Vegas part; "We're in Nevada already?". I crushed his hopes (that is NOT the way to proselytize, by the way).

The landscape turned into a rainbow of color, and I suddenly knew our precise location better than a GPS unit. We had reached the Painted Desert area of Petrified Forest National Park in Arizona. A plateau covered by basalt flows was breached by erosion, exposing the brightly colored layers of the Triassic Chinle Formation. The Triassic rocks reveal the beginnings of the dinosaur domination of our planet, and the floodplain and river deposits contain some of the earliest dinosaur species known. There is the wood, of course, and a stunning variety of amphibians and reptiles, including Phytosaurs, huge crocodile-shaped creatures that exceeded 30 feet in length.

Just west of Petrified Forest, I got the finest treat of the day, a perfect view of Meteor Crater. I put the best of the pictures up in yesterday's post.

A short time later, more colorful rocks came into view, but they were older than the Chinle of Petrified Forest. We had reached the Pennsylvanian and Permian rocks of the Supai Group. These rocks are the same ones exposed in the walls of the Grand Canyon, about eighty miles to the north. This is the edge of the Colorado Plateau, where the high flat landscape gives way to the deep fault valleys of the Basin and Range Province. Because the valleys are so deep, erosion eats away at the edge of the plateau, forming scenic deep gorges like Oak Creek Canyon, north of Sedona.

I was distracted by some wildfires burning in the thick forests of the plateau. I finally realized I was missing one of the more extraordinary features of the Colorado Plateau, the San Francisco Peaks Volcanic Field. The field is a vast basalt lava plain populated by hundreds of cinder cones, and an immense stratovolcano that reaches more than 12,000 feet in elevation, the highest point in all of Arizona. The edifice of the San Francisco Peaks has been altered somewhat by erosion; it was once 4,000 feet higher. It would have been the highest point in the lower 48 states.

The existence of the volcanic field is somewhat of an enigma. There's no obvious reason for it being here. There are suggestions that it is the result of an incipient hot spot, but the idea is not wholly accepted. The field is active; an eruption took place less than a thousand years ago.

Somewhere near the end of the flight, my poor beleaguered seatmate asked a geological question. He was wondering why there was a gigantic hole in the ground that wasn't a meteor impact crater. It was an open pit mine, probably for copper. I almost had a convert to the ages of rock!

Dreams of Summer: Living Under the Threat of Destruction at Wupatki

The San Francisco Peaks, a gigantic stratovolcano, rises beyond the ruins of the Citadel at Wupatki National Monument.

There is a huge difference between living close to the Earth without advanced technology and living in a highly technological society. Well, lots of differences actually, but today I'm thinking about living in ignorance of geological hazards. The thought arose because of our visit to the rather fantastic pueblos of Wupatki National Monument in the region east of Grand Canyon. There are lots of archaeological remains of the people who lived in the Colorado Plateau over the last 12,000 years, but few of them are as spectacular as the pueblos that were built between 1,100 and 1,285 AD. Many, maybe most, were fortresses. Some of these people seemed to be living in fear.

The Citadel ruin at Wupatki is built on the eroded remains of a basalt lava flow.

There has been a mountain of speculation about why the Ancestral Pueblo people and other cultures took such a defensive posture in their architecture. It is well known that most of the Colorado Plateau was abandoned in the late 13th century, and the hypotheses are numerous. There were a series of droughts, including a 25-year-long monster. These was evidence of warfare in a few places. Soils had washed away in many places. There could have been religious or cultural forces in place that caused migrations. It's an interesting issue that will keep archaeologists busy for a long time.

The view of the San Francisco Peaks from the top of the Citadel ruin.

Archaeology played a special part of our summer field studies journey across the Colorado Plateau. Half our students were majors in the subject (or possessed a lot of interest in the subject) who were learning geology. And our geologists were learning archaeology. I've been doing joint trips with our anthropology professors for a decade now, and we find a lot of common scientific ground as we travel through this fascinating landscape.

The hundred room pueblo at Wupatki

Wupatki National Monument preserves structures and sites of numerous ancient cultures, but the most visible were built by the Sinagua people, whose descendants still live in the region (the Hopi, Zuni,  Pima, Tohono O'odham, and Yavapai people). The region was a crossroads of sorts, and direct evidence suggests habitation as early as 500 AD. People lived at the site for 600 years, perhaps never suspecting that they were living on volcanic ground.

That changed in 1085 AD or so when Sunset Crater, a basaltic cinder cone, erupted, sending out lava flows, cinders and ash over a region totaling about 800 square miles (the longest lava flow was 6 miles long). Lava flows covered several villages.

It's possible that some cultural recognition of volcanism existed in the stories and traditions of the people who lived in the path of destruction, but maybe not. Can you imagine the impact of seeing a volcanic eruption in progress for the first time as a people? What kind of stories would be told explaining the phenomenon? Many of the old ruins are built on older volcanic deposits. Did the logical thinkers among the people recognize in a flash the origin of the ground and rock on which their homes were constructed?

In any case, the region was abandoned for a few decades, but settlers came back, finding that the ash had rejuvenated the soils. A gift of the gods? One wonders. They lived and built homes in the region for two more centuries before leaving the land for other places. Although the abandonment was part of a regional pattern, one can wonder if those two centuries included a healthy fear of the fires from down below in the crust?

Sunset Crater, the youngest volcano in the San Francisco Peaks Volcanic Field. It erupted about 1085 AD

The Sinagua people of Wupatki may or may not have known about volcanoes prior to 1085 AD, but in our highly technological society, we understand a great deal about volcanoes, and geology has provided us the tools to figure out the probabilities of future eruptions. Likewise, we are able to calculate to a reasonable degree the probabilities of earthquakes within given time frames (over a 30 year period, for instance). We can calculate flood probabilities before a particular storm arrives.  But that also means we live with a certain amount of fear. This is good in the sense of allowing the society to prepare. But fear can also be manipulated.

I can imagine a shaman or other kind of leader of the Sinagua threatening his or her people with the return of the legendary fire gods of the volcano to achieve some nefarious end. Can we imagine anyone who would be tempted to manipulate scientific knowledge into a fear of volcanoes (can you say "SUPERVOLCANO" nice and loud?) or earthquakes (can you say CASCADIA?) to achieve influence and power?

Source: http://www.cosmostv.org/2014/08/yellowstone-super-volcanoresent-rumors.html (actually, this is good article)

Nah, I'm sure no one would fan the flames of fear in modern society...the internet and other mass media has brought knowledge and wisdom to us all.

Dispatches from the Road: Cold White Volcanoes and Fiery Red Sunsets

Mostly a day on the highway, making the 400 mile long drive from Tucson to the Grand Canyon. Didn't stop for photos at all, really, except for the moment we crossed a snow covered meadow at the base of the San Francisco Peaks, Arizona's active volcanic field (the last eruption was only 900 or so years ago at Sunset Crater). The peaks reach nearly 13,000 feet, and Humphreys Peak is the highest point in Arizona. They once stood much higher. The stratovolcano lost its summit during a major eruption/avalanche similar to Mt. St. Helens, or from the much slower process of glacial erosion.

We arrived in Grand Canyon in the last moments of a beautiful sunset. The canyon was already falling into shadow, but the sky was on fire all around us.

 Getting some rest tonight, and looking forward to some sightseeing tomorrow!

Dispatches from the Road: Pictures I Missed Before

Nothing of great consequence, but I got some pictures on our holiday journey that I wished I had a few months ago. Our road took us through the San Francisco Peaks Volcanic Field, which I discussed in my series on the geologic history of the Colorado Plateau. I had a post on the volcanoes, but my photo archives revealed hardly any usable shots of the San Francisco Peaks (I borrowed some photos from the USGS). As we drove from Grand Canyon to Flagstaff on Highway 89, we passed the massive stratovolcano, topped by Humphreys Peak, which at 12,643 feet is the highest point in Arizona. The mountain, seen above, has a massive east-facing basin that may have formed in the same explosive manner as the crater at Mt. St. Helens. Prior to the destruction of the peak, it may have been the highest mountain in the contiguous United States, at something over 16,000 feet.

The meadow in the foreground lies along the entrance road to Sunset Crater National Monument, which preserves one of the youngest volcanic features in Arizona. A look east from the same meadow reveals Sunset Crater itself.

The crater erupted over a period from 1040 to 1100 A.D., and disrupted life for some of the Ancestral Pueblo/Sinagua people who lived in the area at the time. The monument is a marvelous place to see evidence of recent basaltic volcanism, and adjacent Wupatki National Monument is one of the most spectacular places to see evidence of the ancient Sinagua people.

Time Almost Not Beyond Imagining: Recent Volcanism on the Colorado Plateau

Top photo shows the San Francisco Peaks looming over the ancestral Sinagua ruins at Wupatki National Monument near Sunset Peak. Bottom diagram is a digital topographic map of the San Francisco Peaks Volcanic Field from the USGS Fact Sheet 017-01.

Six million years ago, the Colorado River was just beginning to carve the Grand Canyon. The rest of the Colorado Plateau had risen to thousands of feet above sea level, and was being vigorously eroded, but around the edges, other things were happening: the land was falling away, so to speak. The Basin and Range (and the related Rio Grande Rift) were being stretched, and in response the crust split into numerous fault blocks, some bobbing upwards into mountain ranges, and some blocks sinking to form deep basins (the deepest, such as Death Valley, eventually sank below sea level). Such stretching of the crust is a prelude to the breakup of the North American continent. The splitting of the continent is not an instantaneous process; it has been evolving over the last 20-25 million years as convergence was ending on the west coast of the continent, and the San Andreas fault system was slowly expanding.

The stretching and thinning of the crust released the pressure on the underlying mantle rocks, allowing them to partially melt and start rising through the overlying crust. The faults of the Basin and Range provided an easy avenue for magma to reach the surface, and so volcanism has played a prominent part of the landscape visible to us today on the Colorado Plateau. Recent lava flows and volcanoes can be seen in the Zion National Park area, especially near the towns of St. George and Hurricane, and at Mt. Taylor in New Mexico. But two areas of volcanic activity especially stand out: the San Francisco Peaks Volcanic Field in Arizona, and the Jemez Caldera in New Mexico.

The San Francisco Peaks Volcanic Field is an immense region (around 2,000 square miles) of lava flows and cones that is dominated by the edifice of the San Francisco Peaks, a huge stratovolcano reaching 12,633 feet above sea level. The volcanoes started erupting in the west side of the field about 6 million years ago, with later eruptions in a more eastward direction, culminating in the eruption of Sunset Crater just 1,000 years ago, making it the youngest volcanic feature in the state of Arizona. Humans witnessed (and suffered from) the eruption, since part of the flow covered an Anasazi village. The origin of the magma remains an enigma, but the eastward progress of the eruptions is suggestive of a hot spot, but this is by no means settled as an explanation.

The 600-plus cones in the volcanic field include all manner of cinder cones and lava domes, with compositions ranging from dark black basalt to light colored rhyolite. There is but a single stratovolcano, the San Francisco Peaks, but it dominates the landscape for many miles around. It is the prominent peak seen on the horizon from either rim of the Grand Canyon, and is one of the four sacred peaks of the Navajo people. The mountain grew during a period lasting from about a million years to 400,000 years ago.

There is a gigantic east-facing bowl forming the summit of the mountain. For a long time, geologists thought that it formed as a result of slow erosion of the summit of the mountain by way of streams, mass wasting and glaciation, but the eruption of Mt. St. Helens in 1980 gave them a new hypothesis: it may have formed from a giant explosion and subsequent collapse of the summit towards the east. Certainly a comparison of the summit regions of the two volcanoes lends support to the idea (photo of St. Helens by Garry Hayes, summit bowl of San Francisco Peaks courtey of the USGS).

Even more intriguing is the idea that we are looking at what may briefly have been the highest point in the lower 48 states and Hawaii. Projecting the lava flows along the broken edge of the summit ridges upwards produces a former volcanic summit that may have reached as high as 16,000 feet, about a quarter mile higher than Mt. Whitney in California.

Why I Love the North Rim

Seeing my students graduate is really great, but taking a person to a place like the Grand Canyon for the very first time is an even greater thrill for me as a teacher. We stay most years on the North Rim most years for a number of reasons.

The South Rim gets something like 90% of the visitation, which is reason enough to avoid it, but because more people are there, the rim has more trailheads, more facilities, museums and so on. The North Rim, in contrast, is around 1,000 feet higher, cooler, and more moist, and thus the forest is predominantly composed Ponderosa Pine (instead of pinon), and there are more meadows. One of the nicest aspects is the location of the group campground: it is only a few hundred feet from the rim (South Rim campgrounds are nearly a mile back). I prefer the views from the North Rim; the higher elevation offers a panorama of the landscape south of the rim, including the San Francisco Peaks volcanic field.

Today's picture is a morning shot looking south towards the San Francisco Peaks. I will have to leave it to others who know more about this kind of thing to explain why there is a gigantic composite volcano and associated volcanic field here. I imagine there is a sort of 'manhole' effect where lavas are leaking out from under the thick continental crust of the plateau country where it has been faulted by the current extensional regime, like a sewer system backing up. The high point on the rim, Humphrey's Peak is over 12,000 feet high (Arizona's highest mountain), but the original summit may have been several thousand feet higher. From the east, the complex looks surprisingly like Mt. St. Helens. The field is mostly Pleistocene, and at least one volcano erupted within the last 900 years (Sunset Peak National Monument).