Home From the Back of Beyond: Some Images of Strange and Wonderful Places

Thunderstorm near Bandelier National Monument

No, it's not a volcanic eruption, but with the light show that followed that evening, it might as well have been. We were in the high desert of New Mexico at Bandelier National Monument, and the monsoons had arrived early. The lightning flashed every second or two for hours that night. It was magical.

Joshua Trees outside of Rainbow Basin, Mojave Desert of California

I'm back from a long, but epic journey with my students through one of the most intriguing landscapes in North America, the Colorado Plateau. We crossed the California deserts to Arizona and New Mexico, swinging north through southwestern Colorado and southern Utah. Our last few days brought us through the Basin and Range Province of western Utah and Nevada.

Banshee Canyon in Hole in the Wall, Mojave National Preserve

As with all trips, I try to do new things whenever I can, but the real purpose was to open a different world to our students. This class was a hybrid course that explored the geology and archaeology of the region. It's a marvelous region for doing such a class, as humans have impacted the landscape, and the landscape has left its mark on humans.

The Citadel ruin and San Francisco Peaks from Wupatki National Monument, Arizona

The land has seen a parade of cultures over the centuries. Understanding why they abandoned the region in the past has a lot to do with understanding the limits of life there today. Sometimes the problems are the same. The Ancestral Puebloans may have left because of 25 year drought. We are in the midst of a 15 year drought today, although we experienced a very short reprieve from the dryness. A lot of ran fell in the weeks before our arrival. The desert was unusually green for this time of year.

Meteor Crater was impressive as always, a reminder that sometimes situations on our planet change in a hurry.

The Crystal Forest at Petrified Forest National Park, Arizona

Some of our stops were familiar to most people, such as Petrified Forest National Park. People may have heard of it, but many haven't visited. It's a bizarre landscape of badlands topography and horizontal forests of trees that wouldn't be out of place in the Redwood forests of California, yet are more than 200 million years old.

The slot canyon at Kasha Katuwe Tent Rocks National Monument

Other places are exceedingly obscure, although they don't deserve to be. Kasha Katuwe Tent Rocks National Monument is one of those places. Unless you are from Cappadocia, Turkey, it is one of the most unusual landscapes you'll ever see. The slot canyon is one of my favorite hikes anywhere.

The greenery was really pretty stunning after fifteen years of crippling drought. The drought is not broken by any means, but the rainy conditions over the last few weeks allowed us to imagine this landscape under a different climate regime. At Chaco Culture National Historical Park, the rangers described the plant growth as the most intense they had ever seen. The elks wandering near the campground were looking downright fat (of course the doe was probably about to drop a calf).

Chaco Canyon represented the height of the political power of the Ancestral Puebloans, in the period around 1150 AD. By the 1200s they were building the fortresses of the cliff-dwellings in Mesa Verde. It wasn't the culmination of their society, but the prelude to abandonment. Whatever the reason, the canyons fell silent around 1285. The people had migrated south and east into the Hopi mesas area and the riverlands of the Rio Grande in New Mexico.

Cliff Palace in Mesa Verde National Park, one of the largest of the cliff cities.

One of our stops was especially eerie. Castle Rock was one of the last of the Ancestral Pueblo dwellings to be constructed. It came to an end after only a decade or two with a massacre. Archaeologists discovered more than three dozen slaughtered people in the excavations.

Castle Rock, in Canyons of the Ancients National Monument

The last part of our trip went back to the geological aspects of the plateau country. Despite having visited the Natural Bridges National Monument nearly two dozen times over the years, this was the first time I was able to hike under Sipapu Bridge, probably the second largest natural bridge in the world. The opening is more than 200 feet high, and from the bottom, it is immense. Those are mature cottonwood trees in the picture below!

Sipapu Bridge in Natural Bridges National Monument

We made the very hot hike to Horseshoe Bend near Glen Canyon Dam on the Colorado River. An entrenched meander, the loop formed when the land rose, trapping a river in its floodplain pattern. The stunning cliffs are composed of the Navajo Sandstone, the remnants of a Jurassic-aged sand dune "sea" that once covered many western states.

Horseshoe Bend, near Glen Canyon Dam. The Colorado River runs clear because the dam has captured the silt that once gave the river its name. Algae is able to thrive in the clear water.

The culmination of the Navajo Sandstone is found at Zion National Park in southern Utah. The Virgin River has carved an incredibly deep slot canyon at the Narrows. In many places the river fills the entire valley floor, meaning a hike is a wet affair. I didn't hesitate!

So, I am home for a couple of days, and will try to pick up the pace with a few long-delayed blog entries. You can certainly expect more information from our last couple of trips in the plateau country as well! It's good to be home for a spell.

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.