Sunday, January 08, 2023

An Interesting and Scenic Maar Volcano near Santa Fe, New Mexico

I love Santa Fe, New Mexico. So when I got the opportunity to present a lecture on the Colorado River for Southwest Seminars, we took a few extra days to explore more of the area. My colleague, Kirt Kempter invited us along to see first hand the results of his pandemic project, making a detailed map of a maar volcano to the southwest of the city. These features form when magma interacts with groundwater to create a steam explosion, forming a shallow depression after the explosion. The depression can become filled with scoria (cinders) and lava flows, and sometimes a lava lake, which upon subsequent erosion can leave the post-maar volcanics standing in high relief. This is a difficult thing for beginners to understand since the maar formation creates a depression but the modern feature is a mountain (the infilling lavas are more resistant than the surrounding materials)

Santa Fe's historic Plaza is where the western terminus of the Santa Fe Trail is located. The wooden structure seen in the center of the Plaza here hides an obelisk and plinth that was erected in 1867 to commemorate the perpetuation of the Union after the Civil War. However, one side of the obelisk praised "The heroes who have fallen in the various battles with savage Indians in the territory of New Mexico." In 1974, the word "savage" was chiseled out by an unknown person. On October 12, 2020, the obelisk was toppled and the city began a community conversation on the future of the monument.

We always visit the small town of Chimayo where we buy our year's supply of red and green chile powder. The Virgil Store shown here had a For Sale in front of it - oh the horror!

At the Santuario de Chimayo.

On a nice sunny day, Kirt took us southwest of the city to the Diablo volcano, where he has completed a detailed study of its history and mode of formation. This is a view to the west looking downstream to Diablo Canyon, carved by the intermittent stream of Cañada Ancha.

Google Earth image of the Santa Fe area. The city and the Sangre de Cristo Mountains are on the right. The Cerros del Rio volcanic field and Diablo volcano are on the left. In all of my visits to Santa Fe I never explored to the southwest of the city. I had been east, north, south and west and was always curious about the hills to the southwest of the city. I have also been intrigued for why Santa Fe grew so far from the Rio Grande and on a relatively featureless alluvial plain at the foot of the mountains. I always wondered why the Camino Real diverged from the course of the river to climb onto the alluvium (there was a pueblo village here of some importance). Nevertheless, what existed between the city and river? I soon found out.

Close-up of the Google Earth image. The broad alluvial plain is carved into the Tesuque Formation and overlying Ancha Formation. Note that the Diablo volcano is partially bisected by Cañada Ancha - a big part of this story that will be revealed below!

Beginning our trek up to the top of the volcano, located in the Diablo Canyon Recreation Area. The location is popular with rock climbers who find the columnar joints in the walls of the gorge inviting.

Along the way, volcanic bombs were strewn over the ground, documenting a sub-aerial origin in this instance.

A view to the west of the Lengua del Diablo (Tongue of the Devil). Note the floor of Cañada Ancha on the far left and the Jemez Mountain and caldera on the horizon. The colorful rocks in the ridge of Lengua del Diablo are composed of tephra deposits from the maar explosion (the greenish, lower cliff formed by phreatomagmatic processes), capped with dark basaltic lava, scoria and ash (photo center) that was erupted after the formation of the maar. Note the vertical dike within the phreatomagmatic deposit. This dike episode actually fed the flows on the uppermost part of the cliff. Within the phreatomagmatic deposit a very large blocks of the Tesuque Formation that were also thrown outwards from the steam blast. One of these large, pink-colored clasts can be seen at the base of the green cliff and left of the dike (partially hidden by a small juniper tree. An amazing exposure!

A large dike (center) intrudes through older scoria layers.

Complex interplay of maar tephra (golden color) and post-maar scoria and dikes.

A close-up of the previous photo showing the dark basalt dikes intruding the older tephra (golden).

View to the west from the top of the maar toward the Jemez Mountains and Chicoma Peak. Cañada Ancha is seen in the floor of the valley.

Panoramic view with Kirt Kempter pointing out features.

Another view of the Lengua del Diablo. After spending a few hours looking at the internal features of the volcano, I became curious about its eruptive setting. Kirt had explained that the age of the Cerros del Rio volcanic field is mostly constrained between 2.7 and 2.4 Ma, straddling the time boundary between the Pliocene and Pleistocene. Kirt further explained that the sequence of events went from initial phreatomagmatic eruptions that created a maar depression, which gave way to scoria cone formation and subsequent fluid lava flows and the formation of a lava lake. In the back of my mind, I kept thinking, "Why are we so high above the surrounding terrain? The answer of course, is that 2.5 million years ago, top of the maar was the floor of the valley and erosion of Diablo Canyon had not yet commenced.  

And boy was this evident as we went to the lip of Diablo Canyon! Across Diablo Canyon and Cañada Ancha is a detached portion of a lava lake basalt that once filled the central maar. It has been separated from the foreground by incision of the stream. Thus, Diablo Canyon is approximately 2.5 Ma.
Close-up of the far-side mesa. Note the small rise on top of the mesa - this is composed of rounded cobbles and sand from Cañada Ancha when it was flowing on top of the lava lake. The stream had no idea that its course was on top of the edge of lava lake deposits and as it incised downward its course was not deflected away - superposition in action! How fortunate that these remnant cobbles are left on the high-standing mesa for this interpretation.

Diablo Canyon from the top looking southeast and upstream on the bed of Cañada Ancha. Spectacular.

Kirt with his dogs looking across the top of the maar volcano to the Sanger de Cristo Mountains.

Our group at the end of the hike - Helen, Kirt and John. Thank you Kirt for a great day and a wonderful field trip! Kirt will soon publish a paper on his work and I will add an addendum to this post when it is ready.

Sunday, January 01, 2023

2023 Has Arrived!

At Plateau Point, Grand Canyon, November 2021. Photo by Helen Ranney

A new year has dawned along with the realization that I have been remiss in keeping up with this blog. Blame it on the pandemic and its lack of travel, these uninspiring times, or whatever. I'm aware of it and not pleased either, especially when I look back at some of the detailed and lengthy posts I previously typed here (I simply will not post if there is nothing to say). And, I've also been contemplating what the next phase of this online blog might be? I think readers this new year (if any of you remain) will still see posts pertaining to my love of geology and travel. But I also anticipate more personal reflections. Let me explain.

While everyone seems to wish, hope, pray, and implore that this new year will be everything that the last few have not, for me it is something a bit more. 2023 marks the beginning of a long string of 50-year anniversaries for me that define the beginning my independent, adult life. For the next few years, being completely captive to my insatiable appreciation for the endless march of time, I will mark the the half-century anniversaries where I first took to some fantastic hitchhiking explorations across the continent, fell in love with river trips and backpacking, and living at and within the Grand Canyon.

What sparks this little introduction is my rather sudden awareness that it was the year 1973 - 50 years ago - that I took my first steps at being an adult, stepping away from my cherished place of origin in Southern California and began to explore the larger world that lay beyond the 'California Dream.' I've always been proud to be a native of California, where I could enjoy a childhood of outdoor explorations in the foothills of the San Gabriel Mountains and the last of the area's orange groves. Me and my brothers caught wild frogs and fed them to our pet snakes. We rode our bikes across the entire width of our hometown and only came back in time for dinner. As a freshman in high school, I found a nestling red-tailed hawk that had become separated from its nest and raised it to adulthood. I was a child of nature in a burgeoning urban wave.

But by the time I graduated from high school, urban California had lost its charm. So, in 1973 I set out on the first of some really great adventures. I hope to share these stories with you beginning this year.

Thank you for hanging in there with me. And if this is not the reason you come here to this blog, I understand and will not be offended if you leave. But maybe this is the beginning of the story of my life.

Wednesday, October 26, 2022

The Montevideo Inscription in Grand Canyon

On November 30, 2010, I posted a piece about an inscription found near the South Bass Trail in Grand Canyon. It is in a neatly ornamented style with the word "Montevideo." You can view that posting here and the story that goes with it. A few days later, I posted an addendum and that can be viewed here.

Recently, a friend of my wife visited the site and literally stumbled onto another adjacent inscription that shows the year 1896. While this does not prove that the Montevideo inscription was left in the Wm. Wallace Bass era at Grand Canyon, it does show that Bass was leading people to this site at that time. I think the nearby inscription lends credence to the idea that Montevideo is more recent than the 1540s and from a member of he Cardenas party. The photos above and below are courtesy of Larry Kinser.

Sunday, October 16, 2022

An Autumn Hike in the San Juan Volcanic Field, Colorado

In early October, Helen and I journeyed to southwest Colorado and the San Juan Mountains near Ouray. We embarked on a five-day, four-night backpack along the Dallas Trail, traveling hut to hut. Thus, we carried no sleeping bags or tents to make the load lighter. The fall colors were at their peak and admittedly, this post is more about autumn than the San Juan Volcanic Field.

We had a group of seven and this is near the start of the hike.

Some of the route was along old logging roads.

This is our first hut, called North Pole hut. One of the peaks near here is called North Pole Peak. If you would like to know more about the hut experience you can view San Juan Huts here.

Each hut comes with a separate outhouse not far from the sleeping hut. These were very clean, modern, and well kept.

A view to the northeast toward the Cimarron Range of the San Juan Mountains. Ridgway Colorado sits in the valley of the Uncompahgre River in the valley below.

The Sneffels Range loomed large to our south as we made our way from west to east. An early season snow made the views dramatic against the changing aspens.

More Sneffels Range.

The average elevation of the hike was 10,000 and never deviated from between 11,000 and 9,500 feet.

A wild geranium also was in on the colorful show.

Most of the hike was through forests of aspen and conifer.

An early morning frost.

Finally, we reached Wilson Summit at 11,000 feet and were rewarded with a spectacular view!

Note the previously glaciated valleys in the distance as we took our lunch at the summit.

There was always a threat of rain during the five days (forecasted) but we managed to avoid precipitation.

In the Ridgway hut on night 3 planning the next days route.

An especially beautiful section of trail on day 4.

Aspens, aspens everywhere.

Burn Hut, our fourth and last hut.

Near Burn Hut.

Roots and aspen leaves vie for sunlight.

Approaching our final descent into the Uncompahgre Valley.

Across the way, the San Juan volcanics sit atop a basement of Paleozoic sedimentary rocks. We saw mining shacks at the contact of the two rock types.

Colorful descent - this time in. rocks!

As we descended below the San Juan volcanic rocks, the basement was composed of the Cutler Formation, a Pennsylvanian sandstone, shale and conglomerate that was shed off of the Ancestral Rocky Mountains.

A channel of very coarse conglomerate is set within floodplain mudstone and shale. A very good trip with great people and fantastic weather!

Tuesday, August 30, 2022

From the Erzgebirge to Potosi

I heard from Sean Daly, a mining geologist and author who has published a book called, "From the Erzgebirge to Potosi". He has written a poem that rests inside the front pages of the book and I include that poem here for your reading pleasure. The book looks very interesting for those who may want to better understand the development of mining and its boon to the development of society and civilization. You can visit his personal website here.