This blog is about hiking trips along the Valles Caldera Rim. For more information, see link for the Valles Caldera Rim Trail blog.

Saturday, May 30, 2009

Fraser Goff's Valles Caldera: A Geologic History

I appreciate Fraser Goff's book, Valles Caldera: A Geologic History. The book gives solid, science-based information on the creation of the Valles Caldera 1.25 million years ago as a result of the awakening of the Jemez Volcanic Field, at the intersection of the Rio Grande Rift and the Jemez Lineament. He gives reliable geologic dates for the creation of the Valles Caldera and the eruption between the resurgent dome and caldera wall of subsequent moat rhyolites, such as Cerro del Medio. (Quite interestingly, Goff says that Cerro del Medio, which erupted 1.23 million years ago as the first of the ten moat rhyolite complexes, may have been created in six different eruptions.)

Fraser's book, published May 2009, wasn't out when I posted a photo narrative on selected trail segments of the Valles Caldera Rim in late 2007 (see VCR Blog Archive, November 29-December 3, 2007). For geological dates, I relied on a publication of the New Mexico Geological Society, Geology of the Jemez Region II, Fall Field Conference, Volume 58, 2007 and any abstracts of geologic research papers that I could find online.

While I enjoyed immensely the opportunity to explore the Valles Caldera Rim, the fact remains that I'm no geologist. Frankly, unless it's painfully obvious, like a rockslide, I struggle with trying to understand the story behind the rocks and landforms I see. It's as though it is hidden from me albeit in plain view. Also, the geology research papers that I read, well, it's debatable how much I understand because of the technical language used. That's why it's such a delight to read Fraser Goff's Valles Caldera: A Geologic History because he intelligibly interprets the geological underpinnings of the landscape of the Valles Caldera yet doesn't over-simplify or over-whelm.

The beautifully designed book has 114 pages and 52 figures, including many attractive color photos taken by Fraser Goff, sketch maps, charts, etc.. The figures are plentiful and do a great deal to increase understanding. The book is information dense yet concise. Goff includes the most up to date geologic information on the Valles Caldera, including some of the research done since 2000 when the United States government purchased Baca Location No. 1 and it became the Valles Caldera National Preserve. A brief, helpful glossary of geologic terms used and a bibliography for those who want to read more is included.

Recent research highlighted in the book includes a study of South Mountain lake deposits in the Valle Grande that may help climate change researchers to better understand climate variability in the Southwest. Dating of the 2004 core sample of the lake deposits revealed that South Mountain Lake persisted in the Valle Grande for over 200,000 years and this period spanned "...two complete glacial-interglacial cycles in the late Quaternary."

Goff says that new geologic mapping of the four USGS topographic quadrangles that cover the Valles Caldera - Bland, Redondo Peak, Valle San Antonio,Valle Toledo - is being done and will be completed in 2009 or 2010. This was done at the behest of the Valles Caldera Trust, in cooperation with federal and state agencies. In addition to being useful to the Trust for planning purposes, the new geological mapping has revealed more information about lake history in the Valles Caldera. Goff outlines the various caldera lakes that existed over four periods, beginning immediately after collapse of the Valles Caldera 1.25 million years ago and up to the most recent, 55,000 years ago, a short-lived lake caused by the El Cajete pumice eruption that blocked the East Fork of the Jemez.

I haven't even begun to do this book justice. It's worth reading and rereading. Chapter titles like The Next Valles Eruption and Where Does the Magma Come From and Is There More? give an idea of just how intriguing the book is.

Basically, Goff's book, written by a retired Los Alamos National Lab geologist who is currently an adjunct professor in the Department of Earth and Planetary Sciences at the University of New Mexico, is an excellent source to find the most accurate, enlightening geologic information on the Valles Caldera, located in Valles Caldera National Preserve in northern New Mexico. To meet the man in person, sign up for a Valles Caldera National Preserve geology van tour, which Fraser gives, alongside his geologist wife, Cathy.

Under Acknowledgments, Goff thanks Robert Parmenter,Preserve Scientist, Dennis Trujillo, Preserve Manager, and "...other members of the Valles Caldera National Preserve for their support and funding on this project...". It's wonderful to have a book like Fraser Goff's Valles Caldera: A Geologic History that reveals some of the science that is taking place at the Valles Caldera National Preserve. The Valles Caldera Trust is to be commended for their role in helping Fraser Goff to bring this book to the public. It's especially valuable because it makes clear what a treasure we all have in the Valles Caldera National Preserve. Goff calls the Valles Caldera "...perhaps the world's best example of a resurgent caldera, a giant circular volcano with an uplifted central floor." The geological wonder of the Valles Caldera National Preserve rises far above any importance it may have as a mere cow pasture and working ranch.

Monday, May 18, 2009

Valles Caldera West Rim: Virgin Mesa Above Battleship Rock

This is FR (Forest Road) 607 (Santa Fe National Forest, Jemez Ranger District). It looks benignly flat where we parked to begin the hike but don't believe it. Dorothy's Honda CRV got quite a workout on a steeply downhill, wretchedly rutted, rocky stretch just before this. My gasps were no help; I suppose it was more helpful when I excitedly pointed out boulders that studded the road's side wall.

Dorothy's objective was to finish the Valles Caldera west rim by doing this last short section, all on national forest land, to an overlook of Battleship Rock from high up on Virgin Mesa. The views from the rim made me want to shout "Hallelujah!" I was grateful to get to tag along!

That tiny, insignificant peanut of a volcanic rock formation (looking like an alligator's snout) approximately 1,600' below the rim of Virgin Mesa is Battleship Rock, nearly 7,000' in elevation. Standing beneath it down below, it's a behemoth!

That's Cat Mesa in the background, the south rim of the Valles Caldera. The bulgy peak on the east horizon is Cerro del PiƱo, 9,030'. The East Fork of the Jemez River snakes around between Cat Mesa and Battleship Rock to conflue with San Antonio Creek, coming from La Cueva, and becomes the Jemez River flowing in San Diego Canyon.

I took a lot of photos of Lord Redondo, 11,254', (OK, I added the "Lord" but believe me, it does lord it over the entire Jemez Mountains!) but this one turned out the nicest.

By the end of the day, the clouds over Redondo were looking frankly monsoonal and we even heard distant thunder once or twice but saw no lightning nor even a single rain drop.

NM4 is down below as well as San Antonio Creek; a big apron of Banco Bonito lava flows forms the cliffs you see. I've always studied topo maps of this section of the Valles Caldera Rim where the south rim adjoins the west rim but admit I didn't truly understand it until today. The Banco Bonito lava flows, the youngest volcanic activity of the Valles Caldera, occurred between 45-35 thousand years ago and constrain where things are placed. San Antonio Creek, NM4 and the East Fork of the Jemez River all are forced to go around the Banco Bonito flow. It seems a jumble to me on a topo map but so startlingly clear when you are on top of Virgin Mesa looking down on it all.

View from lunch of Virgin Mesa cliffs - what a hard life! This can give an idea of why there is a discontinuity in following the Valles Caldera Rim at the southwest corner. It's difficult to hike up or down Virgin Mesa's lofty 8,600' heights without ropes and a belayer.

If anyone knows of a trail or route from Cerro Colorado, 7,789', on the south rim of the Valles Caldera (we'll even settle for Battleship Rock picnic area, 6,760'), up to the continuation of the west rim on Virgin Mesa, please let us know.

If you would like to hike to a viewpoint above these particular cliffs, please check out this great book by Joan and Gary Salzman, Hiking Adventures in Northern New Mexico. A hike called Virgin Mesa Road takes you out to above these cliffs.

Looking south toward beautiful Jemez Springs where Valles Caldera National Preserve Headquarters is located. Cat Mesa is on the left side of San Diego Canyon and Virgin Mesa on the right. Sierra Nacimiento Mountains are on the western horizon, above Virgin Mesa.

Dorothy hiking on way back to FR 607 on green gladed path.

To get here, from NM 4 at La Cueva, take NM126 and turn left on FR 376. Go to FR 604 and turn left. Don't forget to stop, near where the road makes a hairpin turn to the right, to look down on the awesome tent rocks above La Cueva. Go to FR 607 and turn left. When you get to any ruts, stop and park if you are squeamish. Walk on FR 607 to waypoint 1 which is where we parked. The abandoned road (last photo above) is about a half mile or less beyond waypoint 1, on the left.

Basically, we went up that abandoned road to a stock tank and then worked our way uphill, gently southeast, into and out of Virgin Canyon (easy to do) and over to waypoints 2 and 3 for the almost-aerial views. There's a lot more to be seen than I've taken photos of. We could even see the north rim (a pinch), San Antonio Mountain, Cerro Pelado, Los Griegos Mountain, Las Conchas Peak and South Mountain.

About Me

My photo
Los Alamos, New Mexico, United States