|Rio Grande Gorge in northern New Mexico, USA. Courtesy BLM.|
In 2009 I took my first road trip through northern New Mexico and discovered that it is a wonderful place for geo-tripping. The geology is visible and scenic, the stories are fascinating, and it is easy to find information online. The New Mexico Bureau of Geology and Mineral Resources (NMBGMR) has put together a great Virtual Geologic Tour website, which was the basis for much of my planning. The Bureau of Land Management’s Outdoor Recreation website for the area also was helpful.
The state of New Mexico advertises itself as the Land of Enchantment, but it is also called The Volcanic State and that definitely was my impression. I toured a series of late Cenozoic volcanic fields (15 million years ago to present), all located near the Jemez Lineament, a zone of crustal weakness trending northeast - southwest across northern New Mexico, possibly an old (Precambrian) continental suture.
|Generalized tectonic and volcanic map of northern New Mexico. VF = volcanic field.|
My first stop was in the Taos Volcanic Field, at the Wild Rivers Recreation Area (BLM) in the Rio Grande Rift. The Rift runs north-south from southern Colorado through New Mexico and into Texas and Mexico. This is a zone of east-west extension and continental thinning between the Colorado Plateau to the west and the High Plains to the east.
The Rio Grande follows this broad valley created by rifting, and has cut spectacular gorges in basalt, including those at the Wild Rivers Recreation Area. I had planned to stay two nights but spent a week instead. There is great hiking and geology touring in the Recreation Area and in many places nearby.
From the Rio Grande Rift I headed west to the Colorado Plateau and stopped at El Malpais (“the bad country”) in the Zuni-Bandera Volcanic Field near Grants. The youngest lava flows of El Malpais are only 3000-5000 years old, and still show flow features such as pahoehoe lava, a-a lava and lava tubes. I explored the rugged flows, and did some neat hikes to cinder cones. Photo above and map below from NMBGMR Virtual Tours.
To the north of El Malpais is the Mount Taylor Volcanic Field. Mount Taylor itself is a classic composite volcano (alternating layers of ash and lava) and a great hike. From the summit one can look east to see Cabezon Peak and the Rio Puerco Volcanic Necks, another good field trip. Photo and cross-section from NMBGMR Virtual Tours.
My first geo-trip to northern New Mexico ended before I could get to even half of what I had planned. I’ve been back twice and still have things I want to see. And now the NMBGMR’s great online information has been expanded and compiled into a book: Geology of Northern New Mexico’s Parks, Monuments, and Public Lands.
The book includes 44 localities in the area from Interstate 40 north, all on public land, including National Parks and Monuments, State Parks, National Forest and Bureau of Land Management lands. It starts with an overview of the geology of New Mexico from Precambrian time to the present, followed by sites grouped by region -- Colorado Plateau, Southern Rocky Mountains, Great Plains, Rio Grande Rift and Valles Caldera. Each section has a discussion of the geology of that region and then detailed treatments of the sites of interest. Most include a generalized geological map overlain on a shaded relief base, often a cross-section, and other diagrams and photographs -- very well illustrated especially considering the modest price.
The goal of the book was to compile the wealth of information “buried” in the scientific literature in a format accessible to laypeople interested in geology:
“... we wanted to provide a compilation for the layperson of the basic geologic framework of each of these areas, paying particular attention to the rock that is exposed at the surface and the geologic features that are most conspicuous ... to present visitors with a summary of what we currently know about these places, in a format that is inviting and easy to understand.”Based on my experience the authors have done a terrific job in achieving their goal.
For those interested in more detail, an excellent complement is the New Mexico Geological Society’s The Geology of New Mexico: a geologic history (2004). This is a collection of technical papers “organized chronologically according to the major depositional and tectonic events in the history of the state.” The Table of Contents can be viewed here.
These books and others can be ordered at the NMBGMR website or by phone (575-835-5490).
The Geology of Northern New Mexico’s Parks, Monuments, and Public Lands. L. Greer Price, ed. 2010. New Mexico Bureau of Geology and Mineral Resources. $24.95 (paperback)
The Geology of New Mexico - A Geologic History. Greg H. Mack and Katheine A.Giles, eds. 2004. New Mexico Geological Society Special Volume - 11. $45.00 (hardcover)