Resilient Land With a Powerful Past – Valles Caldera National Preserve

 We are made wise not by the recollection of our past, 

but by the responsibility for our future.

George Bernard Shaw

Rocky Mountain iris flowers, Valle Grande inside Valles Caldera

Valles Caldera or Jemez Caldera is a nearly 14-mile (22 km) wide volcanic caldera (cauldron-like hollow) surrounded by high peaks that once were the steep slopes of a series of craters that emitted hundreds of cubic yards of hot ash in the Jemez Mountains of northern New Mexico.  

I initially heard of it while visiting Bandelier since the water which feeds, and has sculped, that beautiful National Monument comes from Valles Caldera, about seventeen miles upstream from Bandelier.  Overall, this supervolcano had everything to do with why Bandelier exists today with its volcanic tuff canyon walls, its Pueblo people history, and its fascinating geology.  

First let’s simply explain the difference between a caldera and a crater.  A caldera is created by the inward collapse of a volcano. This is different from a crater which is formed by the outward explosion of rocks and other materials from a volcano (ex: Mount St. Helen, 1980). 

The Pajarito Plateau extends along the southeast border of Valles Caldera and connects to Bandelier.  The Pajarito Plateau is actually a layer of hardened volcanic ash, termed ‘tuff,’ approximately 900-feet deep, deposited 1.25 million years ago (MYA) from the last large Valles Caldera eruption.

Lower Bandelier tuff came from the Toledo Caldera eruption 
Upper Bandelier tuff came from the Valles Caldera eruption

Actually two major volcanic explosion events crafted the landscape of the Pajarito Plateau we see today: Toledo Caldera eruption (1.6 MYA) and Valles Caldera eruption (1.25 MYA).  Both eruptions released 300 cubic kilometers of magma.  After the Valles Caldera explosion, the surrounding plateau was actually completely flat! The canyons seen today are the result of over one million years of erosion!

Hot springs, streams, fumaroles, natural gas seeps and lava domes are found in this vast caldera, with a variety of igneous stone, from pumice to obsidian, bearing witness to an assortment of past volcanic activities as early as 40,000 years ago (El Cajete crater and Banco Bonito lava flow extrusion).

The highest point in the caldera is Redondo Peak (11,253’ – 3,430m), a resurgent lava dome located entirely within the caldera, towering some 2,500 feet above the valley floor.

Additionally in the caldera are several grass valleys, or valles (Spanish), the largest of which is Valle Grande (6 miles x 3 miles), the only one accessible by a paved road.

The caldera and surrounding volcanic structures are one of the most thoroughly studied caldera complexes in the United States. Research studies have covered the fundamental processes of magmatism, hydrothermal systems, and ore deposition. Nearly forty deep cores have been examined, resulting in extensive subsurface data.

NASA used the caldera in October to November 1964 and again in September 1966 to geologically train the Apollo Astronauts in recognizing volcanic features, such as ash flow tuffs, pumice air falls, and rhyolite domes. 

Sign at entrance of National Preserve 
Stages of eruption and formation

Landforms – Plate Tectonics: 

Geologists love this place. In 1964, evidence was found that helped confirm/prove the theory of plate tectonics, now a unifying principle of geology.  

Similarly aged rocks of Valles Caldera and ocean floor rocks were analyzed for their symmetrical stripes of alternating normal and reversed magnetic polarity.  Some of the young reversals of the earth's magnetic field found on the sea floor were also discovered in rocks at three of the tree-covered domes in the northern Valles Caldera: Cerro Abrigo (normal polarity), Santa Rosa I (transitional polarity), and San Luis (reverse polarity). The Valles caldera provided valuable information and confirmation of some fundamental plate tectonic concepts, especially seafloor spreading, leading to widespread acceptance of the theory that has unified the science of geology (Goff 2011).

Mountain biking at 8,800 feet by Ranch Foreman’s cabin (1918)

Historic cabin district
Also an excellent place to view high-elevation ecosystems

Too many Rocky Mountain elk eating the gramma grass of the preserve
Hunting permits are issued yearly to help curb population

Enjoy meandering through 400+ year old ponderosa pines, past ‘Wild West’ homes keeping an eye out for sharp obsidian on the road as you drive, bike, or hike.  Appreciate this beautiful landscape dotted with a very large elk population.  The caldera is also home to prairie dogs, bears, coyotes, cougars, wild turkeys, bald and golden eagles, and other migratory birds.

There are now approximately two thousand five hundred Rocky Mountain elk from the 100 brought in from Wyoming in the 1940-1960’s.  It is the largest population of elk in North America.  The preserve is well known for its legendary trophy bull elk.  A typical hunting season results in the culling of about 250 to 270 animals with a success rate running as high as seventy percent. 

Elk, turkey hunting and trout fishing are allowed as long as they do not jeopardize the site’s natural values.  

Three active calderas in USA

Extent of ash fall within more recent geology: 1.25 million years
There were much larger supervolcanoes earlier on
www.wallaceterrycjr.com

Valles Caldera is one of three active calderas in the United States. It encircles a field of volcanoes whose resurgent domes partition the caldera into five sections, or valles, which means valleys without trees in Spanish. Additionally, there is evidence for a ‘ring’ of approximately fifteen post-caldera lava dome and flow eruptions.  The series of small volcanic domes present around the outer edge of the caldera offer the viewer the opportunity to observe an entire volcanic dome at an easily interpretable scale. 

Valle Grande surrounded by various domes
From 2011 Nature article

It is one of the three ‘supervolcanoes’ in the (seven in the world) USA.  A supervolcano is capable of producing eruptions thousands of times larger than a normal volcano, dispersing magma and rocky particles over an area greater than 240 cubic miles (1,000 cubic km).  As a comparison, Mount Vesuvius produced 100,000 cubic yards of magma per second during the massive explosion that buried Pompeii in 79 CE.  If Mount Vesuvius had been a supervolcano, it would have produced 100 million cubic yards of magma per second.  Modern mankind has never witnessed the eruption of a supervolcano and might not survive it.  Thankfully these catastrophic extinction inducing eruptions, altering weather patterns for years and raining ash across vast areas, are very rare.

Comparison of volumes (BP, before present)
See how ‘trivial’ Mt St Helens was…
www.volcanohotspot.wordpress.com

Relief of Valles Caldera in Jemez Mountain
www.volcanohotspot.wordpress.com

The Valles Caldera is known as the ‘premiere example of a resurgent caldera’,
setting the global standard for study, identification,
and classification of these volcanic features everywhere

Domes above the fog within Valles Caldera National Preserve
www.seesandoval.org

The caldera has also been occasionally filled with water creating series of lakes with their own rich history preserved. The grass ‘meadow’ of the Valle Grande is due to the fact that it was a reoccurring lake bed in the last million years, and it is not particularly friendly nutrition-wise to trees.  The last time the lake had a significant extent was after the El Cajete pumice eruption, and probably lasted for 4,000 to 7,000 years (there have been smaller lakes during damp cool periods usually associated with glacial eras).

Today's beautiful and unique landscape is a testament to this tumultuous geologic history.  Despite of its benign appearance, magma lurks three miles beneath the surface.  Although the Jemez Mountain Volcanic Field will be active again in the future, it is mainly showing signs of exhaustion, and the likelihood of a future, large scale eruption is extremely small.

Before the federal government acquired the caldera in 2000, it had been in the hands of a ranching family for 140 years. Now that the land is public, the board of trustees who manages the preserve limits the number of visitors in order to protect the integrity of the landscape and ‘emphasize quality of experience over quantity of experiences,’ as written in their management principles.

Looking down into a treeless harvest-colored valley (valle)
Buttressed by a horizon of ponderosa and aspen covered domes

Standing in this sunken volcano, its last super-eruption 1.25 million years ago, it’s nearly unfathomable to realize that it was 300-600 times larger (depending how you calculate it) than Mt. St. Helens’ in 1980.  Valles Caldera is one of the world’s best examples of an intact volcanic caldera.  Ejected ash fell as far as Kansas, Utah, and Wyoming.  The science of large-scale explosive volcanism began with studies here.

After the collapse, new magma filled the chamber and caused the caldera floor to heave upward.  A central dome (Redondo Peak) surged.  Valles Caldera is a defining example of the caldera resurgence phenomenon, which researchers first identified here.  Resurgent calderas are the largest volcanic structures on Earth, ranging from 9 to 62 (15 to 100 km) miles in diameter.  They are the result of widespread collapse of vast magma chambers.  

Prehistoric use of the caldera by Native Americans included hunting all sizes of game, trapping small mammals and waterfowl, fishing, collecting an abundance of seeds, nuts, and berries, and gathering various plants for medicine and ceremonies. The signature resource for these indigenous peoples was obsidian. Native Americans gathered this high-quality volcanic glass at extensive quarries in and near the caldera to create spear points (some 11,000 years old), arrowheads, knives, and scrapers.

San Antonio Creek

Valles Caldera also chronicles the history of New Mexico’s enchantment and exploitation, from 19^th century land use after the Treaty of Guadalupe Hidalgo and sheep-grazing under the partido system (a livestock leasing system that allowed a few wealthy landowners to lease out livestock to tenant farmers to tend to the livestock), to subsequent cattle-grazing, timber-harvesting, and geothermal exploration. 

Beginning as a land grant in 1860, the caldera was held in private ownership by a series of four families for over 100 years until it was purchased by the federal government in 2000. Since then, extensive work has been made to restore the health of the ecosystem to improve wildlife habitat as well as the caldera’s role as a water catchment basin at the top of the watershed.

1941 barn, still standing
Historic cabin district

Past people prized the caldera’s obsidian for making knives, arrowheads, and spear points.  Obsidian (volcanic glass) from this area has been found at prehistoric sites in Nebraska, North Dakota, Texas, northern Mexico, and Mississippi.  Since we can trace obsidian to its volcanic origin, we know Valles Caldera was one of North America’s most culturally significant obsidian sources.  At the visitor center, I was told to be aware of the sharp obsidian at two points on the road – beware your tires may be punctured!

Rydberg’s Penstemon along the road

I enjoyed some leisurely high-altitude mountain biking on a washboard gravel road, appreciating and experiencing the landscape at a slow pace.  How else do you absorb 1.25 million years of history?  But now it was time to head out before dark.  

Gunnison’s prairie dogs were seen popping up out of their burrows everywhere near the park’s entrance while raptors hunt them overhead.  Squeaking alerts to each other as I drove by saying goodbye to this gorgeous lush montane grasslands, remember something I read from Thomas Wolfe, a while back: 

Some things will never change. Some things will always be the same. Lean down your ear upon the earth and listen… All things belonging to the earth will never change – the leaf, the blade, the flower, the wind that cries and sleeps and wakes again, the trees whose stiff arms clash and tremble in the dark, and the dust of lovers long since buried in the earth – all things proceeding from the earth to seasons, all things that lapse and change and come again upon the earth – these things will always be the same, for they come up from the earth that never changes, they go back into the earth that lasts forever. Only the earth endures, but it endures forever.

Thomas Wolfe, in You Can’t Go Home Again, 1940

Back home, monsoon season sky