An Introduction to the Black Volcanic Heart of the Sonoran Desert
(See Sources Below)
El Pinacate y Gran Desierto de Altar, or just ‘El Pinacate’ for short, is a federally protected Biosphere Reserve, a UNESCO World Heritage Site, and a relatively undisturbed natural environment located just thirty miles from the US-Mexico Border in Mexico’s northernmost state of Sonora. It is also one of the most sacred sites for the O’odham people, including the Hia C’eḍ Oʼodham, or ‘People who live among the dunes,’ who inhabited this area for many millennia.
As a place of crucial spiritual significance for the Tohono O’odham, this area merits the protection and respect one would be expected to show at any of the world’s most sacred sites. The most recent residents, the Hi’a C’ed O’odham, and their ancestors inhabited the area within the Reserve for more than ten thousand years, possibly forty, according to the most contested dating methods of stone tools found embedded in the natural desert pavements. This means people were here during a time when the craters were full of water and the land was much less arid. The O’odham people in Arizona continue, to this day, a ceremonial pilgrimage on foot to the Pinacate, on which they would have traditionally collected precious salt and seashells – a form of currency. The volcano, Santa Clara Peak, remains central to O’odham cosmology, being the second home, along with Baboquivari Peak, of I’itoi, or “Elder Brother,” a major O’odham deity.
The Pinacate Biosphere comprises a semi-dormant ‘Shield Volcano,’ and the surrounding ‘Erg,’ or sea of dunes known as the Algodones Dune Complex or Gran Desierto de Altar in Spanish (Great Desert Shrine). More than two-thirds of the Gran Desierto is covered by sand, and this is North America’s only Erg, or dune sea of more than 125 km2 (48 sq mi). This aeolian, or wind-blown sand, is the product of millions of years of sandstone erosion by the Colorado River and comprises the sandstone that once filled the Grand Canyon. The nature of these fine sediments and prevailing winds create magnificent ‘Star Dunes,’ many more than 100 meters (330 ft) high, along with transverse or crescentic dunes to the East. The Biosphere Reserve extends from the US-MX border South to the edge of the northern Gulf of California (Sea of Cortez) and includes a portion of the coastline known as Bahia Adair, a critically important wetland habitat just south of the fishing community of El Golfo de Santa Clara.
The northern Gulf of California is famed for having a fraught conservation history, that involves local small-scale fisheries, industrial trawl fisheries for shrimp, exploitation by bad actors, and the saga of the world’s most endangered marine mammal, the vaquita, or Gulf harbor porpoise (Phocoena sinus), a story that has touched the entire world. Less than a dozen of these porpoises are thought to remain in their small habitat, which is now strung with a web of nets that have been illegally placed to catch another protected species, the Totoaba drumfish (Totoaba macdonaldi). Totoaba has been fished in this region since the 1920s when fishermen in dug-out canoes called Falujas followed them North to their spawning grounds at the Colorado River Delta, seeking the large fish for both their meat and an organ called the swim bladder.
Today, the drum’s meat is mostly wasted but the swim bladder, a false aphrodisiac – like most useless endangered species parts, is exported to a black market in Hong Kong and Taiwan. The “cocaine of the sea,” this bladder fishery has long been controlled by drug cartels from as far as Sinaloa, and despite the occasional large bust, not to mention millions spent on failed conservation plans, the nets and illegal drum fishery remain.
Many local fisherfolk have no alternative options, and they are often brutally extorted by the cartels. What is more, all of this violence is fueled by the US arms trade, known as the “river of steel” that flows freely across the border, and of course by the foreign consumption of illegal goods, from drugs to the prized swim bladders. Since the mid-1990s more than 400,000 Mexicans have died thanks to the bogus War on Drugs and related cartel activity, and small fishing communities continue to suffer under the violent hand of bad actors. This is partly why when one makes an argument for conservation in such circumstances, many will point to the need for prioritizing social causes, failing to realize that local people and their habitat are deeply interwoven into the same social, economic, and cultural fabric (See my blog on the northern Gulf).
A major milestone in the region’s conservation history was the joint protection of the El Pinacate Biosphere together with the Upper Gulf of California and Colorado River Delta Reserve, an adjoining protected area northwest. These ecologically interconnected biomes were finally protected in 1993, thanks to the support of diverse stakeholders, including the Mexican government, the Tohono O’odham Nation, and many people in the wider Tucson conservation community, including my supervisor at the Intercultural Center for the Study of Deserts and Oceans (CEDO), Peggy Turk Boyer, and the renowned Mexican ecologist Exequiel Ezcurra, a distinguished professor of plant sciences at the University of California, Riverside.
One can visit these unique protected areas, along with some of the protected Islands of the Gulf of California, with special permission from CONANP, the federal body that manages all of Mexico’s Natural Protected Areas, akin to our US National Parks Service. To enter the Reserve today, a separate fee is also paid to local “ejidetarios” or communal landholders whose Ejidos, or communal landholdings remnant from the Mexican Revolution, were grandfathered into the Reserve system. These families have long petitioned the government for more funding in return for not being able to use these arid lands for ranching, seemingly to little avail. Their protests have meant decades of closures, including to the state-of-the-art solar-powered Shuk Toak Visitor’s Center, and to the only approved route for visiting the dunes.
Photos by Caleb Trainor (Me contemplating El Trebol Crater with ravens above)
At the same time, cattle have been increasingly allowed to graze on the meager pickings, and footprints in the preciously ancient desert pavements that were absent a decade ago are now common. The primary campground is still absent a composting toilet, so one might say that recreational visits here are not so much encouraged as barely tolerated. This is somewhat paradoxical because an incredible amount of infrastructure has already been placed, including the beautiful Visitor’s Center, along with two more half-built visitor centers (go figure), not to mention major paved and dirt roads that allowed me to visit in my Nissan hatchback in 2010.
The Reserve also trains and certifies professional guides, including from the O’odham Nation, and there is excellent signage along the crater route. It is undeniable that if some of the many tourists who drive right by the Reserve on their way to Puerto Peñasco, or Rocky Point, mostly from Phoenix and Tucson, paid to enter the Reserve, which is truly a wonder of the world and much more beautiful than anything in and around Rocky Point, that funding for the area’s protection could begin to flow. At the same time, there are plenty of conservation advocates who prefer less impact overall, and who are not unsatisfied with having a paucity of people in a place that is meant to be wild. Conservation is about compromise, but that is a word more easily said than done.
Another major issue is the cutting-off of critical ecological connectivity, in other words, the movement of animals and water, by the infamous Border Wall, which was erected by bypassing every US environmental regulation under the guise of National Security. Indigenous graves, battlegrounds, and the region’s only ancient “fossil aquifers,” were blasted to erect the useless steel monument, which even proponents of strong border security have admitted does next to nothing to stop people from crossing the border. Instead of providing the direly needed legal infrastructure for processing immigrants, not to mention economic opportunities for people to work legally and in a mutually beneficial way, the US would prefer to arm the cartels and leave the world’s most vulnerable people at their mercy.
Of course, the cartels have no such mercy, and as even the fanatically Catholic Spaniards recognized, neither does the desert. Every year thousands perish on Biblical-like quests to find a better life, and the few non-government organizations trying to alleviate this death and suffering are criminalized by our elected leaders. As for the Border Patrol, they are so severely understaffed and underpaid that corruption is rife. During a recent wave of international migrants arriving at the border crossing in Sonoita, the Biden Administration simply shut down this major checkpoint, cutting off the economic lifeline for Puerto Peñasco, which is today almost entirely reliant on tourist dollars.
The subtropical climate of the Pinacate’s Sonoran Desert environment is much hotter than southern Arizona, with an average annual temperature range of 18°C (64°F) to 22°C (72°F), and maximum temperatures averaging 49°C (120°F) and peaking at 56.7°C (134°F) in June. In winter, nighttime temperatures can fall to -8.3°C (17°F), though this is a rare low. The highlands have somewhat lower temperatures than average and are slightly more humid, but in general solar radiation is intense, evaporation is high, and relative humidity is very low.
The average annual precipitation in the Pinacate is less than 200 mm, with most of this rain falling in winter monsoons. Despite being a hyper-arid environment, the area has some semi-permanent rain-fed waterholes known as Tinajas, that are formed in the lava and rocks and often last year-round due to bi-seasonal monsoon rainfall. These are crucial to the region’s animals, and once supported the Pinacate’s abundant human inhabitants, who would journey from one pool to the next via footpaths that are visible to this day.
The Pinacate is highly valued by the academic community, including by multinational ecologists, geologists, biologists, and archeologists working across borders to understand and bring recognition to the area’s unique flora, fauna, and human history. El Pinacate showcases a wide variety of geological and volcanic features. It is one of the few places in North America where one can see cinder cones, craters, inselbergs, and lava flows all in one place, as well as North America’s only erg, a vast dune ocean of a certain hectarage. What is more, the southern route from Tucson Arizona to the border town of Sonoita takes one through some of the most spectacular deserts of southwestern Arizona, with views of Kitt Peak, Baboquivari Peak, and Organ Pipe National Monument.
Coming from these lush green desert habitats to the moonscape of El Pinacate and witnessing the dramatic micro changes in floral and faunal communities across the northern Reserve is fascinating, especially to the eye of an ecologist. The variety of life and land is the result of this area being located at the confluence of the four Great North American Deserts; the Chihuahuan Desert to the East; and the Great Basin Desert and Mojave Desert to the northeast. With so many rare and endemic species, the Pinacate has some of the highest biodiversity found anywhere in the world.
Particularly famous among its flora are diverse species of cacti, including the giant saguaro, organ pipe, nopal, agave, yucca, senita, and teddy bear cholla, all growing in a variety of distinct communities and flourishing under the shade of the desert ironwood tree, ocotillo, chaparral, and saltbush; keystone engineers of these sunbaked sediments. The fiery yellow flowers of the brittlebush and creosote bush in summer, and the orange and purple wildflower blooms in Spring, along with the bright crimson cones of the ocotillo strike a beautiful contrast against the landscape’s dark obsidian floor, as do the feathers of the hummingbirds that float among them.
Among diverse fauna, the chuckwalla, desert iguana, flat-tailed horned lizard, peregrine falcon, Chihuahuan raven, golden eagle, Sonoran pronghorn, big horn sheep, ringtail, and lesser long-nose bat are some commonly sought by wildlife spotting enthusiasts, but there are many more critters among the Pinacate’s wealth of habitats, including its abundant caves and tunnels hidden within the lava flows. Among my personal favorites is the horned lizard, the Sonoran Desert iguana (Dipsosaurus dorsalis), which I have seen eating the berries of the creosote bush on the rim of El Elegante crater, and the zebra-tailed lizard (below).
The history of mankind here is evident in a wide array of archeological sites and artifacts, all of which are protected today. One can find the wares and paths of pre-historic peoples, including stone tools from the early Clovis Era, geoglyphs, petroglyphs, pottery, mortar holes used to grind foodstuffs, obsidian and stone arrowheads, historical artifacts from 20th-century Indigenous residents, items left behind by 17th-century colonial explorers like the Spaniard Melchior Diaz and Italian Jesuit Missionary, Father Eusebio Kino, and the leavings of cowboys, outlaws, miners, explorers, scientists, and astronauts who came on the scene in the 19th and 20th centuries.
Father Kino was likely the first Westerner to climb Santa Clara Peak on muleback, and it was from here that he was able to discern that the Gulf of California was indeed a Gulf and not a channel as previously considered and that Baja was thus a monumentally long peninsula, three times the length of Florida, and not an island. Kino and other missionaries failed to convert the Comcaac and other tough nomadic peoples of the coast and Pinacate, most of whom did not take to Mission life, and he had much more success in the more agricultural regions further North, such as where San Javier Mission was built on the banks of the Santa Cruz just outside of modern Tucson.
Among my favorite plants of the region, Pholisma sonorae, known locally as Camote, is a perennial herb that grows in the dunes, where it gets its water via stomata in its tiny leaves. Under the mushroom-like head with a ring of purple flowers, is a long fleshy root that can be up to six feet in length, and that was a crucial food source for Indigenous peoples. Absent chlorophyll, this plant’s underground stem attaches itself to the roots of desert shrubs like wild buckwheats, ragweeds, plucheas, and Tiquilias (images below), to steal their nutrients, and is thus a parasitic heterotroph.
Many of the Pinacate’s visitors across the ages traveled just North of the current-day Reserve, along the famed ‘Camino del Diablo,’ or ‘Devil’s Highway,’ which extends from Sonoita East towards Yuma – an ancient route leading to what was likely one of the continent’s densest meeting points for diverse Indigenous populations coming from both North and South. One pre-colonial eyewitness account of the once lush Yuma valley describes campfires burning as far as the eye can see.
Geologically, El Pinacate is what is known as a shield volcano, because from a bird’s eye view, it looks like a giant warrior’s shield. The dark areas are composed of extensive, hardened lava flows along with hard-packed, wind-swept, multi-layered sediments known as Desert Pavements. Santa Clara Peak is the highest peak in the reserve, with an elevation of 1,190m (3,904ft). The name El Pinacate, used to refer to this mountain in particular, comes from pinacatl, a Náhuatl (Central Mexican/Aztec) word for a black stink beetle that is endemic to the Sonoran Desert, and that you will no doubt come across leaving its little tracks among the endless star and crescent-shaped dunes (image below). The tallest volcano’s graceful summit looks much like the abdomen of this shiny black insect when it stands on its front legs in a defensive pose. In the O’odham language, the peak is simply called Schuk Toak, meaning “Black Mountain.”
The Pinacate’s now dormant volcanoes erupted sporadically for a period of about 4 million years, with the earliest eruptions taking place 15-12 million years ago, and again sometime from 10 to 1.5 million years ago. The most recent activity likely took place sometime between 7 – 11,000 years ago and was possibly witnessed by the area’s nomadic residents who have passed these experiences down through the generations via storytelling traditions. El Tecolote, perhaps the most pronounced lava flow, creates a stunning boundary wall where the molten magma cools and ceases flowing, becoming a frozen river of jagged rock known as an A’a type flow in the language of the Hawaiian people, possibly because that’s the sound one makes when walking over it. The other, smoother flows result from cooling at slower rates and these are known as Pahoehoe flows in the same tongue.
In addition to the lava flows and dunes, El Pinacate’s main attractions are twelve massive craters, eight of which are huge Maar, meaning “crater lake” in German, type craters. These are formed by rising magma super-heating underground aquifers and creating pockets of pressurized steam that eventually, and sometimes repeatedly, pop like a bubble, collapsing the ground above them while also ejecting steam-blasted clay and ash to form cones of tuff breccia, a pudding stone cemented by the heat of pyroclastic blasts and made up of colorful ash and older sedimentary rocks embedded into it.
The crater floors, once filled with water, are mostly flat, full of fine sediments, and host small groves of dryland trees such as mesquite, which thrives in these now-dry, ancient lakebeds, or playas (beaches). Some water still gathers at the center of these, during the rainy season, attracting big horn sheep, mountain lions, and other thirsty desert denizens.
Some craters I like to visit, with permission of CONANP, include, MacDougal, Trebol, Sykes, El Elegante, and Cerro Colorado. Each is unique in its depth, diameter, shape, and habitat, and it’s truly difficult to decide which crater is more beautiful and moving, each offering a different perspective, geomorphology, and host of unique communities of plant and animal life around and within.
Nonetheless, I hold a special place in my heart for Cerro Colorado, a tuff cone around a crater with steep walls that are 300ft high and home to birds of prey and ravens. In 2009 I stood on the edge of this crater while a massive earthquake caused rockslides all around me, and I was very close to becoming a victim of this seismic shrug. I also fell in love with a visit to this crater, which is magical when spring showers cause super blooms – colored bands of wildflowers decorating the surrounding playas as far as the eye can see. In 2010 I was fortunate to be able to bring a BBC film crew lunch and to help radio in a helicopter filming the purple, yellow, and pink super bloom rings like banded skirts around the volcanic features. I even helped find actors among the local fisherfolk willing to play pre-historic people and to walk the edge of the crater in bare feet. Sadly I have never seen the footage, but I did get to meet some esteemed videographers, working in the field for months at a time, including the man who famously filmed a horned lizard squirting a coyote in the face with blood from its eyes.
As I mentioned earlier, just South of El Pinacate, but still contained in the Reserve’s buffer zone, is Bahia Adair, a RAMSAR Convention on Wetland Conservation Site of International Significance. This hypersaline, or “negative estuary,” hosts an incredible array of coastal-marine life, including a wide array of resident and migratory seabirds and wading birds.
Perhaps the most abundant is the long-billed curlew, of which a friend counted 75 during our one-stop visit, and there are also a great number of sandpipers, herons, egrets, dowitchers, skimmers, and many more migratory bird species. Bahia Adair is also notable for its vast mud flats and the longest tidal flat on Earth, and its halophytic, or salt-tolerant, plant life, such as Distichlis palmeri, a saltwater marsh grass endemic to the northern Gulf and Islands. Another abundant local plant, Salicornia, a genus of succulent in the Amaranth family, shows promise both as a biofuel and as feed for livestock. These natural solutions should be explored, provided we do not sacrifice our natural habitats and Indigenous lands to develop them, however urgently needed they may be. The fragile northern Gulf is not the only place where these plants grow, and as a global solution to methane production and carbon storage, grassy wetlands can be a major ally, not least as significant carbon sinks. Many great ecologists have advocated for plants that love salt water as a game changer when it comes to mitigating climate change.
What is more, the organic matter from these plants and others is transported through the Bay’s long, winding tidal channels (below), which bring these nutrients out to sea, a foundation upon which the entire marine food web in the upper Gulf is built. Estuaries like Bahia Adair support around half of the Gulf’s fisheries, including blue crab, shrimp, and diverse fishes, and they are also crucial sponges for carbon gas and we must continue to protect them from development. The sheer amount of turban shells I saw there is a sign of their incredible productivity.
I hope you will have the courage to visit the Pinacate responsibly, and like the region’s great ecologists, whose names are found in the region’s modern maps, that you will take the time to sit and contemplate the nuances symbioses that have turned an environment of harshness and scarcity into one of beauty and abundance.
UNESCO Online Resources
CONANP Online Resources
SEMARNAT Online Resources
“Land of Black Volcanoes and White Sands, The Pinacate and Gran Desierto de Altar Biosphere Reserve,” Larry G. Marshall & Clark Blake, 2009
“The Devil’s Highway,” Luis Alberto Urrea, 2021
“The Sierra Pinacate,” Julian D. Hayden, 1998
Thank you to:
Sonoran Rovers LLC
Dr. Paul Dayton
Dr. Miguel Angel Grageda Garcia
The Intercultural Center for the Study of Deserts & Oceans (CEDO)
Credited photography by Caleb Trainor
Text & uncredited photography by Alan Ruiz Berman