Big Bend NP, TX 2013

     In July of 2013, I drove through the Big Bend National Park.  Big Bend National Park encompasses the largest protected area of the Chihuahuan Desert in the United States.  The 800,000-acre national park contains three basic habitats: river, desert, and mountains. The Rio Grande Wild and Scenic River forms its southern boundary, and it’s the only park in the United States that contains a complete mountain range – the Chisos.

Western Texas Area Map

Rocks of volcanic origin dominates much of the visual landscape in Big Bend National Park. The first of a series of volcanic eruptions occurred approximately 42 mya near the present northwest boundary of the park. Upward-moving magma lifted the area that is now the Christmas Mtns and resulting fractures of surface strata allowed lava to spread in great sheets across the land.

Big Bends sunken central block is bordered on the northeast and southwest by faulted , uplifted ranges. Several anticlines and faulted synclines ripple the surface of the sunken block. These structures appeared before alteration of the landscape by volcanic intrusions and activity, (image taken from “Pages of Stone: Geology of Western National Parks & Monuments #3, Chronic,1986).

Between 38 and 32 mya a series of volcanic eruptions occurred within the park. Initial activity began in the appropriately name Sierra Quemada, meaning “burned mountain range” in Spanish, located below and south of the present South Rim of the Chisos Mountains. Volcanic activity that followed in the areas of Pine Canyon, Burro Mesa, and Castolon gave rise to colorful volcanic ash and layered lavas in lower park elevations and for most of the mass of the Chisos Mountains.

     The Basin of the Chisos Mountains is part of a great rift valley that stretches from Colorado to Mexico.  The basin and its mountains sit in a sunken block in the rift, surrounded on either side by more mountains. 

Rift Valley Extension Cross-Section

      The result of this geological convolution is a land of contrasts, (of desert lowlands and moist mountain woodlands). But most of all it is a land of panoramic vistas.

Geologic map of the Big Bend National Park, Public Domain

     Once you reach the Big Bend National Park, the highlight the park is the Ross Maxwell Scenic Drive.  The Ross Maxwell Scenic Highway extends down the west side, between the Chisos Mountains and Burro Mesa through mostly volcanic terrain all the way to Santa Elena Canyon, where you find sedimentary rock in the form of limestone. About 30-40 million years ago, this region witnessed some of the most violent activity known to history.  In fact, many of the rugged mountains in the Chisos Mountains are actually the eroded remains of ancient remains of ancient volcanoes. 

Burro Mesa, (notice the volcanic dike that cuts across the foot of the mountain & foothills)

     Dikes arise from deep magma chambers.  Following paths of least resistance, molten material welled up into subterranean faults or fissures 17 million years ago.  All dikes, including Big Bend’s, cut across other beds of rock.  Softer surrounding rock weathered away, leaving igneous dikes silhouetted across the landscape.

The formation of a more resistant volcanic dike that forms a wall

Named for Ross A. Maxwell, a geologist and the Park’s first administrator, it is replete with remarkable views and even more remarkable geologic features.  Interesting geological phenomena can he seen from the road at several places. In the Chisos Formation, between the Chisos Mountains and the south end of Burro Mesa, are three dikes in the Three Dike Hill.  These appear as rock walls that stand above the surface and are traceable for miles. They are formed of rock similar to that exposed in Ward Mountain and probably came from the Ward Mountain intrusion.

Three Dike Hill on the Maxwell Scenic Drive in the Big Bend N.P.; Texas
Three Dike Hill

Beginning approximately 26 mya, the central area of Big Bend National Park was subjected to development of fracture zones as the continental plate that covers the western part of the U.S. was stretched between the west coast and a point east of the park. Large blocks making up much of the central mass of the park between the Sierra Del Carmens on the eat side of the park and Mesa de Anguila on the west dropped downward along active faults. Limestone layers at the base of both east and west ranges thus match layers found at the top of the mountains (Imaged below).

   Three Dike Hill, the Maxwell Scenic Drive follows the lower graben

     One of the most interesting geological features along the Maxwell highway is Goat Mountain.  In the north-western face of Goat Mountain, (pictured below) one can see the cross section of a former canyon that was cut into volcanic rocks (Chisos Formation) and later filled by younger lava (South Rim Formation).   A new theory, (pictured below), tells a tale of fiery explosions and massive volcanic domes.

Goat Mountain on the Maxwell Scenic Drive in the Big Bend NP 2013

     Pictured left below, an initial explosion created a crater with an older, layered volcanic rock. Possibly the explosion occurred when rising magma (molten rock beneath the Earth’s crust) came into contact with water trapped in the older lava, causing it to flash into steam.      

     Pictured center-left below, silica rich magma continued searching upward, causing repeated pyroclastic eruptions (a mixture of superheated gas, ash, and rock fragments). The flows partially filled the crater, informed a collar of steaming volcanic material around the vents.

Image taken from an interpretive sign in the park

     Pictured center-right above, over time, the gas content of the magma decreased, and the final eruptions produced thick slow, slow moving silica rich lava (magma that reaches the surface). The lava form thick domes that were higher than, and spread over, the crater walls. A dozen or so similar volcanic domes of dotted the landscape between Burro Mesa and Castolon.

     Pictured right above, about 27 million years ago, the region was uplifted and faulted and erosion began to shape the land we see today. The overlying silica rich lava was resistant to erosion and form steep, jointed cliffs.

     Farther on are Mule Ear Peaks (pictured below) formed by dikes that erosion has sculptured into the shape of a mule’s ears.

Mule Ear Peaks along the Maxwell Scenic Drive in the Big Bend NP; Texas 2013

        Pictured above, is of one of the most famous landmarks in the park. From a distance you would swear there was this gigantic animal crouching down behind a ridge with just his ears and the top of his head showing. The ears look very mule-like, hence the name “Mule Ear Peaks”. They are actually the eroded remnants of a pair of dikes.  The rock of these dikes is mapped as Wasp Spring, implying that these dikes used to be volcanic fissures that violently erupted at least some of the Wasp Spring member of the Burro Mesa Formation found in this area of the park.

Image taken from:

     Pictured below, Cerro Castellan – also known as Castolon Peak or Castellan Peak, is a conical volcanic mountain in West Texas that rises 330 m above the desert floor (1,100 m elevation) in Big Bend National Park. Cerro Castellan itself is part of an ancient series of summits once known as the Corazones Peaks that has since succumbed to millennia of erosion by wind, precipitation, searing heat and bitterly cold winters.

Cerro Castellan seen along the Maxwell Scenic Drive in the Big Bend N.P.; Texas

     Geologically, the Cerro Castellan is a remnant of a high stack of volcanic rocks, including ash, lava, and tuffaceous rocks. It is capped by a dense lava flow underlain by various tuffs and basalts. A somewhat northwest fault cuts the eastern face of Cerro Castellan.  Under the Burro Mesa Formation, pictured below, there is a time break, called an unconformity, during which erosion took place. It appears what you are looking at here is what is left of one side of a valley into which the Burro Mesa Formation was deposited. The unconformity may mark what used to be part of the valley floor. However, there may be another unconformity here within the Chisos Formation. Finally, note the talus (debris) from rock falls of the Burro Mesa Formation.

Image taken from:

The last 10 million years or so have been dominated by erosion sculpting the modern Big Bend landscape. As the highlands eroded, gravel and boulders formed a blanket of sediments around the base of the mountains. In the lowlands, sediments filled in the low places and erosion wore down the high places, forming a relatively flat, gently sloping surface called a pediment. Remnants of the pediment can be easily seen along park roads, for example, to the east of the Maverick Entrance Station.

      Although little vegetation grows on the sheer cliffs and steep, pointed profile of its peak, the lower slopes of Cerro Castellan support a sparse growth of Chihuahuan Desert scrub, including most prominently such characteristic species as creosote bush and ocotillo.

Santa Elena Canyon

     The view of Santa Elena Canyon (at the end of Maxwell Scenic Drive) is one of the most spectacular in the Park (pictured above). The Rio Grande, like a giant rasp, has cut through the massive Lower Cretaceous limestone layers in the mesa making a gorge, which in some places is not more than 10 m wide but which has sheer walls approximately 500 m high. The middle of the Rio Grande at the bottom of the canyon is the International Boundary between Mexico and the United States; Sierra Ponce (Mexico), on the left, Mesa de Anguila (United States), on the right.  Santa Elena Canyon is a prominent physical barrier between the United States and Mexico. The canyon is cut across an uplifted block of Lower Cretaceous limestone.

An Agave found on the way out of Big Bend National Park

     There are eleven species of agave in Texas, three of which are found in Big Bend National Park. Pictured on the right above, the gigantic Havard Agave (Agave havardiana) is one of the most visible icons in the Big Bend National Park.  It blooms once in its life after growing 20-50 years. Mexican long-nosed bats pollinate the bright yellow flowers. The leaves of the century plant have a blue-gray color. The century plant also provides an excellent source of fiber for ropes, mats, sandals, etc. The hearts of the plants were harvested by the Native Americans and then baked in a stone-lined pit for two to three days. Once baked, the plant provided a source of food that could be dried and stored to help them to survive the long winter. The dried flower stalks served as building material. Century plants in Mexico provide the alcoholic beverages of pulque, mescal, and tequila.

Lincoln’s Profile Mountain found north on Highway 67 between Presidio and the old mining town of Shafter on the Mexico and United States border.

     A permanent land art project by artists Elmgreen & Dragset. Modeled after a Prada boutique, the structure includes luxury goods from the fall 2005 collection.  However, the sculpture will never function as a place of commerce, the door cannot be opened. 


     Ballroom Marfa is a nonprofit space in Marfa, TX dedicated to contemporary area and culture.  This site was found at the most remote point in Texas, USA.

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