Deborah Painter (USA)
They have become associated with stark alien or other-dimensional landscapes since the 1960s, when the popular American television programme Star Trek used them as dramatic backdrops in two episodes, “Arena” and “Friday’s Child”. Prior to that, the Vasquez Rocks of Agua Dulce in California were a favoured location for American Western programmes, such as Branded, Cheyenne, Zorro and The Adventures of Champion, as well as motion pictures like One Million BC (1940) and Apache (1954), when rocky areas with hiding places, wide overlooks and an overall arid, rugged look were needed.
More recent films and television programmes tend to exploit their odd appearance (Star Trek IV: The Voyage Home (1986), Army of Darkness (1993) and John Carter (2012)). Some films with no fantasy elements also use the rocks as a backdrop, one example being the family “road” comedy, Little Miss Sunshine, released in 2006.
In fact, the Vasquez Rocks now have the distinction of being an overexposed outdoor location simply because of their proximity to the big city of Los Angeles’ filmmaking industry, hence their presence in scores of films, television programmes and music videos. Only about 64.5km from Los Angeles, the Vasquez Rocks are off State Highway 14, between Acton and Santa Clarita in California, USA and can be seen from Highway 14. The signs will direct the motorist to the exit that leads to the Vasquez Rocks Natural Area Park at 10700 Escondido Canyon Road, the Los Angeles county park where the rocks are located.
It is a down-to-earth place, illustrating plate tectonics in a vivid way. The Vasquez Rocks are approximately 4.5km from a continental strike-slip fault – the famous San Andreas Fault. State Highway 14 sports a sign indicating that one is driving over the fault, which is scarcely noticeable when the motorist crosses it at this location. Thus, the Vasquez Rocks are not located directly over the fault. Rather, the Elkhorn Fault, a secondary fault of the San Andreas, runs through the park.
The San Andreas Fault extends much of the length of the state of California and many of the areas it transects in this vicinity have similar, surface-exposed bedrock composed of sandstone and conglomerate. There are also a few inclusions of granitic boulders, which were present before the uplift began. Therefore, a very good question is: Why, then, do the Vasquez Rocks look the way they do?
The answer is that these strata form ridges that are sharply dipping away from the axis of a large anticline and all are pointing toward the northeast. Faulting then occurred and differential erosion is responsible for the features. The famous knife-shaped pinnacle is not the only ridge in the park. Illustrated here are many dozens of lower relief ridges, which have a less jagged overall shape (Fig. 8). Their individual shapes depend on how much wind and rain erosion, and chemical and physical weathering were present.
These lower relief ridges are composed of alluvial sands that became sandstone, and some take on the appearance of having been part of several gigantic pizzas, minus the sauce and toppings, made of rock and placed in angled stacks. When the climate was dry, the sandstone strata were thin, and when wetter, with flooding and the occasional landslide, the strata were thicker.
These famous rock formations are located in the Sierra Pelona Valley, included in the Santa Clarita Valley. The Sierra Pelonas and the San Gabriel Mountains are part of the greater Transverse Ranges that trend west to east across a large area of Southern California, north of Los Angeles. The Transverse Ranges represent a complex of tectonic forces stemming from the interaction of the Pacific Plate and the North American Plate, along the San Andreas Fault system. Their orientation is caused by a bend in the San Andreas Fault.
The crust that makes up the Transverse Ranges – the Salinian Block – was part of the North American Plate. It originated in what is now Mexico. During the mid-Quaternary, approximately 12 to 15 million years ago, the Gulf of California (Baja California) opened due to rifting, as the entire Pacific Plate moved north-westward. As the crust above the Pacific Plate south of the ranges has difficulty turning westward as this plate moves northwest, the crust compresses and rises in sections as it turns (see box: the plate tectonics of the Pacific Plate).
|The wonderful plate tectonics of the Pacific and North American Plates (Seiders and Cox, 1992)|
The wonderful history of this tectonic trek referred to in the text is chronicled in data collected and analysed by Victor M Seiders and Brett S Cox (1992) in their paper for the United States Geological Survey. They studied the stratigraphy, as well as clast composition (pebble counts and chemical analysis) of conglomerates and other clastics collected at more than 50 locations within and bordering the Salinian Block and selected areas within the Baja California. The data indicates a proto-San Andreas Fault that became active before the end of the Cretaceous Period.During early Tertiary times, the Salinian Block was an interior part of a magmatic arc that became exposed to the sea during the displacement. The granites observed at the Vasquez Rocks are a visual reminder of this late Palaeocene – early Eocene magmatic arc. The subduction zone that existed during early Tertiary time shallowed as the Tertiary progressed and gravel deposits in the area of the Transverse Ranges were fed by streams crossing this magmatic arc at its narrowest point. Movement of the Salinian Block northward continued through the Quaternary. Palaeomagnetic data furnished in 1980 and 1986 studies by BP Luyendyk, JS Hornaflus, MJ Kamerling and RR Terres suggests that the Salinian Block has undergone a clockwise rotation of approximately 90%.
The Sierra Pelonas are composed of a Precambrian Pelona schist that is overlain by an early Quaternary alluvium valley floor, overlain in turn by the Oligocene Vasquez Formation and the Mint Canyon Formation. The Lower Vasquez Formation is the oldest, with geologists estimating an age of approximately 25.6 to 23.6 million years, and a thickness of approximately 1,300m. The Vasquez Formation is approximately 5,800m thick and is approximately 20 million years old. The newest formation – the Mint Canyon Formation – is a mere 16 million years old and approximately 1,550m thick. Quaternary sediment sources for all these formations were the San Gabriel Mountains and Sierra Pelonas.
The first people to live in the Santa Clarita Valley were the Tataviam people. Now extinct as a distinct tribe, the Tataviam had limited success in growing crops here. Archaeological evidence includes bunks and grinding holes still in existence near the park. The Spanish arrived in 1789 while on a mapping expedition. The general area was afterward used primarily for ranching and is the location of several historic borax and gold mines. Tiburcio Vasquez, a brazen thief for whom the rocks were named, once was the subject of a five thousand dollar “Wanted: Dead or Alive” poster circulated around Southern California as part of the largest manhunt in Californian history.
The many clefts in the rocks in the park served him well as hiding places, but eventually he was arrested in 1877 and paraded around several streets in the small city of Los Angeles so the citizens could see him. So notorious was Vasquez that a playwright asked the sheriff in charge of him if the outlaw could be let out of his cell long enough to play himself onstage. Not long afterward, Vasquez was hanged for a murder in the town of Tres Pinos that he and his gang had invaded. Ironically, none of the fictional motion pictures or television shows featuring the rocks ever had this bandito as a featured subject. The only documentary on his life has not yet been completed, due to lack of funding.
Vasquez Rocks was privately owned for many decades and, beginning in the 1910s, the owners made it available to filmmakers. Its recent history includes a time when its future as a quiet and scenic locale was in doubt: a developer tried to buy it to construct condominiums nearby and naming the new neighbourhood “Moon Valley”. Very fortunately for the rest of the world, this did not happen. Los Angeles County acquired the area and established a 377.167-hectare park. In 2013, the Los Angeles Parks system completed construction of a visitor centre featuring geological displays and reptile exhibits. The visitor centre earned Platinum Certification by the United States Green Building Council in 2015.
The highest pinnacle is smooth but not slick and there are no loose rocks to cause slipping. The pinnacle affords enough friction for shoes and hands to climb without any special equipment. The day my friend, Michael Ramsey, and I visited, dozens of children and adults were making the relatively easy ascent up the slope to the peak, approximately 45.5m above the smooth parking area you see in Fig. 1. Mike climbed it twice in one afternoon and this is how he obtained such interesting and rarely photographed views.
The Park is open daily, unless a film-making crew is working in the area of the rocks. Contact the visitors centre at +1-661-268-0840 for further information.
About the author
Deborah Painter is an ecologist and general environmental scientist, specialising in transportation and industrial development planning to minimise deleterious environmental impacts. She lives in the United States.
Ballard, Michael. 2018. Brief Explanation of the Geology of the Santa Clarita Valley.
Boston, John, 2009. Santa Clarita Valley Images of America. Arcadia Publishing, 128 pages.
Brewer, Sara. 2016. Geology of Vasquez Rocks. SCVHistory.com.
Carreño, Ana Luisa and Judith Terry Smith. 2007. Stratigraphy and Correlation for the Ancient Gulf of California and Baja California Peninsula, Mexico. Issue 371 of Bulletins of American Paleontology 146 pages.
Hornaflus, J. S, B. P. Luyendyk, R. R. Terres, and M. J. Kamerling. 1986. Timing and extent of Neogene tectonic rotation in the western Transverse Ranges, California: Geological Society of America Bulletin v. 97, p. 1476-1487.
Luyendyk, B. P., M. J. Kamerling and R. R, Terres. 1980. Geometric model for the Neogene crustal rotation in Southern California. Geological Society of America Bulletin v. 91, p. 211-1217.
Seiders, V. M., and B. S. Cox. 1992. Place of Origin of the Salinian Block, California, as based on Clastic Composition of Upper Cretaceous and Lower Tertiary conglomerates. U. S. Geological Society Professional Paper 1526. United States Government Printing Office, Washington, D. C. 91 pages.