The Carrizo Plain (Obispeño: tšɨłkukunɨtš, "Place of the rabbits") is a large enclosed grassland plain, approximately long and up to across, in southeastern San Luis Obispo County, California, United States, about northwest of Los Angeles. The southern portion of the Carrizo Plain is within the Carrizo Plain National Monument, which also includes most of the Caliente Range. The Carrizo Plain is the largest single native grassland remaining in California. It includes Painted Rock in the Carrizo Plain Rock Art Discontiguous District, which is listed on the National Register of Historic Places. In 2012, it was further designated a National Historic Landmark for its archaeological value. The San Andreas Fault occurs along the eastern edge of the Carrizo Plain at the western base of the Temblor Range.
The plain is enclosed between the Temblor Range to the northeast and the Caliente Range to the southwest and drains inward to Soda Lake, a closed alkali basin with no outlet. The climate is semi-arid, with of rain a year falling mostly between November and April; in wet years the plain produces wildflower displays that draw visitors from across the state. Surveys of the monument have recorded 51 vegetation alliances, most of them shrub-dominated, with juniper and oak woodland on the surrounding slopes. The grassland supports species that have lost most of their range elsewhere in the San Joaquin Valley, among them the giant kangaroo rat, San Joaquin antelope squirrel and pronghorn.
The territories of the Chumash, Salinan and Yokuts peoples met on the plain, and the pictographs at Painted Rock, made over a span of some three thousand years, are among the most significant rock art in North America. Europeans settled from the 1860s, running wheat and cattle, but rising costs ended most farming by 1980 and the land passed to the federal government and The Nature Conservancy. President Bill Clinton proclaimed the national monument on January 12, 2001. Oil and gas leasing, solar development and grazing have all been contested on the plain since.
Geography
The Carrizo Plain extends northwest from the town of Maricopa, following the San Andreas Fault. Bordering the plain to the northeast is the Temblor Range, on the other side of which is California's Central Valley. Bordering the plain to the southwest is the Caliente Range. The community of California Valley is in the northern part of the plain. The average elevation of the plain is about . Soda Lake, a alkaline lake, is in the center of the plain with the popular Painted Rock containing Chumash and Yokuts rock art nearby. As the central depression in an enclosed basin, Soda Lake receives all of the runoff from both sides of the plain. At , Caliente Mountain, southwest of the plain, stands as the highest point in San Luis Obispo County. The climate type of the Carrizo Plain is semi-arid grassland, and annual rainfall is around . The valley floor is treeless; juniper, oak and riparian woodland occur on the surrounding slopes and canyons rather than on the plain itself.
The Carrizo Plain is an easily accessible place to see surface fractures of the San Andreas Fault; they are clearly visible along the eastern side of the plain, at the foot of the Temblor Range. They are best seen in early-morning and evening light, when shadows accentuate the topography. In addition to its spring wildflower displays,What you need to know about the ‘super bloom’ at Carrizo Plain National Monument – Los Angeles Times April 7, 2017 Carrizo Plain is also famous for Painted Rock, a sandstone alcove adorned with pictographs created by the Chumash people around 2000 BC.
Wallace Creek
Wallace Creek is a small stream that drains into Soda Lake and remains dry most of the year. It drains perpendicular to the San Andreas Fault, and the creek bed is currently offset by due to the movement of the fault. About of the displacement was created during the 1857 Fort Tejon earthquake. The current segment began forming 3,700 years ago. Sometime between 1540 and 1630 A.D., the creek was offset by about feet in an even larger earthquake.
Two other older creek beds lie northwest along the San Andreas Fault. The first creek bed was formed around 13,000 years ago, when climate change carved it into a large, active alluvial fan. The second bed was formed about 11,000 years ago. Sieh and Jahns measured an offset of about accumulated over roughly the past 3,400 years, giving the first slip rate determined along the San Andreas Fault; a later re-excavation of their trenches reproduced the rate within measurement uncertainty.
Geologists have carefully studied the creek to identify a correlation between the offset and historical events, such as earthquakes, along the San Andreas Fault. Although Wallace Creek is not the only creek that the San Andreas Fault has offset, it is the most spectacular.Santa Maria, Jed. "Stop 21: Wallace Creek" 3 Mar. 2008. <>
Access
State Route 166 passes the south entrance to the Carrizo Plain, and State Route 58 crosses through the northern portion. Connecting them is the narrow Soda Lake Road, the only dependable passable road through the plain. Still, even this may become impassable during or soon after a rain, since the middle portion is gravel.
Climate The plain has a semi-arid climate, with warm dry summers and cool wet winters. The Bureau of Land Management records average summer temperatures ranging from the low 50s °F at night to the upper 90s during the day, with daytime readings often above and a record high of . Winter averages run from highs in the mid 60s to lows in the mid 30s, and the record low is .
Rainfall on the valley floor averages between a year and falls mostly between November and April, with occasional snow. Totals vary widely from year to year, and the wet winters that produce the plain's wildflower displays are irregular.
Geology San Andreas Fault The most prominent geologic feature of the Carrizo Plain is the San Andreas Fault, which runs along the northeast side of the plain, at the base of the Elkhorn Scarp. The section of the fault in the Carrizo Plain is the oldest section along the entire fault zone.Matthews, V., 1973, The Pinnacles-Neenach correlation: a restriction for models of the origin of the Transverse Ranges and the big bend in the San Andreas Fault; Geological Society of America Bull., V. 84, p. 683-688 Displacement on the San Andreas is responsible for the development of distinctive features, including shutter ridges, diverted or decapitated stream channels, and sag ponds."The San Andreas Fault Zone in the Carrizo Plain, California: Review of Quaternary Geologic Investigations, Landforms, and Fault Activity" Arrowsmith, J R., 1995, Appendix C, Coupled tectonic deformation and geomorphic degradation along the San Andreas Fault System, PhD. Dissertation, Stanford University, pp. 312–346. 3 Mar. 2008. <>. One feature relating to the San Andreas Fault and aligned to it in the Carrizo Plain is the Dragon's Back pressure ridge.
Other faults The Big Spring Fault, the San Juan Fault, the Morales Fault, and the White Rock Fault are small faults that run parallel to the San Andreas Fault along the Caliente Range on the western boundary of the Carrizo Plain.
Soil taxonomy
The parent materials for soils in the Carrizo Plain are predominantly alluvium deposits. Alluvium is soil that has been deposited by rivers or flowing water. The Paso Robles formation is a Pleistocene-aged alluvium deposit that reaches up to thick near the San Andreas fault and thins out toward the north and west. The Paso Robles formation is a well-known aquifer that has been reliably productive for ground wells throughout the area. The upper layers of soil are more recent alluvium. This recent layer is thickest near Soda Lake and thins out toward the mountains to the east and west. Throughout the valley, the soil composition varies greatly and includes clay loams, silty clay loams, loams, sandy loams, and gravelly loams. The sandier soils tend to occur near the valley slopes and provide better drainage, while the soils with more clay are located on the valley floor near Soda Lake and have much poorer drainage. The soils in the Carrizo Plain have very low fertility because of their high alkalinity content and low rainfall due to the semi-arid climate.
Flora The plain carries a wide range of plant communities, from playas and alkali herbaceous flats through grassland and semi-desert scrub to shrubby hillsides and stands of woodland.
Between 2005 and 2010 the California Native Plant Society and the California Department of Fish and Game, with funding from the Bureau of Land Management, carried out baseline vegetation surveys across more than of the national monument. The work drew on 1,019 field surveys, 45 long-term monitoring plots and more than a thousand reconnaissance points, and produced a floristic classification of the area.
The survey identified 51 vegetation alliances in the monument, of which three were newly described and three provisional. More than thirty of them are shrub-dominated, among them several chaparral and semi-desert scrub types. Four are tree alliances, covering juniper and oak stands and riparian woodland, and thirteen are herbaceous, including wetland and perennial types together with the annual forblands and grasslands that produce the plain's wildflower displays.
Fauna
The Carrizo Plain is home to 13 species listed as endangered either by the state or federal government, the largest concentration of endangered species in California."Too Wild to Drill" The Wilderness Society. 3 Mar. 2008.<>. Some of these species include the San Joaquin kit fox, the San Joaquin antelope squirrel, the blunt-nosed leopard lizard, the giant kangaroo rat, greater and lesser sandhill cranes, and the California condor. The tule elk, pronghorn, black-tailed jackrabbit, western coyotes, and Le Conte's thrasher all also make their homes in the Carrizo Plain. The hotter climate and ecology of Carrizo Plain allows the Le Conte's thrasher of the Southwestern United States to have a small disjunct range farther north than normal. San Joaquin kit fox – a small nocturnal subspecies of the kit fox that was formerly common throughout the San Joaquin Valley but has recently become endangered. Blunt-nosed leopard lizard – a small, 3–5 inch gray to brown lizard with large dark spots and cream-colored cross bands. It has a broad, triangular-shaped head and is endemic to California. It inhabits the grasslands and alkali flats of the San Joaquin Valley and the surrounding foothills and valleys."Gambelia Sila – Blunt-nosed Leopard Lizard" CaliforniaHerps.com. 3 Mar. 2008.<>. Giant kangaroo rat – the largest of all kangaroo rats. The giant kangaroo rat is also endemic to California and now only occupies about 2% of its original range, making it critically endangered. San Joaquin antelope squirrel – a light tan squirrel with a white belly and a white stripe down its back and sides. Most of its habitat is used for agriculture, making the Carrizo Plain home to most of the remaining population.
History Indigenous peoples The plain lies where the territories of the Chumash, Salinan and Yokuts met, and the Bureau of Land Management records that Chumash, Yokuts and other native peoples lived, hunted and traded in this part of central California. The pictographs at Painted Rock were made over a long period, some painted over earlier images, and are estimated to be between 200 and 3,000 years old; the agency describes the style as among the most impressive in North America.