San Joaquin Hills

The San Joaquin Hills are a set of low hills in coastal Orange County, California. They extend in a northwest-southeast direction, starting in the northwest in Newport Beach at the southern edge of the Los Angeles Basin, and extending southeast to San Juan Capistrano.

Geography and habitats

Named summits in the San Joaquin Hills include (from north to south)French Hill in Turtle Rock, Irvine;Signal Peak and Pelican Hill, both of which are near the Newport Coast neighborhood of Newport Beach;Temple Hill in Laguna Beach, more commonly known as "Top of the World" after the neighborhood situated on its peak;and Niguel Hill in Laguna Niguel. [Gnis|242498|French Hill, elevation 397 ft. / 121 m. Gnis|249461|Signal Peak, elevation 1161 ft. / 354 m. Gnis|1661209|Pelican Hill, elevation 725 ft. / 221 m. Gnis|1661555|Temple Hill, elevation 1007 ft. / 307 m. Gnis|246545|Niguel Hill, elevation 935 ft. / 285 m. (prior to grading for real estate development).] A fault line, the San Joaquin Hills blind thrust, lies eight miles below the hills. [citation|last=Robbins|first=Gary|date=March 11, 1999|title=Fault found beneath San Joaquin Hills: The 23-mile-long system is similar to the one that produced the Northridge shaker|publisher=Orange County Register; citation|last=Robbins|first=Gary|date=November 1, 2001|title=Scientists to evaluate seismic threat in San Joaquin Hills|publisher=Orange County Register; citation|title=Orange County's Hills Hold Key To Earthquake Findings|publisher=KNBC|date=April 15, 2004|url=http://www.knbc.com/news/3008807/detail.html; citation|title=County at risk for Northridge-size quakes say UCI researchers|date=April 22, 2004|publisher=Orange County Register.] Scientists have suggested that the San Joaquin Hills have been formed by uplift from this fault. [citation|first1=Lisa B.|last1=Grant|first2=Karl J.|last2=Mueller|first3=Eldon M.|last3=Gath|first4=Hai|last4=Cheng|first5=R. Lawrence|last5=Edwards|first6=Rosalind|last6=Munro|first7=George L.|last7=Kennedy|title=Late Quaternary uplift and earthquake potential of the San Joaquin Hills, southern Los Angeles Basin, California|journal=Geology|year=1999|volume=27|issue=11|pages=1031–1034|doi=10.1130/0091-7613(1999)027<1031:LQUAEP>2.3.CO;2.]

The native vegetation of the hills is largely coastal sage scrub, but other habitat types include grasslands, oak woodlands, wetlands, and riparian habitats along several streams. [ [http://www.ocparks.com/awresources/AWCWP_RMP_OpenHouse_Booklet.pdf Aliso and Wood Canyons Wilderness Park] open house booklet, Orange County Park System, 2006.] In past ages the land that is now the San Joaquin Hills lay under the ocean: construction for the San Joaquin Hills Toll Road unearthed a number of artifacts and more than 40,000 fossils, up to 35 million years old, including 5-million-year-old fossilized whales. [citation|last=Roan|first=Shari|title=San Joaquin tollway work breaks historical ground|publisher=Orange County Register|date=November 19, 1989; citation|last=Downey|first=Cheryl|title=Fine whale skeletons unearthed: Paleontologists discover nearly intact skeletons along route of San Joaquin Hills toll road|publisher=Orange County Register|date=April 28, 1993; citation|last=Downey|first=Cheryl|title=A window to our past: Scientists who are checking the San Joaquin Hills tollway route remove and preserve fossils millions of years old before construction starts|date=May 11, 1993|publisher=Orange County Register; citation|last=Brennan|first=Pat|title=Fossil whale makes a delicate journey to county museum: Five million-year-old `Bones' is carefully loaded onto a truck for its trip to Buena Park|publisher=Orange County Register|date=June 18, 1993; citation|last=Brennan|first=Pat|title=Highway to history: Bones reveal a scenic road through the county's past|date=April 4, 1998|publisher=Orange County Register; citation|last=Chang|first=Daniel|title=Dig this!|publisher=Orange County Register|date=May 1, 1999; citation|last=Peralta|first=Jessica|title=Bones about it: Toll road construction unearths fossil treasure trove for school lectures|publisher=Orange County Register|date=May 17, 2002.]

History

The hills take their name from Rancho San Joaquin, owned by Jose Andres Sepulveda. Formed in 1842 by the merger of two smaller ranches, this ranch included the northern part of the hills and likely had Laguna Canyon as its southeastern boundary. Rancho San Joaquin later became part of the Irvine Ranch. [citation|title=History buff likes telling the story of Jose Sepulveda|url=http://216.173.246.226/Bstories/june13/history.html|publisher=Irvine World News|last=Goetz|first=Peggy|date=June 13, 2002.]

The San Joaquin Hills blind thrust may be the source of the earliest recorded earthquake in California, a large earthquake felt in what is now northern Orange County on July 28, 1769 by Gaspar de Portolà. [citation|first1=Lisa B.|last1=Grant|first2=Leslie J.|last2=Ballenger|first3=Eric E.|last3=Runnerstrom|title=Coastal Uplift of the San Joaquin Hills, Southern Los Angeles Basin, California, by a Large Earthquake since A.D. 1635|journal=Bulletin of the Seismological Society of America|year=2002|volume=92|issue=2|pages=590–599|doi=10.1785/0120010119; citation|last=Coledan|first=Stefano|journal=Popular Mechanics|title=California Earthquake Described By 18th Century Spanish Explorer|url=http://www.popularmechanics.com/technology/industry/1285611.html|date=April 2002. Listed by the United States Geological Survey as the earliest recorded earthquake in California on their [http://earthquake.usgs.gov/learning/facts.php Earthquake Facts] web page.]

Development

Two neighborhoods within the San Joaquin Hills take the name of the hills for their own:
San Joaquin Hills, Newport Beach, California, a former census-designated place annexed to the city of Newport Beach, and San Joaquin Hills, Laguna Niguel, California, a master-planned community located in the city of Laguna Niguel. Other neighborhoods set in and named after hills in this range include University Hills and Turtle Rock in Irvine.

State Route 73, also called the San Joaquin Hills Toll Road, extends through the length of the hills from Newport Beach to San Juan Capistrano. State Route 133 crosses the hills through Laguna Canyon in Laguna Beach, and they are also crossed in several other places by less major roads.

Notes and references