Geology The main ridge of the San Joaquin Hills runs southeast from the
Upper Newport Bay area, attaining its maximum height of roughly near
Laguna Beach. Many of the high ridges exceed in height. The hills stretch over a distance of about and can be up to broad. In many places, the San Joaquin Hills drop directly into the Pacific Ocean, creating the steep
sea cliffs that characterize the region. Streams that originate on the west slope of the range include Buck Gully, Los Trancos Creek, Muddy Creek, El Moro Creek, Emerald Creek, Prima Deshecha Cañada, Segunda Deshecha Cañada, and
Christianitos Canyon. The east side is drained by
Bonita Creek,
Sand Canyon Wash, San Joaquin Wash, and La Cañada Wash. Cities bordering the range include Newport Beach,
Irvine,
Laguna Hills,
Aliso Viejo, Laguna Beach,
Laguna Niguel,
Dana Point,
San Juan Capistrano, and
San Clemente. Scientists have suggested that the San Joaquin Hills have been formed by uplift from a
blind thrust fault line lying eight miles below the hills similar to the one that produced the
1994 Northridge Earthquake. Because of erosion phenomena during the previous
Ice Age, the San Joaquin Hills are not one continuous mountain range, but instead are bisected by numerous
water gaps cut by rivers flowing southwest from the
Santa Ana Mountains. In the north, Newport Bay was formed by the
Santa Ana River switching its course to the south, cutting across the northern part of the range.
Laguna Canyon was formed by
San Diego Creek, but eventually the larger creek changed course and left a
wind gap through the hills. The largest canyon by far is
Aliso Canyon, cut by
Aliso Creek. Further south, the hills dissipate into smaller ridges and are bisected by the canyon of
Salt Creek. The southern extent of the hills are cut by
San Juan Creek.
Named summits 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 on its peak; and Niguel Hill in
Laguna Niguel.
Flora and fauna The native vegetation of the hills is in the
California coastal sage and chaparral and
California chaparral and woodlands ecoregions, largely
coastal sage scrub, but other habitat types include
grasslands,
oak woodlands,
wetlands, and
riparian habitats along several streams. 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. ==History==