Perris Block

The Perris Block is the central block of three major fault-bounded blocks of the northern part of the Peninsular Ranges. The Perris Block lies between the Santa Ana Block to the west and the San Jacinto Block to the east.^[1] The Perris Block, was named by Walter A. English in 1925 for the city of Perris, located near the center of the block.^[2]

Structurally stable for millions of years, the Perris Block is an internally unfaulted, eroded mass of Cretaceous and older granitic rocks of the Southern California Batholith and metasedimentary basement rocks. These rocks compose various ranges of mountains and hills and monadnocks and underlie the valleys within it. It is bounded on the west by the Elsinore Trough, on the east and northeast by the San Jacinto Fault Zone including the San Jacinto Valley graben. It is bounded on the north by the Cucamonga Fault Zone, in the San Bernardino Valley and San Jose Hills Fault in the Pomona Valley. To the south, the Perris Block is bounded by the San Felipe Fault Zone between it and the Temecula, Aguanga, and Anza sedimentary basins that lie between Temecula and Anza.^[3]^[4] The interior of the Perris Block has various low bedrock mountains, hills and bedrock plains with intervening sediment-filled valleys, that make up six erosional surfaces sculpted by the effects of the vertical oscillation of the block during the Plio - Pleistocene era.^[5]^[3]

Northern Perris Block

The northern part of the Parris Block lies north of the Santa Ana River. Here in the Pomona Valley and San Bernardino Valley it has been mostly buried by the sediments from the Transverse Ranges as they rose over the last 2-3 million years. Exceptions are the Jurupa Mountains and Pedley Hills that still rise above that deposition. The now obliterated Slover Mountain also did so before it was mined out of existence. These sediments under the Pomona and San Bernardino Valleys form the Inland Santa Ana Basin aquifer.

East of the Santa Ana River lie the La Loma Hills, Box Springs Mountains and northeastward of them, across the canyon of Spring Brook and of the Pigeon Pass Valley, the range of mountains formed by Blue Mountain, Reche Summit, Olive Hill and the Kalmia Hills that border the northeast edge of the Parris Block along the San Jacinto Fault Zone to the Parris Plain.

Central Perris Block

The western side of the central Perris Block and across its width eastward south of the Santa Ana River, is bordered by the range of the Temescal Mountains. They run southeastward along the Elsinore Trough to the Temecula Basin. Eastward, these mountains run to the south of the Santa Ana River to Sycamore Canyon, bordering on the Box Springs Mountains. They enclose the Gavilan Plateau and partially enclose the Riverside Valley on the west, south and east. They extend their ancient eroded surfaces eastward to the Perris Plain and the Plains of Leon, which they border on the west, southward to the Temecula Basin.

Perris Plain

The Perris Plain, an uplifted peneplain, is drained primarily in the San Jacinto Basin, the San Jacinto River watershed flowing into Lake Elsinore, that is dotted by monadnocks and by several other ranges of mountains and hills. Above the San Jacinto Basin, the northwest corner of the Perris Plain is drained by Sycamore Canyon and Tequesquito Arroyo into the Santa Ana River. Below the San Jacinto Basin, the Perris Plain is bounded on the south by the Plains of Leon, which continues the plains of the Perris Block and by the mountains of the southern Perris Block.

Plains and Valleys of the Perris Block within the San Jacinto Basin:

Perris Plain
- Menifee Valley
- Moreno Valley
- Paloma Valley
- Perris Valley
- San Jacinto Valley
- Eastern Diamond Valley

Mountains and hills of the Perris Block within the San Jacinto Basin include:

Bell Mountain
Bernasconi Hills
- Mount Russell
Domenigoni Mountains
- Searls Ridge
Double Butte
Hemet Butte
Hules Hill
Kalmia Hills
Lakeview Mountains
Tres Cerritos

Southern Perris Block

The Perris Block south of the Perris Plain and San Jacinto Basin is characterized by the extension of the Perris Plain, the Plains of Leon that includes within it the Domenigoni Valley and western Diamond Valley, the upper part of the valley of Warm Springs Creek and connecting tablelands, French Valley, Auld Valley and Buck Mesa.^[6] The southern Perris Block also includes the hills and mountains to the east and south of the Perris Plain, that with the Plains of Leon are all drained by the creeks tributary to the Santa Margarita River into the Temecula Basin.

Tucalota Creek, drains the Rawson Mountains (south of Diamond and Domenigoni Valleys),^[7] Black Mountain, the western slopes of Red Mountain, the Magee Hills, the Tucalota Hills and Bachelor Mountain into Lake Skinner then to Warm Springs Creek, a tributary of Murrieta Creek.^[8] The west slope of the southern Magee Hills, and the north slope of the Black Hills are drained by Santa Gertrudis Creek or its tributaries, another Murrieta Creek tributary. Billy Goat Mountain, Oak Mountain, Round Top the west and south slopes of the Black Hills are drained by Temecula Creek or its tributaries, as are the south slopes of Red Mountain, Little Cahuilla Mountain and Cahuilla Mountain.

References

↑ Earth Resources Technical Report PREPARED FOR: RIVERSIDE PUBLIC UTILITIES BY: POWER ENGINEERS, INC, June 2010, p.3
↑ Walter Atheling English, Geology and Oil Resources of the Puente Hills Region Southern California, Geological Survey Bulletin 768, U.S. Government Printing Office, 1926.
1 2 Morton, D.M. and Matti, J.C., A vanished late Pliocene to early Pleistocene alluvial-fan complex in the northern Perris block, Southern California. In Conglomerates in Basin Analysis: A Symposium Dedicated to A.O. Woodford, (I.P. Colburn, P.L. Abbott and J. Minch, eds.), Pacific Section S.E.P.M., 1989, Vol. 62, p. 73-80.
↑ Greg T. Cranham, editor, Water for Southern California: Water Resources Development at the Close of the Century, San Diego Geological Soc, Dec 1, 1999 - pp. 45-46, fig. 3 Regional geologic map (modified from Woodford et al, 1971)
↑ ALFRED O. WOODFORD, JOHN S. SHELTON, DONALD O. DOEHRING and RICHARD K. MORTON, Pliocene-Pleistocene History of the Perris Block, Southern California, Geological Society of America Bulletin, 971
↑ U.S. Geological Survey Geographic Names Information System: Buck Mesa
↑ [Greg T. Cranham, editor, Water for Southern California: Water Resources Development at the Close of the Century, San Diego Geological Soc, Dec 1, 1999 - pp. 43-44, 44 fig. 2 Project Features Map, 47-49, 47 fig. 2]
↑ "Murrieta Creek". Geographic Names Information System. United States Geological Survey.

Inland Empire

Counties	Riverside San Bernardino

Major cities	Riverside San Bernardino

Cities and towns 100k+	Corona Fontana Moreno Valley Murrieta Ontario Rancho Cucamonga Temecula Victorville

Cities and towns 25k–100k	Apple Valley Banning Beaumont Cathedral City Chino Chino Hills Coachella Colton Desert Hot Springs Eastvale Hemet Hesperia Highland Indio Jurupa Valley Lake Elsinore Menifee Montclair Norco Palm Desert Palm Springs Perris Redlands Rialto Rubidoux San Jacinto Twentynine Palms Upland Valle Vista Wildomar Yucaipa

Cities and towns 10k–25k	Adelanto Barstow Big Bear City Bloomington Blythe Cabazon Canyon Lake Crestline Glen Avon Grand Terrace La Quinta Loma Linda Mira Loma Pedley Rancho Mirage Twentynine Palms Yucca Valley

Cities and towns under 10k	Big Bear Lake Calimesa Devore El Cerrito Oak Glen Highgrove Home Gardens Indian Wells Joshua Tree Lake Arrowhead Landers Mentone Muscoy Needles Romoland San Antonio Heights Sunnyslope Wrightwood Woodcrest

Regions	Coachella Valley Cucamonga Valley Elsinore Trough High Desert Morongo Basin Perris Plain Plains of Leon San Bernardino Mountains San Bernardino Valley San Jacinto Mountains San Jacinto Valley Santa Ana Mountains Temescal Mountains Victor Valley

Seismically active fault zones and tectonic blocks of California

Statewide Faults	San Andreas Fault

Faults, zones, and blocks of Southern California	Brawley Seismic Zone Chino Fault Elsinore Fault Zone Elysian Park Fault Garlock Fault Hosgri Fault Imperial Fault Zone Laguna Salada Fault Newport–Inglewood Fault Peninsular Ranges Puente Hills Fault Raymond Fault Rose Canyon Fault Salton Trough Salinian Block San Cayetano Fault San Felipe Fault Zone San Gabriel Fault San Jacinto Fault Zone Santa Maria River Fault Santa Ynez Fault Shoreline Fault Ventura Fault White Wolf Fault Whittier Fault Yorba Linda Fault

Faults and zones of Northern California	Bartlett Springs Fault Calaveras Fault Clayton-Marsh Creek-Greenville Fault Concord Fault Hayward Fault Zone Healdsburg Fault Maacama Fault Mendocino Fracture Zone Mendocino Triple Junction Mount Diablo Thrust Fault Monta Vista Fault Pleasanton Fault San Gregorio Fault San Pablo Fault Seal Cove Fault Serra Fault Silver Creek Fault Tesla Fault West Napa Fault

Sierra Nevada faults, zones, and blocks	Death Valley Fault Zone Furnace Creek Fault Zone Honey Lake Fault Zone Kern Canyon Fault Maria fold and thrust belt Owens Valley Fault Rescue Lineament-Bear Mountains fault zone Sierra Nevada Batholith Sierra Nevada Fault Sierra Nevada-Great Valley Block Smartville Block Walker Lane

Category California Geological Survey Seismic Hazards Mapping Act Mexico (list)

Coordinates: 33°51′9″N 117°15′19″W / 33.85250°N 117.25528°W / 33.85250; -117.25528

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