San Bruno Mountain

Infobox Mountain
Name = San Bruno Mountain
Photo = San Bruno Mountain.jpg
Photo size = 300px
Caption = San Bruno Mountain, from Daly City
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pushpin_label_position = right
pushpin_map_caption = Location of San Bruno Mountain in California
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coordinates_ref= cite web | url=Gnis3|232381 | title=San Bruno Mountain | work=Geographic Names Information System | publisher=United States Geological Survey | accessdate=2008-08-26 ]
latd= 37 |latm= 41 |lats= 14.76 |latNS= N
longd=122 |longm=26 |longs=10.90 |longEW=W
Elevation = Convert|1314|ft|m|0cite web
url = http://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=RC2244
title = NGS Data Sheet
publisher = U.S. National Geodetic Survey
accessdate = 2008-03-31 ]
Location = San Mateo County, California
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Topographic

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Pronunciation = coord|37|41|14.76|N|122|26|10.90|W|type:mountain_region:US_source:gnis_elevation:400|display=title

San Bruno Mountain, situated in northern San Mateo County, California, is the northernmost part of the Santa Cruz Mountains. Most of the mountain lies within the 2,326 acre (9.41 km²) San Bruno Mountain State Park, which is a landmark of local and regional significance as well as a county park, standing as a unique open-space island in the midst of the San Francisco Peninsula's urbanization. It is adjacent to the southern boundary of San Francisco, surrounded by the cities of South San Francisco, Daly City, Colma, and Brisbane.

San Bruno Mountain is topped by a four mile long ridge. Trails to the summit afford expansive views of the San Francisco Bay Area. Radio Peak (elevation 1,314 feet or 400.5 meters) is the highest point, hosting several radio broadcast towers and NBC's KNTV Television, serving a huge area that would otherwise have poor service in the topographically complex Bay Area region.

The mountain provides habitat for several species of rare and endangered plants and butterflies. The endangered San Bruno elfin butterfly inhabits this mountain along with certain other limited locations.

Recorded history

The expedition of Gaspar de Portola discovered San Francisco Bay in 1769 and were the first westerners to note San Bruno Mountain. Five years later Fernando Rivera and four soldiers climbed the mountain and watched sunrise across the bay. The mountain was named by Bruno de Heceta for his patron saint. San Bruno Mountain consists of portions of five Mexican land grants, the southernmost being Buri Buri. Jose Antonio Sanchez, who rode by mule as a child from Sonora, Mexico was given Buri Buri in 1827, with confirmation in 1835. Buri Buri extended from the bay salt flats to San Andreas Valley and from Colma to Burlingame.

The rancho Canada de Guadalupe, la Visitacion y Rodeo Viejo contained most of the present day San Bruno Mountain; this rancho contains the city of Brisbane, Guadalupe Valley, Crocker Industrial Park, Visitacion Valley and the old rodeo grounds by Islais Creek. In 1835 this rancho was granted to Jacob P. Leese. In 1884 banker Charles Crocker acquired core holdings of this rancho amounting to 3,997 acres (16.2 km²) from Leese's successors, and that land devolved to the Crocker Estate Company, who are the present day owners of San Bruno Mountain.

Three other ranchos held minor portions of the northern flank of San Bruno Mountain. The cities that have ground up around the mountain are San Francisco to the north, Brisbane to the east, South San Francisco to the south and both Daly City and Colma to the west.

KRON (Channel 4) became the first television station to place a transmitter tower on Radio Peak, in 1949, followed by KQED and KTVU, though these tenants have moved their transmitters to Sutro Tower in the 1970s. A number of FM stations also built transmitter towers on the mountain, and in 2005, KNTV moved its transmitter to the mountain, on the former KCSM-TV tower.

Topography, geology and climate

The name "San Bruno Mountains" was first affixed by the Geological Survey of California in 1865, describing the place as a short range extending from Sierra Point nearly to the Pacific Ocean.The mountain itself actually consists of two parallel northwest trending ranges separated by the Guadalupe Valley. These two ranges are united by a saddle at the northern end of Colma Canyon. The northernmost range attains a peak of 850 feet (259 m), while the southern range rises abruptly from Merced Valley at the south to reach Radio peak in a horizontal distance of only 0.8 mile. (1.3 km) This southern range is often referred to as San Bruno Mountain., while the northern range is called the Crocker Hills.

The region is drained by two major streams:
*(a) Guadalupe Creek flowing through Guadalupe Valley, and
*(b) Colma Creek from a source in the Flower Garden into the deep cleft of Colma Canyon and thence into Merced Valley.

In the 1850s, San Francisco Bay lapped against the eastern sandstone cliff flank of San Bruno Mountain, whereas today the entire shoreline is bay fill.

These two mountains are underlain primarily with late Cretaceous dark greenish-gray graywacke, a poorly sorted sandstone containing angular rock fragments, about ten percent feldspar and detrital chert. The angular unsorted content implies a rapid erosion and burial in a depositional basin, with an outcome of few fossils. Exposed graywacke can be observed on high ridges and on the steep canyon walls. Radiolarian chert is exposed on certain south facing slopes of San Bruno Mountain and at Point San Bruno.

The most important rock type is serpentine, a greenish soft material that is the California State Rock. Outcrops of this rock are found near Serbian Ravine and at Point San Bruno. Serpentine's importance is its unusual and diverse mineral composition which imparts to associate soils the ability to host rare plants, not usually supported on common soils. Therefore, San Bruno Mountain is a habitat for a variety of uncommon plants, which in turn host even rarer animal life.

Since the climate is dominated by marine air flow, temperatures are milder in the winter and summer on these mountains. Furthermore, summer temperatures are further reduced by the annual appearance of marine fog enshrouding the mountains most mornings between late June and late August; this fog is particularly pronounced on the western slopes. Minimum credible temperature might extend as low as 20°F (-6.6°C) in the sheltered valleys. Winds are higher than on reference locations at surrounding points; in fact, on ridges it is not uncommon for the most fierce winter storms to produce gusts from 50 to 80 miles-per-hour (80.5 - 129 km/h). Precipitation is similar to surrounding cities, or about 22 inches (56 cm) per-annum, with approximately 66 days-per-annum realizing perceptible rain. On several occasions, the mountain has been temporarily covered by snow, including December 1932, January 1952, January 1957, January 1962, and February 1976.

Vegetation

There are a variety of habitats in this mountainous area, and notably the following rare or endangered flora:

* Coast rock cress ("Arabis blepharophylla")
* Franciscan Wallflower ("Erysimum franciscanum")
* Montara Manzanita ("Arctostaphylos montaraensis")
* Pacifica Manzanita ("Arctostaphylos pacifica")
* San Bruno Mountain Manzanita ("Arctostaphylos imbricata")
* San Francisco Campion ("Silene verecunda")
* San Francisco Owl's Clover ("Orthocarpus floribundus")

Bibliography

* "Climate Survey of San Bruno Mountain", prepared for Crocker Land Company by Metronics Associates, Palo Alto, Ca., October 20, 1967

* Elizabeth McClintock and Walter Knight, "A Flora of the San Bruno Mountains, San Mateo County, California", Proceedings of the California Academy of Sciences, Fourth Series, Volume XXXII, no. 20, pp. 587-677, November 29, 1968

* J.D. Whitney, "Geological Survey of California" (1865)

* John Hunter Thomas, "A Flora of the Santa Cruz Mountains" (1960)

See also

* List of California state parks
* List of summits in the San Francisco Bay Area
* Mission blue butterfly
* Mission blue butterfly habitat conservation

References

External links

* [http://www.co.sanmateo.ca.us/smc/department/home/0,,5556687_12313315_12345092,00.html Environmental Services Agency of San Mateo County] , information on history, trails, park map, activities, park hours.
* [http://www.topozone.com/map.asp?z=10&n=4170468&e=550221&s=100&size=l&datum=nad83&layer=DRG100 Topographic Map]
* [http://www.parks.ca.gov/default.asp?page_id=518 San Bruno Mountain State Park]
* [http://www.mountainwatch.org San Bruno Mountain Watch] , whose mission is to preserve San Bruno Mountain's native American village sites and endangered habitats.
* [http://www.trailspotting.com/2008/01/san-bruno-mountain.html Trailspotting: Hiking the San Bruno Mountain Summit Loop Trail] Description, Photos and GPS/mapping data]