Mount Umunhum (

Ohlone The Ohlone, formerly known as Costanoans (from Spanish meaning 'coast dweller'), are a Native American people of the Northern California coast. When Spanish explorers and missionaries arrived in the late 18th century, the Ohlone inhabited the ...

for "Resting Place of the Hummingbird") is a peak in the

Santa Cruz Mountains The Santa Cruz Mountains, part of the Pacific Coast Ranges, are a mountain range in central and Northern California, United States. They form a ridge down the San Francisco Peninsula, south of San Francisco. They separate the Pacific Ocean from ...

, located in

Santa Clara County Santa Clara County, officially the County of Santa Clara, is the sixth-most populous county in the U.S. state of California, with a population of 1,936,259, as of the 2020 United States Census, 2020 census. Santa Clara County and neighboring Sa ...

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

. It is the fourth-highest

peak Peak or The Peak may refer to: Basic meanings Geology * Mountain peak ** Pyramidal peak, a mountaintop that has been sculpted by erosion to form a point Mathematics * Peak hour or rush hour, in traffic congestion * Peak (geometry), an (''n''-3)-di ...

in the Santa Cruz Mountains, after

Loma Prieta Loma Prieta (from Spanish ''loma'' -hill, ''prieta'' -dark) is high and is the highest peak in the Santa Cruz Mountains in Northern California. Although the 1989 Loma Prieta earthquake was named for this mountain, the actual epicenter was fi ...

, Crystal Peak, and Mt. Chual. Most of the mountain is located within the

Sierra Azul Open Space Preserve Sierra Azul Open Space Preserve is managed by the Midpeninsula Regional Open Space District in Santa Clara County, California. It is approximately in area. The preserve is named for the Sierra Azul or "Blue Mountains", the name the colonizing Spa ...

Geology

Mt. Umunhum consists of a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

that is known as the ''

Coast Range Ophiolite The Coast Range Ophiolite is an ophiolite of Middle to Late Jurassic age located in the California Coast Ranges. They form the basement of the extreme western margin of central and northern California. Exposures straddle the coast from Santa Barba ...

.'' This

ophiolite An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks. The Greek word ὄφις, ''ophis'' (''snake'') is found i ...

is a piece of Middle

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

oceanic crust Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumu ...

and

mantle A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that. Mantle may refer to: *Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear **Mantle (vesture), an Eastern Orthodox ve ...

that has been obducted onto land and largely been converted to

serpentinite Serpentinite is a rock composed predominantly of one or more serpentine group minerals, the name originating from the similarity of the texture of the rock to that of the skin of a snake. Serpentinite has been called ''serpentine'' or ''ser ...

. It has been extensively faulted and

diapir A diapir (; , ) is a type of igneous intrusion in which a more mobile and ductily deformable material is forced into brittle overlying rocks. Depending on the tectonic environment, diapirs can range from idealized mushroom-shaped Rayleigh–T ...

ically

uplifted ''Uplifted'' is the second studio album by Nigerian singer Flavour N'abania. It was released on July 20, 2010, by Obaino Music and 2nite Entertainment. The album features guest appearances from Jay Dey, Oloye, Stormrex, Waga Gee, Asemstone, M-Jay, ...

and

eroded Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust, and then sediment transport, tra ...

to form Mt. Umunhum and extensive

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Features Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial ...

areas throughout the Santa Cruz Mountain foothills and elsewhere. The Coast Range Ophiolite is also known to underlie the rocks of the Great Valley throughout central California. The exposure on the northeast face of Mt. Umunhum is one of the best Bay Area exposures of the Coast Range Ophiolite.Bailey, E. H., Blake Jr, M. C., and Jones, D. L. (1970). ''On-land Mesozoic oceanic crust in California coast ranges.''
US Geological Survey Professional Paper
', 700, C70-C81.Stoffer, P. W. and Messina, P. (2002)
''Field-Trip Guide to the Southeastern Foothills of the Santa Cruz Mountains In Santa Clara County, California.
' ''US Geological Survey Open-File Report'', 2, p. 121. Mount Umunhum and nearby

are pushed upward by local collision forces associated with a left bend in the

San Andreas fault The San Andreas Fault is a continental transform fault that extends roughly through California. It forms the tectonics, tectonic boundary between the Pacific Plate and the North American Plate, and its motion is Fault (geology)#Strike-slip fau ...

. Starting near

Uvas Canyon Uvas Canyon County Park is a natural park located in upper Uvas Canyon on the eastern side of the Santa Cruz Mountains, west of Morgan Hill, California. The park has several small waterfalls, some of which flow perennially, that feed into tribu ...

, the fault stops trending northwest but instead bends west-northwest for about eight miles before continuing its northwest direction. This left bend is renowned among geologists as a archetypal restraining bend which acts to oppose

strike-slip In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

motion along the fault. From the perspective of Mount Umunhum and other mountains atop the

Sierra Azul block Sierra (Spanish for "mountain range" and "saw", from Latin '' serra'') may refer to the following: Places Mountains and mountain ranges * Sierra de Juárez, a mountain range in Baja California, Mexico * Sierra de las Nieves, a mountain range i ...

, the

Pacific Plate The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and Iza ...

is trying to shear them off the

North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacific ...

but can't break them off. Rather, the resulting

transpression In geology, transpression is a type of strike-slip deformation that deviates from simple shear because of a simultaneous component of shortening perpendicular to the fault plane. This movement ends up resulting in oblique shear. It is generally ve ...

force pushes up the local terrain and helps explain why these are the highest peaks in the

History

The Cube, a

radar tower A radar tower is a tower whose function is to support a radar facility, usually a local airport surveillance radar, and hence often at or in the vicinity of an airport or a military air base. In addition, radar towers are used for the installatio ...

which housed an 85.5-ton

AN/FPS-24 The AN/FPS-24 Radar was a long range early warning radar used by the United States Air Force Air Defense Command. It used a two-frequency signal in order to avoid fluctuation loss, which causes signals on single-frequency radars to fade in and ou ...

radar, was completed in 1962 and used to watch for hostile aircraft during the

Cold War The Cold War is a term commonly used to refer to a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term '' cold war'' is used because the ...

. Its signal caused electronic interference in many radio, TV and sound systems within its 250-mile range on each rotation. The summit was closed to the public due to hazardous materials and unsafe conditions caused by partially demolished structures from the former

Air Force An air force – in the broadest sense – is the national military branch that primarily conducts aerial warfare. More specifically, it is the branch of a nation's armed services that is responsible for aerial warfare as distinct from an a ...

station. Plans were made to clean it up and restore it for public use. "In 2009, with federal funding,

Midpeninsula Regional Open Space District Formed in 1972 by voter initiative, the Midpeninsula Regional Open Space District (MROSD) is a non-enterprise special district in the San Francisco Bay Area. It has acquired and preserved a regional green belt of open space land and provides o ...

removed 3,000 cubic yards of hazardous materials, including

lead paint Lead paint or lead-based paint is paint containing lead. As pigment, lead(II) chromate (, "chrome yellow"), lead(II,IV) oxide, (, "red lead"), and lead(II) carbonate (, "white lead") are the most common forms.. Lead is added to paint to acceler ...

asbestos Asbestos () is a naturally occurring fibrous silicate mineral. There are six types, all of which are composed of long and thin fibrous crystals, each fibre being composed of many microscopic "fibrils" that can be released into the atmosphere b ...

, fuel storage containers and PCB transformers; and deconstructed 13,680 tons of concrete, asphalt, wood and other materials." Despite these measures access to the summit area surrounding the cube was closed again in 2018 pending additional cleanup. The demolition of the cube was considered, but in May 2016, the

Board of Supervisors listed it on the County Heritage Resource Inventory, giving it official historic status and protecting it from demolition. On September 18, 2017, the road, a

mountain biking Mountain biking is a sport of riding bicycles off-road, often over rough terrain, usually using specially designed mountain bikes. Mountain bikes share similarities with other bikes but incorporate features designed to enhance durability and pe ...

and

hiking Hiking is a long, vigorous walk, usually on trails or footpaths in the countryside. Walking for pleasure developed in Europe during the eighteenth century.AMATO, JOSEPH A. "Mind over Foot: Romantic Walking and Rambling." In ''On Foot: A Histor ...

trail to the summit were opened. Facilities include new pavement, restrooms, interpretive displays and a small parking lot at the summit. It is a spur of the

Bay Area Ridge Trail The Bay Area Ridge Trail (Ridge Trail) is a planned multi-use trail along the hill and mountain ridgelines ringing the San Francisco Bay Area, in Northern California. Currently, have been established. When complete, the trail will connect ov ...

. In 2017, the

granted an

easement An easement is a nonpossessory right to use and/or enter onto the real property of another without possessing it. It is "best typified in the right of way which one landowner, A, may enjoy over the land of another, B". An easement is a propert ...

to the tribal band, descendants of the

Native American people who inhabited the region before it was settled by Europeans. The easement authorized the band to build a garden and hold ceremonies on the mountaintop. In March 2022, the $2 million renovation project to preserve the historical building was completed.

Facilities

The mountain is topped by an eight and a half story (84.5 feet tall) concrete radar tower (5 floors interior), known locally as "the Cube" or "the Box". The tower was part of Almaden Air Force Station, a radar

surveillance Surveillance is the monitoring of behavior, many activities, or information for the purpose of information gathering, influencing, managing or directing. This can include observation from a distance by means of electronic equipment, such as c ...

post which operated from 1958 to 1980. The mountain is also the site of the Bay Area

NEXRAD NEXRAD or Nexrad (Next-Generation Radar) is a network of 160 high-resolution S-band Doppler weather radars operated by the National Weather Service (NWS), an agency of the National Oceanic and Atmospheric Administration (NOAA) within the United ...

weather radar Weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly puls ...

. The high elevation is necessary for line of sight in the region's varied terrain, but it also limits the ability to detect storms with bases lower in the atmosphere.

Gallery

Image:P3030017MtUmunhumSnow crwb.jpg, Mt. Umunhum is occasionally dusted with snow File:Umunhum2017.jpg, Aerial view from the north File:Mount Umunhum aerial with Monterey Bay.jpg, Aerial view with Monterey Bay in background File:View of radar tower on Mount Umunhum.jpg, The abandoned radar tower and parking lot File:Mount Umunhum Cube from close up.jpg, The abandoned radar tower File:Mount Umunhum - NEXRAD Weather Radar.jpg, NEXRAD weather radar File:Mount Umunhum - West from Mount Umunhum Rd.jpg, Mt. Umunhum, looking west from Mount Umunhum Rd File:Mount Umunhum from Bald Mountain.jpg, Mt. Umunhum as seen from Bald Mountain

References

External links

* * 10m, 18s. * * * * {{DEFAULTSORT:Umunhum, Mount Mountains of Santa Clara County, California Mountains of the San Francisco Bay Area Santa Cruz Mountains Mountains of Northern California