Ring Mountain, California
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Ring Mountain is an elevated landform on the
Tiburon Peninsula The Tiburon Peninsula (), or simply "the Tiburon" (''le Tiburon''), is a region of Haiti encompassing most of Haiti's southern coast. It starts roughly at the southernmost point of the Haiti-Dominican Republic border and extends westward near C ...
in
Marin County Marin County ( ) is a county located in the northwestern part of the San Francisco Bay Area of the U.S. state of California. As of the 2020 census, the population was 262,231. Its county seat and largest city is San Rafael. Marin County is ac ...
,
California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
. This mountain was named for George E. Ring, who served as a Marin County Supervisor from 1895 to 1903. A number of rare and
endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...
plant species inhabit Ring Mountain. The mountain's twin summits consist of
serpentinite Serpentinite is a metamorphic rock composed predominantly of serpentine group minerals formed by serpentinization of mafic or ultramafic rocks. The ancient origin of the name is uncertain; it may be from the similarity of its texture or color ...
, a rock which is very high in
magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...
, producing soils of unusual chemistry (
serpentine soil Serpentine soil is an uncommon soil type produced by weathered ultramafic rock such as peridotite and its metamorphic derivatives such as serpentinite. More precisely, serpentine soil contains minerals of the serpentine subgroup, especially an ...
). The landscape is strewn with many sizable boulders which exhibit a variety of
lithologies The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lith ...
including high-pressure
metamorphic rock Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, caus ...
s of
amphibolite Amphibolite () is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase feldspar, but with little or no quartz. It is typically dark-colored and dense, with a weakly foliated or schistose ...
,
blueschist Blueschist (), also called glaucophane schist, is a metavolcanic rock that forms by the metamorphism of basalt and similar rocks at relatively low temperatures () but very high overburden pressure, pressure corresponding to a depth of . The b ...
,
greenschist Greenschists are metamorphic rocks that formed under the lowest temperatures and pressures usually produced by regional metamorphism, typically and 2–10 kilobars (). Greenschists commonly have an abundance of green minerals such as Chlorite ...
, and
eclogite Eclogite () is a metamorphic rock containing garnet ( almandine- pyrope) hosted in a matrix of sodium-rich pyroxene ( omphacite). Accessory minerals include kyanite, rutile, quartz, lawsonite, coesite, amphibole, phengite, paragonite, zoisit ...
grade. Native American pecked curvilinear nucleated
petroglyph A petroglyph is an image created by removing part of a rock surface by incising, picking, carving, or abrading, as a form of rock art. Outside North America, scholars often use terms such as "carving", "engraving", or other descriptions ...
s created by the
Coast Miwok The Coast Miwok are an Indigenous people of California that were the second-largest tribe of the Miwok people. Coast Miwok inhabited the general area of present-day Marin County and southern Sonoma County in Northern California, from the Golde ...
people are also found here.


History


The Coast Miwok

Ring Mountain is the ancestral home of the
Coast Miwok The Coast Miwok are an Indigenous people of California that were the second-largest tribe of the Miwok people. Coast Miwok inhabited the general area of present-day Marin County and southern Sonoma County in Northern California, from the Golde ...
, who maintain deep cultural ties to the land. Ring mountain has been protected as a public open space since 1981, being one of the most culturally significant landscapes in Marin County.


Naming of Ring Mountain

In 1834, Ring Mountain was acquired by the Reed family, though the mountain itself later became associated with George E. Ring. Ring, originally a dairyman who later became a Marin County Supervisor, acquired enough land on the Tiburon Peninsula to have his name affixed to the mountain.


Historical military presence

Ring Mountain remains largely undeveloped, however, during the
Cold War The Cold War was a period of global Geopolitics, geopolitical rivalry between the United States (US) and the Soviet Union (USSR) and their respective allies, the capitalist Western Bloc and communist Eastern Bloc, which lasted from 1947 unt ...
in the 1950s, a military installation was built on its eastern peak, designed to house anti-aircraft guns. A remnant of this period is the presence of radiolarian chert, a type of red rock brought from the Marin Headlands for use in the installation. The installment was decommissioned in the 1960s, leaving behind these rocks to this day.


Conservation efforts

In the mid-1960s, the Reed family's descendants ceased cattle and horse grazing on Ring Mountain and sold over 400 acres to a developer, sparking a movement to protect the land from further development. This led to a years-long campaign to preserve the mountain as a protected open space. In 1981 and 1984,
The Nature Conservancy The Nature Conservancy (TNC) is a global environmental organization headquartered in Arlington, Virginia, United States. it works via affiliates or branches in 79 countries and territories, as well as across every state in the US. Founded in ...
purchased over 300 acres of Ring Mountain in three transactions. Initially, this area was managed as a nature preserve, but in 1995, Ring Mountain was transferred to Marin County while retaining a
conservation easement In the United States, a conservation easement (also called conservation covenant, conservation restriction or conservation servitude) is a power invested in a qualified land conservation organization called a "land trust", or a governmental (muni ...
to ensure the land would be used for scientific and educational purposes. Ring Mountain continues to be an area with high-effort conservation. Since 2011, The Nature Conservancy has been funding this conservation from a
bequest A devise is the act of giving real property by will, traditionally referring to real property. A bequest is the act of giving property by will, usually referring to personal property. Today, the two words are often used interchangeably due to thei ...
by J. Lowell Groves, supporting the Ring Mountain Stewardship and Habitat Restoration Program. The program aims to preserve the area's unique ecosystem and natural beauty long-term.


Phyllis Ellman

Phyllis Ellman, a biochemist, and member of the Marin chapter of the Native Plant Society, played a key role in the campaign to preserve Ring Mountain from development during the 1970s. Known as “Mother Botany” for her expertise in local wildflowers, Ellman's efforts were instrumental in creating the preserve. Today, a roughly two-mile-long trail was named in her honor.


Ecology


Fauna

Though Ring Mountain is an island ecosystem surrounded by Highway 101 and suburbs, it is home to a diverse range of wildlife, including
coyote The coyote (''Canis latrans''), also known as the American jackal, prairie wolf, or brush wolf, is a species of canis, canine native to North America. It is smaller than its close relative, the Wolf, gray wolf, and slightly smaller than the c ...
s,
mule deer The mule deer (''Odocoileus hemionus'') is a deer indigenous to western North America; it is named for its ears, which are large like those of the mule. Two subspecies of mule deer are grouped into the black-tailed deer. Unlike the related whit ...
, over 45 species of birds, and hundreds of insect species.


Flora

Ring Mountain is the home of the only population of Tiburon mariposa lily in the world. This flower grows near the summit of the mountain in the grassy areas. Ring Mountain is also home to other rare plants such as the Tiburon jewelflower and the Tiburon paintbrush. The Nature Conservancy bought the land around the mountain and has been responsible for preserving the rare native plant species of the area. In addition to these rare plant species, an estimated 330 other plant species inhabit the mountain.


Geology

Ring Mountain is a unique geological site, where rocks that formed in ancient
subduction zone Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...
s can be observed. Serpentinized
peridotite Peridotite ( ) is a dense, coarse-grained igneous rock consisting mostly of the silicate minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium (Mg2+), reflecting the high pr ...
crops out on the two summits of the mountain, and the steep upper slopes are underlain by serpentinite-matrix
mélange In geology, a mélange is a large-scale breccia, a mappable body of rock characterized by a lack of continuous bedding and the inclusion of fragments of rock of all sizes, contained in a fine-grained deformed matrix. The mélange typically con ...
. The melange contains blocks of high-pressure, low-temperature metamorphic rocks associated with subduction zone metamorphism. Melanges of this general style are known from the
Franciscan Complex The Franciscan Complex or Franciscan Assemblage is a geology, geologic term for a late Mesozoic terrane of heterogeneous rock (geology), rocks found throughout the California Coast Ranges, and particularly on the San Francisco Peninsula. It was n ...
, but this melange is particularly notable for the size and variety of the metamorphic blocks. Dating of metamorphic minerals in the blocks indicates that they were produced over a protracted history of subduction which began ~175 million years ago. The blocks preserve mineral assemblages characteristic of greenschist facies, blueschist facies, amphibolite facies, and eclogite facies metamorphism and is the type location of the mineral
Lawsonite Lawsonite is a hydrous calcium aluminium sorosilicate mineral with formula CaAl2Si2O7(OH)2·H2O. Lawsonite crystallizes in the orthorhombic system in prismatic, often tabular crystals. Crystal twinning is common. It forms transparent to transluce ...
. The lower slopes are underlain by greywacke sandstones and shales of prehnite-pumpellyite metamorphic grade, but the contact between the sandstones and the serpentinite-matrix melange is not exposed.
Landslides Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslide ...
and their deposits are abundant on Ring Mountain, for example at
Triangle Marsh Triangle Marsh is a wetland of the San Francisco Bay, situated at the base of Ring Mountain at the north end of the Tiburon Peninsula in Marin County, California. Archaeological Pecked curvilinear nucleated petroglyphs, and recovery on Ring M ...
, and they carry serpentinite and metamorphic blocks far downslope from their ''in situ'' positions. The origins of the serpentinite-matrix melange, and the mechanism of mixing the metamorphic blocks of different ages and apparent thermal-burial histories, has been a matter of debate. Some authors argue that the metamorphic rocks were exposed at the surface, eroded and re-deposited into a subduction trench to form the melange as an
olistostrome An olistostrome is a sedimentary deposit composed of a chaotic mass of heterogeneous material, such as blocks and mud, known as olistoliths, that accumulates as a semifluid body by submarine (geology), submarine gravity sliding or Slump (geology ...
. Others interpret the melange as having formed in a subduction plate boundary where blocks of meta-basalt from the downgoing plate were mixed with serpentine from the upper plate mantle. Ring Mountain is one of the featured field trips found in the Streetcar 2 Subduction online field trip guide series released in December 2019 by the
American Geophysical Union The American Geophysical Union (AGU) is a 501(c)(3) nonprofit organization of Earth, Atmospheric science, atmospheric, Oceanography, ocean, Hydrology, hydrologic, Astronomy, space, and Planetary science, planetary scientists and enthusiasts that ...
.


Recreation

Ring Mountain is a popular hiking and rock climbing destination and provides spectacular 360 degree views of the northern Bay Area.


See also

*
Calochortus tiburonensis ''Calochortus tiburonensis'', the Tiburon Mariposa lily, is a rare member of the genus ''Calochortus'' in the family Liliaceae. It is endemic to Marin County, California, where it is known only from one population on Ring Mountain east of Mill V ...
*
Castilleja neglecta ''Castilleja affinis'' is a species of ''Castilleja'' known by the common name coast Indian paintbrush. It is native to western North America from Washington (U.S. state), Washington to Baja California, where it grows on hills and mountains slo ...
*
Streptanthus niger ''Streptanthus glandulosus'' subsp. ''niger'' is an endangered subspecies of flowering plant within the family Brassicaceae. Like other genus members, this herb has wavy petal margins with perimeter calluses that discourage larval herbivory. This ...
*
Triangle Marsh Triangle Marsh is a wetland of the San Francisco Bay, situated at the base of Ring Mountain at the north end of the Tiburon Peninsula in Marin County, California. Archaeological Pecked curvilinear nucleated petroglyphs, and recovery on Ring M ...
* Endemic flora of California


References


External links

*
Ring Mountain Preserve
{{Commons category, Ring Mountain (California) Mountains of the San Francisco Bay Area Mountains of Marin County, California Petroglyphs in California Miwok Native American history of California Natural history of California Mountains of Northern California