Ring Mountain (California)

Last updated
Ring Mountain
Ring Mountain Open Space Preserve.jpg
Highest point
Elevation 603 ft (184 m)  NAVD 88 [1]
Prominence 402 ft (123 m) [2]
Coordinates 37°54′35″N122°29′09″W / 37.909691528°N 122.485779814°W / 37.909691528; -122.485779814 [1]
Geography
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Ring Mountain
Location in California
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Ring Mountain
Ring Mountain (the United States)
Location Marin County, California, U.S.
Topo map USGS San Quentin

Ring Mountain is an elevated landform on the Tiburon Peninsula in Marin County, California. This mountain was named for George E. Ring, who served as a Marin County Supervisor from 1895 to 1903. [3]

Contents

A number of rare and endangered plant species inhabit Ring Mountain. [4] The mountain's twin summits consist of serpentinite, [5] a rock which is very high in magnesium, producing soils of unusual chemistry (serpentine soil). The landscape is strewn with many sizable boulders which exhibit a variety of lithologies including high-pressure metamorphic rocks of amphibolite, blueschist, greenschist, and eclogite grade. [6]

Native American pecked curvilinear nucleated petroglyphs created by the Coast Miwok people are also found here. [7]

History

The Coast Miwok

Ring Mountain is the ancestral home of the Coast Miwok, who maintain deep cultural ties to the land. Ring mountain has been protected as a public open space since 1981 [8] , 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. [8] 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. [9]

Historical military presence

Ring Mountain remains largely undeveloped, however, during the Cold War 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. [8]

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. [8] This led to a years-long campaign to preserve the mountain as a protected open space.

Phyllis Ellman Trailhead on Ring Mountain PhyllisEllmanTrail.jpg
Phyllis Ellman Trailhead on Ring Mountain

In 1981 and 1984, The Nature Conservancy 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 to ensure the land would be used for scientific and educational purposes [8] .

Ring Mountain continues to be an area with high-effort conservation. Since 2011, The Nature Conservancy has been funding this conservation from a bequest 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. [8]

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. [9] Known as “Mother Botany” for her expertise in local wildflowers, Ellman’s efforts were instrumental in creating the preserve. [8] 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 coyotes, mule deer, over 45 species of birds, and hundreds of insect species [8] .

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. [10] In addition to these rare plant species, an estimated 330 other plant species inhabit the mountain. [8]

Geology

Pecked curvilinear nucleated petroglyphs on a rock on Ring Mountain Pecked curvilinear nucleated petroglyphs on Ring Mountain.jpg
Pecked curvilinear nucleated petroglyphs on a rock on Ring Mountain

Ring Mountain is a unique geological site, where rocks that formed in ancient subduction zones can be observed. [11] Serpentinized peridotite crops out on the two summits of the mountain, and the steep upper slopes are underlain by serpentinite-matrix mélange. [5] 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, [12] 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. [13] The blocks preserve mineral assemblages characteristic of greenschist facies, blueschist facies, amphibolite facies, and eclogite facies metamorphism [14] and is the type location of the mineral Lawsonite. [15] The lower slopes are underlain by greywacke sandstones and shales of prehnite-pumpellyite metamorphic grade, [16] but the contact between the sandstones and the serpentinite-matrix melange is not exposed. Landslides and their deposits are abundant on Ring Mountain, for example at Triangle Marsh, and they carry serpentinite and metamorphic blocks far downslope from their in situ positions.

Blueschist block embedded in serpentinite matrix melange on the west side of Ring Mountain. Turtle Rock blueschist block on Ring Mountain.jpg
Blueschist block embedded in serpentinite matrix melange on the west side of Ring Mountain.

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. [17] 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. [18]

Ring Mountain is one of the featured field trips found in the Streetcar 2 Subduction online field trip guide series [19] released in December 2019 by the American Geophysical Union. [20]

Recreation

Ring Mountain is a popular hiking and rock climbing destination and provides spectacular 360 degree views of the northern Bay Area. [21]

See also

Related Research Articles

<span class="mw-page-title-main">Metamorphic rock</span> Rock that was subjected to heat and pressure

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 150 to 200 °C and, often, elevated pressure of 100 megapascals (1,000 bar) or more, causing profound physical or chemical changes. During this process, the rock remains mostly in the solid state, but gradually recrystallizes to a new texture or mineral composition. The protolith may be an igneous, sedimentary, or existing metamorphic rock.

<span class="mw-page-title-main">Ophiolite</span> Uplifted and exposed oceanic crust

An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed, and often emplaced onto continental crustal rocks.

<span class="mw-page-title-main">Coesite</span> Silica mineral, rare polymorph of quartz

Coesite is a form (polymorph) of silicon dioxide (SiO2) that is formed when very high pressure (2–3 gigapascals), and moderately high temperature (700 °C, 1,300 °F), are applied to quartz. Coesite was first synthesized by Loring Coes, Jr., a chemist at the Norton Company, in 1953.

<span class="mw-page-title-main">Eclogite</span> Metamorphic rock formed under high pressure

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, zoisite, dolomite, corundum and, rarely, diamond. The chemistry of primary and accessory minerals is used to classify three types of eclogite. The broad range of eclogitic compositions has led to a longstanding debate on the origin of eclogite xenoliths as subducted, altered oceanic crust.

<span class="mw-page-title-main">Blueschist</span> Type of metavolcanic rock

Blueschist, also called glaucophane schist, is a metavolcanic rock that forms by the metamorphism of basalt and rocks with similar composition at high pressures and low temperatures, approximately corresponding to a depth of 15–30 km (9.3–18.6 mi). The blue color of the rock comes from the presence of the predominant minerals glaucophane and lawsonite.

<span class="mw-page-title-main">Ultramafic rock</span> Type of igneous and meta-igneous rock

Ultramafic rocks are igneous and meta-igneous rocks with a very low silica content, generally >18% MgO, high FeO, low potassium, and are usually composed of greater than 90% mafic minerals. The Earth's mantle is composed of ultramafic rocks. Ultrabasic is a more inclusive term that includes igneous rocks with low silica content that may not be extremely enriched in Fe and Mg, such as carbonatites and ultrapotassic igneous rocks.

<span class="mw-page-title-main">Serpentinization</span> Formation of serpentinite by hydration and metamorphic transformation of olivine

Serpentinization is a hydration and metamorphic transformation of ferromagnesian minerals, such as olivine and pyroxene, in mafic and ultramafic rock to produce serpentinite. Minerals formed by serpentinization include the serpentine group minerals, brucite, talc, Ni-Fe alloys, and magnetite. The mineral alteration is particularly important at the sea floor at tectonic plate boundaries.

<span class="mw-page-title-main">Mélange</span> Large-scale breccia typically consisting of a jumble of large blocks of varied lithologies

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 consists of a jumble of large blocks of varied lithologies. Both tectonic and sedimentary processes can form mélange.

<span class="mw-page-title-main">Omphacite</span> Member of the clinopyroxene group of silicate minerals

Omphacite is a member of the clinopyroxene group of silicate minerals with formula: (Ca, Na)(Mg, Fe2+, Al)Si2O6. It is a variably deep to pale green or nearly colorless variety of clinopyroxene. It normally appears in eclogite, which is the high-pressure metamorphic rock of basalt. Omphacite is the solid solution of Fe-bearing diopside and jadeite. It crystallizes in the monoclinic system with prismatic, typically twinned forms, though usually anhedral. Its space group can be P2/n or C2/c depending on the thermal history. It exhibits the typical near 90° pyroxene cleavage. It is brittle with specific gravity of 3.29 to 3.39 and a Mohs hardness of 5 to 6.

<span class="mw-page-title-main">Lawsonite</span>

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 translucent colorless, white, pink, and bluish to pinkish grey glassy to greasy crystals. Refractive indices are nα = 1.665, nβ = 1.672 – 1.676, and nγ = 1.684 – 1.686. It is typically almost colorless in thin section, but some lawsonite is pleochroic from colorless to pale yellow to pale blue, depending on orientation. The mineral has a Mohs hardness of 7.5 and a specific gravity of 3.09. It has perfect cleavage in two directions and a brittle fracture. Not to be confused with Larsonite, a fossiliferous jasper mined in Nevada.

<span class="mw-page-title-main">Franciscan Complex</span> Late Mesozoic terrane of heterogeneous rocks in the California Coast Ranges

The Franciscan Complex or Franciscan Assemblage is a geologic term for a late Mesozoic terrane of heterogeneous rocks found throughout the California Coast Ranges, and particularly on the San Francisco Peninsula. It was named by geologist Andrew Lawson, who also named the San Andreas Fault that defines the western extent of the assemblage.

<span class="mw-page-title-main">Tiburon Peninsula (California)</span> Peninsula of the Marin Peninsula in California, United States

The Tiburon Peninsula is a landform of the San Francisco Bay Area's Marin County and is home to the incorporated municipalities of Tiburon, Belvedere, and a portion of Corte Madera, California. Much of the peninsula is unincorporated, including portions of the north side and the communities of Paradise Cay and Strawberry. Richardson Bay separates the peninsula from the Marin County mainland. Angel Island lies app. 1 mile south of the peninsula's southern tip. Much of the land area of the Tiburon Peninsula was part of a Spanish land grant originally given to the early Californian John Reed. A prominent feature of the Tiburon Peninsula is Ring Mountain, Marin County, which forms the backbone of the peninsula and is the highest elevation of the peninsula. The Tiburon Peninsula is the location of a number of rare and endangered flora species, and is also the site of ancient Native American rock carvings. The mineral lawsonite was first described from an occurrence on the Tiburon Peninsula.

<span class="mw-page-title-main">Metamorphic facies</span> Set of mineral assemblages in metamorphic rocks formed under similar pressures and temperatures

A metamorphic facies is a set of mineral assemblages in metamorphic rocks formed under similar pressures and temperatures. The assemblage is typical of what is formed in conditions corresponding to an area on the two dimensional graph of temperature vs. pressure. Rocks which contain certain minerals can therefore be linked to certain tectonic settings, times and places in the geological history of the area. The boundaries between facies are wide because they are gradational and approximate. The area on the graph corresponding to rock formation at the lowest values of temperature and pressure is the range of formation of sedimentary rocks, as opposed to metamorphic rocks, in a process called diagenesis.

Ultra-high-pressure metamorphism refers to metamorphic processes at pressures high enough to stabilize coesite, the high-pressure polymorph of SiO2. It is important because the processes that form and exhume ultra-high-pressure (UHP) metamorphic rocks may strongly affect plate tectonics, the composition and evolution of Earth's crust. The discovery of UHP metamorphic rocks in 1984 revolutionized our understanding of plate tectonics. Prior to 1984 there was little suspicion that continental rocks could reach such high pressures.

<span class="mw-page-title-main">Eclogitization</span> The tectonic process in which the dense, high-pressure, metamorphic rock, eclogite, is formed

Eclogitization is the tectonic process in which the high-pressure, metamorphic facies, eclogite, is formed. This leads to an increase in the density of regions of Earth's crust, which leads to changes in plate motion at convergent boundaries.

<span class="mw-page-title-main">High pressure metamorphic terranes along the Bangong-Nujiang Suture Zone</span> Geological features

High pressure terranes along the ~1200 km long east-west trending Bangong-Nujiang suture zone (BNS) on the Tibetan Plateau have been extensively mapped and studied. Understanding the geodynamic processes in which these terranes are created is key to understanding the development and subsequent deformation of the BNS and Eurasian deformation as a whole.

Paired metamorphic belts are sets of parallel linear rock units that display contrasting metamorphic mineral assemblages. These paired belts develop along convergent plate boundaries where subduction is active. Each pair consists of one belt with a low-temperature, high-pressure metamorphic mineral assemblage, and another characterized by high-temperature, low-pressure metamorphic minerals.

<span class="mw-page-title-main">Subduction zone metamorphism</span> Changes of rock due to pressure and heat near a subduction zone

A subduction zone is a region of the Earth's crust where one tectonic plate moves under another tectonic plate; oceanic crust gets recycled back into the mantle and continental crust gets produced by the formation of arc magmas. Arc magmas account for more than 20% of terrestrially produced magmas and are produced by the dehydration of minerals within the subducting slab as it descends into the mantle and are accreted onto the base of the overriding continental plate. Subduction zones host a unique variety of rock types formed by the high-pressure, low-temperature conditions a subducting slab encounters during its descent. The metamorphic conditions the slab passes through in this process generates and alters water bearing (hydrous) mineral phases, releasing water into the mantle. This water lowers the melting point of mantle rock, initiating melting. Understanding the timing and conditions in which these dehydration reactions occur, is key to interpreting mantle melting, volcanic arc magmatism, and the formation of continental crust.

<span class="mw-page-title-main">Rodingite</span>

Rodingite is a metasomatic rock composed of grossular-andradite garnet, calcic pyroxene, vesuvianite, epidote and scapolite. Rodingites are common where mafic rocks are in proximity to serpentinized ultramafic rocks. The mafic rocks are altered by high pH, Ca2+ and OH− fluids, which are a byproduct of the serpentinization process, and become rodingites. The mineral content of rodingites is highly variable, their high calcium, low silicon and environment of formation being their defining characteristic. Rodingites are common in ophiolites, serpentinite mélanges, ocean floor peridotites and eclogite massifs. Rodingite was first named from outcrops of the Dun Mountain Ophiolite Belt in the Roding River, Nelson, New Zealand.

<span class="mw-page-title-main">Old Saint Hilary's Open Space Preserve</span>

Old Saint Hilary's Open SpacePreserve is a county park located in Marin County, California. It is 122 acres large and is connected to the Tiburon Uplands, which is 24 acres. The preserve was created by several local initiatives in the 90’s to save the land from development. It is a popular place for hikers because of its views and other features. There have been initiatives to expand the preserve, such as one that passed in 2022 that aims to connect it with undeveloped, but formerly privately owned land on its perimeter.

References

  1. 1 2 "Ring". NGS Data Sheet. National Geodetic Survey, National Oceanic and Atmospheric Administration, United States Department of Commerce . Retrieved 2014-02-12.
  2. ↑ "Ring Mountain, California". Peakbagger.com. Retrieved 2014-02-13.
  3. ↑ "Ring Mountain, Open Space Preserve". County of Marin. Archived from the original on 2008-06-21. Retrieved 2009-12-07.
  4. ↑ Earth Metrics Inc. (1989) Marinero Estates Environmental Impact Report, Tiburon, California, prepared for the city of Tiburon, Ca.
  5. 1 2 Bero, David A. (2014). "Geology of Ring Mountain and Tiburon Peninsula, Marin County, California". National Geologic Map Database. Retrieved 2019-09-28.
  6. ↑ Anczkiewicz, Robert; Platt, John P.; Thirlwall, Matthew F.; Wakabayashi, John (2004-08-30). "Franciscan subduction off to a slow start: evidence from high-precision Lu–Hf garnet ages on high grade-blocks". Earth and Planetary Science Letters. 225 (1): 147–161. Bibcode:2004E&PSL.225..147A. doi:10.1016/j.epsl.2004.06.003. ISSN   0012-821X.
  7. ↑ Hogan, C. Michael (2008). Andy Burnham (ed.). "Ring Mountain, The Megalithic Portal".
  8. 1 2 3 4 5 6 7 8 9 "Ring Mountain - Marin County Parks". www.parks.marincounty.org. Retrieved 2024-10-21.
  9. 1 2 correspondent, Emily Willingham | IJ (2023-02-20). "Marin County's Ring Mountain has much more to offer than views". The Mercury News. Retrieved 2024-10-21.{{cite web}}: |last= has generic name (help)
  10. ↑ Groves, Craig R.; Weakley, Alan S. (2000). "Owning Up to Our Responsibilities: Who Owns Lands Important for Biodiversity?". Precious Heritage. doi:10.1093/oso/9780195125191.003.0016. ISBN   978-0-19-512519-1 . Retrieved 2021-11-08.
  11. ↑ Tsujimori; Matsumoto; Wakabayashi; Liou (2006). "Franciscan eclogite revisited: Reevaluation of the P-T evolution of tectonic blocks from Tiburon Peninsula, California, USA". Mineralogy and Petrology. 88 (1–2): 243. Bibcode:2006MinPe..88..243T. doi:10.1007/s00710-006-0157-1. S2CID   55963012.
  12. ↑ Raymond, Loren (1 August 2019). "Origin of Mélanges of the Franciscan Complex, Diablo Range and Northern California: An Analysis and Review". Geosciences. 9 (8): 338. Bibcode:2019Geosc...9..338R. doi: 10.3390/geosciences9080338 .
  13. ↑ Mulcahy, Sean R.; Starnes, Jesslyn K.; Day, Howard W.; Coble, Matthew A.; Vervoort, Jeffrey D. (2018). "Early Onset of Franciscan Subduction". Tectonics. 37 (5): 1194–1209. Bibcode:2018Tecto..37.1194M. doi: 10.1029/2017TC004753 . ISSN   1944-9194.
  14. ↑ Tsujimori, T.; Matsumoto, K.; Wakabayashi, J.; Liou, J. G. (2006-08-22). "Franciscan eclogite revisited: Reevaluation of the P–T evolution of tectonic blocks from Tiburon Peninsula, California, U.S.A.". Mineralogy and Petrology. 88 (1): 243. Bibcode:2006MinPe..88..243T. doi:10.1007/s00710-006-0157-1. ISSN   1438-1168. S2CID   55963012.
  15. ↑ Ransome, Frederick L. (1895). "On lawsonite, a new rock forming mineral from the Tiburon Peninsula, Marin County, California". University of California. Bulletin of the Department of Geology. 1 (10): 301–312.
  16. ↑ Blake, M. C. Jr.; Howell, D. G.; Jayko, A. S. (1984). "Tectonostratigraphic Terranes of the San Francisco Bay Region": 5–22.{{cite journal}}: Cite journal requires |journal= (help)
  17. ↑ Wakabayashi, John (2012-09-28). "Subducted sedimentary serpentinite mélanges: Record of multiple burial–exhumation cycles and subduction erosion". Tectonophysics. Chaos and Geodynamics: Melanges, Melange Forming Processes and Their Significance in the Geological Record. 568–569: 230–247. Bibcode:2012Tectp.568..230W. doi:10.1016/j.tecto.2011.11.006. ISSN   0040-1951.
  18. ↑ Ernst, W. G. (2016-04-03). "Franciscan mélanges: coherent blocks in a low-density, ductile matrix". International Geology Review. 58 (5): 626–642. Bibcode:2016IGRv...58..626E. doi:10.1080/00206814.2015.1108879. ISSN   0020-6814. S2CID   129947605.
  19. ↑ "Google Earth". earth.google.com. Retrieved 2019-12-22.
  20. ↑ "Streetcar2Subduction". www.agu.org. Retrieved 2019-12-22.
  21. ↑ "Recreation - County of Marin". www.marincounty.org. Retrieved 2017-03-21.
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