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54-515: The park and hollow offer an experience of San Francisco's diverse terrains as they appeared before the intense development of the region in the late 19th and the 20th centuries. The park incorporates free-flowing Islais Creek and the associated riparian habitat, an extensive grassland with adjoining trees that supports breeding pairs of red-tailed hawks and great horned owls , striking rock outcrops, and arid patches covered by " coastal scrub " plant communities. In all, about 63 acres (25 ha) of

108-634: A bascule bridge. Greywacke Greywacke or graywacke ( German grauwacke , signifying a grey, earthy rock) is a variety of sandstone generally characterized by its hardness (6–7 on Mohs scale ), dark color, and poorly sorted angular grains of quartz , feldspar , and small rock fragments or sand-size lithic fragments set in a compact, clay -fine matrix. It is a texturally immature sedimentary rock generally found in Paleozoic strata . The larger grains can be sand- to gravel-sized, and matrix materials generally constitute more than 15% of

162-482: A building material and a sculptural material across many eras and societies. Its oldest known uses date to the early third millennium BCE , in Egypt's early dynastic period . Its wide use in sculpture and vessels is thought to have been due to its fine grain size and resistance to fracturing, making it suitable for fine detail and intricate shapes. Aside from its structural uses, greywacke stone (or molds taken from it)

216-448: A compact village, and proximity to transit and the canyon. Every new development project, whether public or private, must incorporate these features based on principles of good design and human scale." A section of Bosworth Street connects the southern entrance to Glen Canyon Park with the central commercial district of Glen Park that lies about a third of a mile east. This section presents an important opportunity for urban design because

270-529: A lawsuit that went up to the California Supreme Court called The People of the State of California ex relatione The Board of State Harbor Commissioners VS. The Potrero And Bay View Railroad Company, Islais Creek was declared a non-navigable waterway in 1883. In 1871, the area along the creek became known as the city's "New Butchertown" when more than 100 slaughterhouses opened. Since then, the condition of

324-521: A picnic ground -- mainly for adults. Crocker Real Estate added tables and benches, a baseball diamond and a running track. It was fenced and rented to organizations for company picnics that often turned into boisterous drinking brawls. Neighborhood children had to find other places to play. The Crocker era ended in 1922 when the City of San Francisco purchased the 101-acre (0.41 km) Glen Canyon Park and Recreation site. At present, O'Shaughnessy Boulevard defines

378-724: A waterfront park in Islais Creek. The initial plan for a park was finally launched in 1988 with a $ 50,000 grant from the State Department of Water Resources as well as community groups in The Bayview . With an additional of $ 100,000 federal and local grants as well as supports from non-profit organizations and governmental agencies, namely the Sierra Club , San Francisco Municipal Railway (Muni), Department of Public Works, Public Utilities Commission , Port of San Francisco , and Caltrans ,

432-524: A wider creek, it ran parallel to Alemany Boulevard and I-280 and debouched into the Islais Creek estuary, near Industrial Street and Oakdale Avenue. Precita Creek , a nearby creek that originated from Noe Valley , also joined Islais Creek at the Cesar Chavez Street and Evans Avenue intersection. From its sources in the Glen Canyon, the entire creek stretched about 3.5 miles (5.6 km) to

486-593: Is a small creek in San Francisco , California . The name of the creek is derived from a Salinan Native American word " slay " or " islay ", the name for the Prunus ilicifolia wild cherries. Around the time of the Gold Rush, the area became an industrial hub, and the condition of the creek worsened. After the devastating 1906 San Francisco earthquake , the city decided to reclaim the creek using earthquake debris, reducing

540-610: Is difficult to characterize mineralogically, it has a well-established place in petrographical classifications because these peculiar composite arenaceous deposits are very frequent among Silurian and Cambrian rocks, and are less common in Mesozoic or Cenozoic strata. Their essential features are their gritty character and their complex composition. By increasing metamorphism , greywackes frequently pass into mica- schists , chloritic schists and sedimentary gneisses . The term "greywacke" can be confusing, since it can refer to either

594-654: Is due to the different weathering of the layers. The bedrock of the canyon is made up of rocks of the Marin Headlands terrane . The terrane is a large packet of rock that extends diagonally from the Marin Headlands (just north of the Golden Gate ), through the Twin Peaks and Glen Canyon area, and on to the southeast. This terrane is from 100 to 200 million years old (i.e. the Cretaceous and Jurassic periods). The bedrock of

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648-560: Is easily entered at its southeastern corner (end of Bosworth Street). Somewhat further north, there is a wooden stairway leading down into the park (the Sussex Street entrance). There are also trails leading into the park from the Diamond Heights Shopping Center. Of one of these, Joseph Stubbs has written, "It is a dramatic, sudden revelation of the park interior from high up, which is simply stunning. It occurs midsection of

702-428: Is next to Cargo Way and 3rd Street. It is home to a historical information sign, a short trail, public art created from a copra loading crane, and a pier with a dock for small boats. As of December, 2017, the copra crane is lying on its side and the restoration project on hold due to jurisdiction and cost problems. Since Islais Creek is a culvert that carries storm water, domestic sewage, and industrial wastewater, it

756-597: Is possible for the sewage to overflow. Such overflow can cause a public health hazard as Islais Creek displays higher level of heavy metals , PCBs , bacteria , as well as organochlorines than other parts of the San Francisco Bay. The Third Street Bridge is the major crossing of the creek, carrying T Third Street light rail line and Third Street. It is a bascule-type drawbridge . The Port of San Francisco extended Illinois Street across Islais Creek in 2006 to relieve traffic for Third Street. This crossing also uses

810-801: Is sometimes calcareous . Greywackes are abundant in Wales , the south of Scotland , the Longford-Down Massif in Ireland and the Lake District National Park of England ; they compose the majority of the main Southern Alps that make up the backbone of New Zealand . Both feldspathic and lithic greywacke have been recognized in Ecca Group in South Africa . Greywackes are also found in parts of

864-428: Is surrounded by willow thickets. In earlier times, the creek had an open water channel sustained by a much larger water flow, and was "more of a river than a creek". Urban development has reduced the watershed of Islais Creek by as much as 80 percent. At the southern end of the canyon, Islais Creek enters a culvert which carries it to its exit into San Francisco Bay. The creek has a meager but year-round natural flow, and

918-636: The Eastern Desert east of the Nile . They were an early object of geological study in Britain where the Geological Society was founded in 1807, and excited much public interest in geology. Greywacke was interesting because it was found in many places in Britain and its occurrence in particular places was evidence of the pattern of geological strata that had been laid down. Greywacke stone has been used as

972-516: The Franciscan formation that makes up much of coastal California. During subduction - 160 to 80 million years ago - and the subsequent uplift, the terrane was twisted, broken and disrupted, and the chert was deformed into the tight folds now visible in road cuts along O'Shaughnessy Boulevard (see photo). These rock outcrops provide some of the best outdoor rock climbing in San Francisco, primarily in

1026-555: The San Francisco Bay . The mouth was nearly 2 miles (3.2 km) wide, providing up to 85% of the drinking water in San Francisco. Due to urban development, however, the watershed of Islais Creek has been reduced by roughly 80% from its historical extent. A large number of neighborhoods in San Francisco today, such as Bernal Heights , Hunters Point , Visitacion Valley , parts of the Mission and Potrero Hill , were once covered by

1080-448: The 18th century. The name Los Islais first appeared on Mexican maps in 1834, named for the Islay cherries that grew wildly in the area. By 1850, water from the creek was used by farmers to irrigate crops. The Gold Rush marked the decline of the creek as large numbers of gold rushers swarmed into the city. A railroad trestle was built over the creek and tidal flats in the 1860s and in

1134-622: The 1980s, only four were found between 2001 and 2007. A reintroduction was done in April 2009. Reintroduction may also be possible in Glen Canyon Park. Here the main issue appears to be re-establishing the native plant " silver bush lupine ", whose leaves are the larval food of these butterflies. A substantial fraction of Glen Canyon Park is now covered by non-native species including eucalyptus forest (17 acres), French broom (6 acres), and field mustard , but no specific proposal for re-introduction of

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1188-478: The California State Highway Department proposed a Crosstown Freeway that would have followed Bosworth Street through the neighborhood of Glen Park and then O'Shaughnessy Boulevard through Glen Canyon Park. The plan was abandoned due to opposition by several groups of residents. Six other freeways planned for San Francisco in the late 1940s were cancelled at about the same time; the conflicts over

1242-589: The City of San Francisco in the 1990s using eminent domain . The area was being considered for residential development. The 3.6-acre parcel was named O'Shaughnessy Hollow. The city government of San Francisco mandated the development of management plans for all the "natural areas" under the city's control, and this process culminated in release of the Significant Natural Resources Areas Management Plan in February 2006. The plan favors

1296-565: The aerial photograph). These facilities include a community recreation center, ball fields and tennis courts, playgrounds, and a ropes course. The park is also well used by local rock climbers, who consider it one of the best "bouldering" sites near San Francisco. An additional building about halfway up the canyon near Islais Creek serves the Silver Tree Day Camp and the Glenridge Cooperative Nursery School. The park

1350-400: The canyon to develop a neighborhood that would attract homebuyers. As Jeanne Alexander has written, Crocker installed a mini-amusement park with an aviary, a mini-zoo--bears, elephants and monkeys, a bowling alley, and, for extra thrills, hot-air balloon rides, and an intrepid tight-rope walker who performed on a wire stretched across the canyon. From 1907-1922, Glen Canyon Park was operated as

1404-522: The creek deteriorated, literally becoming a dumping place of garbage, sewage, animal waste , and unsold meat products. The condition became so bad that the creek was commonly referred to as " Shit Creek" by San Franciscans, according to historian Karl Kortum. After the 1906 earthquake , San Francisco Board of Supervisors voted to fill the creek with earthquake debris, reducing the creek to its present size. During World War II , it served as docking areas for large ocean-going tugs. The area also located

1458-525: The creek for the Muni Metro T Third Street light rail line, cracked the concrete sewer underground which carries more than 80 million gallons of sewage a day. The incident flooded the creek and its adjacent Muwekma Ohlone Park with sewage. The park had to be excavated to make way for the repairing of the sewer pipe. It was estimated that it would take more than $ 101,660 to repair and $ 65,000 for wildlife habitat restoration. The remaining Islais Creek Park

1512-448: The creek gradually improved after the construction of a water treatment plant in 1970. Today, the majority of the creek is covered and transformed into a culvert with its remnants flowing at Glen Canyon and near the bay. Many local community organizations were set up to improve the condition of the creek and nearby areas. Friends of Islais Creek, established back in 1984, and David Erickson, a local community figure, were committed to build

1566-470: The creek would be established both by re-planting sections of the creek's banks with different plants and by the introduction of "scouring" structures. Glen Canyon Park used to support populations of two rare species: the "vulnerable" San Francisco forktailed damselfly and the "endangered" Mission blue butterfly . The plan proposes changes in the management of the park that would promote self-sustaining populations of these insects. The damselfly population in

1620-411: The diversity of species living along Islais Creek. The plan envisions the removal of an additional 120 trees (of the total of 6000 trees in the park) to further improve the creek, to increase the extent of the park's grasslands, and to promote forest understory plants. The plan also seeks to restore some open-water areas along the creek, which is nearly totally obscured by the willow thickets. The change in

1674-499: The extent of the creek. In 2007, the San Francisco Public Utilities Commission , which manages the city's water, began investigating the possibility of " daylighting " underground portions of the creek. As of 2009, remnants of the creek remain inside the Glen Canyon Park and a 1-mile (1.6 km) channel near Third Street where Islais Creek debouched into the bay. The history of Islais Creek dates to

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1728-399: The finer beds associated with them. Their component particles are usually not very rounded or polished, and the rocks have often been considerably indurated by recrystallization , such as the introduction of interstitial silica . In some districts, the greywackes are cleaved, but they show phenomena of this kind much less perfectly than the slates. Although the group is so diverse that it

1782-621: The form of bouldering . The park's history commences with Adolph Sutro 's purchase in the 1850s of 76 acres (310,000 m) of the canyon, which he named "Gum Tree Ranch" after the blue gum eucalyptus trees he had planted. The first commercial manufacturing of dynamite in the U.S. occurred in the canyon; on March 19, 1868, the Giant Powder Company began production at its first manufacturing plant, under exclusive license from Alfred Nobel to produce his new explosive in America. The plant

1836-505: The freeway plan for San Francisco were among the earliest incidents in the Highway revolts in the United States of the 1960s and 1970s. Six years later, in 1964, homes and businesses along Bosworth Street were demolished in order to greatly widen the section of the street leading to O'Shaughnessy Boulevard. An undeveloped, very steep area just west of O'Shaughnessy Boulevard was acquired by

1890-420: The immature (rock fragment) aspect of the rock or its fine-grained (clay) component. Greywackes are mostly grey, brown, yellow, or black, dull-colored sandy rocks that may occur in thick or thin beds along with shales and limestones . Some varieties include feldspathic greywacke , rich in feldspar , and lithic greywacke , rich in other tiny rock fragments. They can contain a very great variety of minerals ,

1944-474: The largest copra coconut processing plant in the United States West Coast . In fact, the abandoned five-story high copra crane, used to transport large amount of copras from ships to the plant as late as 1974, still remains on the creek bank preserved as a historic landmark. In the 1950s, Islais Creek was home to the largest sardine canning industry in the world. The deteriorated condition of

1998-443: The lava. The ooze was colored red by iron from hydrothermal springs . Both lava and chert were formed in the deep ocean near the equator, and were rafted northeast on the gradually-moving ocean floor toward California. Near shore, greywacke accumulated on the chert in some areas, including a small part of the southeast slope of Glen Canyon. Subduction then squeezed the terrane against the continent, and it eventually became part of

2052-412: The lower slopes of the canyon - largely hidden under slope debris/ravine fill - is pillow lava or greenstone; these erupted from fissures in the deep ocean floor when the terrane was located hundreds of miles southwest of its present location. The upper slopes and cliffs are of layered chert, which hardened into rock from the ooze of remains of countless radiolarian creatures that accumulated on top of

2106-500: The lupine was included in the Management Plan. The importance of Glen Canyon Park to its surrounding neighborhoods is indicated by a recent community plan for Glen Park that contains the following statement: "The Glen Park community's special character is created by the unique combination of eclectic building styles, pedestrian scale, the layering of green space and buildings climbing into the canyon, public spaces, walkable streets,

2160-494: The park and hollow are designated as undeveloped Natural Area . Elevations in Glen Canyon Park range from approximately 225 feet (69 m) above sea level at the south end of the park to 575 feet (175 m) above sea level at the north end and along the eastern rim of the canyon; the walls of the canyon are extremely steep, with many slopes approaching a length-to-height ratio of 1:1 (100 percent). Formal recreational facilities in Glen Canyon Park are mostly located at its southern end (see

2214-420: The park behind Diamond Heights Shopping Center and George Christopher Playground." A branch of Islais Creek (named after the wild cherry islay ) originates in the canyon. It is the largest remaining creek in San Francisco with public access. The bottom of the canyon, where Islais Creek flows, is irregular but moderate in slope, dropping 350 feet (107 m) over a distance of about 1 mile (1.6 kilometer). The creek

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2268-663: The park was finished in 1998. Located adjacent to Pier 80 on the shores of the creek, the Muwekma Ohlone Park or the Muwekma Ohlone Sanctuary is named after the native inhabitants and has since become an important habitat for a wide array of wildlife, including the Pacific Chorus Frog and Mission blue butterfly . On November 19, 2001, construction crews, while preparing to drill an electrical conduit (consisting of six large 115kV electrical cables) across

2322-508: The park was studied by John Hafernik and his colleagues in the 1980s prior to its local extinction; they re-introduced a population of these damselflies in 1996 that persisted for two seasons. The damselflies need open water habitat, which has proven difficult to maintain. There has been a declining population of Mission blue butterflies at the nearly contiguous Twin Peaks Natural Area; while park employees logged about 150 butterflies in

2376-495: The principal ones being quartz, orthoclase and plagioclase feldspars, calcite , iron oxides and graphitic, carbonaceous matters, together with (in the coarser kinds) fragments of such rocks as felsite , chert , slate , gneiss , various schists , and quartzite . Among other minerals found in them are biotite , chlorite , tourmaline , epidote , apatite , garnet , hornblende , augite , sphene and pyrites . The cementing material may be siliceous or argillaceous and

2430-690: The properties along the north side have remained undeveloped since their acquisition by the City in the 1950s. The community plan proposes that this land be developed into a greenway and pedestrian plaza. The plan also suggests that Islais Creek , which runs underneath this section of Bosworth Street, be "daylighted" in this section. The plan was formally endorsed by the San Francisco Planning Commission in 2004, but implementation has not been funded as of 2007. Islais Creek Islais Creek or Islais Creek Channel (previously known as Du Vrees Creek , Islais Channel and Islais Swamp )

2484-585: The re-establishment of native species and species diversity in the city's parks. Some aspects of the plan have been controversial. For example, the plan envisions the removal of some large, mature trees (often eucalyptus, which was imported from Australia) to favor smaller native plants. The plan also includes new restrictions on recreational use of the park, such as the closure of some trails and of some areas for rock climbing, and prohibitions against unleashed dogs. In Glen Canyon Park, about 20 mature eucalyptus trees were removed in 2004 as part of an effort to increase

2538-444: The resulting deposits may exhibit a variety of sedimentary features. Supporting the turbidity origin theory is the fact that deposits of greywacke are found on the edges of the continental shelves , at the bottoms of oceanic trenches , and at the bases of mountain formational areas. They also occur in association with black shales of deep-sea origin. As a rule, greywackes do not contain fossils , but organic remains may be common in

2592-407: The rock by volume. The origin of greywacke was unknown until turbidity currents and turbidites were understood, since, according to the normal laws of sedimentation , gravel , sand and mud should not be laid down together. Geologists now attribute its formation to submarine avalanches or strong turbidity currents. These actions churn sediment and cause mixed-sediment slurries, in which

2646-480: The sand dunes south of Golden Gate Park. The site of the plant has been designated as California Historical Landmark #1002, although no marker has been placed on the site yet. The Good Brothers Dairy was located where Glenridge Cooperative Nursery School is today. Cows grazed as early as the 1850s, and likely earlier. The dairy remained until the 1920s. In 1889, the Crocker Real Estate Company bought

2700-626: The southern slope of Twin Peaks , slightly north of Portola Drive. It flowed downstream southeastward through the Glen Canyon Park paralleling Bosworth Street and eventually reaching the bottom of the Mission Street viaduct at I-280 . The other branch began at the intersection of Cayuga Avenue and Regent Street. It flowed generally eastward along Mission Street and reached the I-280 viaduct. Together, as

2754-495: The water and resulting vegetation provide a habitat for animals, including skunks , opossums , raccoons , red-tailed hawks , red-shouldered hawks , great horned owls , coyotes , and the rare native San Francisco forktail damselfly , Ischnura gemina . The scenery of Glen Canyon Park is also distinguished by numerous large outcrops of rock. The most striking of these consist of reddish, layered " Franciscan " chert . These outcrops have clearly visible banding (see photo) which

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2808-487: The waterbody to its present size. Though much of Islais Creek has been converted to an underground culvert , remnants still exist today at both Glen Canyon Park and Third Street. Several community organizations are dedicated to preserve these remnants, as they are important wildlife habitats. The historic Islais Creek, the largest body of water in the city covering an area of nearly 5,000 acres (7.813 sq mi; 20.234 km ), had two main branches. One originated near

2862-589: The western perimeter of Glen Canyon Park. In conjunction with an extension of Bosworth Street, the Boulevard was built in 1935 using roadcuts and filled slopes on the canyon's steep slopes. It was named after Michael O'Shaughnessy , who was for many years the Chief Engineer of the city. The recreation center at the south end of the park was built by the Works Progress Administration in 1937. In 1958,

2916-409: Was apparently located near the present recreation center, at the southern end of the park. The factory did not last long. On November 26, 1869, an explosion completely destroyed the entire facility, turning every one of the buildings on the site and the surrounding fencing, into "hundreds of pieces", according to a newspaper account. Two people were killed, and nine injured; the plant was later rebuilt in

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