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{{Short description|Nature preserve in the San Francisco Bay Area}}
{{Infobox park {{Infobox park
| name = Robert Sibley Volcanic Regional Preserve | name = Robert Sibley Volcanic Regional Preserve
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| image_size = 300px | image_size = 300px
| image_alt = | image_alt =
| image_caption = Round Top, an extinct volcano at Sibley Volcanic Regional Preserve | image_caption = View from ] at Sibley Volcanic Regional Preserve
| map = <!-- or | map_image = --> | map = <!-- or | map_image = -->
| map_width = | map_width =
| type = | type =
| location = Alameda & Contra Costa Counties, California | location = Alameda and Contra Costa Counties, California
| nearest_city = Oakland, California | nearest_city = ]
| coordinates = {{Coord|37.85495|-122.20326|type:landmark_region:US-CA|display=title}} | coordinates = {{Coord|37.85495|-122.20326|type:landmark_region:US-CA|display=inline,title}}
| area = {{convert|928|acres|km2}} | area = {{convert|928|acres|km2}}
| created = 1936 | created = 1936
| operator = East Bay Regional Parks District | operator = ]
| visitation_num = | visitation_num =
| status = | status =
Line 19: Line 20:
| open = | open =
}} }}
'''Robert Sibley Volcanic Regional Preserve''' is located in the ] of the ] region of the ], ].<ref name="ebrp"></ref> The park is part of the East Bay Regional Parks District (EBRPD), covers {{convert|928|acres|km2}}, and lies partly in ] and partly in ], east of ]. It can be entered from Oakland on Skyline Boulevard, or from Contra Costa County on Old Tunnel Road.<ref name="ebrp"/> '''Robert Sibley Volcanic Regional Preserve''' is located in the ] of the ] region of the ], ].<ref name="ebrp">{{Cite web|title=EBRPD - Sibley|url=https://www.ebparks.org/parks/sibley/|access-date=2021-05-11|website=www.ebparks.org}}</ref> The park is part of the East Bay Regional Parks District (EBRPD), covers {{convert|928|acres|km2}}, and lies east of ], partly in ] and partly in ]. It can be entered from Oakland via Skyline Boulevard, or from Contra Costa County via Old Tunnel Road.<ref name="ebrp"/>


==History== ==History==
The park was one of the first three parks established by the ] (EBRPD) in 1936.{{efn|The other two original parks were Tilden and Temescal.<ref name="ebrp"/>}} It was originally named '''Round Top Regional Park'''. ] (elevation 1,761 feet/537m) is an extinct volcano in the Berkeley Hills. It is home to several stone ]s of recent origin. The park was renamed after the second president of the EBRPD, Robert Sibley, shortly after his death.<ref name="ebrp"/> The park was one of the first three parks established by the ] (EBRPD) in 1936.{{efn|The other two original parks were Tilden and Temescal.<ref name="ebrp"/>}} It was originally named '''Round Top Regional Park'''. ] (elevation {{Convert|1761|ft|m|disp=sqbr}}) is named for an extinct volcano in the Oakland Hills which started to erupt 10.2 Million years ago. It is home to at least two stone ]s of recent origin. The park was renamed after the second president of the EBRPD, ], shortly after his death.<ref name="ebrp"/> U.C. Berkeley Professor Emeritus ] studied the Sibley Regional Preserve extensively, dating the volcano to be 10.2 million years old.<ref name=":1">{{Cite web |last=Slack |first=Gordy |title=Voice of the Volcano - |url=https://baynature.org/article/voice-of-the-volcano/ |access-date=2022-10-22 |website=Bay Nature |language=en-US}}</ref> Since 10.2 million years ago, the Pacific tectonic plate has slowly pushed the volcano north.<ref name=":1" />


==Geology== ==Geology==
The preserve contains a ] volcanic center that, about 10 million years ago, produced most of the lavas that underlie the East Bay ridges from Inspiration Point in ] to ]. Geologists refer to this local volcanism as the ].<ref name="usgs">, by J. E. Case, GEOLOGICAL SURVEY BULLETIN 1251-J, 1968.</ref><ref></ref><ref></ref> Subsequent compressive strains produced by various local faults including the ] folded the lava-bearing rock formations, tilting the Round Top vent complex on its side. The preserve contains a ] volcanic center that, about ten million years ago, produced most of the lavas that underlie the East Bay ridges from Inspiration Point in ] to ]. Geologists refer to this local volcanism as the ].<ref name="usgs">, by J. E. Case, GEOLOGICAL SURVEY BULLETIN 1251-J, 1968.</ref><ref></ref><ref></ref> Subsequent compressive strains produced by various local faults such as the ] folded the lava-bearing rock formations, tilting the Round Top vent complex on its side. The results of such compressive strains of local faults has altered the volcano's original landscape, and Round Top now tilts towards the east.<ref name=":2">{{Cite web |title=Exploring Sibley Volcanic Regional Preserve |url=https://www.kqed.org/quest/15110/sibley-volcanic-regional-preserve-exploration |access-date=2022-10-22 |website=KQED |language=en-us}}</ref> Such local faults, notably ] and ], have also caused the volcano to form a trough that is the ].<ref name=":1" />


Folding, erosion, and a quarry operation exposed a cross section of the great volcano, providing an excellent means to study a ] volcano. Lava within the vent has been dated by ] at 9.5 million years old.<ref></ref> Folding, erosion, and a quarry operation exposed a cross section of the volcano, providing an excellent means to study a ] volcano. The mountain ] is not the volcano. The ancient volcano has eroded away. It has also tilted on its side, so it doesn't look like a volcano. (https://www.kqed.org/news/11876393/wait-there-was-a-volcano-in-the-east-bay-hills) The construction corporation used the region as a quarry, leaving the volcanic region open and exposed.<ref name=":2" /> Lava within the vent has been dated by ] at 9.5 million years old.<ref>{{Cite web|last=Chao|first=Julie|date=2010-07-06|title=Berkeley Lab Geologist Studies the Ground Beneath His Feet|url=https://newscenter.lbl.gov/2010/07/06/geologist-studies-ground/|access-date=2021-05-11|website=News Center|language=en-US}}</ref>


=== Rock Formations ===
⚫ ]
The region has remnants of rocks from the ] and the ].<ref name="ebrp" /><ref name=":1" /><ref name="usgs" /> From the Orinda Formation rocks include "river gravel, sandstone, and mudstone." The river gravel are red in color. The sandstones are around 65 million years old. From the Claremont Formation, rocks include marine rocks.<ref name=":1" />


The surface of the ] found on the ] of Round Top are of the color "light brownish or rusty gray" and the interior of the basalt is of the color "gun steel blue."<ref name=":1" />
⚫ ==Activities==
⚫ There are several trails in the preserve, with most restricted for hiking and horseback use. Only a few are available for multi-purpose use. Round Top Road is paved from the Visitor Center to the top of Round Top.<ref name=ebrp/> There are no campgrounds or picnic areas in the Preserve. The Visitor Center at the Skyline Boulevard entrance is unstaffed, but has displays depicting the areas geology. It also offers brochures to assist visitors making self-guided tours.<ref name="ebrp"/>


=== Bake Zone ===
⚫ * '''East Bay Skyline Regional Trail''', which is {{convert|31|miles|km}} long, traverses the Sibley preserve on the ridgeline that separates between ] and ].
A bake zone is a region where heat from the lava of the volcano changed the color of the surrounding rocks to red. Such rocks include rhyolite tuff, lapilli agglomerate, and vesicular basalt.<ref name=":1" /> Rhyolite tuff are remnants of ash from a northern volcano around {{convert|4|mi}} away. Lapilli agglomerate are remnants of volcanic cinders. Vesicular basalt are remnants of gas bubbles from cooling lava.
⚫ * '''Round Top Road''' goes from the Sibley visitor center to the top of Round Top. '''Round Top Loop Trail''' circles Round Top peak.

⚫ * '''Volcanic Trail''', once a quarry haul road, contains most of the stops on the self-guided volcanic tour.
=== The Stone Property ===
The Stone Property is a restricted region of the park. The area consists of pure basalt around {{convert|100|ft}} wide, as well as "autobrecciating basaltic flow" which occurs when lava continues to flow under a cooled surface.<ref name=":1" />

⚫ == Activities ==
⚫ ]]]
⚫ There are several trails in the preserve. Most are restricted to hiking and horseback use and only a few are available for multi-purpose use. Round Top Road is paved from the visitor center to the top of ]. There are no picnic areas in the preserve; however, there are plenty of benches good for a rest, view and snack, as well as a campground. The visitor center at the Skyline Boulevard entrance is unstaffed and offers brochures for self-guided tours. It also features depictions of the region's geology.<ref name="ebrp"/>

===Hiking trails===
⚫ * '''East Bay Skyline Regional Trail''', which is {{convert|31|miles|km}} long, traverses the Sibley preserve on the ridgeline that separates ] and ].
⚫ * '''Round Top Road''' goes from the Sibley visitor center to the peak of Round Top. CLOSED
* '''Round Top Loop Trail''' circles Round Top's peak.
⚫ * '''Volcanic Trail''', once a quarry haul road, contains most of the stops on the self-guided volcanic tour.
* '''Quarry Trail''' connects the middle of Volcanic Trail to a point lower down on Quarry Road. * '''Quarry Trail''' connects the middle of Volcanic Trail to a point lower down on Quarry Road.
* '''Pond Trail''' is a short trail segment that descends to a couple of ponds on the north side of the preserve.<ref name="ebrp"/> * '''Pond Trail''' is a short trail segment that descends to a couple of ponds on the north side of the preserve.<ref name="ebrp"/>
]


=== Labyrinths ===
{{clearleft}}
At least two man-made labyrinths exist within RSVRP. The first, and arguably most frequently visited, is known as the Mazzariello Labyrinth. Constructed in 1990 and donated as a "gift to the world" by East Bay resident Helena Mazzariello,{{efn|Helena Mazzariello is a sculptor, psychic, and shamanic practitioner who lived in Oakland's Montclair District. The labyrinth she created is known as The Sibley Labyrinth, or "Mazzariello's labyrinth"<ref name="FOL"> Accessed July 13, 2018</ref>}} it is a favorite destination for hikers who come to pray, meditate, and examine talismans left in the center by previous visitors.<ref name="Jones"> Accessed July 13, 2018.</ref> In this labyrinth, she would walk her goats, stating that, "I can enter with a question, and inevitably, I will emerge with some insight. It is a powerful spot."<ref name=":1" /> Notwithstanding the official gate hours listed below, Friends of the Labyrinth claims that the labyrinth has visitors 24 hours a day, 7 days a week.<ref name="FOL" />

The next marker along the Round Top Loop Trail leads to the Volcanic Trail, which crosses to the left. At Post No. 4, the hiker can see a smaller, heart-shaped labyrinth. It is not nearly as elaborate as the Mazzariello Labyrinth, and apparently not as heavily used.<ref name="Jones"/>

There have been claims of other, earlier labyrinths hidden in the preserves, but Friends of the Labyrinth dismisses these as urban legends, as no evidence has been found. The organization reports that analysis of high-resolution aerial photographs show no trace of such activity.<ref name="FOL"/>


==Visiting the park== ==Visiting the park==
The park is open year round, park and gate hours are: The park is open year-round. The park and gate hours are:
* November - February 7AM - 6PM * November - February 7AM - 6PM
* March - October 7AM - 10PM * March - October 7AM - 10PM
There is no parking fee and no dog fee. There is no parking fee and no dog fee.<ref name="ebrp"/>

⚫ ==Notes==
{{notelist}}


==See also== ==See also==
Line 55: Line 71:
* {{C|Pliocene California|Pliocene California geology}} * {{C|Pliocene California|Pliocene California geology}}
* {{C|Volcanism of California}} * {{C|Volcanism of California}}

⚫ ==Notes==
{{reflist|group=lower-alpha}}


==References== ==References==
Line 60: Line 79:


==External links== ==External links==
⚫ {{Commons category|Robert Sibley Volcanic Regional Preserve}}
* *
⚫ {{Commonscat|Robert Sibley Volcanic Regional Preserve}}
* *

{{-}}


{{East Bay Regional Parks}} {{East Bay Regional Parks}}

Latest revision as of 18:24, 9 July 2024

Nature preserve in the San Francisco Bay Area
Robert Sibley Volcanic Regional Preserve
View from Round Top at Sibley Volcanic Regional Preserve
LocationAlameda and Contra Costa Counties, California
Nearest cityOakland, California
Coordinates37°51′18″N 122°12′12″W / 37.85495°N 122.20326°W / 37.85495; -122.20326
Area928 acres (3.76 km)
Created1936
Operated byEast Bay Regional Park District

Robert Sibley Volcanic Regional Preserve is located in the Oakland Hills of the East Bay region of the San Francisco Bay Area, California. The park is part of the East Bay Regional Parks District (EBRPD), covers 928 acres (3.76 km), and lies east of Oakland, partly in Alameda County and partly in Contra Costa County. It can be entered from Oakland via Skyline Boulevard, or from Contra Costa County via Old Tunnel Road.

History

The park was one of the first three parks established by the East Bay Regional Parks District (EBRPD) in 1936. It was originally named Round Top Regional Park. Round Top (elevation 1,761 feet ) is named for an extinct volcano in the Oakland Hills which started to erupt 10.2 Million years ago. It is home to at least two stone labyrinths of recent origin. The park was renamed after the second president of the EBRPD, Robert Sibley, shortly after his death. U.C. Berkeley Professor Emeritus Garniss Curtis studied the Sibley Regional Preserve extensively, dating the volcano to be 10.2 million years old. Since 10.2 million years ago, the Pacific tectonic plate has slowly pushed the volcano north.

Geology

The preserve contains a Pliocene epoch volcanic center that, about ten million years ago, produced most of the lavas that underlie the East Bay ridges from Inspiration Point in Tilden Regional Park to Moraga. Geologists refer to this local volcanism as the Moraga Volcanics. Subsequent compressive strains produced by various local faults such as the Hayward Fault folded the lava-bearing rock formations, tilting the Round Top vent complex on its side. The results of such compressive strains of local faults has altered the volcano's original landscape, and Round Top now tilts towards the east. Such local faults, notably Hayward and Moraga, have also caused the volcano to form a trough that is the Siesta/Gateway Valley.

Folding, erosion, and a quarry operation exposed a cross section of the volcano, providing an excellent means to study a California Coast Ranges volcano. The mountain Round Top is not the volcano. The ancient volcano has eroded away. It has also tilted on its side, so it doesn't look like a volcano. (https://www.kqed.org/news/11876393/wait-there-was-a-volcano-in-the-east-bay-hills) The construction corporation Kaiser Sand & Gravel used the region as a quarry, leaving the volcanic region open and exposed. Lava within the vent has been dated by UC Berkeley at 9.5 million years old.

Rock Formations

The region has remnants of rocks from the Orinda Formation and the Claremont Formation. From the Orinda Formation rocks include "river gravel, sandstone, and mudstone." The river gravel are red in color. The sandstones are around 65 million years old. From the Claremont Formation, rocks include marine rocks.

The surface of the basalt found on the dike of Round Top are of the color "light brownish or rusty gray" and the interior of the basalt is of the color "gun steel blue."

Bake Zone

A bake zone is a region where heat from the lava of the volcano changed the color of the surrounding rocks to red. Such rocks include rhyolite tuff, lapilli agglomerate, and vesicular basalt. Rhyolite tuff are remnants of ash from a northern volcano around 4 miles (6.4 km) away. Lapilli agglomerate are remnants of volcanic cinders. Vesicular basalt are remnants of gas bubbles from cooling lava.

The Stone Property

The Stone Property is a restricted region of the park. The area consists of pure basalt around 100 feet (30 m) wide, as well as "autobrecciating basaltic flow" which occurs when lava continues to flow under a cooled surface.

Activities

A view from Round Top

There are several trails in the preserve. Most are restricted to hiking and horseback use and only a few are available for multi-purpose use. Round Top Road is paved from the visitor center to the top of Round Top. There are no picnic areas in the preserve; however, there are plenty of benches good for a rest, view and snack, as well as a campground. The visitor center at the Skyline Boulevard entrance is unstaffed and offers brochures for self-guided tours. It also features depictions of the region's geology.

Hiking trails

  • East Bay Skyline Regional Trail, which is 31 miles (50 km) long, traverses the Sibley preserve on the ridgeline that separates Wildcat Canyon Regional Park and Anthony Chabot Regional Park.
  • Round Top Road goes from the Sibley visitor center to the peak of Round Top. CLOSED
  • Round Top Loop Trail circles Round Top's peak.
  • Volcanic Trail, once a quarry haul road, contains most of the stops on the self-guided volcanic tour.
  • Quarry Trail connects the middle of Volcanic Trail to a point lower down on Quarry Road.
  • Pond Trail is a short trail segment that descends to a couple of ponds on the north side of the preserve.
American vetch is native to California and can be found at Sibley Volcanic Regional Preserve.

Labyrinths

At least two man-made labyrinths exist within RSVRP. The first, and arguably most frequently visited, is known as the Mazzariello Labyrinth. Constructed in 1990 and donated as a "gift to the world" by East Bay resident Helena Mazzariello, it is a favorite destination for hikers who come to pray, meditate, and examine talismans left in the center by previous visitors. In this labyrinth, she would walk her goats, stating that, "I can enter with a question, and inevitably, I will emerge with some insight. It is a powerful spot." Notwithstanding the official gate hours listed below, Friends of the Labyrinth claims that the labyrinth has visitors 24 hours a day, 7 days a week.

The next marker along the Round Top Loop Trail leads to the Volcanic Trail, which crosses to the left. At Post No. 4, the hiker can see a smaller, heart-shaped labyrinth. It is not nearly as elaborate as the Mazzariello Labyrinth, and apparently not as heavily used.

There have been claims of other, earlier labyrinths hidden in the preserves, but Friends of the Labyrinth dismisses these as urban legends, as no evidence has been found. The organization reports that analysis of high-resolution aerial photographs show no trace of such activity.

Visiting the park

The park is open year-round. The park and gate hours are:

  • November - February 7AM - 6PM
  • March - October 7AM - 10PM

There is no parking fee and no dog fee.

See also

Notes

  1. The other two original parks were Tilden and Temescal.
  2. Helena Mazzariello is a sculptor, psychic, and shamanic practitioner who lived in Oakland's Montclair District. The labyrinth she created is known as The Sibley Labyrinth, or "Mazzariello's labyrinth"

References

  1. ^ "EBRPD - Sibley". www.ebparks.org. Retrieved 2021-05-11.
  2. ^ Slack, Gordy. "Voice of the Volcano -". Bay Nature. Retrieved 2022-10-22.
  3. ^ USGS.gov: "Upper Cretaceous and Lower Tertiary Rocks Berkeley and San Leandro Hills, California", by J. E. Case, GEOLOGICAL SURVEY BULLETIN 1251-J, 1968.
  4. Oakland Geology Blog: "Grizzly Peak and Moraga basalt"
  5. Geology.about.com: "California Transect - Stop 30, Orinda Formation and Moraga Volcanics"
  6. ^ "Exploring Sibley Volcanic Regional Preserve". KQED. Retrieved 2022-10-22.
  7. Chao, Julie (2010-07-06). "Berkeley Lab Geologist Studies the Ground Beneath His Feet". News Center. Retrieved 2021-05-11.
  8. ^ "Mazzariello's Maze." Friends of the Labyrinth. Undated Accessed July 13, 2018
  9. ^ Jones, Nicole. "Sibley Regional Preserve: A walk on Oakland’s wild and volcanic side." Oakland North. July 22, 2011. Accessed July 13, 2018.

External links

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