Robert Sibley Volcanic Regional Preserve
Robert Sibley Volcanic Regional Preserve | |
---|---|
Location | Alameda and Contra Costa Counties, California |
Nearest city | Oakland, California |
Coordinates | 37°51′18″N 122°12′12″W / 37.85495°N 122.20326°W |
Area | 928 acres (3.76 km2) |
Created | 1936 |
Operated by | East Bay Regional Park District |
Robert Sibley Volcanic Regional Preserve is located in the
History
The park was one of the first three parks established by the
Geology
The preserve contains a
Folding, erosion, and a quarry operation exposed a cross section of the volcano, providing an excellent means to study a
Rock Formations
The region has remnants of rocks from the Orinda Formation and the Claremont Formation.[1][2][3] 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.[2]
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."[2]
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.[2] 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.[2]
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 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.[1]
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.[1]
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,[b] it is a favorite destination for hikers who come to pray, meditate, and examine talismans left in the center by previous visitors.[9] 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."[2] 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.[8]
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.[9]
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.[8]
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.[1]
See also
- basaltic lavaformation in park.
- Pliocene California geology
- Volcanism of California
Notes
References
- ^ a b c d e f g h i "EBRPD - Sibley". www.ebparks.org. Retrieved 2021-05-11.
- ^ a b c d e f g h i Slack, Gordy. "Voice of the Volcano -". Bay Nature. Retrieved 2022-10-22.
- ^ a b USGS.gov: "Upper Cretaceous and Lower Tertiary Rocks Berkeley and San Leandro Hills, California", by J. E. Case, GEOLOGICAL SURVEY BULLETIN 1251-J, 1968.
- ^ Oakland Geology Blog: "Grizzly Peak and Moraga basalt"
- ^ Geology.about.com: "California Transect - Stop 30, Orinda Formation and Moraga Volcanics"
- ^ a b "Exploring Sibley Volcanic Regional Preserve". KQED. Retrieved 2022-10-22.
- ^ Chao, Julie (2010-07-06). "Berkeley Lab Geologist Studies the Ground Beneath His Feet". News Center. Retrieved 2021-05-11.
- ^ a b c "Mazzariello's Maze." Friends of the Labyrinth. Undated Accessed July 13, 2018
- ^ a b Jones, Nicole. "Sibley Regional Preserve: A walk on Oakland’s wild and volcanic side." Oakland North. July 22, 2011. Accessed July 13, 2018.