History edit
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U.C. Berkeley Professor Emeritus Garniss Curtis studied the Sibley Regional Preserve extensively, dating the volcano to be 10.2 million years old.[2] Since 10.2 million years ago, the Pacific tectonic plate has slowly pushed the volcano north.[2] This region and the city of Berkeley rests on native Ohlone land.[3]
Geology edit
The results of such compressive strains of local faults has altered the volcano's original landscape. Round Top now tilts towards the east.[4] Such local faults, notably Hayward and Moraga, have also caused the volcano to form a trough that is the Siesta/Gateway Valley.[2]
The construction corporation Kaiser Sand & Gravel used the region as a quarry, leaving the volcanic region open and exposed.[4]
Rock Formations edit
The region has remnants of rocks from the Orinda Formation and the Claremont Formation.[5][1][2] 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 edit
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 away. Lapilli agglomerate are remnants of volcanic cinders. Vesicular basalt are remnants of gas bubbles from cooling lava.
The Stone Property edit
The Stone Property is a restricted region of the park. The area consists of pure basalt around 100 feet wide, as well as "autobrecciating basaltic flow" which occurs when lava continues to flow under a cooled surface.[2]
Activities edit
Sibley Labyrinths edit
In 1980, Helena Mazzariello had an art installation in one of the labyrinths where she would walk her goats. Mazariello stated that, "I can enter with a question, and inevitably, I will emerge with some insight. It is a powerful spot."[2]
References edit
- ^ a b "Sibley Volcanic Regional Preserve". East Bay Parks. Retrieved 2022-10-22.
- ^ a b c d e f g h i Slack, Gordy. "Voice of the Volcano -". Bay Nature. Retrieved 2022-10-22.
- ^ Lobo, Susan; Talbot, Steve; Carlston, Traci Morris (2016-02-19). Native American Voices. Routledge. ISBN 978-1-317-34616-6.
- ^ a b "Exploring Sibley Volcanic Regional Preserve". KQED. Retrieved 2022-10-22.
- ^ USGS.gov: "Upper Cretaceous and Lower Tertiary Rocks Berkeley and San Leandro Hills, California", by J. E. Case, GEOLOGICAL SURVEY BULLETIN 1251-J, 1968.