history and geology of the oakland hills
DESCRIPTION
A geological look at the Oakland Hills regional parks.TRANSCRIPT
History and Geology of the Oakland Hills
Home to the East Bay’s Urban Redwood Forest
Susan GardProfessor LawlerGeology 103, Summer 2014Aug. 3, 2014
Presentation Contents
• Geologic history of area• Observable rocks• Redwood Regional Park• Redwood Regional Park fauna• Redwood Regional Park flora
Background and Methodology
• I live below the Oakland Hills and visit East Bay Regional Parks regularly with my dog
• Information for report gathered on visits to various sites within hills parks including:– Redwood Regional Park
– Robert Sibley Volcanic
Regional Preserve
– Joaquin Miller Park
• Some photos are mine
and some come from
online research
Geologic History of Oakland Hills• Region first at floor of Pacific Ocean—later covered
in shallow seas• 12 million years ago became coastal lowland filled
by sediment• Active continental margin: – Pacific plate drifting eastward– North American plate drifting
westward• Pacific plate sinks into
mantle where two plates come together
Geologic History of Oakland Hills
• Eight to 10 million years ago volcanos covered lowlands with thick basalt lava flows
• Four million years later force of transpression made lowlands begin to rise
• Tilted up to and beyond vertical in some places (Rademacher 2012)
Geologic History of Oakland Hills
• One million years ago reached current heights• Still rising about 1/16 inch/year squeezed
between Hayward fault to west and Calaveras fault to east
• Actual growth minimal because erosion nearly balances tectonic uplift
Basalt Lava• Abundant in Robert Sibley Volcanic Regional
Park• Hard, dense, dark volcanic rock• Dated at UC • Berkeley—
10.2 million years old (Edwards)
• Quarried in modern times
Breccia• Many varieties of breccia in Sibley: – Tuff breccia—volcanic ash hardened to stone
containing jumble of blocks and chunks of lava– Basaltic breccia—composed of fragments of basalt
and other rocks cemented together– Autoclastic basaltic breccia—basaltic breccia
formed in place by grinding of dike rock
Chert
• A microcrystalline or cryptocrystalline sedimentary rock material composed of silicon dioxide
• Formed when microcrystals of silicon dioxide grew within soft sediments (Geology.com)
Actinolite Schist• Found in Joaquin Miller Regional Park
• Foliated metamorphic rock dominated by the mineral actinolite
• Actinolite: dark
greenish-colored
amphibole calcium
Ferromagnesian
hydroxy-silicate
that forms long
blades or
needle-like crystals
(St. John)
Serpentinite• Composed of one or more serpentine group minerals
• Metamorphic version of peridotite—deep-seated, low-silica rock that forms upper mantle and bottom of oceanic plates
• Study of serpentinite in
California contributed to
understanding of modern
plate tectonic theory
• Unique association with
California due to gold
deposits and thought to
promote slower ‘creep’
along faults
(Romans 2010)
Serpentine Prairie
• Many unique plants grow in serpentinite-rich soils
• Redwood Regional Park’s Serpentine Prairie home to rich array of native plants
Redwood Regional Park• Millions of years ago
redwood trees found across North America
• Drying and cooling climates preceding last Ice Age drove redwoods to Pacific Coast
• Now only survive in narrow fog-influenced belt
• Climate in East Bay Hills generally too arid
Redwood Regional Park
• Adapted to catch summer fog in needles and drip it down to roots
• Today’s redwoodssecond and third generation clones of ancient giants
• Redwood forest supports unique ecosystem (Slack 2004)
Redwood Regional Park Fauna• Steelhead trout found and named in Redwood Creek in
1855
• Redwood Creek cut off from
San Francisco Bay in 1869
• Steelhead and rainbow trout
same species, but steelhead
metabolically morph to tolerate
salt water and return to fresh
water to spawn
• Current rainbow trout in creek
direct descendants of steelhead
Redwood Regional Park Fauna
• California or coastal newt (taricha torosa) 10 million years old
• Amphibious—must stay near water because no amniotic egg
• Glands in skin secrete potent neurotoxin tetrodotoxin
• Garter snake only natural predator
• Evolved resistance to tetrodotoxin
• Locked in “arms race” as
tetrodotoxin-resistant snakes
cause natural selection to favor
ever-more poisonous newts and
more poisonous newts drive selection
for higher resistance in snakes
(Shelby 2008)
Convergent Ladybird Beetle• Feed on aphids and other soft-bodied insects in
grasslands and Bay wetlands• When rains stop and prey begin to disappear fly to
ancestral spots in East Bay Hills• Not understood how know to fly to specific ancestral
sites• Enter energy-saving semi-hibernative state• Clusters in Redwood Park in March contain hundreds
of thousands of insects (Bauer 2007)• http://science.kqed.org/quest/video/ladybug-pajama-
party/
Redwood Regional Park Flora• Forest also supports evergreens, chaparral and
grasslands• Western trillium, native wild-ginger, yellow
stream violet and wood violet abundant
ReferencesBauer, Chris Feb 27, 2007. Ladybug Pajama Party Video Story for QUEST Northern California
Romans, Brian Aug 5, 2010. Learn the Facts About Serpentinite Before It's Removed as California's State Rock. Retrieved From: http://science.kqed.org/quest/2010/08/05/learn-the-facts-about-serpentinite-before-its-removed-as-californias-state-rock/
Slack, Gordy July 1, 2004. In the Shadow of Giants: The Redwoods of the Oakland Hills. Bay Nature. Retrieved From: http://baynature.org/articles/in-the-shadow-of-giants/
Oakland Geology. Retrieved From: http://oaklandgeology.wordpress.com/
Rademacher, Horst January 6, 2012. From the Inside Out: Digging the Geology of the East Bay Hills. Bay Nature. Retrieved From: http://baynature.org/articles/from-the-inside-out/
Martin, Shelby March 12, 2008. Snakes slither past toxic newts in evolving race. Stanford News. Retrieved From: http://news.stanford.edu/news/2008/march12/newts-031208.html
Edwards, Stephen. A Self-Guided Tour of Round Top Volcanoes. Retrieved From: http://www.ebparks.org/Assets/_Nav_Categories/Parks/Maps/Sibley+map.pdf
Geology.com. What Is Chert, How Does It Form and What Is It Used For? Retrieved From http://geology.com/rocks/chert.shtml
St. John, James. OSU-Newark Geology. Retrieved From: http://www.newark.osu.edu/facultystaff/personal/jstjohn/Documents/Home-page.htm