history and geology of the oakland hills

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