Historical Geology: San Francisco

Bay/Berkeley, CA Region

Ryan ShieldsLake Tahoe Community College

Professor Mark Lawler

(Knights Inn, 2015).

Brief Introducti

on The bay area and Berkeley, CA are

home to many different rock forms and wildlife including the famous, Indian Rock Park. The park was a gift to the City of Berkeley from Mason-McDuffie Real Estate Company during its development of the Northbrae area.

1.18 acres

Features: rock outcrop with carved steps and areas for rock climbing, Multi-purpose turf, Picnic area, and Vista/overlook with gorgeous view of the San Francisco Bay

Geological Background

(Indian Rock Plaques, 2003).

• The bay region is underlain by some of the most complex and active geology in the world.

• Made up of everything from iron- and magnesium-rich rocks to sand and gravel recently deposited by the streams and rivers.

(GeoMap, 2014).

The Berkeley Squirrel

(Shields, 2016).

How/When Have They Evolved and Changed

Over Time? The earliest fossil evidence for squirrels was found in

western North America and dated to about 36 million years ago.

At about 11 million years ago, there was an explosive diversification of genera of squirrels that inhabited the islands and continental land masses of Southeast Asia.

There is evidence for the Asia-North America migration of certain ground squirrel lineages, which appears to come after a subsequent period when there were rising sea levels.

(Squirrels Family Tree, 2003).

Berkeley Hills Deer

(Shields, 2016).

How/When Have They Evolved and Changed

Over Time? Deer are believed to have evolved from antlerless, tusked

ancestors that resembled modern duikers and diminutive deer in the early Eocene (Wikipedia, 2016).

Evolution took nearly 30 million years. Large deer with impressive antlers evolved during the

early Pleistocene (Wikipedia, 2016).

California Manroot (Marah fabaceus)

(Shields, 2016).

Evolutionary History of the California Manroot

Native to the San Francisco Bay Area.Native American Tribes once used it to soothe

aches and pains. Has some medicinal use. Also referred to as the Wild Cucumber plant.

Metamorphic Hornfel

(SF Bay, Shields, 2016).

• Non-foliated metamorphic rocks

• Produced by contact metamorphism

• Lower grade hornfels often include porphyroblasts and inclusion-rich phases. Mineralogy of hornfels is highly variable and varies with the nature of the protolith, pressure and temperature, and composition of co-magmatic fluids that may be present.

(Rock Library, 2013).

Igneous Rhyolite• Many rhyolites form from granitic magma that

has partially cooled in the subsurface. When these magmas erupt, a rock with two grain sizes can form. The large crystals that formed beneath the surface are called phenocrysts, and the small crystals formed at the surface are called groundmass (Geology, 2016).

• Rhyolite usually forms in continental or continent-margin volcanic eruptions where granitic magma reaches the surface. Rhyolite is rarely produced at oceanic eruptions.

Sedimentary Sandstone

(Shields, 2016).

• Sandstone is a sedimentary rock composed of sand-size grains of mineral, rock, or organic material. It also contains a cementing material that binds the sand grains together and may contain a matrix of silt- or clay-size particles that occupy the spaces between the sand grains.

• Sandstone is one of the most common types of sedimentary rock and is found in sedimentary basins throughout the world. It is often mined for use as a construction material or as a raw material used in manufacturing. In the subsurface, sandstone often serves as an aquifer for groundwater or as a reservoir for oil and natural gas.(Geology, 2013).

Principle of Inclusions The principle of inclusions

states that inclusions found in other rocks (or formations) must be older than the rock that contain them (Sand Atlas, 2012).

Inclusions are really made of matter that is foreign to the rock that contains them.

DisconformityAn erosion surface

between two packages of sediment.

The lower package of sediments was not tilted prior to deposition of the upper sediment package.

(Shields, 2016).

References Retrieved from http://www.sandatlas.org/principle-of-inclusions/

Retrieved from http://berkeleyplaques.org/wp-content/uploads/2014/01/IndianRock_03.jpg

Retrieved from http://www.knightsinnberkeley.com/blog/wp-content/uploads/2015/11/Indian-Rock-Park.jpg

Retrieved from http://geomaps.wr.usgs.gov/sfbay/geomap.html

Deer - Wikipedia, the free encyclopedia. (n.d.). Retrieved June 12, 2016, from https://en.wikipedia.org/ wiki/Deer#Evolution

Rhyolite: An extrusive igneous rock. Photos and definition. (n.d.). Retrieved from http://geology.com/ rocks/rhyolite.shtml

Rock Library | Imperial College London. (n.d.). Retrieved from https://wwwf.imperial.ac.uk/earthscienceandengineering/rocklibrary/viewglossrecord.php?Term=hornfels

Squirrels' Evolutionary Family Tree Reveals Influence of Climate, Geology | Duke Today. (n.d.). Retrieved from https://today.duke.edu/2003/02/squirreltree0302.html