FOLSOM LAKE STATE

RECREATION AREAChancellor Tzomes

GEL 103 7/29/12

INTRODUCTIONI am very fortunate to live in the city of FOLSOM, California.

It is located in Sacramento County and situated in the

westernmost foothills of the Sierra Nevada Mountains, on

the Southwest side of the American River in Northern

California.

There is a lot of rich history in the geology and landscape of the area. It sits 27 miles from Coloma, CA, where gold was originally discovered, and is about 85 miles from Lake Tahoe, Nevada.

It’s most commonly known for its gold rush history and prison.

FOLSOM HISTORYFolsom has rich Western expansion history, with the California Gold

Rush and arrival of the railroad. Gold was first discovered along the

south bank of the American River in the area known as Negro Bar.

The discovery led to huge gold mining operations, along with the

need for a rail service (“Celebrating”, n.d.).

It’s named in honor after U.S. Army Captain, Joseph Folsom,

who purchased the land in 1847 and established the town for supporting

gold mining and dredging activity. The area is surrounded by rolling hills,

and was the final destination of the Pony Express (from Missouri) when it was functional

in the mid-1800s.

FOLSOM STATE RECREATION AREAThe Folsom Lake State Recreation Area (FSRA) is a massive

reservoir that Was formed by the Folsom Dam, constructed in 1955 to

control the American River. It has over 11,500 surface acres, almost

75 miles of shoreline, and was placed just below the convergence of

the north and south forks of

The American River.

The dam and lake are both

part of the “Folsom Project”,

which provides flood control,

drinking water, irrigation,

And hydroelectricity to the

area (Crockett, n.d.).

FSRA GEOLOGYThe Folsom Lake State Recreation Area is located between

the central Sierra Nevada and the Central Valley geomorphic

provinces. The Sierra Nevada is characterized by a north-

northwest trending mountain belt with a broad region of

foothills along the western gradient. Located above the

Folsom Dam, it occupies the lower sections of canyons of

the North and South Forks of the American River, with a

peninsula stretching between the two arms of the lake.

Lake Natoma, located downstream from the dam occupies a broad river valley that is cut into sedimentary rocks, and ends at another dam called the Nimbus Dam. It occupies the stretch between both dams.

FSRA GEOLOGYThree major geologic divisions occur in the area:

A north-northwest belt of metamorphic rocks with included ultramafic rocks (dense, rich in iron and magnesium).

Granitic plutons that intruded and destroyed some of the metamorphic belt.

Low-lying deposits of volcanic ash, debris flow, and alluvial fan deposits that overlie the older rocks.

These divisions have created a varied and interesting

geology for the area (“Environmental Conditions”, 2003).

FSRA GEOLOGYThere are four primary rock divisions found in

the area:

Ultramafic Methamorphics Granodiorite and Granitic Volcanic Mud Flows

Each is linked with a particular part of tectonic history, and each has distinct mineral resources

(“Environmental Conditions”, 2003).

FSRA GEOLOGY Ultramafic rocks - The ones found here represent the lowest part

of the Earth’s crust, and have been lifted as much as 20 miles vertically by the faulting and regression of other pieces of crust – most likely when it was added to North America by accretion. Minerals associated with the rocks in the area include chromite, talc, asbestos, and nickel (“Environmental Conditions”, 2003).

Metamorphics – are bands of metamorphosed sediments and igneous rocks that occur through most of the peninsula and southern area of the lake. They represent ancient chains of volcanic island arcs and the respective seafloor sediments over a long time period (Jurassic and Cretaceous). The terranes are separated by faults, and the age of these rocks go back over 160 million years. Minerals associated with the rocks in the area include copper, zinc, and gold (“Environmental Conditions”, 2003).

FSRA GEOLOGY Granodiorite/Granitic rocks – slightly different than granite, they

have slightly more iron and magnesium producing materials, and less quartz than granite. The crystals range in size, and the rock is coarse with a grainy appearance. The granitic rocks actually form the core of the Sierra Nevada, cooled from rock melted during the subduction process.

Volcanic Mud Flows – the west side

of Lake Natoma (area below the Dam)

volcanically collected sediments mixed

with volcanic mudflows

(Miocene – Pliocene aged). Above them

is a sequence of gravel, sand, and slit

derived from granitic and metamorphic sources

by way of debris flow and stream deposits –

called the “Laguna Formation” (Pilocene aged) (Clark, 1970).

FSRA WILDLIFE

Rabbits, raccoons, skunks, possums, deer, grey foxes, geese, and

coyotes are regularly seen in the park and surrounding area. The

park also houses California horned lizards and western pond

turtles. Mountain lions, bobcats, and rattlesnakes also frequent

the area but are rarely seen (“Folsom Lake”, n.d.).

FSRA PLANTLIFE

The area is abundant with oak trees (live & blue) and

foothill pine trees. Wildflowers bloom all during

the spring and summer (“Folsom Lake”, n.d.).

BIKE AND PEOPLE TRAILS FSRA also maintains 34 miles of bike and pedestrian trails

which follow various creeks, dredger trails, and riverbank

forests. Many of the trails intersect the city’s open space

areas, greenbelts, and wetland areas.

The “American River Trail” is considered to be one of the finest bike trails in the state of California. It loops under the Folsom Lake crossing and continues alongside the west shoreline of the American River. There are incredible views of the river and surrounding habitat such as the oak trees, granite rocks, native vegetation and wildlife (“Discover”, n.d.).

MY FIELD RESEARCHDuring my exploration around FSRA, I located granodiorite, granitic, and

metamorphic rocks. I also located California Pine and Oak trees, and

spotted geese swimming along the riverbank.

ALL of the following pictures were taken by me with my own camera!

View from above Folsom Lake View from Folsom Lake (ground level)

MY FIELD RESEARCH

Trees behind me (including Oak) Metamorphic rocks right in front of me.

A better view. I HAD to touch it!

MY FIELD RESEARCH

MY FIELD RESEARCH

This looks like Granite! It IS Granite!

The ground nearby.

MY FIELD RESEARCH

Video below (auto play)!

MY FIELD RESEARCH

Looking east at the rolling foothills. Alongside Folsom-Dam Road.

Almost my size. Yikes!This granite is HUGE!

MY FIELD RESEARCH

Looks like Granodiorite.

Base of the dam. Lots of granite beds.The Folsom Dam – close as I could get.

MY FIELD RESEARCH

Downstream from dam. Prison on left. There’s granite everywhere in Folsom!

California Pine along the American River.California Pine Tree.

MY FIELD RESEARCH

The American River. Upstream (towards Folsom Dam).

Underneath an Oak Tree.All along the riverbank.

MY FIELD RESEARCH

Furthest downstream at Nimbus Dam. Facing upstream, eastern foothills in back.

Geese came right up to me!

Nimbus Dam.All along the riverbank.

SELECT LIST OF REFERENES City of Folsom: Celebrating Folsom’s Rich History (n.d.). Retrieved from:

www.folsom.ca.us/about/history.asp.

Discover Folsom.com: Recreation, Folsom Trails (n.d.). Retrieved from: www.discoverfolsom.com/recreation/folsom-trails/.

Geotechnical Consultants, Inc. (2003). Environmental Conditions Geology: Folsom Lake State Recreation Area. Retrieved from: www.parks.ca.gov/pages/files/Geology.pdf.

Golden Gate: Granitic and Grandiorite FAQ (n.d.). Retrieved from: www.nps.gov/goga/forteachers/granite-and-granodiorite-faq.htm.

Parks Guide: Folsom Lake State Recreation Area (n.d). Retrieved from: www.parksguide.com/folsom-lake-state-recreation-area/.

Todd Crockett (n.d.). Folsom Lake Information Guide: Folsom Lake-Good Fishing for Sacramento Residents. Retrieved from: http://www.jimporter.org/lakes/folsum/.

W.B. Clark, (1970). Gold Districts of California: California Department of Conservation, Division of Mines and Geology, Bulletin 193. Retrieved from: http://museumca.org/goldrush/dist-folsom.html.

Wikipedia: Folsom, California (n.d.). Retrieved from: www.en.wikipedia.org/wiki/Folsom,_California.