Field Research Presentation - Folsom Late State Recreation Area

1. Chancellor Tzomes
GEL 103 7/29/12

2. INTRODUCTION
I 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.

3. FOLSOM HISTORY
Folsom 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.

4. FOLSOM STATE RECREATION AREA
The 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.).

5. FSRA GEOLOGY
The 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.

6. FSRA GEOLOGY
Three 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).

7. FSRA GEOLOGY
There are four primary rock divisions found in
the area:
 Ultramafic
 Methamorphics
 Granodioriteand Granitic
 Volcanic Mud Flows
Each is linked with a particular part of tectonic history, and
each has distinct mineral resources
(“Environmental Conditions”, 2003).

8. 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).

9. 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).

10. 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.).

11. 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.).

12. 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.).

13. MY FIELD RESEARCH
During 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)

14. MY FIELD RESEARCH
Trees behind me (including Oak) Metamorphic rocks right in front of me.
A better view. I HAD to touch it!

15. MY FIELD RESEARCH

16. MY FIELD RESEARCH
This looks like Granite! It IS Granite!
The ground nearby.

17. MY FIELD RESEARCH
Video below (auto play)!

18. MY FIELD RESEARCH
Looking east at the rolling foothills. Alongside Folsom-Dam Road.
This granite is HUGE! Almost my size. Yikes!

19. MY FIELD RESEARCH
Looks like Granodiorite.
The Folsom Dam – close as I could get. Base of the dam. Lots of granite beds.

20. MY FIELD RESEARCH
Downstream from dam. Prison on left. There’s granite everywhere in Folsom!
California Pine Tree. California Pine along the American River.

21. MY FIELD RESEARCH
The American River. Upstream (towards Folsom Dam).
All along the riverbank. Underneath an Oak Tree.

22. MY FIELD RESEARCH
Furthest downstream at Nimbus Dam. Facing upstream, Geese came right up to me!
eastern foothills in back.
All along the riverbank. Nimbus Dam.

23. 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.