2. Basic Facts About The American River
● The River is 120 miles long.
● It ranges from the Sierra Nevada Mountain Range to its confluence with
the Sacramento River.
● The river is fed from the melting snow of the Sierra Nevada along with
its fellow tributaries: North Fork of American River, Middle Fork, and
South Fork.
● Mostly known for the discovery of gold at Coloma that led to the
California Gold Rush.
● Rocks found along the river include: graanite, conglomerates, sandstones,
claystones, and lahars.
4. Basic Facts About The Sierra Nevadas
● Elevation is 14,505 ft (4,421 m)
● It is 400 Miles long, About 70 Miles
wide.
● It includes the largest alpine lake in
North America: Lake Tahoe.
● Its peak is Mount Whitney, the
highest point in the United States.
● Also Includes Yosemite Valley.
● It is the home of 3 National Parks:
Yosemite, Sequoia, and Kings Canyon.
5. Evolutionary History
● During the Cretaceous period, a
subduction zone formed, causing
an oceanic plate to dive under
the North American plate.
● Magma then began to form
through the subduction of plutons
underground, this mass formed
the “Sierra Nevada batholith”.
● These plutons formed at
different various times eventually
forming the first of the Sierra
Nevada mountains about 66
million years ago.
● Next, volcanic activity occurred
within the Sierra, about 10
million years ago a block of crust
began to form between the Coast
Range and the Basin and Range
Province causing the west to tilt
entirely.
● Rivers started to cut through the
canyons while lava filled some of
these canyons, which eroded and
left table mountains that follow
the old river channels.
About 2.5 million years ago the Earth's climate began to cool, then the ice ages started.
Glaciers then carved out U-shaped canyons throughout the Sierras. The combination of the
river and glacier erosions exposed the uppermost portions of the plutons that were emplaced
millions of years ago, leaving a remnant of metamorphic rock on top of some Sierra peaks.
6. Animal That Lives On The American River:
The Beaver!
● Mostly Nocturnal, and are semi-aquatic
creatures.
● Genus: Castor, there are two extant
species, the North American beaver and
Eurasian beaver.
● Known for building dams along the river,
in addition to canals and their homes.
● They are the second largest rodent in
the world.
● Population used to be more than 60
million but has declined due to more
general hunting or specifically for beaver
fur.
7. Evolutionary History Of The Beaver
● Rodents first appear in the fossil record
about 65 million years ago, around the time
when the non-avian dinosaurs became
extinct.
● Today’s beavers and their relatives appear
in the fossil record near the end of the
Eocene period.
● Castoroides leiseyorum was an ancestor that
lived over 2.5 million years ago, found in the
fossil record and shows direct relation since
their fossils have only been found in North
America. (Existed in the Pleistocene era)
● First Castoroides fossils
were discovered in 1837 in
Ohio.
9. Facts About The California Wildrose
● Grows through the coast,
foothills of California, and
throughout the mountains up
to elevations of 6000 feet.
● It is deciduous, and grows on a
shrub with prickly stems.
● They grow open-faced and
with five petals in any shade
of pink ranging from
almost-white to deep magenta.
● It can go summer dormant if it
doesn't get enough water.
● Berries may or may not happen
to grow.
● Can grow up to 10 ft. tall and 10
ft. wide.
● Smells very pleasant! (:
10. Evolutionary History
● Rosaceae (Part of the Rose Family)
● Molecular clock analysis revealed an estimated
age of about 101.6 million years for crown
Rosaceae and divergence times of tribes and
genera, providing a geological and climate
context for fruit evolution.
● Rosaceae is a moderately large angiosperm
family in the order Rosales, with about 3000
species, 3 subfamilies, 16 tribes, and 88–100
genera.
● Rosaceae likely originated near the boundary of
early to late Cretaceous period.
● Rosaceae species are classified into three
subfamilies , with two large ones, Rosoideae and
Amygdaloideae, and Dryadoideae.
● Among the three largest tribes
having over 500 species, Rubeae
diverged earlier at 75 Ma in Late
Cretaceous; the other two tribes
originate under relatively
stressful conditions than current
environment: Potentilleae during
Paleocene shortly after a global
catastrophe at the boundary of
Cretaceous and Paleocene (66
Ma), and Maleae during the
hottest and most humid period in
the Cenozoic Era.
12. Rock #1: Granite
● Granite is an igneous rock with grains large
enough to be visible with the unaided eye.
● It forms from the slow crystallization of
magma below Earth's surface.
● Granite is composed mainly of quartz and
feldspar along with minor amounts of mica,
amphiboles, and other minerals.
● Can come in colors such as red, pink, gray, or
white color with dark mineral grains visible
throughout the rock itself.
● Granite is the best-known igneous rock
● Many people recognize
granite since it is the most
common igneous rock found
at Earth's surface &
because granite is used to
make many objects that we
encounter in daily life.
13. Identification Of Granite
● The large mineral crystals in
granite are evidence that it cooled
slowly from molten rock material.
● The texture of the granite
indicated a phaneritic texture with
coarse grains, easily visible.
● This picture consists of tan,
smoother granite rocks with specs
of darker crystals, lying on top of
one another.
-Picture taken from the North Fork of
The American River-
14. Rock #2: Sandstone
● Sandstone is defined as a detrital sedimentary
rock, meaning it is made up of solid particles such
as gravel, sand, silt, and clay from parent
material.
● Quartz sandstone is the most common, being
mostly made of quartz.
● Contains a cementing material that binds the
sand grains together & may contain a matrix of
silt or clay-size particles that occupy the spaces
between the sand grains.
● Quartz content of these sandstones can be very
high, up to 90% or more. These are called
“mature” since they have been worked and
reworked.
● Other sands can contain
significant amounts of
feldspar, if they came
from a source rock with
a significant quartz
content, they are said to
be "immature."
15. Identification Of Sandstone
● The grains in these sandstones indicated a
mixture of particles, possibly mineral,
rock, and other organic material.
● The tiny grains make it known that these
materials must have been reduced to
"sand" size by weathering, then
transported to their depositional site by
the action of moving water, wind, or ice
● These particular rocks were found by a
much bigger rock formation, the rocks
resembled this and may have derived from
this parent rock.
-Picture taken from The American
River in Fair Oaks, Ca-
16. Rock #3: Conglomerate
● Conglomerate is a clastic sedimentary rock
that contains large rounded clasts.
● The space between the clasts is generally
filled with smaller particles and or a
calcite/quartz cement that binds the rock
together.
● As a clastic sedimentary rock, it can contain
clasts of any rock material or weathering
product that is washed downstream or down
current.
● Particles such as quartz or feldspar may be
found, materials may be sedimentary,
metamorphic, or igneous rock fragments.
● Clasts of quartzite,
sandstone, limestone,
granite, basalt, and gneiss
are especially common.
17. Identification Of Conglomerate
● Conglomerate is easier to identify since it
is obvious when there are larger clasts
within the rock itself.
● The clasts must be greater than 2 mm in
diameter, in this picture they are indeed.
● The clasts are held together by minerals
such as quartz or calcite in a cement
binding the materials as one.
● There are a ton of conglomerates around
the river since the strong water current
tends to transport and shape the particles
as they tumble down the stream, forming
conglomerates.
-Picture of conglomerate
rock by the river-
19. The Law Of Superposition
● A basic law of geology
stating that in any
undisturbed sequence of
rocks deposited in layers,
the youngest layer is on
top and the oldest on
bottom, each layer being
younger than the one
beneath it and older than
the one above it.
20. Identification Of Superposition
● In this picture, the layers of this
land become very clear.
● According to the law, the lowest
layers, closest to the water are
the oldest, while the upper layers
on the top with the trees, are the
youngest.
● Here there are many layers, which
becomes very interesting as the
layers themselves are history
telling its story, layering more as
more time passes.
22. Identification Of Disconformity
● An erosion surface between
two packages of sediment,
yet the lower package of
sediments was not tilted
prior to deposition of the
upper sediment package.
● The red line indicates
where the top package of
sediment ends and where
the lower half starts.
● The lower package of
sediment is tilted slightly.
24. References:
Sierra Nevada (U.S.). (2018, May 29). Retrieved from https://en.wikipedia.org/wiki/Sierra_Nevada_(U.S.)#Geologic_history
Beaver. (2018, June 24). Retrieved from https://en.wikipedia.org/wiki/Beaver
Castoroides. (2018, June 24). Retrieved from https://en.wikipedia.org/wiki/Castoroides
Pepper, D. (n.d.). Castoroides. Retrieved from http://www.prehistoric-wildlife.com/species/c/castoroides.html
American River. (2018, June 25). Retrieved from https://en.wikipedia.org/wiki/American_River
About the American River. (n.d.). Retrieved from https://www.theamericanriver.com/rivers/
Sartore, J. (2010, September 10). Beaver. Retrieved from https://www.nationalgeographic.com/animals/mammals/b/beaver/
Rosa californica (California Wild Rose). (n.d.). Retrieved from
http://www.parksconservancy.org/conservation/plants-animals/native-plant-information/california-wild-rose.html
California Wildrose, Rosa californica. (n.d.). Retrieved from http://calscape.org/Rosa-californica-()
25. References (continued):
X., Y., H., C., Y., W., . . . H. (2016, November 17). Evolution of Rosaceae Fruit Types Based on Nuclear Phylogeny in the Context of
Geological Times and Genome Duplication | Molecular Biology and Evolution | Oxford Academic. Retrieved from
https://academic.oup.com/mbe/article/34/2/262/2528249
Granite. (n.d.). Retrieved from https://geology.com/rocks/granite.shtml
Sandstone. (n.d.). Retrieved from https://geology.com/rocks/sandstone.shtml
Conglomerate. (n.d.). Retrieved from https://geology.com/rocks/conglomerate.shtml
Law of superposition. (n.d.). Retrieved from http://www.dictionary.com/browse/law-of-superposition
Unconformities. (n.d.). Retrieved from http://www.indiana.edu/~geol105b/images/gaia_chapter_6/unconformities.htm
