This document summarizes information from a geology field assignment to Rattlesnake Bar near Folsom Lake. It describes the geology of the area, including metamorphic rocks formed from ancient volcanic islands, intrusive granite formations, and oak trees. It also provides details on wildlife spotted in the area such as rattlesnakes, king snakes, and their evolutionary origins. References are cited at the end from parks and science websites.
2. American River/Folsom
Lake
This river runs from the Sierra
Nevada mountain range.
It runs through Sacramento
where it meets the Sacramento
River and hits San Francisco
Bay.
The river also runs through
Folsom beneath the Folsom
Lake.
3. Metamophic Rocks
Rattlesnake bar near Folsom
Lake
Metamorphic rocks are rocks
subjected to sufficient heat,
pressure and fluid activity to
change their mineral
composition texture or both.
(The Changing Earth, pg.182)
4. Metamorphic Rocks
Metamorphic rocks, known as the Copper Hill
Volcanics, occur east of Rattlesnake Bar, These
rocks represent ancient chains of volcanic islands
(island arcs) and the associated seafloor
sediments that have since been buried, squeezed,
and heated to form metasedimentary and
metavolcanic rocks. During the Jurassic period,
from about 160 to 140 million years ago, the
island arcs were added as the ocean plate in
which they were embedded was subducted
beneath western North America. (parks.ca.gov)
5. Granite
Granite is an intrusive
igneous rock
Its light colored
Black and white
Course grained
Contains quartz and
fedspar
6. Granite
Folsom Lake contains younger granitic
intrusive plutons that intruded and
obliterated some of the metamorphic belt
and nearly flat-lying deposits of volcanic
ash, debris flows, and alluvial fan deposits
that overlie the older rocks. (parks.ca.gov)
7. Oak Tree
Oak trees are a type of deciduous tree. These are
broad-leaved trees that shed all their leaves during
one season.
The oak trees produce acorns once a year during the
fall.
A mature oak tree draws up to 50 or more gallons of
water per day through its roots.
Oak trees can live 200 or more years.
Height up to 30 m.
8. Oak Tree
Oaks (Quercus spp.), members of the Beech
family (Fagacea), are trees and shrubs having
simple, alternate leaves found throughout the
world. Characterized by their strong, complex
wood, wind-pollinated flowers, fruits called
acorns, and their ability to live for centuries, oaks
have played an important role in temperate
landscapes. Of the 500 species in the genus
Quercus, approximately 90 are found in the
United States and Canada, with another 112
species in Mexico. Another member of the Beech
family that is closely related to the oaks is the
tanoak (L. densiflorus), which is found in
California and is the only representative of this
Asian genus found in North America. It has
flowers similar to the chinkapin (Castanopsis) and
bears acorns like the oaks, thus making it a
possible evolutionary link between the two
genera. (Science.jrank.org)
9. Rattlesnake
California rattlesnake species include the
northern Pacific rattlesnake (in northern
California), and the Western Diamondback,
Sidewinder, Speckled rattlesnake, Red Diamond
rattlesnake, Southern Pacific, Great Basin
rattlesnake and the Mojave rattlesnake (all found
in Southern California). (dfg.ca.gov)
Found from sea level to the inland prairies and
desert areas and to the mountains at elevations of
more than 10,000 feet. (dfg.ca.gov)
Native venomous snake.(dfg.ca.gov)
Generally not aggressive, rattlesnakes strike when
threatened or deliberately provoked, but given
room they will retreat. (dfg.ca.gov)
The shaking of their tail (rattle shaking) is a
warning sign.
10. California King Snake
Prey on rattlesnakes and have become immune to their
venom. They can also mimic the rattlesnakes rattle to
intimidate other rattlesnakes.
Generally not aggressive.
Found in parts of North America and Mexico.
Powerful constrictor.
Normally about 48 inches long.
Few weeks ago I was walking on a trail near the Folsom
Lake around dusk and a 3ft long California King Snake was
in the middle of the path and struck at me. Luckily, I
reacted fast enough and jumped away and it ran away too!
11. Scientists have concluded that the snakes probably
evolved from a family of lizards during the time of the
dinosaurs. Snakes and lizards share a number of distinct
features in the structure of their skull; both, for
instance, possess a moveable quadrate bone at the back
of the jaw, and both are missing the quadratojugal bone
at the rear of the skull. (Flank)
One of the earliest snakes to appear in the fossil record
has been given the scientific name Lapparentophis
defrenni. It was found in the Saharan Desert and has
been dated to the early Cretaceous period, about 130
million years ago. (Flank)
