Lab field assignment

1. Geology 103
Lab/Field
Assignment
Valley Springs, New Hogan Lake
By: Ger Ly

2. Valley Springs is in the oak and
brush-covered foothills of the
Sierra Nevada Mountains. The
4,400-acre lake was created in
1964 with the completion of New
Hogan Dam.
When full, the lake has 50 miles
of shoreline and extends nearly
eight miles upstream to the
confluence of the north and
south forks of the Calaveras River.
The dam provides flood
protection to the city of Stockton
and water for irrigation, drinking
and hydroelectric power (New
Hogan Lake 2006).

3. History:
• Valley Springs was once called Spring Valley, due to having another post office called Spring Valley in another county; the
name was switched to Valley Springs. (New Hogan Lake 2006). The Valley Springs Formation is a volcanic tuff (from the
Italian “tufo”, a type of rock made of volcanic ash ejected from a vent during an eruption), formed from pyroclastic flow
deposits, that is thickest closer to Sonora Pass and thinner at the base of the Sierra foothills. The volcanic vent system that
produced the ash likely existed to the east of Sonora Pass and was active during Oligocene time (approximately 35-23 Ma
(million years ago)). The ash has been age dated at 20-33 Ma. The tuff has been reworked by water and deposited in the
Central Valley. It overlies the older Ione Formation, another volcanic ash and sedimentary deposit along the foothills of the
Sierra and it underlies the younger Mehrten Formation. The Ione Formation has been hypothesized to have formed during
Eocene time (approximately 55-35 Ma). It is no younger than 37-40 million years old. The Mehrten Formation (volcanic
mudflows, lava flows, and volcanic ash deposits) formed during the late Miocene to Pliocene (approximately 14-3 Ma)
(Valley Springs Formation 2019).
• During the 1950s the Hogan Dam was deemed ineffective when floods reoccurred. With the flooding problems, the
construction of New Hogan Dam was created to control floods. “The new Lake and Dam were built between 1960 and
1963 and now supply irrigation and drinking water to the Calaveras county Water District and Stockton East Water District,
in addition to serving as a recreational area (New Hogan Lake 2006).”
• Today: The New Hogan Lake is now a fishing, boating, and camping ground for locals and visitors. New Hogan Lake
offers a total of 177 campsites in its developed campgrounds.
• There is boat launching for water skiing, fishing, canoeing, sailing, cruising or swimming.
• Since it’s opening there has been many hiking trails added into the location.
• The condition there today is an average of 23.47 rain fall per year and lowest temperatures at around 39° and highest at
105°.

4. Oak Trees
Taken at New Hogan Lake, Valley Springs
by: Ger Ly

5. Oak Trees
History
• The oaks (Family Fagaceae, genus
Quercus) belong to an old lineage of trees
and shrubs that dates back to at least the
Late Cretaceous (about 85 million years
ago). The oldest fossils are most closely
aligned with Fagus, the beeches, but there
are also suggestions of chestnuts
(Castanea) in some of these ancient
materials (The Origins of Oaks 2011).
Based on the fossil record the first oaks
appeared about 32-35 million years ago.
Oaks are categorized by their fruits. For
example, by the characteristic of the acorn
categorizes the oaks. These acorns have
also separate evolutionary backgrounds.
Today
• There are more than sixty types of oak
species today. Oak trees live very long
about two hundred years plus. Part of their
longevity is that it takes up to fifty years
before oak trees produce their first acorns.
Oaks consume about fifty gallons of water
a day. That is why they are mostly found
in water ways. Since oak trees existed
during the ancient times, making them
native trees. The state of California bans
the removal of these trees. Expect if you
are a homeowner and the tree pose a
health or safety risk, and with a petition it
may be removed (Oak Tree Removal
Laws in California 2017).

6. Striped Bass Fish
Taken at New Hogan Lake, Valley Springs by: Ger Ly

7. Striped Bass
Habitat
• The Striped Bass is very popular for local
fisherman here at Valley Springs,
especially at New Hogan Lake. They have
large mouths and jaws that extend below
their eyes. There are seven or eight stripes
that runs across the body from head to
tail. They normally don’t migrate the first
two years of life. When they do migrate it
is north during spring and south during
summer. Their diet consist of other fishes,
shell fishes, seaworms, and squid.
Evolutionary
• Fish were dominated by invertebrates and
minority members of the ecosystem. It
wouldn’t be until the Silurian period,
roughly 420 million years ago, that jawed
fishes evolved and began to compete
effectively with the invertebrates (What
Evolutionary History of Fish? 2003). The
Devonian was a great milestone in the
evolutionary history for fishes. From the
extinct fishes evolved many lob-finned
fishes, that evolved into terrestrial
vertebrates. Fishes took out population of
other marine species and became
dominant marine animals.

8. Toads
Taken at New Hogan Lake, Valley Springs by: Ger Ly

9. Toads
Habitat
Toads usually live in damp places. They
camouflage very well with their
surroundings and can stay still for many
hours. Their diet consist of insects, spiders,
slugs, worms, and larvae. Larger toads can
also consume small snakes and mice,
swallowing it alive.
Evolutionary
The first Amphibians were the tetrapod.
They were known as the four-legged fish.
Tetrapod were able to crawl into shallow
seas and breath gulps of air with their lungs.
Then during the Carboniferous period about
300 million years ago, the first true
amphibians evolved. The Eogyrinus, a
slender crocodile-like creature that
measured 15 (Giant Amphibians Ruled the
Earth 2010). The evolution of amphibians
continued until frogs and salamanders
evolved. The evolution of frogs are still a
debate; however it was during the Triassic
period that from frogs, toad were evolved.

10. Sandstone grained
sedimentary rock
• Taken at New Hogan Lake,
Valley Springs

11. Sandstone grained sedimentary rock:
The rock looks like a sandstone grained sedimentary rock covered with lichen. With it’s sand like
texture color and the binding of the rock. As well as clay like particles, my results suggested that it
could be a sandstone grained sedimentary rock.
What is sandstone grained
sedimentary rock and formation?
• 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 (Rocks
2005). It is formed by sand transporting
during weathers, such as water, wind, or ice.
Once the sand is deposited to a rock source
it will start to form with the rock.
What is Lichen?
• Lichens consist of a fungus and algae
working together. The algae create
photosynthesis as food for the fungus. The
fungus in return protects and provide
moisture for the algae. They grow on rocks,
soil, and tree barks.

12. Conglomerate
sedimentary rock
Taken at New Hogan Lake, Valley Springs by: Ger Ly

13. Conglomerate
sedimentary
rock
This rock looks like a conglomerate sedimentary rock
with the details of smaller particles and pebbles that
forms the rock.
What is Conglomerate sedimentary rock and
formation?
• Conglomerate is a clastic sedimentary rock that
contains large (greater than two millimeters in
diameter) rounded clasts. The space between the clasts
is generally filled with smaller particles and/or a
calcite or quartz cement that binds the rock together
(Rocks 2005). It is formed by the mixture of clasts
traveling downstream current. Then bonded together
with sand, mud, and chemical cement.

14. Shale sedimentary
rock
Taken New Hogan Lake, Valley Spring by: Ger Ly

15. Shale sedimentary rock and
formation
This rock looks like s Shale sedimentary rock with its thin layers and sharp edges binding it together.
Close up you can see the thin layers next to each other. As well as the broken thin sharp edges on the
ground.
What is Shale sedimentary rock?
Shale is distinguished from other mudstones because it is fissile and laminated. "Laminated" means
that the rock is made up of many thin layers. "Fissile" means that the rock readily splits into thin pieces
along the laminations (Rocks 2005).

16. Steno’s Laws and
Principles, and
Unconformities
Not much of Steno’s Laws and
Principles were present here at this
location. However I made the most
of what I can observed.
Steno’s Laws and Principles:
The principle of original Horizontal.
No erosion, intrusion, or faults.
Principle of Unconformities
A sequence of Horizontal
sedimentary rock beds.

17. References
300 Million Years Ago, Giant Amphibians Ruled the Earth. (2010, March 17). Retrieved from
https://www.thoughtco.com/300-million-years-of-amphibian-evolution-1093315
About > The Origins of Oaks. (2011). Retrieved from http://www.oaksofchevithornebarton.com//about-history-
of-garden.cfm?
Geocaching. (2019, January 15). Valley Springs Formation. Retrieved from
https://www.geocaching.com/geocache/GC77P0B_valley-springs-formation?guid=2879434c-0624-4355-8d3c-
c4bbedae437f
New Hogan Lake. (2006, May 22). Retrieved from https://en.wikipedia.org/wiki/New_Hogan_Lake
Oak Tree Removal Laws in California. (2017, July 21). Retrieved from https://www.hunker.com/12003648/oak-
tree-removal-laws-in-california
Rocks. (2005). Retrieved from https://geology.com/rocks/sandstone.shtml
What is the Evolutionary History of Fish? (2003). Retrieved from https://www.wisegeek.com/what-is-the-
evolutionary-history-of-fish.htm#didyouknowout
What Two Roles Do Lichens Play in an Ecosystem? (2017, April 25). Retrieved from https://sciencing.com/two-
roles-lichens-play-ecosystem-8789.html