3. Geologists divide rocks into three (3) major groups:
- Igneous; formed when molten rock, magma, cools and solidifies.
-Sedimentary; sediments, or raw materials for sedimentary rocks, accumulate in layers
at the Earths surface.
-Metamorphic; produced from pre-existing igneous, sedimentary, or even other
metamorphic rocks.
Geologists define a mineral as any naturally
occurring, inorganic solid that possesses an orderly
crystalline structure and a well defined chemical
composition.
Minerals exhibit the following characteristics:
-Naturally Occurring
-Solid Substance
-Orderly Crystalline Structure; atoms are arranged in an orderly, repetitive manner
4. Morro Rock At Morro Bay, California
A remnant of a long eroded volcano, Morro Rock belongs to a line of more than a dozen
volcanic plugs stretching from San Luis Obispo to Morro Bay. A volcanic plug is a core of
solid rock that solidifies from magma in the throat of a volcano when eruptions cease, the
chain of “Nine Sisters” erupting approximately 20 to 27 million years ago.
5. Granite in Springville, California
A coarse grained intrusive rock rich in light
colored silicate minerals, quartz and feldspar,
granite is a major constituent of the continental
crust. Subsequent uplift and erosion expose this
rock at the surface.
Seated in the foothills of the Sierra
Nevada mountain range,
Springville is known as the
“Gateway to the Giant Sequoias.”
6. Petrified Wood, as landscaping,
Springville, CA
Woody land plants have existed since 400 million years ago during the Devonian Period.
Meaning “to turn into stone,” petrified wood is a type of fossil. During petrification small
internal cavities and pores of the original structure are filled with precipitated mineral
matter or cell walls, and other solid material are removed and replaced with mineral
matter while maintaining original structure.
7. Slate, as landscaping, Springville, CA
Slate is formed during low grade regional metamorphism when sedimentary shale becomes
more compact. Metamorphism occurs in one of three settings; when rock is intruded by a
magma body (contact or thermal metamorphism), when igneous activity provides heat
required to drive chemical reactions that circulate hot, ion-rich water through fractures in the
parent rock (hydrothermal metamorphism), or during mountain building when great
quantities of of deeply buried rock are subjected to directed pressures and high temperatures
(regional metamorphism).
8. Quartz, Los Padres National Forest, California
Seated along
Highway 33, the Los
Padres National
Forest is one of the
most scenic and
entertaining drives in
the Southern
California. Pieces of
sedimentary rock
and quartz can be
found roadside.
Quartz is hard,
resistant to
weathering, and does
not have cleavage.
Quartz is also the
only common silicate
material consisting
entirely of silicon
and oxygen.
10. The San Andreas Fault
Parkfield, California
A fault is a fracture in the crust along which appreciable displacement has taken place.
Parkfield, CA, the “Earthquake Capitol of the World,” where the Pacific and North
American Plates meet in a ground shaking dip-slip fault.
11. Weathering: the
disintegration and
decomposition of rock at or near
the surface of Earth.
Morro Rock, an example of mechanical
weathering exhibiting fractures from
sheeting, and parallel joints formed from
forces during mountain building.
12. Weathering, Continued
Oxidation, a chemical reaction that occurs when
electrons are lost from one element during the
reaction. Iron loses its electrons to oxygen, forming
iron oxide, or rust as we commonly call it.
Oxidation of iron progresses slowly in a dry
environment.
Dew from morning fog speeds the
reaction of oxidation.
13. Mass Wasting: the downslope
movement of rock, regolith, and
soil under the direct influence of
gravity.
On a hillside in Malibu, CA one can see where sliding
movement of an unconsolidated material (debris and earth)
has caused mass wasting.
14. Erosion: the removal of material by a mobile agent, usually
water, wind, or ice.
Animals play a vital role in
soil formation, while the
loss of topsoil from
agricultural overuse is a
growing problem.
Root erosion
15. Sedimentary Environments, or an environment of deposition,
is a geographic setting where sediment accumulates. Placed into one
of three categories, sedimentary environments include many specific
sub-environments.
Continental Environments: dominated by erosion and deposition associated with
streams.
Marine Environments: divided according to depth; shallow marine environment
reaches to depths of nearly 700 feet extending from the shore to the outer edge of
the continental shelf; deep marine environments lie seaward of the continental
shelf in waters deeper than 200 meters.
Transitional Environments: the transition zone between marine and continental
environments (shoreline).
* The following slide depicts an example of each of the three environments at Morro Beach
and the North Fork of the Tule River.
17. Practical Uses of Geology:
Dams: built to store floodwater and then release
it in a timely manner. In addition to flood control,
dams provide water for agriculture, hydroelectric
power generation, and some provide recreational
facilities.
Decor and
Landscaping:
a simple, natural, and
somewhat costly, home
improvement.
18. Works Cited
Baylor, Katherine J. (2010). California ROCKS! A Guide to Geologic Sites in
the Golden State. Missoula, MT: Mountain Press Publishing Co.
http://geology.about.com/
Lutgens, K., Tarbuck, E., & Tasa, D. (2011). Earth: An Introduction to
Physical Geology. Upper Saddle River, NJ: Pearson Education, Inc.
