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
Morro Rock At Morro Bay, CaliforniaA remnant of a long eroded volcano, Morro Rock belongs to a line of more than a dozenvolcanic plugs stretching from San Luis Obispo to Morro Bay. A volcanic plug is a core ofsolid 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.
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.”
Petriﬁed Wood, as landscaping, Springville, CAWoody 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.
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 heatrequired to drive chemical reactions that circulate hot, ion-rich water through fractures in the parent rock (hydrothermal metamorphism), or during mountain building when greatquantities of of deeply buried rock are subjected to directed pressures and high temperatures (regional metamorphism).
Quartz, Los Padres National Forest, California Seated alongHighway 33, the Los Padres National Forest is one of the most scenic andentertaining drives in the SouthernCalifornia. Pieces of sedimentary rock and quartz can be found roadside. Quartz is hard, resistant toweathering, and does not have cleavage. Quartz is also theonly common silicate material consisting entirely of silicon and oxygen.
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.
Weathering: the disintegration anddecomposition 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.
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.
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 slidingmovement of an unconsolidated material (debris and earth) has caused mass wasting.
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
Sedimentary Environments, or an environment of deposition,is a geographic setting where sediment accumulates. Placed into oneof 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 environmentreaches 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.
Practical Uses of Geology:Dams: built to store ﬂoodwater and then releaseit 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, andsomewhat costly, home improvement.
Works CitedBaylor, Katherine J. (2010). California ROCKS! A Guide to Geologic Sites inthe Golden State. Missoula, MT: Mountain Press Publishing Co.http://geology.about.com/Lutgens, K., Tarbuck, E., & Tasa, D. (2011). Earth: An Introduction toPhysical Geology. Upper Saddle River, NJ: Pearson Education, Inc.
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