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Murrieta Hogbacks
The Murrieta Hogbacks are Miocene basalt capped granitic hogbacks located in northeastern Murrieta on the southern end of the Temescal Mountains of Riverside County, California. Geology The Murrieta Hogbacks are underlain by Cretaceous granitic rocks of the Peninsular Ranges Batholith. On the north half of the hogbacks, by foliated biotite- hornblende tonalite and on the southern half by hornblende gabbro Gabbro () is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coarse-grained gabbro is che .... The basalt is potassium-argon dated to 10.4 to 10.8 million years and is a remnant of a channel-filling basalt flow, overlying a thin deposit of unconsolidated gray stream gravel, indicating that the basalt had filled in a former water course.M.P. Kennedy and D.M. Morton, PRELIMINARY GEOLOGIC MAP OF THE U.S. Geological Surve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Riverside County, California
Riverside County is a County (United States), county located in the southern California, southern portion of the U.S. state of California. As of the 2020 United States Census, 2020 census, the population was 2,418,185, making it the fourth-most populous county in California and the List of the most populous counties in the United States, 10th-most populous in the United States. The name was derived from the city of Riverside, California, Riverside, which is the county seat. Riverside County is included in the Riverside-San Bernardino, California, San Bernardino-Ontario, California, Ontario Metropolitan Statistical Area, also known as the Inland Empire. The county is also included in the Los Angeles-Long Beach, California, Long Beach Greater Los Angeles Area, Combined Statistical Area. Roughly rectangular, Riverside County covers in Southern California, spanning from the greater Los Angeles area to the Arizona border. Geographically, the county is mostly desert in the central a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hogback (geology)
In geology and geomorphology, a hogback or hog's back is a long, narrow ridge or a series of hills with a narrow crest and steep slopes of nearly equal inclination on both flanks. Typically, the term is restricted to a ridge created by the differential erosion of outcropping, steeply dipping (greater than 30–40°), homoclinal, and typically sedimentary strata. One side of a hogback (its backslope) consists of the surface (bedding plane) of a steeply dipping rock stratum called a dip slope. The other side (its escarpment, frontslope or "scarp slope") is an erosion face that cuts through the dipping strata that comprises the hogback.Huggett, JR (2011) ''Fundamentals of Geomorphology,'' 3rd ed., Routledge, New York. 516 pp. Cotton, CA (1952) ''Geomorphology An Introduction to the Study of Landforms, 6th ed.'' John Wiley and Sons, New York. 505 pp.Fairbridge, RW (1968) ''Hogback and Flatiron.'' In RW Fairbridge, ed., pp. 524-525, ''The Encyclopedia of Geomorphology'' (Encyclopedia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
K–Ar Dating
Potassium–argon dating, abbreviated K–Ar dating, is a radiometric dating method used in geochronology and archaeology. It is based on measurement of the product of the radioactive decay of an isotope of potassium (K) into argon (Ar). Potassium is a common element found in many materials, such as feldspars, micas, clay minerals, tephra, and evaporites. In these materials, the decay product is able to escape the liquid (molten) rock, but starts to accumulate when the rock solidifies ( recrystallizes). The amount of argon sublimation that occurs is a function of the purity of the sample, the composition of the mother material, and a number of other factors. These factors introduce error limits on the upper and lower bounds of dating, so that the final determination of age is reliant on the environmental factors during formation, melting, and exposure to decreased pressure or open air. Time since recrystallization is calculated by measuring the ratio of the amount of accumulated to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gabbro
Gabbro () is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coarse-grained gabbro is chemically equivalent to rapid-cooling, fine-grained basalt. Much of the Earth's oceanic crust is made of gabbro, formed at mid-ocean ridges. Gabbro is also found as plutons associated with continental volcanism. Due to its variant nature, the term ''gabbro'' may be applied loosely to a wide range of intrusive rocks, many of which are merely "gabbroic". By rough analogy, gabbro is to basalt as granite is to rhyolite. Etymology The term "gabbro" was used in the 1760s to name a set of rock types that were found in the ophiolites of the Apennine Mountains in Italy. It was named after Gabbro, a hamlet near Rosignano Marittimo in Tuscany. Then, in 1809, the German geologist Christian Leopold von Buch used the term more restrictively in his descri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tonalite
Tonalite is an igneous, plutonic ( intrusive) rock, of felsic composition, with phaneritic (coarse-grained) texture. Feldspar is present as plagioclase (typically oligoclase or andesine) with alkali feldspar making up less than 10% of the total feldspar content. Quartz (SiO2) is present as more than 20% of the total quartz-alkali feldspar-plagioclase-feldspathoid ( QAPF) content of the rock. Amphiboles and biotite are common accessory minerals. In older references tonalite is sometimes used as a synonym for quartz diorite. However the current IUGS classification defines tonalite as having greater than 20% quartz, while quartz diorite varies its quartz content from 5 to 20%. The name is derived from the type locality of tonalites, adjacent to the Tonale Line, a major structural lineament and mountain pass, Tonale Pass, in the Italian and Austrian Alps. The name was first applied by Gerhard vom Rath in 1864. The term ''adamellite'' was originally applied by A. Cathrein in 1890 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hornblende
Hornblende is a complex inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common in igneous and metamorphic rocks. The general formula is . Physical properties Hornblende has a hardness of 5–6, a specific gravity of 3.0 to 3.6, and is typically an opaque green, dark green, brown, or black color. It tends to form slender prismatic to bladed crystals, diamond-shaped in cross-section, or is present as irregular grains or fibrous masses. Its planes of cleavage intersect at 56° and 124° angles. Hornblende is most often confused with the pyroxene series and biotite mica, which are also dark minerals found in granite and charnockite. Pyroxenes differ in their cleavage planes, which intersect at 87° and 93°. Hornblende is an inosilicate (chain silicate) mineral, built around double chains of silica tetrahedra. These chains extend the length of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biotite
Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous end-members include siderophyllite and eastonite. Biotite was regarded as a mineral ''species'' by the International Mineralogical Association until 1998, when its status was changed to a mineral ''group''. The term ''biotite'' is still used to describe unanalysed dark micas in the field. Biotite was named by J.F.L. Hausmann in 1847 in honor of the French physicist Jean-Baptiste Biot, who performed early research into the many optical properties of mica. Members of the biotite group are sheet silicates. Iron, magnesium, aluminium, silicon, oxygen, and hydrogen form sheets that are weakly bound together by potassium ions. The term "iron mica" is sometimes used for iron-rich biotite, but the term also refers to a flaky micaceous form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Foliation (geology)
Foliation in geology refers to repetitive layering in metamorphic rocks.Marshak, Stephen, ''Essentials of Geology,'' W. W. Norton 3rd Ed, 2009 Each layer can be as thin as a sheet of paper, or over a meter in thickness. The word comes from the Latin ''folium'', meaning "leaf", and refers to the sheet-like planar structure. It is caused by shearing forces (pressures pushing different sections of the rock in different directions), or differential pressure (higher pressure from one direction than in others). The layers form parallel to the direction of the shear, or perpendicular to the direction of higher pressure. Nonfoliated metamorphic rocks are typically formed in the absence of significant differential pressure or shear. Foliation is common in rocks affected by the regional metamorphic compression typical of areas of mountain belt formation (orogenic belts). More technically, foliation is any penetrative planar fabric present in metamorphic rocks. Rocks exhibiting foliat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peninsular Ranges Batholith
A peninsula (; ) is a landform that extends from a mainland and is surrounded by water on most, but not all of its borders. A peninsula is also sometimes defined as a piece of land bordered by water on three of its sides. Peninsulas exist on all continents. The size of a peninsula can range from tiny to very large. The largest peninsula in the world is the Arabian Peninsula. Peninsulas form due to a variety of causes. Etymology Peninsula derives , which is translated as 'peninsula'. itself was derived , or together, 'almost an island'. The word entered English in the 16th century. Definitions A peninsula is usually defined as a piece of land surrounded on most, but not all sides, but is sometimes instead defined as a piece of land bordered by water on three of its sides. A peninsula may be bordered by more than one body of water, and the body of water does not have to be an ocean or a sea. A piece of land on a very tight river bend or one between two rivers is sometimes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Murrieta, California
Murrieta is a city in southwestern Riverside County, California, United States. The population of Murrieta was 110,949 as of the 2020 census. Murrieta experienced a 133.7% population increase between 2000 and 2010, making Murrieta one of the fastest-growing cities in the state during that period. Largely residential in character, Murrieta is typically characterized as a bedroom community. Murrieta is bordered by the city of Temecula to the south, the cities of Menifee and Wildomar to the north, and the unincorporated community of French Valley to the east. Murrieta is located in the center of the Los Angeles-San Diego mega-region. Murrieta is named for Juan Murrieta, a Californio ranchero who founded the town. History For most of its history, Murrieta was not heavily populated. On June 9, 1873, Domingo Pujol, Francisco Sanjurjo, and Juan and Ezequiel Murrieta purchased the Rancho Pauba and Rancho Temecula Mexican land grants, comprising in the area. Ezequiel returned to S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Granitic
A granitoid is a generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz-poor monzonites to quartz-rich quartzolites. As only two of the three defining mineral groups (quartz, plagioclase, and alkali feldspar) need to be present for the rock to be called a granitoid, foid-bearing rocks, which predominantly contain feldspars but no quartz, are also granitoids. The terms ''granite'' and ''granitic rock'' are often used interchangeably for granitoids; however, granite is just one particular type of granitoid. Granitoids are diverse; no classification system for granitoids can give a complete and unique characterization of the origin, compositional evolution, and geodynamic environment for the genesis of a granitoid. Accordingly, multiple granitoid classification systems have been developed such as those based ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territories of the United States by population, most populous U.S. state and the List of U.S. states and territories by area, 3rd largest by area. It is also the most populated Administrative division, subnational entity in North America and the 34th most populous in the world. The Greater Los Angeles area and the San Francisco Bay Area are the nation's second and fifth most populous Statistical area (United States), urban regions respectively, with the former having more than 18.7million residents and the latter having over 9.6million. Sacramento, California, Sacramento is the state's capital, while Los Angeles is the List of largest California cities by population, most populous city in the state and the List of United States cities by population, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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