Geology

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Texas A&M University *

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101

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Geology

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Oct 30, 2023

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docx

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Uploaded by DeaconLoris3762

Geology 101 3 types: crater lake, Hawaiian, Yellowstone age of earth: our understanding of radioactivity helps us accurately determine numerical dates for rocks that represent important events in earth's past. Earth is about 4.6 billion years old. agents of chemical weathering: dissolution, oxidation, hydrolysis agents of erosion: moving water, wind, gravity, ice Asthenosphere: "weak sphere" 400km deep, small amount of melting, mechanically detached from lithosphere, which can move independently basaltic: compositional group of igneous rocks indicating that the rock contains substantial dark silicate minerals and calcium-rich plagioclase feldspar Batholith: large mass of igneous rock formed when magma was emplaced at depth, crystallized, and subsequently exposed by erosion Bowen's reaction series: concept by N.L. Bowen that illustrates the relation- ships between magma and the minerals crystallizing from it during the formation of igneous rocks Breccia: sedimentary rock composed of angular fragments that were lithified; as material precipitates from water that percolates through sediment, open spaces are filled and particles are joined into a solid mass burial metamorphism: low grade metamorphism that occurs in the lowest layers of very thick accumulations of sedimentary strata caldera: a volcanic crater that has a diameter of >1 and is produced by a collapse following a massive eruption carbonic acid: a very weak acid formed in solution when carbon dioxide dis- solves in water chemical sedimentary rocks: form by precipitation or the growth of new mineral in water. Precipitation can create large sedimentary structures like stalactites and stalagmites, which grow in caves chemical weathering: dissolves minerals in the rocks and precipitates them classification of sedimentary rocks: composition, what they ar made of and how they were formed ex, clastic sedimentary rocks are composed of rock, minerals or fossils that have been cemented together. clastic: a sedimentary rock texture consisting of broken fragments of preexisting rock compaction: a type of lithification in which the weight of overlying material compresses more deeply buried sediment; most important in the fine-grained sedimentary rocks such as shale compression: differential stress that shortens a rock body conglomerate: sedimentary rock composed of rounded, gravel size particles contact metamorphism: changes in rock caused by the heat from a nearby magma body continental drift: hypothesis credited to Alfred Wegener, suggested that all present continents once existed as a single supercontinent over 200 million years ago. The supercontinent began breaking into small continents, which then drifted to their present positions. convection currents: in the mantle, where warm buoyant rocks rise and cool, dense rocks sink, is the underlying driving force of plate tectonics (the transfer of heat by the mass movement or circulation of a substance)

convergent boundaries: where 2 plates move together, resulting either in oceanic lithosphere descending beneath an overriding plate, eventually to be reabsorbed into the blocks to create a mountain belt cooling rate: rate at which temperature decreases with time cooling rate: the slower it cools the larger the crystals faster it cools the smaller the crystals. country rock: rock native to an area crater: funnel-shaped depression at the summit of most volcanic cones, generally less than 1 km in diameter. craton: interior of a continent, oldest part crossbedding: structure in which relatively thin layers are inclined at an angle to the main bedding; formed by currents of wind or water density: defined as mass per unit of volume, determines how plates react at subduction zones. detrital: accumulation of material that originates and is transported as solid particles derived from both mechanical and chemical weathering. (the sedimentary rocks that they form are called detrital sedimentary rocks. diagenesis: change genesis- origin; a collective term for all the chemical, physical, and biological changed that take place after sediments are deposited and during and after lithification differentiation: all of the processes by which earth came to its present interior structure dike: tabular shaped intrusive igneous feature that cuts through surrounding rock dissolution: the dissolving of certain minerals in water (halite) divergent boundaries: where 2 plates move APART, resulting in upwelling of hot material from the mantle to create new seafloor earth's spheres: hydrosphere, atmosphere, geosphere, biosphere environments of metamorphism: low grade and high grade extrusive: igneous activity that occurs at earth's surface facies: portion of a rock unit that possesses a distinctive set of characteristics that distinguish it from other parts of the same unit felsic: compositional group of igneous rocks indicating the rock is composed almost entirely of light-colored silicates foliation: linear arrangement of textural features often exhibited by metamorphic rocks; gives the rock a layered appearance for normal growth gases geologic hazard: natural processes that become hazards only when people try to live where these processes occur geothermal gradient: gradual increase in temperature with depth in the crust granitic: type of intrusive, igneous rock; typically, quartz and or feldspar humus: the decayed remains of animal and plant life (organic matter) hydrolysis: silicates are decomposed by the process of hydrolysis, the reaction of any substance with water

hydrothermal metamorphism: chemical alterations that occur as hot, ion-rich water circulates through fractures in a rock hypothesis: tentative or untested explanation for how or why things happen in the manner observed igneous: rock formed from the crystallization of magma interface: a common boundary where different parts of a system interact intrusive: igneous rock formed below earth's surface ion: positively and negatively charged atoms isotopes: varieties of the same element that have different mass numbers; their nuclei contain the same number of protons but different numbers of neutrons laccolith: a massive igneous body intruded between preexisting strata lava flow: 90% is basaltic lava, <10% of lava is andesitic and 1% is rhyolitic lava: exploded magma layers of the earth: iron-rich core (outer and inner), mantle (upper and lower), and the thin crust lithification: process by which unconsolidated sediments are transformed into solid sedimentary rocks basic lithification processes include compaction and cementation. lithology: study of general physical characteristics of rocks lithosphere: "sphere of rock" the entire crust plus the uppermost portion of the mantle; forms the cool, rigid outer shell, 100-250 km thick mafic: mostly basalt- used to describe igneous rocks magma: is molten rock that usually contains some crystals and varying amounts of dissolved magma: molten rock below the earth's surface, including any dissolved gases and crystals magnetic reversal: a change in Earth's magnetic field from normal to reverse or vice versa mantle plume: mass of hotter-than-typical mantle material that ascends toward the surface, where it may lead to igneous activity. These plumes of solid, mobile material may originate as deep as the core-mantle boundary. metamorphic grade (recognize rocks): the degree to which a parent rock changes during metamorphism; varies from low grade (low temps and pressures) to high grade (high temps and pressures) metamorphism: changes in mineral composition and texture of a rock subject- ed to high temperatures and pressures within the earth mid-ocean ridge: a continuous mountainous ridge on the floor of all major ocean basins and varying in width from 500 to 5000 kilometers (300 to 3000 miles). the rifts at the crests of these ridges represent divergent plate boundaries. mineral: naturally occurring, generally inorganic, solid, orderly crystal structure, definite chemical comp ex. quartz, feldspar mineralogy: study of minerals minerals; texture in metamorphic rocks molecule: atoms joined together by chemical bonds natural disaster: natural event that causes great damage and or loss of life organic: sedimentary rock composed of carbon remains of plants that died and accumulated

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on the floor of a swamp; primary example is coal. oxidation: the process of rusting, occurs when oxygen combines with iron to form iron oxide oxide: a binary compound of oxygen with another element of group Paleomagnetism: the natural remnant magnetism in rock bodies. The permanent magnetization acquired by rock that can be used to determine the location of the magnetic poles and the latitude of the rock at the time it became magnetized Pangaea: the proposed supercontinent that 200 million years ago began to break apart and form the present landmass parent rock: the rock from which a metamorphic rock formed physical weathering: processes break rocks down into pieces or sediments plate tectonics: a theory which proposed that earth's outer shell consists of individual plates that interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself plate tectonics: proposes that Earth's outer shell consists of individual plates that interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust porphyroblasts: particularly large grains are surrounded by a fine grained matrix of other pyroclastic: volcanoes eject pulverized rock and lava fragments called pyroclastic materials (particles range in size from fine dust, to sand-sized ash, to large rocks) quiescent: volcanoes that are quiet, don't erupt recrystallization: the formation of new mineral crystals in a rock that tends to be larger than the original crystals regional metamorphism: metamorphism associated with large-scale mountain building regolith: rhegos = blanket, lithos = stone, the layer of rock and mineral fragments produced by residual soil: soil developed on bedrock rift valley: a long, narrow trough bounded by normal faults. It represents a region where divergence is taking place rifting: moving apart forming cracks, breaks, or fissures ring of fire: circus pacific ring of fire where most active volcanoes are found scoria: reddish/brown porous rock from forth basaltic and andesitic lava seafloor spreading: a hypothesis, first proposed in the 1960's by Harry Hess, which suggested that new oceanic crust is produced at the crests of mid-ocean ridges, which are the sites of divergence sediment: unconsolidated particles created by the weathering and erosion of rock by chemical precipitation from solution in water, or from the secretions of organisms, and transported by water, wind, or glaciers. sheeting: the process that generates onion-like layers, takes place due to the great reduction in pressure that occurs as the overlying rock is eroded away, a process called unloading. shield: expansive, flat region composed largely of deformed igneous and meta- morphic rocks shock metamorphism / impact metamorphism: occurs when high speed projectiles called meteorites strikes earth's surface; heat energy and shock waves pass through the surrounding rocks which result in pulverized, shattered, and sometimes melted rock silicate: most common type of minerals, account for >90% of earths crust. Silicon and oxygen

make up the basic building blocks of silicate minerals sill: a tabular igneous body that was intruded parallel to the layering of preexisting rock slab pull -: a mechanism that contributes to plate motion in which cool, dense oceanic crust stinks into the mantle and "pulls" the trailing lithosphere soil: a combination of mineral and organic matter, water, and air- the portion of the regolith that supports the growth of plants sorting: degree of similarity in particle size in a sedimentary rock. Example: if all samples of sandstone are the same size they are considered well sorted, if there is mixture of large and small, it is poorly sorted. spheroidal: weathering that creates rounded edges, like a sphere strata: sedimentary rocks form as layer upon layer of sediments accumulates in various depositional environments, these layers called Strata or beds are probably the single most common characteristic feature of sedimentary rocks. subduction zone: a long, narrow zone where one lithosphere plate and trans- ported into the mantle talus: the pile of rocks that accumulates the base of a cliff, chute, or slope texture: size, shape, and distribution of the particles that collectively constitute a roc theory: a hypothesis that has survived extensive scrutiny when other competing hypotheses have been eliminated; well-tested and widely accepted view that the scientific community agrees best explains certain trace elements: chemical element required only in minute amount by living organisms transform boundaries: a boundary in which two plates slide past one another without creating or destroying lithosphere transported soil: soils developed on unconsolidated sediment trench: a narrow, elongated depression of the seafloor types of coal: peat, lignite, bituminous, anthracite types of volcanoes: shield volcanoes, cinder cones and composite volcanoes types of weathering: mechanical (changes shape) and chemical (changes composition) uniformitarianism: James Hutton's principle that the physical, chemical, and biological laws that operate today have also operated in the geologic past (the present is the key to the past) vesicles: they are bubbles found inside of fossils and rocks vesicular: aphanitic igneous rocks that contain small opening or cavities for the original purpose of escaping gases viscosity: is a measure of a materials resistance to flow (ex. syrup is more viscous than water) volatile: gaseous component of magma dissolved in the melt; will form a gas at surface pressure volcanic arc: chain of volcanic islands generally located in a few hundred kilometers from a trench where there is active subduction of one oceanic plate beneath another weathering weathering: the formation of both types of sedimentary rocks (clastic and chemical) begin with the weathering of any igneous, sedimentary, or metamorphic rocks.