Geology 101!

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

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 soi l: 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.

Geol 101 Exam 1 study guide Earth history Earth- characterized by water; 4.56 billion years old Earth is abundant in Fe (iron); 35%f the earth is composed of Fe Formed by accretion- the coming together and cohesion of matter under the influence of gravitation to form larger bodies Core of earth formed within 30 mil years of earth Zonal structure of earth ● Core ○ Inner core ○ Outer core ● Mantle ○ Lithosphere- brittle ○ Asthenosphere- weak plastic ○ Mesosphere- strong plastic ● Crust Crust formation - 4.4 bil years Oldest earth mineral 4.4 bil yrs( zircon crystal) Crust stabilizes by 3 b.y. When modern plate tectonics starts Great events in earth history 1. Formation of earth's core by smelting iron from rock- 4.5 b.y. 2. Spread of life over the Earth- 4 b.y. 3. Release of free oxygen to ocean =s and atmosphere- 2.5 b.y. 4. Origin of multicellular life- 600 million years ago Ancient earth 4.5 - 3.5 B.Y. Very active volcanism and tectonism Volcanic emissions produce atmosphere Microbial life appears 3.5 - 1 B.Y. Release oxygen to atmosphere Deposition of iron rich sediment to ocean Plate tectonics and continental drift *great oxygenation event (2. - 2 B.Y.) Last 1 B.Y. Multi Celled life

● Averages about 100 km in thickness but may be 250 km or more thick beneath the older portions of the continents Tectonic plates ● Lithosphere zone of earth ● Brittle rock zone on surface of earth ● Composed of crust at top and layer of brittle mantle rock below Asthenosphere*soft plastic* ● Below lithosphere ● Slippery layer defined by partial melting ● Depth of about 660 km ● Allows the lithosphere to move independent of underlying mantle Soft plastic layer below brittle crust makes it possible foro plates to move Dense cooled crust sinks into mantle Continental drift ● Fit of atlantic continents ● Rock type and structural similarities ● Fossil evidence ● Paleoclimatic evidence ● Congruent climate Paleomagnetism Earth’s magnetic field periodically reverses polarity These reversals are recorded in the earth’s crust This reversal is shown symmetrically in the crust formed in seafloor spreading Both the direction and rate of seafloor spreading can be shown Magnetism Rocks and minerals with metal atoms capture a bit of the Earth’s magnetic field when they form Earth’s magnetic field is dipolar; there is an organized flow in the outer core Field is produced by turbulent motion of liquid iron in outer core Inner core rotates faster than the earth's surface and axis of rotation is offset about 10 degrees from the earth's poles causing liquid iron to flow Tectonic plates Plate motion controls continent movement Pangea

Plate boundaries Types of plate boundaries ● Divergent ○ Constructive margins ○ New crust is being formed on plate margins ● Convergent ○ Destructive margins ○ Crust is being consumed as it sinks into mantle ● Transform ○ Conservative margins ○ Margins slide along fault surface Mid-ocean ridges As basaltic crust moves away from ridge, it cools and thermally contracts and the lithosphere becomes more dense Ocean crust forms by extrusive volcanism and intrusions into lower layers, forming roc of different composition than mantle Four layers of oceanic crust ● Unconsolidated sediments ● Zone of basaltic pillow lavas ● Numerous interconnected dikes called sheet dikes ● gabbro , in a sequence of rocks called an ophiolite complex Hot water vents on ridges Interactions between seawater and oceanic crust ● Seawater circulates downward through crust ● Basaltic rock is altered by hydrothermal metamorphism ● Hydrothermal fluids dissolve ions of various metals and precipitate them on the seafloor as particle-filled clouds called black smokers Hot water vents occur because ocean crust cracks as it cools and water seeps into lower levels where it is heated, then rises to surface as along fractures as hot water subduction zones- Older portions of oceanic plates are returned to the mantle in these destructive plate margins Subduction is the process of cooled ocean crust sliding back into the earth interior along linear zones