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Geology 102
Essentials of geology 3rd ed
| Question | Answer |
|---|---|
| Scientific method | A sequence of steps for systematically analyzing scientific problems in a way that leads to verifiable results. |
| Catastrophism | Change that takes place either instantaneously or rapidly in geologic time. |
| Uniformitarianism | the principle that the same physical processes observed today are responsible for the formation of ancient geologic features; put concisely, “the present is the key to the past.” |
| Cosmoslogy | The study of the overall structure of the Universe |
| Big bang | A cataclysmic explosion that scientists suggest represents the formation of the Universe; before this event, all matter and all energy were packed into one volumeless point. |
| Nebula theory | The concept that plantes grow out of rings of gas, dust, and ice surrounding a new-born star. |
| Star | A large sphere, composed dominantly of hydrogen and helium, in which fusion reactions are producing energy. |
| Plant | A relatively large, spherical object that orbits a star and has cleared its orbit of most debris. |
| Super Nova | A short-lived, very bright object in space tthat results from the cataclusmic explosion marking the death of a bvery lage star; the explosion ejects large quantities of matter into space to form new nebulae. |
| Differentiation | In the context of planet formation, the process by which a planet separates into a metallic core and a rocky mantle very early in its history. |
| Crust | The rock that makes up the outermost layer of the Earth. |
| Mantle | The thick layer of rock below the Earth’s crust and above the core. |
| Core | The dense, iron center of the earth |
| silicate rocks | Rock composed of silicate minerals. |
| magnetic field | the region affected by the force emanating from a magnet. |
| Moon | A solid object of ice and/or rock and metal that orbits a planet. |
| continental drift | The idea that continents have moved and are still moving slowly across the Earth’s surface |
| Alfred Wegener | Proposed that all continents once were a supercontinent called pangaea and gave four points to support his idea. |
| Pangaea | A supercontinent that assembled at the end of the Paleozoic Era. |
| Marie Tharp | A pioneer of modern oceanography, Tharp was the first to map details of the ocean floor on a global scale |
| Ocean ridge | elongate submarine mountain ranges whose peaks lie only about 2 to 2.5km below sea level |
| Fracture zone | A narrow band of vertical fractures in the ocean floor; fracture zones lie roughly at right angles to a mid-ocean ridge, and the actively slipping part of a fracture zone is a transform fault. |
| Abyssal plain | A broad, relatively flat region of the ocean that lies at least 4.5 km below sea level. |
| Sea floor spreading | The gradual widening of an ocean basin as new oceanic crust forms at a mid-ocean ridge axis and then moves away from the axis. |
| Basalt | A fine-grained mafic igneous rock. |
| Harry Hess | obsservations led to the hypothesis of sea-floor spreading. |
| Paleomagnetism | The record of ancient magnetism preserved in rock. |
| Polar wander | The phenomenon of the progressive changing through time of the position of the Earth’s magnetic poles relative to a location on a continent; significant polar wander probably doesn’t occur—in fact, poles seem to remain fairly fixed, while continents move |
| Magnetic anomaly | The difference between the expected strength of the Earth’s magnetic field at a certain location and the actual measured strength of the field at that location. |
| Magnetic reversal | The change of the Earth’s magnetic polarity; when a reversal occurs, the field flips from normal to reversed polarity, or vice versa. |
| Plate tectonics | The theory that the outer layer of the Earth (the lithosphere) consists of separate plates that move with respect to one another. |
| Lithosphere | The relatively rigid, nonflowable, outer 100- to 150-km-thick layer of the Earth; constituting the crust and the top part of the mantle. |
| Asthenosphere | The layer of the mantle that lies between 100–150 km and 350 km deep; the asthenosphere is relatively soft and can flow when acted on by force. |
| Plate boundary | The border between two adjacent lithosphere plates. |
| Active margin | A continental margin that coincides with a plate boundary. |
| Passive margin | A continental margin that is not a plate boundary. |
| Divergent boundary | A boundary at which two lithosphere plates move apart from each other; they are marked by mid-ocean ridges. |
| Convergent boundary | A boundary at which two plates move toward each other so that one plate sinks (subducts) beneath the other; only oceanic lithosphere can subduct. |
| Transform boundary | A boundary at which one lithosphere plate slips laterally past another. |
| Continental rifting | The process by which a continent stretches and splits along a belt; if it is successful, rifting separates a larger continent into two smaller continents separated by a divergent boundary. |
| Seduction | The process by which one oceanic plate bends and sinks down into the asthenosphere beneath another plate. |
| Granite | A coarse |
| Collision | The process of two buoyant pieces of lithosphere converging and squashing together. |
| Hot spot | A location at the base of the lithosphere, at the top of a mantle plume, where temperatures can cause melting. |
| Plate velocity | the speed in which plates drift |
| Mineral | A homogenous, naturally occurring, solid inorganic substance with a definable chemical composition and an internal structure characterized by an orderly arrangement of atoms, ions, or molecules in a lattice. Most minerals are inorganic. |
| Rock | A coherent, naturally occurring solid, consisting of an aggregate of minerals or a mass of glass. |
| Crystal lattice | The orderly framework within which the atoms or ions of a mineral are fixed. |
| Element | is a pure chemical substance consisting of one type of atom distinguished by its atomic number |
| Atom | is a basic unit of matter that consists of a dense, central nucleus surrounded by a cloud of negatively charged electrons. |
| Chemical bond | is an attraction between atoms or molecules that allows the formation of chemical compounds |
| Cat ion | an ion with a positive charge |
| Anion | an ion with a negative charge |
| Color | minerals depends on the presence of certain atoms, such as iron or chromium which strongly absorb portions of the light spectrum |
| Streak | The color of the powder produced by pulverizing a mineral on an unglazed ceramic plate. |
| Luster | The way a mineral surface scatters light. |
| Hardness | In mineralogy, hardness refers to the resistance of a mineral to scratching; a harder mineral can scratch a softer mineral. |
| Crystal habit | The general shape of a crystal or cluster of crystals that grew unimpeded. |
| Cleavage | (1) The tendency of a mineral to break along preferred planes; (2) a type of foliation in low-grade metamorphic rock. |
| Conchoidal fracture | Smoothly curving, clamshell-shaped surfaces along which materials with no cleavage planes tend to break. |
| Silicate minerals | Minerals composed of silicon-oxygen tetrahedra linked in various arrangements; most contain other elements too. |
| Silicon oxygen tetrahedral | The basic building block of silicate minerals; it consists of one silicon atom surrounded by four oxygen atoms. |
| Carbonate rocks | Rocks containing calcite and/or dolomite. |
| Rock | A coherent, naturally occurring solid, consisting of an aggregate of minerals or a mass of glass. |
| Cement | Mineral material that precipitates from water and fills the spaces between grains, holding the grains together. |
| Crystalline | Containing a crystal lattice. |
| Igneous rock | Rock that forms when hot molten rock (magma or lava) cools and freezes solid. |
| Sedimentary rock | Rock that forms either by the cementing together of fragments broken off preexisting rock or by the precipitation of mineral crystals out of water solutions at or near the Earth’s surface. |
| Metamorphic rock | Rock that forms when preexisting rock changes into new rock as a result of an increase in pressure and temperature and/or shearing under elevated temperatures; metamorphism occurs without the rock first becoming a melt or a sediment. |
| Rock cycle | The succession of events that results in the transformation of Earth materials from one rock type to another, then another, and so on. |
| Melt | Molten (liquid) rock. |
| Lava | Molten rock that has flowed out onto the Earth’s surface. |
| Magma | Molten rock beneath the Earth’s surface. |
| Extrusive | Rock that forms by the freezing of lava above ground, after it flows or explodes out (extrudes) onto the surface and comes into contact with the atmosphere or ocean. |
| Intrusive | Rock formed by the freezing of magma underground. |
| Geothermal gradient | The rate of change in temperature with depth. |
| Volatiles | Elements or compounds such as H2O and CO2 that evaporate easily and can exist in gaseous forms at the Earth’s surface. |
| Felsic intermediate | An adjective used in reference to igneous rocks that are rich in elements forming feldspar and quartz. |
| Mafic | A term used in reference to magmas or igneous rocks that are relatively poor in silica and rich in iron and magnesium. |
| Ultramafic | A term used to describe igneous rocks or magmas that are rich in iron and magnesium and very poor in silica. |
| Partial melting | The melting in a rock of the minerals with the lowest melting temperatures, while other minerals remain solid. |
| Fractional crystallization | The process by which a magma becomes progressively more silicic as it cools, because early-formed crystals settle out. |
| Bowen’s reaction series | The sequence in which different silicate minerals crystallize during the progressive cooling of a melt. |
| Dike | A tabular (wall |
| Sill | A nearly horizontal table-top-shaped tabular intrusion that occurs between the layers of country rock. |
| Pluton | is an intrusive igneous rock (called a plutonic rock) body that crystallized from magma slowly cooling below the surface of the Earth. |
| Batholiths | A vast composite, intrusive, igneous rock body up to several hundred kilometers long and 100 km wide, formed by the intrusion of numerous plutons in the same region. |
| Phaneritic | A textural term used to describe coarse-grained igneous rock. |
| Aphanitic | A textural term for fine-grained igneous rock. |
| Porphyritic | A textural term for igneous rock that has phenocrysts distributed throughout a finer matrix. |
| Fragmental texture | Fragments of igneous material that have been stuck together to form a coherent mass. |
| Glassy texture | Igneous rock consisting entirely of glass, or of tiny crystals surrounded by a glass matrix. |
| Obsidian | An igneous rock consisting of a solid mass of volcanic glass. |
| Pegmatite | A coarse |
| Volcano | (1) A vent from which melt from inside the Earth spews out onto the planet’s surface; (2) a mountain formed by the accumulation of extrusive volcanic rock. |
| Crater | (1) A circular depression at the top of a volcanic mound; (2) a depression formed by the impact of a meteorite. |
| Caldera | A large circular depression with steep walls and a fairly flat floor, formed after an eruption as the center of the volcano collapses into the drained magma chamber below. |
| Shield volcano | A subaerial volcano with a broad, gentle dome, formed either from low-viscosity basaltic lava or from large pyroclastic sheets. |
| Cinder cone | A subaerial volcano consisting of a cone-shaped pile of tephra whose slope approaches the angle of repose for tephra. |
| Strato volcano | A large, cone-shaped subaerial volcano consisting of alternating layers of lava and tephra. |
| Pyroclastic debris | Fragmented material that sprayed out of a volcano and landed on the ground or sea floor in solid form. |
| Ash | Tiny glass shards formed when a fine spray of exploded lava freezes instantly upon contact with the atmosphere. |
| Lapilli | Marble-to-plum-sized fragments of pyroclastic debris. |
| Bomb | A large piece of pyroclastic debris thrown into the atmosphere during a volcanic eruption. |
| Tuff | A pyroclastic igneous rock composed of volcanic ash and fragmented pumice, formed when accumulations of the debris cement together. |
| Lahar | A thick slurry formed when volcanic ash and debris mix with water, either in rivers or from rain or melting snow and ice on the flank of a volcano. |
| Viscosity | The resistance of material to flow. |
| Pahoehoe | A lava flow with a surface texture of smooth, glassy, rope-like ridges. |
| ‘a’ a | A lava flow with a rubbly surface. |
| Effusive | An eruption that yields mostly lava, not ash. |
| Explosive | Violent volcanic eruption that produces clouds and avalanches of pyroclastic debris. |
| Sediment | An accumulation of loose mineral grains, such as boulders, pebbles, sand, silt, or mud, that are not cemented together. |
| Chemical weathering | The process in which chemical reactions alter or destroy minerals when rock comes in contact with water solutions and/or air. |
| Physical weathering | The process in which intact rock breaks into smaller grains or chunks. |
| Dissolution | A process during which materials dissolve in water. |
| Hydrolysis | The process in which water chemically reacts with minerals and breaks them down. |
| Oxidation | A reaction in which an element loses electrons; an example is the reaction of iron with air to form rust. |
| Hydration | The absorption of water into the crystal structure of minerals; a type of chemical weathering. |
| Differential weathering | What happens when different rocks in an outcrop undergo weathering at different rates. |
| Jointing | Naturally formed cracks in rocks. |
| Frost wedging | The process in which water trapped in a joint freezes, forces the joint open, and may cause the joint to grow. |
| Residual concentration | Soils in which the residuum left behind after leaching by rainwater is so concentrated in metals that the soil itself becomes an ore deposit. |
| Soil | Sediment that has undergone changes at the surface of the Earth, including reaction with rainwater and the addition of organic material. |
| Humus | The amorphous, ordinarily dark-colored, colloidal matter in soil; a complex of the fractions of organic matter of plant |
| Regolith | Any kind of unconsolidated debris that covers bedrock. |
| Soil profile | A vertical sequence of distinct zones of soil. |
| Soil horizon | Distinct zones within a soil, distinguished from each other by factors such as chemical composition and organic content. |
| Desertification | The process of transforming nondesert areas into desert. |
| Sedimentary rocks | Rock that forms either by the cementing together of fragments broken off preexisting rock or by the precipitation of mineral crystals out of water solutions at or near the Earth’s surface. |
| Clastic | Sedimentary rock consisting of cemented-together detritus derived from the weathering of preexisting rock. |
| Chemical | Sedimentary rock made up of minerals that precipitate directly from water solution. |
| Organic | Sedimentary rock (such as coal) formed from carbon-rich relicts of organisms. |
| Principle of original horizontality | Layers of sediment, when originally deposited, are fairly horizontal. |
| Principle of superposition | In a sequence of sedimentary rock layers, each layer must be younger than the one below, for a layer of sediment cannot accumulate unless there is already a substrate on which it can collect. |
| Erosion | The grinding away and removal of Earth’s surface materials by moving water, air, or ice. |
| Deposition | The process by which sediment settles out of a transporting medium. |
| Lithification | The transformation of loose sediment into solid rock through compaction and cementation. |
| Cementation | The phase of lithification in which cement, consisting of minerals that precipitate from groundwater, partially or completely fills the spaces between clasts and attaches each grain to its neighbor. |
| Roundness | roundness |
| Sorting | (1) The range of clast sizes in a collection of sediment; (2) the degree to which sediment has been separated by flowing currents into different- size fractions. |
| Conglomerate | Very coarse-grained sedimentary rock consisting of rounded clasts. |
| Breccias | Coarse sedimentary rock consisting of angular fragments; or rock broken into angular fragments by faulting. |
| Sandstone | Coarse-grained sedimentary rock consisting almost entirely of quartz. |
| Shale | Very fine-grained sedimentary rock that breaks into thin sheets. |
| Limestone | Sedimentary rock composed of calcite. |
| Coquina | incompletely consolidated sedimentary rock. Coquina was formed in association with marine reefs and is a variety of "coral rag |
| Chalk | Very fine-grained limestone consisting of weakly cemented plankton shells. |
| Travertine | A carbonate rock formed by precipitation of carbonate minerals from water at springs or on the surface of caves. |
| Chert | A sedimentary rock composed of very fine-grained silica (cryptocrystalline quartz). |
| Evaporate | The process of transforming a liquid into a gas. |
| Coal | An organic sedimentary rock formed from plant debris. |
| Bed | A distinct layer of sedimentary strata. |
| Strata | A succession of sedimentary beds. |
| Sedimentary structures | A characteristic of sedimentary deposits that pertains to the character of bedding and/or the surface features of a bed. |
| Mud cracks | An irregular fracture formed by shrinkage of clay, silt, or mud under the drying effects of atmospheric. |
| Ripple marks | Wave-like ridges and troughs on the surface of a sedimentary layer formed during deposition in a current. |
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