Glossary from Physical Geology地质术语名词解释文档格式.docx

1、abyssal plain :A vast flat area on the seafloor adjacent to the continental rises of passive continental margins.active continental margin :A continental margin characterized by volcanism and seismicity at the leading edge of a continental plate where oceanic lithosphere is subducted. See also passi

2、ve continental margin.alluvial fan :A cone-shaped alluvial deposit formed where a stream flows from mountains onto an adjacent lowland.alluvium :A general term for all detrital sediment transported and deposited by running water.angular unconformity :An unconformity below which older rocks dip at a

3、different angle （usually steeper） than the overlying strata. See also disconformity and nonconformity.anticline :A convex upward fold in which the oldest exposed rocks coincide with the fold axis and all strata dip away from the axis.aphanitic texture :An igneous texture in which individual minerals

4、 are too small to be seen without magnification.arte :A narrow, serrated ridge separating two glacial valleys or adjacent cirques.artesian system :A confined aquifer in which high hydrostatic （fluid） pressure builds up causing water to rise above the level of the aquifer.aseismic ridge :A ridge or b

5、road area rising as much as 2 to 3 km above the surrounding seafloor and lacking seismic activity.ash :Pyroclastic material measuring less than 2 mm.assimilation :A process in which magma changes composition as it reacts with country rock.asthenosphere :The part of the mantle that lies below the lit

6、hosphere; behaves plastically and flows.atom :The smallest unit of matter that retains the characteristics of an element.atomic :mass number The total number of protons and neutrons in the nucleus of an atom.atomic number :The number of protons in the nucleus of an atom.aureole :A zone surrounding a

7、 pluton in which contact metamorphism took place.Bbarchan dune :A crescent-shaped dune with the tips of the crescent pointing downwind.barrier island :A long, narrow island composed of sand oriented parallel to a shoreline but separated from the mainland by a lagoon.basal :slip A type of glacial mov

8、ement in which a glacier slides over its underlying surface.basalt :plateau A large area built up by numerous flat-lying lava flows erupted from fissures.base level :The lowest level to which a stream can erode.basin :The circular fold in which all strata dip toward a central point, and the youngest

9、 exposed rocks are in the center.batholith :A discordant, irregularly shaped pluton with a surface area of at least 100.baymouth bar :A spit that has grown until it closes off a bay from the open sea.beach :A deposit of sediment extending landward from low tide to a change in topography or where per

10、manent vegetation begins.bed （bedding） :A bed is an individual layer of rock, especially sedimentary rock, whereas bedding is the layered arrangement of rocks. See also stratification.bed load :The part of a streams sediment load transported along its bed; consists of sand and gravel.berm :The backs

11、hore area of a beach, consisting of a platform composed of sediment deposited by waves. Berms are nearly horizontal or slope gently landward.Big Bang :A model for the evolution of the universe in which a dense, hot state was followed by expansion, cooling,and a less dense state.biochemical sedimenta

12、ry rock :A sedimentary rock resulting from the chemical processes of organisms.black smoker :A submarine hydrothermal vent that emits a plume of black water colored by dissolved minerals.body wave :An earthquake wave that travels through Earth.Both P- and S-waves are body waves.bonding :The process

13、whereby atoms are joined to other atoms.Bowens reaction series :A mechanism accounting for the derivation of intermediate and felsic magmas from mafic magma. It has a discontinuous branch of ferromagnesian minerals that change from one to another over specific temperature ranges and a continuous bra

14、nch of plagioclase feldspars whose composition changes as the temperature decreases.braided stream :A stream with multiple dividing and rejoining channels.breaker :A wave that steepens as it enters shallow water until its crest plunges forward.butte :An isolated, steep-sided, pinnacle-like hill formed by the breaching of a resistant cap rock, which allows rapid erosion of the less resistant underlying rocks.Ccaldera: A large, steep-sided circular to oval volcanic depression usually formed by summit collapse resulting from partial draining of the underlying magma