Geology Test #1

Cross-Bedding

depositional feature of sedimentary rock that forms as inclined layers of sediment are carried forward across a horizontal surface

Topography

is a field of planetary science comprising the study of surface shape and features of the Earth and other observable astronomical objects including planets, moons, and asteroids. It is also the description of such surface shapes and features (especially their depiction in maps).

Mineral

solid homogeneous inorganic substances occurring in nature having a definite chemical composition

Magma Chamber

the pocket beneath a volcano where magma collects

Country Rock

the preexisting envelope of rocks into which an igneous magma is intruded

Quartzite

hard metamorphic rock consisting essentially of interlocking quartz crystals

Rhyolite

igneous rock consisting mostly of feldspar and quartz. very fine-grained. composed of the same minerals as granite

Pumice

igneous- very light gray to a medium gray- contains a large number of gas bubbles each surrounded by a thin layer of volcanic glass- looks something like a sponge- very light weight- most pieces will float in water- flow lines or bands may show

Batholith

large mass of intrusive igneous rock believed to have solidified deep within the earth

Gravel

rock fragments and pebbles

Extrusive igneous rock

rock that forms from the cooling and solidification of lava at Earth's surface

Crystallization

The formation and growth of a crystalline solid from a liquid or gas.

Inner Core

The solid most inner layer of the earth about 1216 kilometers (754 miles) in radius.

Sill

(geology) a flat (usually horizontal) mass of igneous rock between two layers of older sedimentary rock

Xenolith

(geology) a piece of rock of different origin from the igneous rock in which it is embedded

Pyroclast

A volcanic rock fragment ejected into the air during an eruption.

Intrusive Igneous Rock

rock formed from the cooling and solidification of magma beneath Earth's surface

Graded Bedding

Bedding in which the particle sizes become progressively heavier and coarser toward the bottom layers

Isotope

one of two or more atoms with the same atomic number but with different numbers of neutrons

Andesite

a fine-grained, extrusive igneous rock. It is intermediate becuase it contains some minerals that are common to rhyolite, and some common to basalt.

Pegmatite

a form of igneous rock consisting of extremely coarse granite resulting from the crystallization of magma rich in rare elements

Metasomatism

A type of metamorphism in which a rock's bulk composition changes only because of fluid transport of chemical substances into or out of the rock.

Amphibolite

A usually nonfoliated metamorphic rock made up mainly of amphibole and plagioclase feldspar. Foliated amphibolites can be produced by deformation.

Salinity

the relative proportion of salt in a solution

Foliation

(geology) the arrangement of leaflike layers in a rock

Earth Systems

(geophysics) The atmosphere, oceans, biosphere, cryosphere, and geosphere, together.

Continental Drift

A Hypothesis, credited largely to Alfred Wegener, that suggested all present continents once existed as a single supercontinent. Further, beginning about 200 million years ago, the supercontinent began breaking into smaller continents, which then "drifted" to their present positions.

Thermal Subsidence Basin

A basin produced in the later stages of rifting, when newly formed continental plates are drifting away from each other. The lithosphere that was thinned and heated during the earlier rifting stage cools, leading to an increase in density, which in turn leads to subsidence below sea level, where sediments can accumulate.

Flexural Basin

A basin that develops within zones of tectonic convergence, where one lithospheric plate pushes up over the other and the weight of the overriding plate causes the overridden plate to bend or flex downward.

Divergent Boundary

A boundary in which two plates move apart, resulting in upwelling of material from the mantle to create new seafloor.

Convergent Boundary

A boundary in which two plates move together, resulting in oceanic lithosphere being thrust beneath an overriding plate, eventually to be reabsorbed into the mantle. It can also involve the collision of two continental plates to create a mountain system.

Island Arc

A chain of volcanic islands generally located a few hundred kilometers from a trench where there is active subduction of one oceanic plate beneath another.

Lithospheric Plates

A coherent unit of Earth's rigid outer layer that includes the crust and upper unit.

Basalt

A dark, dense, igneous rock with a fine texture, found in oceanic crust

Shale

A fine-grained clastic rock composed of silt plus a significant component of clay, which causes it to break readily along bedding planes.

Gabbro

A mafic, coarse-grained igneous rock composed predominantly of ferromagnesian minerals and with lesser amounts of calcium-rich plagioclase feldspar.

Eclogite

A metamorphic rock formed under very high pressure and moderate to high temperature, typically containing minerals such as coesite (a very dense, high-pressure form of quartz).

Sedimentary Basin

A region of considerable extent where the combination of deposition and subsidence has formed thick accumulations of sediment and sedimentary rock.

Diorite

A rock: igneous, has a moderate amount of dark silicates and has a coarse-grained texture.

Phyllite

A rock: metamorphic, foliated, fine grained texture, looks like shiny, often wavy, parent rock is slate.

Carbonate Sediment

A sediment formed from the accumulation of carbonate minerals precipitated organically or inorganically.

Evaporite Rock

A sedimentary rock formed from evaporite sediments.

Carbonate Rock

A sedimentary rock formed from the accumulation of carbonate minerals precipitated organically or inorganically.

Precipitate

A solid that forms from a solution during a chemical reaction

Asthenosphere

A subdivision of the mantle situated below the lithosphere. This zone of weak material exists below a depth of about 100 kilometers and in some regions extends as deep as 700 kilometers. The rock within this zone is easily deformed.

Porphroblastic Texture

A texture of metamorphic rocks in which particularly large grains are surrounded by a fine-grained matrix of other minerals.

Ultramafic Rock

An igneous rock consisting primarily of mafic minerals and containing less than 10 percent feldspar.

Intermediate rock

An igneous rock midway in composition between mafic and felsic, neither as rich in silica as felsic rocks nor as poor in it as mafic rocks.

Principle of Uniformitarianism

Just over a century later James Hutton, known as the father of geology, suggested that the earth was much older and that processes occurring in the present were the same processes that had operated in the past, and would be the processes that operate in the future.

Bomb

Large, semi-molten, peice of rock ejected from a volcano

Seafloor Metamorphism

Metamorphism associated with mid-ocean ridges, in which changes in a rock's bulk chemical composition are produced by fluid transport of chemical components into or out of the rock.

Shock Metamorphism

Metamorphism that occurs when minerals are subjected to the high pressures and temperatures of shock waves generated when a meteorite collides with Earth.

Oceanic Lithosphere

Oceanic lithosphere is typically about 50-100 km thick.Oceanic consists mainly of mafic crust and ultramafic mantle (peridotite) and is denser than the continental lithosphere, for which the mantle is associated with crust made of felsic rocks. Oceanic lithosphere thickens as it ages and moves away from the mid-ocean ridge.

Dike

a slab of volcanic rock formed when magma forces itself across rock layers

Mantle

One of Earth's compositional layers. The solid rocky shell that extends from the base of the crust to a depth of 2900 kilometers

Foraminifera

One of a group of tiny single-celled organisms that live in surface waters and whose secretions and calcite shells account for most of the ocean's carbonate sediments.

Decompression Melting

Partial melting of hot mantle rock when it moves upward and the pressure is reduced to the extent that the melting point drops to the temperature of the body.

Sorting

Process of selection and separation of sediment grains according to their grain size (or grain shape or specific gravity).

Volcanic Ash

Sand-sized particles of igneous rock that form when a spray of liquid magma is blown from a volcanic vent by escaping gas.

Mafic rock

Silica-deficient igneous rock with a relatively high content of magnesium, iron, and calcium.

Core

The innermost layer of earth based on composition. It is thought to be largely an iron-nickel alloy with minor amounts of oxygen,silicon, and sulfur

Granodiorite

The granitic rock that makes up most of the continental crust.

Carbonate

a salt or ester of carbonic acid (containing the anion CO3)

Limestone

a sedimentary rock consisting mainly of calcium that was deposited by the remains of marine animals

Atomic Number

The number of protons in the nucleus of an atom

Porosity

The percentage of the total volume of a rock or sediment that consists of open spaces.

Cementation

The process by which dissolved minerals crystalize and glue particles of sediment together into one mass.

Partial Melting

The process by which most igneous rocks melt. Since individual minerals have different melting points, most igneous rocks melt over a temperature range of a few hundred degrees. If the liquid is squeezed out after some melting has occurred, a melt with a higher silica content results.

Compaction

The process by which sediments are pressed together under their own weight.

Fractional Crystallization

The process by which the crystals formed in a cooling magma are segregated from the remaining liquid at progressively lower temperatures.

Lithification

The process that converts sediments into solid rock by compaction or cementation.

Seafloor Spreading

The process that creates new sea floor as plates move away from each other at the mid-ocean ridges

Sandstone

a sedimentary rock consisting of sand consolidated with some cement (clay or quartz etc.)

Spreading Center

The region at the crest of a mid-ocean ridge, where new crust is being formed by seafloor spreading.

Lithosphere

The rigid out layer of Earth, including the crust and upper mantle.

Geology

The science that examines Earth, its form and composition, and the changes that it has undergone and is undergoing.

Electron sharing

The sharing of electrons between atoms to form covalent bonds

Cleavage

The tendency of a mineral to break along planes of weak bonding

Plate Tectonic System

The theory that proposes that earth's outer shell consist of individual plates that interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself.

Convection

The transfer of heat by the mass movement or circulation of a substance.

Atomic Mass

Total mass of the protons and neutrons in an atom, measured in atomic mass units

Polymorph

Two or more minerals having the same chemical composition but different crystalline structures. Exemplified by the diamond and graphite forms of carbon.

Regional Metamorphism

a change in the texture, structure, or chemical composition of a rock due to changes in temperature and pressure over a large area, generally as a result of tectonic forces.

Contact Metamorphism

a change in the texture, structure, or chemical composition of a rock due to contact with magma

Covalent Bond

a chemical bond that involves sharing a pair of electrons between atoms in a molecule

Diagenesis

a collective term for all the chemical, physical, and biological changes that take place after sediments are deposited and during and after lithification

Conglomerate

a composite rock made up of particles of varying size

Peridotite

a dark coarse-grained igneous rock consisting principally of olivine

Slate

a fine-grained metamorphic rock that can be split into thin layers

Subduction

a geological process in which one edge of a crustal plate is forced sideways and downward into the mantle below another plate

Marble

a hard crystalline metamorphic rock that takes a high polish

Gneiss

a laminated metamorphic rock similar to granite

Isochron

a line on an isotope ratio diagram denoting a suite of rock or mineral samples all formed at the same time. The slope of the line is related to the age of the rock or mineral suite.

Rock

a lump or mass of hard consolidated mineral matter

Anion

a negatively charged ion

Granoblastic Rock

a nonfoliated metamorphic rock composed mainly of crystals that grow in equant shapes, such as cubes and spheres, rather than in platy or elongate shapes.

Cation

a positively charged ion

Crystal

a rock formed by the solidification of a substance

Granite

a usually light-colored igneous rock that is found in continental crust

Wegener's Hypothesis

all the continents were once joined together in a single landmass and have since drifted apart - continental drift

Electron transfer

an electron is split away from one molecule and is transferred to another molecule

Discordant intrusion

an igneous intrusion that cuts across the layers of the country rock it intrudes

Concordant intrusion

an igneous intrusion whose boundaries lie parallel to layers of bedded country rock

Pluton

an intrusive igneous structure that results from the cooling and hardening of magma beneath the surface of Earth

Mid-ocean Ridge

an undersea mountain chain where new ocean floor is produced; a divergent plate boundary

Porphyry

any igneous rock with crystals embedded in a finer groundmass of minerals

Schist

any metamorphic rock that can be split into thin layers

Physical Weathering

any process that breaks rock down into smaller pieces without changing the chemistry of the rock; typically wind and water.

Sedimentary Structure

any structure formed in sedimentary rock during deposition or by later sedimentary processes (ex: bedding)

Magnetic anomaly

are areas of magnetism that are either higher or lower than the average magnetic field for the area.

Siliciclastic Sediments

clastic sediment porduced by the weathering of rocks composed largely of silicate minerals.

Oceanic Crust

is the part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium. It is thinner than continental crust, or sial, generally less than 10 kilometers thick, however it is denser, having a mean density of about 2.9 grams per cubic centimeter.

Felsic Rock

light colored, less dense than dark mafic rocks, rich in aluminum, potassium, sodium, and silicon

Burial Metamorphism

low-grade metamorphism that occurs in the lowest layers of very thick accumulations of sedimentary strata

Migmatite

mixed igneous and metamorphic rock; forms when metamorphic rock partially melts

Magma

molten rock in the earth's crust

Crude Oil

petroleum as it comes out of the ground and before it has been refined or processed into useful products

Lava

rock that in its molten form (as magma) issues from volcanos

Transform Boundary

the boundary between tectonic plates that are sliding past each other horizontally

Magnetic Time Scale

the detailed history of earth's magnetic-field reverasls going back into geologic time, as determined by measuring the thermormanent magnetization of rock samples.

Magmatic Differentiation

the formation of one or more secondary magmas from a single parent magma

Continental Crust

the layer of the earth that underlies the continents and continental shelves; the thick part of the earth's crust that form large land masses

Pangea

the name of the single landmass that broke apart 200 million years ago and gave rise to today's continents

Chemical Weathering

the process by which rocks break down as a result of chemical reactions

Subsidence

the sinking of regions of the Earth's crust to lower elevations