Combo with Earth Science Chapter 5,6,7,8

Fossil Magnetism

When fossils have the magnetic polarity of the time during which they were formed. They provide us with a way to see where the magnetic poled were at various times in the past.

foreshock

a small earthquake that often precedes a major earthquake; days or years before

Paleoclimatic Data

ancient climate data

Transform Fault Boundary

boundary formed where two lithpospheric plates slide past each other

fold

A bent rock layer or series of layers that were originally horizontal and subsequently deformed.

fault

A break in a rock mass along wich movement has occured.

Shield Volcano

A broad, genty sloping volcano built from fluid basaltic lavas.

Hot-spot Track

A chain of now-dead volcanoes transported off the hot spot by the movement of a lithosphere plate.

Volcanic Island Arc

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

Magnetic Reversal

A change in polarity of Earth's magnetic field that occurs over time intervals of roughly 200,00.

basin

A circular downfolded structure.

fault scarp

A cliff created by movement along a fault. It represents the exposed surface of the fault prior to modificaion by weathering and erosion.

Lithospheric Plates

A coherent unit of Earth's rigid outer layer that inclues the crust and uppermost mantle.

Hot Spot

A concentration of heat in the mantle of capable of producing magma, which in turn extrudes onto Earth's surface. The intraplate volcanism that produced the Hawaiian Islands is one example.

Vent

A conduit that connects a magma chamber to a volcanic crater.

Fissure

A crack in rock along which there is a distinct separation.

dip-slip fault

A fault in which the movement is paralled to the dip of the fault.

anticline

A fold in sedimentary strata that resembles an arch.

Pyroclastic Flow

A highly heated mixture, largely of ash and pumice fragments, traveling down the flanks of a volcano or along the surface of the ground.

Caldera

A large depression typically caused by collapse or ejection of the summit area of a volcano.

Batholith

A large mass of igneous rock that formed when magma was emplaced at depth, crystallized, and subsequently exposed by erosion.

Accretionary wedge

A large wedge-shaped mass of sediment that accumulates in subduction zones. Here sediment is scraped from the subducting oceanic plate and accreted to the overriding crustal block.

Pahoehoe Flow

A lava flow with a smooth-to-ropey surface.

Continental Rift

A linear zone along which continental lithosphere stretches and pulls apart. Its creation may mark the beginning of a new ocean basin.

Lava Tube

A long tunnel formed by pahoehoe lava as it cools along the surface.

Subduction Zone

A long, narrow zone where one lithospheric plate descends beneath another.

Reverse Polarity

A magnetic field opposite to what which exists at present.

Normal Polarity

A magnetic field that is the same as that which exists at present.

Laccolith

A massive igneous body intruded between preexisting strata.

Viscosity

A measure of a fluid's resistance to flow.

Ridge Push

A mechanism that may contribute to plate motion. It involves the oceanic lithosphere sliding down the oceanid ridge under the pull of gravity.

fault-block mountains

A mountain formed by the displacement of rock along a fault.

Volcano

A mountain formed of lava, and/or pyroclastics.

Deep-ocean Trench

A narrow, elongated depression on the floor of the ocean.

Columnar Joint

A pattern of cracks that that form during cooling of molten rock to generate columns that are generally six-sided.

Conduit

A pipelike opening through which magma moves toward Earth's surface. It terminates at a surface opening called a vent.

Divergent Boundary

A plate boundary where two plates move away from each other.

Stocks

A pluton similar to but smaller than a batholith.

Cinder Cone

A rather small volcano built primarily of pyroclastics ejected from a single vent.

Rift Valley

A region of Earth's crust along which divergence is taking place.

dome

A roughly circular upfolded structure similar to an anticline.

Magnetometer

A sensitive instrument used to measure the intensity of Earth's magnetic field.

Mantle Plume

A source of some intraplate basaltic magma, these structures originate at great depth and, upon reaching the crust, spread laterally, creating a localized volcanic zone called a hot spot.

Island Arc

A string of islands formed by the volcanoes along a deep-ocean trench.

Pluton

A structure that results from the emplacement and crystallization of magma beneath the surface of Earth.

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.

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.

Oceanic Ridge System

A system of continuous elevated zones on the floor of all major ocean basins and varying in width from 500 to 5000 km (300 to 3000 mi). The rifts at the crests of ridges represent divergent plater boundaries.

Sill

A tabular igneous body that was intruded parallel to the layering of preexisting rock.

Dike

A tabular- shaped intrusive igneous feature that cuts through the surrounding rock.

Concordant

A term used to describe intrusive igneous masses that form parallel to bedding of the surrounding rock.

Discordant

A termused to describe plutons that cut across existing rock structures, such as bedding planes.

AA Flow

A type of lava flow that has a jagged blocky surface

ductile deformation

A type of solid-state flow that produces a change in the size and shape of a rock body without fracturing. Occurs at depths where temperatures and confining pressures are high.

Fumarole

A vent in a volcanic area from which fumes or gases escape.

Pipe

A vertical conduit through which magmatic materials have passed.

Parasitic Cone

A volcanic cone that formes on the flank of a larger volcano.

Composite Cone (Stratavolcano)

A volcano composed of both lava flows and pyroclastic material.

Continential Drift

Hypothesis that maintained that the Earth was once a supercontinent that divided and slowly drifted a part.

Intrplate Volcanism

Igneous avtivity that occurs within a tectonic plate away from plate boundaries.

Nuee Ardente

Incandescent volcnaic debris buoyed up by hot gases that moves downslope in an avalanche fashion.

Hot Spot

An area where magma from deep within the mantle melts through the crust above it.

aftershock

An earthquake that occurs after a larger earthquake in the same area.

Fissure Eruption

An eruption in which lava is exruded from narrow fractures or cracks in the crust.

Massive

An igneous pluton that is not tabular in shape.

Volcanic Neck

An isolated, steep-sided, erosional remnant consisting of lava that once occupied the vent of a volcano.

Eruption Columns

Buoyant plaumes of hot, ash-laden gases that can extend thousands of meters into the atmoshpere.

Flood Basalt

Flows of basaltic lava that issue from numerous cracks or fissures and commonly cover extensive areas to thickness of hundreds of meters.

Volatiles

Gaseous components of magma dissolved in the melt. Volatiles will readily vaporize (form a gas) at surface pressures.

deformation

General term for the processes of folding, faulting, shearing, compression, or extension.

Fracture Zone

Linear zone of irregular topography on the deep-ocean floor that follows transform faults and their inactive extensions.

Intrusions

Magma that has pushed into cracks in existing rocks.

Continental Volcanic Arc

Mountains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent. Examples include Andes and Cascades.

Continental Volcanic Arc

Mountains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent. Examples include the Andes and the Cascades.

Lahar

Mudflows on the slopes of volcanoes that result when unstable layers of ash and debris become saturated and flow downslope, usually following stream channels.

Plate

One of numerous rigid sections of the lithosphere that moves as a unit over the material of the asthenosphere.

Tectonic Plates

Sections of the Earth's crust that move due to convection currents.

body wave

Seismic waves that travel through Earth's interior.

Tabular

Term used to describe a feature such as an igneous pluton having two dimensions that are much longer than the third. A pluton that is thin in one dimension.

Crater

The depression at the summit of a volcano, or that which is produced by a meteorite impact.

Magnetic Time Scale

The history of magnetic reversals through geologic time.

core

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

epicenter

The location on Earth's surface that lies directly above the forces of an earthquake.

brittle failure or brittle deformation

The losss of strength by a material usually in the form of sudden fracturing.

Paleomagnetism

The natural remnant megnetism 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.

Partial Melting

The process by which ost 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 occured, a melt with a higher silica content results.

Seafloor Spreading

The process of producing new seafloor between two diverging plates.

Pangea

The proposed supercontinent, which 200 million years ago began to break apart and form the present landmasses.

Spreading Center

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

footwall block

The rock surface below a fault.

elastic rebound

The sudden release of stored strain in rocks that results in movement along a fault.

Curie Point

The temperature above which a material loses its magnetization.

Plate Tectonics

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

crust

The very thin outermost layer of Earth.

earthquake

The vibration of Earth PRoduced by the rapid release of energy.

Pyroclastic Materials

The volcanic rock ejected during an eruption, including ash, bombs, and blocks.

focus

The zone within Earth where rock displacement produces an earthquake.

Supercontinent

This is the single continent on Earth, named Pangaea, that occurred around 225 million years ago before the continental plates broke apart to eventually form individual continents

active continental margin

Usually narrow and consisting of highly deformed sediments. They occur where oceanic lithosphere is being subducted beneath the margin of a continent