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94 Cards in this Set

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The vibration of Earth produced by the rapid release of energy.
Earthquake
Smaller earthquakes that follow the main earthquake.
Aftershocks
An unconformity in which the strata below dip at an angle different from that of the beds above.
Angular Unconformity
A subdivision of the mantle situated below the lithosphere. This zone of weak material exists below a depth of about 100km and in some regions extends as deep as 700km. The rock within this zone is easily deformed i.e. is very pliable
Asthenosphere
Seismic waves that travel through Earth's interior.
Body Waves
The concept that Earth was shaped by catastrophic events of a short-term nature.
Catastrophism
A span on the geologic time scale beginning about 65 million years ago following the Mesozoic era.
Cenozoic Era
Layers of rock that were deposited without interruption.
Conformable
A theory that originally proposed that the continents are rafted about. It has essentially been replaces byt the plate tectonics theory.
Continental Drift Theory
MOuntains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent.
Continental volcanic arc
A boundary in which two plates move together, causing one of the slabs of lithosphere to be consumed in to the mantle as it descends beneath on an overriding plate.
Convergent plate boundary
Located beneath the mantle, it is the innermost layer of Earth.
Core
The core is divided into an outer core and an inner core.
Establishing the equivalence of rocks of similar age in different areas.
Correlation
A principle of relative dating. A rock or fault that is younger than any rock (or fault) through which it cuts.
Cross-cutting (relationship)
The very thin outermost layer of Earth.
Crust
The temperature above which a material loses its magnetization.
Curie point
An elongated depression in the seafloor produced by bending of oceanic crust during subduction.
Deep-ocean trench
A type of unconformity in which the beds above and below are parallel.
Disconformity
A region where the rigid plates are moving apart, typified by the mid-oceanic ridges.
Divergent plate boundary
The sudden release of stored strain in rocks that results in movement along a fault.
Elastic rebound
The largest time unit on the geologic time scale, next in order of magnitude above era.
Eon
The location on Earth's surface that lies directly above the focus of an earthquake.
Epicenter
A unit of the geological calendar that is a subdivision of period.
Epoch
A major division on the geologic calendar that is divided into shorter units called periods.
Era
A break in a rock mass along which movement has occurred.
Fault
Displacement along a fault that is so slow and gradual that little seismic activity occurs.
Fault creep
A cliff created by movement along a fault. It represents the exposed surface of the fault prior to modification by weathering and erosion.
Fault scarp
The zone within Earth where rock displacement produces an earthquake.
Focus
Small earthquakes that often precede a major earthquake.
Foreshocks
The remains or traces of organisms preserved from the geologic past.
Fossils
Fossil organisms that succeed one another in a definite and determinable order, and any time period can be recognized by its fossil content.
Fossil succession
Any break or rupture in rock along which no appreciable movement has taken place.
Fracture
The division of Earth history into blocks of time- eons, eras, periods, and epochs.
Geologic Time Scale
The time scale was created using relative dating priciples.
The time required for one half of the atoms of a radioactive substance to decay.
Half-life
A concentration of heat in the mantle capable of producing magma, whicch in turn extrudes on Earth's surface. The intraplate volcanism that produced the Hawaiian Islands is one example.
Hot spot
A piece of one rock unit contained within another.
Inclusion
Inclusions are used in relative dating. The rock mass adjacent to the one containing the inclusion must have been there first in order to provide the fragment.
A fossil that is associated with a particular span of geologic time.
Index fossil.
The solid innermost layer of Earth. 800miles in radius.
Inner core
A measure of the degree of earthquake shaking at a given locale based on the amount of damage.
Intensity
A phenomenon, somtimes associated with earthquakes, in which soils and other unconsolidated materials containing abundant water are turned into a fluidlike mass that is not capable of supporting buildings.
Liquefaction
The rigid outer layer of Earth, including the crust and upper mantle.
Lithosphere
The total amount of energy released during an earthquake.
Magnitude
The 1800 mile thick layer of Earth located below the crust.
Mantle
A mass of hotter-than-normal mantle material that ascends toward the surface, where it may lead to igneous activity.
Mantle plume
These plumes of solid yet mobile material may originate as deep as the core-mantle boundary.
The part of the mantle that extends from teh core-mantle boundary to a depth of 660km.
Mesosphere- ie the Lower mantle
A span on the geologic time scale between the Paleozoic and Cenozoic eras from about 248 million to 65 million years ago.
Mesozoic era
A 12-point scale developed to evaluate earthquake intensity based on the amount of damage to various structures.
Modified Mercalli intensity scale
The boundary separating the crust from the mantle, disernible by an increase in seismic velocity.
Moho dicontinuity
A more precise measure of earthquake magnitude than the Richter scale that is derived from teh amount of displacement that occurs along a fault zone.
Moment magnitude
An unconfomity in which older metamorphic or intrusive igneous rocks are overlain by younger sedimentary strata.
Nonconformity
A magnetic field that is the same as that which exists at present.
Normal polarity
Date that specifies tha actual number of years that have passed since an even occurred.
Numerical date
A continuous elevated zone on the floor of all the major ocean basins and varying in width from 300-3000miles.
Oceanic ridge
The rifts at the crests of ridges represent divergent plate boundaries.
Layers of sediments are generally deposited in a horizontal or nearly horizontal position.
Original horizontality
A layer beneath the mantle about 1364 miles thich that has the properties of a liquid.
Outer core
The escape of gases that had been dissolved in magma.
Outgassing
The natural remnant magnetism in rock bodies. The premanent 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.
Paleomagnetism
The systematic study of fossils and the history of life on Earth.
Paleontology
A span on the geologic time scale between the eons of the Precambrian and Mesozoic era about 540 million to 248 million years ago.
Paleozoic era
The proposed supercontinent that 200million years ago began to break apart and form the present landmasses.
Pangaea
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.
Partial melting
A basic unit of the geologic calendar that is a subdivision of an era.
Period
Periods may be divided into smaller units called epochs.
That part of geologic time represented by rocks containing abundant fossil evidence. The eon extending from the end of the Proterozoic eon (about 540 million years ago) to the present.
Phanerozoic eon
One of numerous rigid sections of the lithosphere that moves as a unit over the material of the asthenosphere.
Plate
The theory that proposes that Earth's outer shell consists of individual plates that interact iin various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself.
Plate tectonics
All geologic time prior to the Paleozoic era.
Precambrian
A type of seismic wave that involves alternating compression and expansion of the material through which it passes.
Primary (P) wave
The spontaneous decay of certain unstable atomic nuclei.
Radioactive decay
The radioactive isotope of carbon, which is produced continuously in the atmosphere and is used in dating events from the very recent geologic past (the last few tens of thousands of years).
Radiocarbon (carbon 14)
Used in radiocarbon dating
The procedure of calculating the absolute ages of rocks and mineralsthat contain radioactive isotopes.
Radiometric dating
Rocks are placed in their proper sequence or order. Only chronological order of events is determined.
Relative dating
A magnetic field oposite to that which exists at present.
Reverse polartiy
A scale of earthquake magnitude based on the motion of a seismograph.
Richter scale
A mechanism that may contribute to plate motion. It involves the oceanic lithosphere sliding down the oceanic ridge under the pull of gravity.
Ridge push
A region of Earth's crust along which divergence is taking place.
Rift zone
The process of producing new seafloor between two diverging plates.
Seafloor spreading
A seismic wave that involves oscillation perpendiular to the direction of propagation.
Secondary (S) wave
A rapidly moving ocean wave generated by earthquake activity capable of inflicting heavy damage in coastal regions.
Seismic sea wave
The record made by a seismograph.
Seismogram
An instument that records earthquake waves.
Seismograph
The study of earthquakes and seismic waves.
Seismology
The zone between 104 and 143 degrees distance from an earthquake epicenter in which direct waves do not arrive because of refraction by Earth's core.
Shadow zone
A large, relatively flat expanse of ancient metamorphic rock within the stable continental interior.
Shield
A mechanism that contributes to plate motion in which cool, dense oceanic crust sinks into the mantle and "pulls" the trailing lithosphere along.
Slab pull
Structures that are deposited by algae and consist of layered mounds of calcium, carbonoate.
Stromatolite
The process of thrusting oceanic lithosphere into the mantle along a convergent boundary.
Subduction
A long, narrow zone where one lithospheric plate descends beneath another.
Subduction zone
In any underformed sequence of sedmentary rocks, each bed is older than the layers above and younger than the layers below.
Superposition
Seismic waves that travel along the outer layer of the Earth.
Surface waves
A major strike-slip fault that cuts through the lithosphere and accommodates motion between two plates.
Transform fault
A boundary in which two plates slide past on another without creating or destroying lithosphere.
Transform fault boundary
A surface that represents a break in the rock record, caused by erosion or nondeposition.
Unconformity
The concept that the processes that have shaped Earth in the geologic past are essentially the same as those operating today. "The present is the key to the past."
Uniformitarianism
A chain of volcanic islands generally located a few hundred kilometers from a trench where active subduction of one oceanic slab beneath another is occurring.
Volcanic island arc