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136 Cards in this Set

  • Front
  • Back
angle of dip
-is measured with in a vertical plane that is perpendicular to both the bedding and the horizontal planes.
-is measured downward from the horizontal plane to the bedding plane
an upward arching fold in land
axial plane
-an imaginary plane containing all of the hinge lines of a fold
-it divides the fold into its two limbs
a type of behavior that rocks exhibit at stresses higher than their elastic limit (like a rubber band will break if stretched too far)
compressive stress
-common along convergent plate boundaries and typically results in rocks being deformed by a shortening strain
dip-slip fault
creates movement parallel to the dip of the fault surface
direction of dip
the compass direction in which the angle of dip is measured
when a rock acts in a plastic manner and bends while under stress and does not return to its original shape after relaxation of the stress (like silly putty)
when a deformed body recovers its original shape after the stress is reduced or removed
elastic limit
the limit a rock can with stand stress before it deforms permanently
a fracture in bedrock along which movement has taken place
a bend or wavelike feature in layered rock
the underlying surface of an inclined fault plane
hanging wall
the overlying surface of an inclined fault
geologic cross section
represents a vertical slice through a portion of Earth
geologic map
-uses standardized symbols and patterns to represent rock types and geologic structures
-produced from the field map for a given area
hinge line
the axis of a fold
isoclinal fold
a fold in which limbs are parallel to one another (implies intense compressive or shear stress
a fracture or crack in bedrock that exists when no displacement occurs
joint set
where joints are oriented approximately parallel to one another
left-lateral fault
a stream or other displaced feature would appear to the left across the fault
the type of hill that connects each anticline and adjacent syncline
normal fault
when the hanging wall block has moved downward relative to the footwall block
oblique-slip fault
has both strike-slip and dip-slip components
(parallel and horizontal motion)
open folds
-have limbs that dip gently
-the more open the fold, the less intense the stress involved
overturned fold
-when the limbs of a fold dip in the same direction
-imply that unequal compressive stresses or even a shearing stress caused the upper limb of the fold to override the lower limb
plunging fold
folds in which the hinge lines are not horizontal
recumbent fold
-overturned to such an extent that the limbs are essentially horizontal
-found in the cores of mountain ranges such as the Canadian Rockies
reservoir rock
a rock that contains oil
reverse fault
the hanging-wall block has moved upward relative to the footwall block
right-lateral fault
when a displaced stream is to the right of a fault
shear stress
due to forces parallel to one another, but in opposite directions along a discrete surface such as a fault
tensional stress
is caused by forces pulling away from one another in opposite directions
the change in size, shape, or both, while an object is undergoing stress
a force per unit area
source rock
-always a sedimentary rock
-must be present for oil to form
the compass direction of a line formed by the intersection of an inclined plane with a horizontal plane
strike-slip fault
a fault where the movement is predominantly horizontal and parallel to the strike of the fault
structural basin
when the beds dip toward a central point
structural dome
a structure in which the beds dip away from a central point
-troughlike fold
-the bottommost part of the trough of a fold
structural geology
the branch of geology concerned with the shapes, arrangement, and interrelationships of bedrock units and the forces that cause them
thrust fault
a reverse fault in which the dip of the fault plane is at a low angle to horizontal
small earthquakes that follow the main shock of an earthquake
Benioff zones
zone of inlcined seismic activity
body waves
seismic waves that travel through the earth's interior, spreading outward from the focus in all directions
circum-Pacific belt
its a belt which encircles the rim of the Pacific Ocean
depth of focus
distance between focus and epicenter
a trembling or shaking of the ground caused by the sudden release of energy stored in rocks benearth earth's surface
elastic rebound theory
the classis explanation of why earthquakes take place
the point on the earth's surface directly above the focus
the point within the earth where seismic waves first originate
a measure of an earthquake's effect on people and buildings
island arc
when benioff zones slope under a continent or a curved line of islands
love waves
most like S waves that have no vertical displacement
a measure of the energy released during an earthquake
mediterranean-Himalayan belt
the bet which runs through the Mediterranean Sea, crosses the Mideast and the Himalayas, and passes through the East Indies to meet the circum-Pacific belt north of Australia
modified Mercalli scale
the scale that determines the intensities of earthquakes
moment magnitude
the most objective way of measuring the energy released by a large earthquake
P wave
a compressional (or longitudinal) wave in which rock vibrates back and forth parallel to the direction of wave propagation
Rayleigh waves
behave like rolling ocean waves but they cause the groud to move in an elliptical path opposite to the direction the wave passes
Richter scale
a numerical scale of earthquake magnitudes
seismic sea wave
tsunamis - they usually are caused by great earthquakes that disturb the sea floor bu tthey also result from submarine landslides or volcanic explosions
seismic waves
the waves of energy produced by an earthquake
can be used to measure the strength of an earthquake
a recording device that produces a permanent record of Earth motion detected by a seisometer
surface wave
a seismic wave that travels on Earth's surface away from the epicenter, like water waves spreading out from a pebble thrown into a pond
S wave
-a type of a body wave
-a slower, transverse wave that travels through near surface rocks at 2 to 5 kilometers per second
-it is propagated by a shearing motion much like that in a stretched shaken rope
travel-time curve
plots seismic-wave arrival time against distance
-a seismic wave
-caused by great earthquakes that disturb the sea floor but also result from submarine landslides or volcanic explosions
-the zone extending to a depth of perhaps 200 kilometers
-the place where rocks are closest to the melting point
a circulation pattern in which low density material rises and high density material sinks
-the central zone of Earth
-it is metallic and is the source of Earth's magnetic field
the outer layer of rock which forms a skin on Earth's surface
crustal rebound
the rise of the crust after the removal of the ice
Curie point
-580 Degrees celcius
-when rocks are cooled below or at this point, they retain their magnetic record
the application of physical laws and principles to a study of earth
geothermal gradient
the temperture increase with depth into Earth
gravity meter
a tool for studying the crust and upper mantle
-measures the gravitational attraction between Earth and a mass with in the instrument
heat flow
the gradual loss of heat through the Earth's surface
a balance or equilibrium of adjacent blocks or brittle crust "floating" on the upper mantle
isostatic adjustment
the concept of vertical movement to reach equilibrium
the crust and uppermost mantle
magnetic field
a region of magnetic force that surrounds the Earth
magnetic poles
-the north and south poles of the magnetic field
-the strength of the magnetic field is greates at the magnetic poles
magnetic reversal
a change in the polarity of the magnetic field when north and south switch in polarity
an instrument used to measure the strength of Earth's magnetic field
a thick shell of rock that separates the crust above from the core below
MOHOrovicic discontinuity
the boundary that separates the crust from the mantle beneathe it
negative gravity anomaly
a gravity reading lower than the normal regional gravity
negative magnetic anomaly
a reading of magnetic field strength that is lower than the regional average
the study of ancient magnetic fields
positive gravity anomaly
a gravity reading higher than the normal regional gravity
positive magnetic anomaly
a reading of magnetic field strength that is higher than the regional average
P-wave shadow zone
the region between 103 degrees and 142 degrees which lakes P waves
seismic reflection
the return of some of the energy of seismic waves to Earth's surface after the waves bounce off a rock boundary
seismic refraction
the bending of seismic waves as they pass from one material to another (similar to how light waves bend when they pass through the lenses of eyeglasses)
S-wave shadow zone
-s-waves are not recorded in the entire region more than 103 degrees away from the epicenter
-indicates that S waves do not travel through the core at all
abyssal fans
-found at the base of many submarine canyons
-made up of land-derived sediment that has moved down the submarine canyons
abyssal plains
very flat regions usually found at the base of the continental rise
active continental margin
characterized by earthquakes and by a young mountain belt and volcanoes on land, consists of a continental shelf, a continental slope, and an oceanic trench
aseismic ridges
-volcanic chains on the sea floor
-submarine ridges that are not associated with earthquakes
a circular reef that rims lagoons and is surrounded by deep water
barrier reefs
parallel to the shore but are separated from it by wide, deep lagoons
continental rise
a wedge of sediment that extends from the lower part of the continental slope to the deep sea floor
continental slope
a relatively steep slope that extends from a depth of 100 to 200 meters at the edge of the continental shelf down to oceanic depths
contour current
a bottom current that flows parallel to the slopes of the continental margin, along the contour rather than down the slope
fracture zone
major lines of weakness in Earth's crust that cross the mid-oceanic ridge at approximately right angles
fringing reefs
flat, tablelike reefs attached directly to shore
flat-topped seamounts found mostly in the western Pacific Ocean
mid-oceanic ridge
a giant undersea mountain range that extends around the world like the seams on a baseball
oceanic trench
a narrow, deep trough parallel to the edge of a continent or an island arc
-distinctive rock sequences found in many mountain chains on land
-the top layer consists of marine sedimentary rock and below lies a zone of pillow basalt which is underlain by a sheeted-dike complex that probably served as feeder dikes for the pillowed lava and layers
passive continental margin
includes a continental shelf, continental slope, and continental rise and generally extends down to an abyssal plain at a depth of about 5 kilometers
-it usually develops on geologically quiet coasts that lack earthquakes, volcanoes, and young mountain belts
pelagic sediment
-sediment that settles slowly through the ocean water
-made up of fine-grained clay and the skeletons of microscopic organisms
-wave-resistant ridges of coral, algae, and other calcareous organisms that form in warm, shallow, sunlit water that is low in suspended sediment
-they stand above the surrounding sea floor
rift valley
a tensional valley bounded by normal faults
-found at diverging plate boundaries on continents and along the crest of the mid-oceanic ridge
conical undersea mountains that rise 1,000 meters or more above the sea level
submarine canyons
V-shaped valleys that run across continental shelves and down continental slopes
terrigenous sediment
land-derived sediment that has found its way to the sea floor
turbidity currents
great masses of sediment-laden water that are pulled downhill by gravity
asthenosphere (2)
a zone of low seismic-wave velocity that behaves plastically because of increased temperature and pressure
continental drift
the idea that continents move freely over Earth's surface, changing their positions relative to one another
convergent plate boundary
lies between plates that are moving toward each other
divergent plate boundary
a boundary between plates that are moving apart
island arc
a curved line of volcanoes that form a string of islands parallel to the oceanic trench
lithosphere (2)
plates that make up a relatively rigid outer shell of Earth
magmatic arc
a broad term used both for island arcs at sea and for belts of igneous activity on the edges of continents
mantle plumes
narrow columns of hot mantle rock that rise through the mantle, much like smoke rising from a chimney
a large, mobile slab of rock that is part of Earth's surface
an episode of intense deformation of rocks in a region
-usually accompanied by metamorphism and igneous activity
fold and thrust belts
characterized by large thrust faults stacked one upon another
Precambrian shield
a complex of Precambrian metamorphic and plutonic rocks exposed over a large area
the region of a continent that has been structurally stable for a prolonged period of time
mountain range
a group of closely spaced mountains or parallel ridges
major mountain belts
chains thousands of kilometers long composed of numerous mountain ranges