GEOL 101 - 3rd Exam Review - 2005
Terms
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- angle of dip
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-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 - anticline
- 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 - brittle
- 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
- ductile
- 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)
- elastic
- 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
- fault
- a fracture in bedrock along which movement has taken place
- fold
- a bend or wavelike feature in layered rock
- footwall
- 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
- joint
- 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
- limb
- 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
- strain
- the change in size, shape, or both, while an object is undergoing stress
- stress
- a force per unit area
- source rock
-
-always a sedimentary rock
-must be present for oil to form - strike
- 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
- syncline
-
-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
- afershock
- 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
- earthquake
- 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
- epicenter
- the point on the earth's surface directly above the focus
- focus
- the point within the earth where seismic waves first originate
- intensity
- a measure of an earthquake's effect on people and buildings
- island arc
- a curved line of volcanoes that form a string of islands parallel to the oceanic trench
- love waves
- most like S waves that have no vertical displacement
- magnitutde
- 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
- seismogram
- can be used to measure the strength of an earthquake
- seismograph
- 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
- tsunami
-
-a seismic wave
-caused by great earthquakes that disturb the sea floor but also result from submarine landslides or volcanic explosions - asthenosphere
-
-the zone extending to a depth of perhaps 200 kilometers
-the place where rocks are closest to the melting point - convection
- a circulation pattern in which low density material rises and high density material sinks
- core
-
-the central zone of Earth
-it is metallic and is the source of Earth's magnetic field - crust
- 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 - geophysics
- 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
- isostasy
- 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
- lithosphere
- 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
- magnetometer
- an instrument used to measure the strength of Earth's magnetic field
- mantle
- 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
- paleomagnetism
- 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 - atoll
- 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
- guyots
- 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
- ophiolites
-
-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 - reefs
-
-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 - seamounts
- 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
- 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
- plate
- a large, mobile slab of rock that is part of Earth's surface
- orogeny
-
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
- craton
- 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