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GEOLOGY TEST 3
Terms in this set (158)
Shaking and vibration at the surface of the earth resulting from a sudden release of energy in the rocks beneath earth's surface
foreshock, main earthquake, and aftershock
Sequence of earthquake generation
elastic rebound theory
theory that rocks that are strained past a certain point will fracture and spring back to their original shape
the sudden release of stored strain in rocks that results in movement along a fault
vibrations that travel through Earth carrying the energy released during an earthquake
the study of earthquakes and seismic waves
A device that records ground movements caused by seismic waves as they move through Earth
the record of an earthquake's seismic waves produced by a seismograph
The point beneath Earth's surface where rock breaks under stress and causes an earthquake
place on the surface directly above where the earthquake takes place: Directly above the focus
80% along Pacific Rim, convergent plate boundaries, transform plate boundaries, divergent plate boundaries, and intraplate
where earthquakes occur
convergent plate boundary
A tectonic plate boundary where two plates collide, come together, or crash into each other (shallow or deep, 20-700km)
divergent plate boundary
Boundary between tectonic plates in which the two plates move away from each other, and new crust is created between them (shallow, 20km)
transform plate boundary
Boundary between two plates that are sliding past each other (San Andreas fault, <80km)
Away from plate boundaries; these are the results of stresses caused by plate motions acting in solid lithosphere (New Madrid fault, 50km)
an area where earthquakes are likely, often where tectonic plates meet
The probable building damage, and number of people that are expected to be hurt or killed if a likely earthquake on a particular fault occurs. Earthquake risk and earthquake hazard are occasionally used interchangeably.
seismic waves that travel through the Earth's interior; outward from focus (P&S)
seismic waves that travel along the Earth's surface; outward from epicenter (L&R)
Primary Waves (P-Waves)
compression waves that travel through solids and liquids, compressing and expanding the material they pass through, temporarily changing volume
Secondary Waves (S Waves)
type of seismic body waves that are Slower and only travel through solids
Love waves (L-waves)
change in shape
acts perpendicular (normal) to travel direction; move side to side and travel through solids
Rayleigh wave (R-waves)
a surface wave in which individual particles of material move in an elliptical path within a vertical plane oriented in the direction of wave movement; travel through solids
The difference in arrival times of P and S waves
How an earthquake's epicenter is located
A scale that rates earthquakes according to their intensity and how much damage they cause at a particular place
only in inhabited regions
depends on distance from epicenter
depends on nature of surface material
depends on building design
Shortcomings of Mercalli scale
A scale that rates an earthquake's magnitude based on the size of its seismic waves.
log scale; difficult to measure earthquakes >7
shortcomings of Richter scale
moment magnitude scale
A scale that rates earthquakes by estimating the total energy released during the earthquake
The principal cause of structural damage, injury, and loss of life during an earthquake. The provisions of the Uniform Building Code provide resistance
80-90% damage in the 1906 San Francisco Earthquake
The sudden and rapid movement of a large amount of material down a slope triggered by ground shaking; cause extensive damage
occurs when an earthquake's violent shaking suddenly turns loose, soft soil into liquid mud (like quicksand); causes buildings to sink into the ground (Alaska 1964)
permanent displacement of the land surface
relative movement of rock bodies on opposite sides of fault
a long high sea wave caused by an earthquake, submarine landslide, or other disturbance; move at 800 km/hr
Minimize effects of earthquakes
monitoring of foreshocks, establishing network of seismographs, landform studies, animal behavior
the physics of the earth
mapping earth's interior & exploration of resources
uses for seismic waves
seismic wave reflection
waves are reflected from interface between two different materials
seismic wave refraction
waves are bent as they pass through different material
How do we have knowledge of earth's interior?
the boundary between the earth's crust and the upper part of the Asthenosphere; seismic waves change speed at this boundary
The thin and solid outermost layer of the Earth above the mantle
thinner, more dense, younger crust making ocean floor
the relatively thick part of the earth's crust that forms the large landmasses. It is generally older and more complex than the oceanic crust.
The layer of hot, solid material between Earth's crust and core.
the solid, outer layer of the earth that consists of the crust and the rigid upper part of the mantle
the upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur.
process in which different minerals melt into magma at different temperatures, changing its composition; can drive plate tectonics
P-wave shadow zone
The region on Earth's surface, 103° to 142° away from an earthquake epicenter, in which P waves from the earthquake are absent.
S-wave shadow zone
the zone ≥103° from the epicenter of an earthquake; suggests the outer core is a liquid, careful observations of P-wave refraction patterns indicate inner core is a solid. This means that S-waves cannot pass through the core at all.
iron and nickel
What is the composition of the inner core?
Seismic Exploration for Petroleum
uses artificial sources of seismic energy, such as dynamite
branch of geology that studies the shapes, arrangement, and interrelationships of rock units and the forces that cause them.
the bending, tilting, and breaking of Earth's crust; the change in the shape of rock in response to stress
tends to change size, shape, or volume; caused by tectonic forces or confining pressure
change in size, shape, or volume in response to stress
compressional, tensional, and shear forces
types of stress
differential stress that squeezes/shortens a rock mass, folding, reverse fault, convergent boundary
The type of stress that tends to pull a body apart.
elastic, plastic (ductile), brittle
types of strain
a type of deformation in which the material returns to its original shape when stress is relaxed
plastic (ductile) strain
strain that causes deformation in which the rock deforms but does not return to its original shape when the strain is removed.
Cracking or rupturing of a body under stress
material behavior: temperature
material behavior: pressure
material behavior: strain rate= deformation/time
clay, mica, calcite: plastic
quartz, feldspar, olivine: brittle
material behavior: composition
strike and dip
sedimentary rocks that are inclined or bent indicate that the layers were deformed following deposition
measurement of geological structures
use of strike and dip
ductile deformation which causes bends in rock that form when compression shortens and thickens part of Earth's crust over a long time; low deformation rate
-bends upward (upside down U shape), oldest rocks are in the middle, youngest rocks are on the outside
-bends downward (U shape), oldest rocks are on the outside, youngest rocks are in the middle
oldest beds in the core
youngest beds in the core
Fold limbs are mirror images of each other
a structural feature in which the fold limb is tilted beyond vertical, which results in both limbs inclined in the same direction, but not at the same angle
A fold overturned to such an extent that the limbs are essentially horizontal (Greenland)
A fold in which the hinge line (or axis) is not horizontal (Sheep Man, Wyoming)
domes and basins
circular or oval folds
fractures along which no movement has occurred; very little stress in required
Erosion along joints creates __________ which then erode to arches.
fractures along which differential movement has taken place
A fault in which the movement is parallel to the dip of the fault.
A type of fault where the hanging wall slides downward; caused by tension in the crust
a type of fault where the hanging wall slides upward; caused by compression in the crust
A type of fault in which rocks on either side move past each other sideways with little up or down motion.
a fault in which sliding occurs diagonally along the fault plane
Formed by two continental plates colliding and forcing each other upwards.
fault caused by tension
reverse fault (high angle)
thrust fault (low angle)
fault caused by compression
fault caused by shearing
A group of closely spaced mountains or parallel ridges.
Chains of mountian ranges that are thousands of kms long
Major mountain belts with taller ranges are ________________.
Mountain belts with lower elevation are ______________ due to weathering and erosion.
A long-lived block of durable continental crust commonly found in the stable interior of a continent.
an assemblage of folds and related thrust faults that develop above a detachment fault
accumulation, orogenic, and uplift & block faulting stages
Evolution of a mountain belt; stages
Stage in the evolution of major mountain belts characterized by the accumulation of great thicknesses (several kilometers) of sedimentary or volcanic rocks.
opening ocean basin
accumulation stage in a(n) _____________________; passive continental margin, forms sequences of shales, sandstones, and limestones
accumulation stage along a(n) _______________________; active continental margin, igneous rocks formed by volcanoes and limestone is usually absent
episode of intense deformation usually accompanied by metamorphism and igneous activity; subduction leads to this
oceanic-continental convergent plate boundary
orogenic stage at a(n) _________________; accretionary wedge forms, fold and thrust belts develop
a large wedge-shaped mass of sediment that accumulates in subduction zones
island arc collides w/ a continent, arc is not subducted, subjecting crust breaks and subduction continues in the opposite direction
Where two continents converge, the crust crumples and thickens, creating high mountains and a wide plateau
uplift and block-faulting stage
following convergence, period of uplifting and erosion occurs
-large portions of mountain belts move vertically upward
-erosion accompanies vertical movement
-can be caused by isostatic adjustment
Concept of vertical movement of sections of Earth's crust to achieve balance or equilibrium.
a subsided block of rock surrounded on two sides by faults. Similar to rift valleys.
A tilted fault block in which the higher side is associated with mountainous topography and the lower side is a basin that fills with sediment
Is the development of two reverse faults causing a block of rock to be pushed up.
Basin and Range Province
A broad, Cenozoic continental rift that has affected a portion of the western United States in Nevada, Utah, and Arizona; in this province, tilted fault blocks form ranges, and alluvium-filled valleys are basins.
accretionary wedge, volcanic and intrusive rocks, accretion of microplates
Continents grow by _________________________________________________.
a piece of lithosphere that becomes part of a larger landmass when tectonic plates collide at a convergent boundary.
the downslope movement of rock, regolith, and soil under the direct influence of gravity
landslides, rock falls, and slumping
examples of gravity driven mass wasting
little/no warning, fas, destructive
damage of mass wasting
1556 China landslide
a slide of a large mass of dirt and rock down a mountain or cliff
rate of movement, type of material, and type of movement
classification used in mass movement processes
Gravity, Water, Triggering mechanism, Orientation of weakness planes, Climate, Vegetation
controlling factors of mass wasting
Water in mass wasting ___________________ cohesion.
Water saturation in mass wasting ______________ cohesion.
Water in mass wasting _______________ friction.
shocks, undercutting, slope modification, exceptional precipitation, human-induced mass movement
Triggering mechanisms of mass wasting
Excavation at the base of a slope that results in the formation of an overhang (natural/human)
the slow downhill movement of weathered rock material
Slow-moving downslope movement of water-saturated, clay-rich sediment, most characteristic of humid regions
Quickly moving downhill flow of soil and rock fragments containing a large amount of water
Very rapid and turbulent mass wasting of debris, air, and water.
primarily caused by frost wedging; fastest mass movement down a steep slope
single intact unit of rock moves along a slip plane
cut and fill, benching, and rock bolts
Safety procedures used as protection against mass wasting
erosion, transport, and deposition
Water is the single important geological agent in ___________________________________________.
the study of water and its effects on and in the earth and in the atmosphere
a channel through which water is continually flowing downhill
a drainage pattern for rivers that looks like a tree, with progressively bigger rivers, all ending into one large river at the bottom.
A flow pattern where streams flow outward and downward from a central elevated point.
A flow pattern in which streams consist mainly of straight line segments with right angle bends and tributaries join larger streams at right angles.
drainage pattern in which most of the streams occupy parallel valleys, pattern usually develops on folded strata of rocks with differing resistance to erosion
velocity, gradient, channel shape, discharge
factors affecting stream erosion and deposition
A measurement of the downstream distance traveled per unit of time
Clay or silt or gravel carried by rushing streams and deposited where the stream slows down
ridges of sediment deposited in the middle or along the sides of a stream
a deposit that contains a valuable mineral that has been concentrated by mechanical action
A stream or river that is composed of multiple channels that divide and rejoin around sediment bars
Meandering Streams and Point Bars
Older, well defined streams tend to develop sinuous curves
deposit of sediment build up by a river on the inside bend of a meander
A new, shorter channel across the narrow neck of a meander
A meander that has been cut off from the river
Flat land near the edges of rivers formed by mud and silt deposited by floods
A landform made of sediment that is deposited where a river flows into an ocean or lake
the process in which water flowing through a channel cuts into the substrate and deepens the channel relative to its surroundings
Sideways erosion by a river on the outside of a meander channel. It eventually leads to the widening of the valley and contributes to the formation of the flood plain.
the process by which a stream channel lengthens up its slope as the flow of water increases
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