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99 Cards in this Set
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Seafloor Spreading
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Henry Hess- plates are separated along crests of mid-oceanic ridges
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Divergent plate boundaries
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plates move apart, constructive margins, zone of seafloor spreading, plates grow along these boundaries
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Convergent plate boundaries
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plates move toward each other, destructive margins, subduction zones in deep ocean trenches, plate destroyed along margin
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Examples: Oceanic-Oceanic- Aleutian Arc; Oceanic-Continental- Andes Mts; Continental-Continental- Himalaya Mts
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Transform fault boundaries
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conservative margins, transform
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Example: San Andres Fault, California
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Alfred Wegener
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theory of continental drift
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Nebula Hypothesis
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origin of Solar System
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Big Bang Theory
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origin of galaxies
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Two Divisions of Crust
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Oceanic- composed of basalt, dense, heavy, thin
Continental- composed of granite, less dense, less heavy, and 2 to 3 times as thick |
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Mantle
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composed of peridotite
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Core
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composed of iron-nickel alloy, generates Earth's magnetic field
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Pangea
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formed in the Paleozoic Era
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Age of Earth
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4.6 billion years
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What tells us about Earth's composition?
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meteorites
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Paleomagnetism
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magnetic stripes are indicators of magnetic reversals depicted as red and white stripes parallel to oceanic ridges
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Driving force of tectonic plates
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convective flow exports heat from deep in the mantle to the top of the asthenosphere (lava-lamp). Convective flow forms because hot matter is less dense and it ascends toward the surface.
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Other examples: slab pull and slab suction (?)
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Earth's layers defined by chemical compostion
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crust, mantle, core
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Earth's layers defined by physical properties
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Lithosphere- crust and uppermost mantle
Astenosphere- beneath lithosphere, in upper mantle, small amount of melting in the top Mesosphere- lower mantle |
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Core of Earth
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Outer core- liquid layer. Convective flow of metallic iron in it generates Earth's magnetic field
Inner core- solid and strong due to immense pressure |
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Elements
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building blocks of minerals
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Minerals
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building blocks of rocks
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Rock
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aggregate of minerals
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Most common elements
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silicon and oxygen
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Most common minerals
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Silicates
Including: Quartz, clay minerals, mica group (mineral muscovite) |
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Most common non-silicate minerals
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Carbonates- composed of Calcite (rain and groundwater dissolves rocks made of this mineral)
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Cleavage vs. Fracture
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Cleavage- tendency to break along planes of weak bonding
Fracture- absence of cleavage when a mineral is broken |
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Two types of Igneous Rocks
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Intrusive (plutonic)
Extrusive (volcanic) |
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Texture
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shape, size, and arrangement of mineral grains, tell us about rock origins
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Examples: Intrusive rocks- slow rate of cooling (large crystals)
Extrusive rocks- fast rate of cooling (small crystals) *very fast cooling forms glass |
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What are igneous rocks primarily composed of?
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silicate minerals
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Dark silicates (ferromagnesian): olivine, pyroxene, amphibole, biotite mica
Light silicates (nonferromagnesian): quartz, muscovite mica, feldspars |
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Igneous Compostions
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Granitic- continental crust
Andesitic- continental crust, stratovolcanoes Basaltic- oceanic crust Ultramafic (rock:peridotite)- composition of mantle |
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Shield Volcano
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largest volcano
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Composite Cone (stratovolcano)
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medium sized volcano
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Cinder Cone
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smallest volcano
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Lahar
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deadly pyroclastic flow
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Global distribution
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NOT random
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Ring of Fire
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Pacific Ocean
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Intraplate volcanism
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located within the lithospheric plate, associated with mantle plumes (below surface) and rift zone (on surface)
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subduction zones
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convergent plate boundaries
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mid-ocean ridges
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divergent plate boundaries
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Two types of weathering
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Mechanical and chemical
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Mechanical weathering
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breaking of rocks into smaller pieces
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Chemical weathering
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breaks down rocks components and internal structures of minerals
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End products: clay and quartz
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Rate of weathering depends on:
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surface area, rock characteristics, and climate (warm and moist is most effectively disintegrate and decompose rock)
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Evidence of weathering
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rounded corners, spots around minerals, traces of dissolution
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Types of sedimentary rocks
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detrital and chemical
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Detrital sedimentary rocks
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formed from particles which have been transported, deposited, buried, and undergone the lithification process
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Chief constitutes (minerals) of detrital rocks
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clay and quartz
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also common: mica and feldspars
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Chemical sedimentary rocks
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precipitated from solution or through activities of water-dwelling organisms (corals, bivalves etc.)
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Textures of sedimentary rocks:
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Clastic, Bioclastic, Nonclastic
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Clastic
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made of inorganic particles, all detrital rocks have a clastic texture
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Bioclastic
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rocks containing parts of animal skeletons, shells, tests
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Nonclastic
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crystalline structure (rock salt, rock gypsum have this texture)
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Metamorphism
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"change of form"
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Agents of metamorphism
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heat, pressure, active fluids
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Parent rock
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determines the chemical composition of metamorphic rock
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Metamorphic textures
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foliated and nonfoliated
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Schistosity
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“fish scale” appearance (mica minerals are the most common)
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Idea behind relative dating
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place geologic events in order
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Relative Dating
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Principle of Superposition
Principle of Faunal/Fossil succession Principle of Original Horizontality Principle of Cross-Cutting relationships Unconformities |
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Unconformities
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Angular- young flat lying strata overlie older, tilted strata
Disconformity- no tilting, strata are at the same orientation above and below Nonconformity- sed rocks overlie older igneous rocks |
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Atomic structure
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Nucleus: Proton (+) and Neutrons (no charge)
Revolving around nucleus: electrons: (-) |
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Atomic number
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sum of protons
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Mass number
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sum of protons and neutrons
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Isotopes
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same element with different number of neutrons in the nucleus
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What rock is best for radiometric dating?
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Igneous rocks
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Geologic Time Scale
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product of relative dating
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Structure of the Time Scale
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Eon, Era, Period
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Eon
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largest span of geologic time
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ex: Phanerozoic Eon (which means "visible life")
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Era
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Paleozoic ("ancient" "life")
Mesozoic ("middle" "life") Cenozoic ("recent" "life") |
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Periods
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Cambrian, Ordovician
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Precambrian time
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No fossil record found
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When does deformation occur?
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force = stress surpasses the elastic limit of rocks
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Rocks deform by:
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folding, flowing (ductile/plastic), fracturing (brittle)
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Types of stress
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Compressional, tensional, shear
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Anticline
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upfolded, arched rock layers
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Syncline
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downfold, trough in rock layers
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Monocline
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large step-like folds in otherwise horizontal sedimentary strata. result of buried fault
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Faults
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produced by vertical, horizontal, and oblique movements of blocks of Earth crust
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Types of faults
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Dip-slip- vertical
Normal- tensional stress Reverse- compressive stress Strike-slip- horizontal |
Types of Reverse faults: thrust or oblique, dip at less than 45
Type of Strike-slip: transform (San Andres fault) |
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Joints
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fractures with no displacement
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What are earthquakes connected to?
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activities along plate boundaries
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Elastic rebound
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H.F. Reid- 1906, San Fransico
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Types of seismic waves
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Body waves: S and P waves
Surface waves: L wave |
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P wave
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primary wave– “pull-push” motion, most fast, travels through solids, liquids & gases, smallest amplitude on seismogram
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S wave
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secondary or shear waves, shacking motion, can travel through solids (only), intermediate amplitude on a seismogram
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L wave
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long waves- slowest & most destructive, they have highest amplitude on a seismogram
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Earthquake scales
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Mercalli Intensity Scale- amount of damage
Richter Magnitude Scale- amount of energy released |
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Bedrock
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most stable materials during an earthquake
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What do seismic waves and earth's structure have in common?
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Abrupt changes in seismic-wave velocities that occur at particular depths helped seismologists to conclude that Earth must be composed of distinct shells
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Earth's magnetic field
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produced by weak electric currents in the Outer core
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Bathymetric techniques
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sound energy to map ocean flood (echo sounder or sonar)
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Ophiolite complex
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structure of ocean crust made up of 4 layers
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Black smokers
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hydrothermal (hot) fluids, rich in iron and sulfur, found along mid-oceanic ridges
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Orogenesis
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mountain building includes: compressional forces, metamorphism, igneous activity, folding, fault thrusting
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associated with horizontal movements of lithospheric plates
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Compressional mountains
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Convergent- Himalayan Mtn. (45 m.y.o.) intense folding and thrust faulting called a fold-thrust-belt.
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Suture zone
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where two continents collide
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Fault-block mountains
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Divergent- Basin and Range province.
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Mountain building is associated with what kind of movement?
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vertical movement in the crust
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Isostasy
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Less dense crust floats on top of the denser and deformable rocks of the mantle
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crust subsides when weight is added. crust rebounds when weight is removed.
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Crustal substance
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regions once covered by ice during the last Ice Age were uplifted when all ice was gone
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