Exam 3 Flashcards
(216 cards)
1
Q
eruptions can
A
effect climate
2
Q
3 products of volcanic eruptions
A
lava flows, pyroclastic debris, and volcanic gases
3
Q
lava flows
A
molten rock that moves over the ground
4
Q
pyroclastic debris
A
fragments blown out of a volcano
5
Q
volcanic gases
A
expelled vapor and aerosols
6
Q
lava can be
A
thin and runny or thick and sticky
7
Q
Viscosity depends on
A
composition, especially silica, Fe, Mg content, temp., gas content, crystal content
8
Q
mafic lava
A
very hot, low silica, and low viscosity
9
Q
Basalt flows are often
A
Thin and fluid
10
Q
Lava tubes
A
Conduit for basaltic lava, cooled crust on basalt flow, prevent cooling, become caves that can transmit water
11
Q
Products of volcanic eruptions
A
Basaltic (most mafic) , andesitic, rhyolite (most felsic)
12
Q
Pahoehoe
A
Basaltic, glassy , ropy texture, forms when extremely hot, skin
13
Q
Aa
A
Basaltic, solidifies with a jagged, sharp angular texture, forms when hot
14
Q
Columnar joints
A
Basaltic, solidified flows contract creating vertical fractures, hexagonal, indicates former lava
15
Q
Pillow basalt
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Basaltic, round blobs of basalt cooled in water, common at mid ocean ridges
16
Q
Andesitic lava flows
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High silica content, viscous, Do not follow rapidly, crest fractures into rubble, remains close to vent
17
Q
Rhyolitic lava flows
A
Highest silica content, most viscous, rarely flows, lava plugs events as a lava dome, sometimes lava domes are blown into smithereens
18
Q
Volcaniclastic deposits include
A
Pyroclastic debris, pre-existing rock, landslide debris, and lahars
19
Q
Preexisting rock
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Blasted apart by irruption
20
Q
Lahars
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Transported as water rich slurries
21
Q
Basaltic eruption
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Eject clots and drops off molten magma
22
Q
Lapilli
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P sized fragments
23
Q
Peles tears
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Frozen droplets
24
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Peles hair
A
Thin glass strands
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Blocks
Large fragments
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Bombs
Streamlined blocks
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Pumice
Frothy volcanic glass
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Ash
Fragments less than 2 mm in diameter
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Pumic lapilli
Angular pumice fragments
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Accretion lapilli
Clumps formed by falling through moist air
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Pyroclastic flow
Spewing hot ash, deadly
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Tephra
Deposits of pyroclastic debris of any size
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Tuff
Lithified Ash, may or may not contain lapilli
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Air fall tuff
Flows and falls like snow
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Ignimbrite
Tuff deposited while hot that welds together
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Volcanolistic deposit
Any fragmental igneous material
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Three categories of deposits
Pyroclastic, volcanic sedimentary, fragmented lava
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Pyroclastic
Material accumulated from clouds of debris
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Volcani sedimentary
Material moved after deposition
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Fragmented lava
Material from broken lava flows, hot lava skin, crest cracks in the fragments
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Volcanoes are gravitationally
Unstable
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Volcanic debris flow
Welted debris that moves down hill
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Percent of magma that is a gas
1 to 9%
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Gases
Water which is most abundant, carbon dioxide second abundant, sulfur dioxide i.e. rotten egg smell
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Felsic magma Has more gas true or false
True
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Gases are expelled when
Magma rises, pressure drops
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Sulfur dioxide. Reacts with water
Aerosol sulfuric acids
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Low viscosity (basalt)
Easy gas escape, mellow eruption
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High viscosity (rhyolite)
Difficult gas escape violent release
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Vesicles
Gas bubbles in rock
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Volcanoes have characteristic features
Magma chamber, fixtures and vents, craters, calderas, distinctive profiles
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Distinctive profiles
Shield volcano, Cindercone’s, straddle volcano
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Magma chambers are located in the
Upper crust, make cool to form intrusive rods, May rise to form volcano
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Magma erupts due to
Conduit, linear tear (fissure)
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Crater
Bowl shaped depression at top of a volcano, up to 500 m across, 200 m deep, form from erupted lava piles
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Summit eruptions
Located within the summit crater
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Flank eruption
Located along the side of a volcano
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Caldera
Gigantic volcanic depression
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Magma chamber empties
Volcano collapses into it
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Shape and size of volcanoes are governed by
Magma type
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Categories of volcanoes
Shield, Cindercone’s, Strato volcano
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Shield volcanoes
Largest, broad slightly dome shaped, low slope
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Cinder cones
Smallest, conical piles of tephra, angled slope
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Stratovolcanos
Intermediate in size, large cone shaped, steep slopes, made of alternating layers of lava, tephra, and debris, often symmetrical
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One feature that all volcanoes share
Magma chamber
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Volcanic types link to plate tectonics
Mid ocean ridges, convergent boundaries, continental rifts, hotspot
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Mid ocean ridges
Spreading axes
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Convergent boundaries
Subduction zones
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Continental rifts
Incipient ocean basins, partial melting of mantle or crust
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Hotspots
Where are mantle plumes cut the lithosphere
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Oceanic hotspot
Plume under an oceanic plate, decompression, Melting, basaltic composition
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Continental hotspot
Up through a continental plate
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Yellow stone
Irruption 640 KA created a 75 km caldera, 3 eruptions, fuel geysers
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Flood basalt
Voluminous lava eruption above a plume, mantle plume intersects vase of rifting lithosphere, creates large igneous province
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Eruptive hazard lava flow
Lava threats are mostly from basaltic lava, rare for lava flows to kill people
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Eruptive hazard threat of pyroclastic flow’s
Superheated ash clouds, extremely fast, hot, kills every living thing, flattens things
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Eruptive hazard threat of falling ash and lapilli
Can bury landscapes, Tephra is heavy, collapse route, Tephra gritty, abrodes engines, can move by floodwater
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Eruptive hazard blast
Rare explosions are ejected sideways
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Eruptive hazards landslides
Eruption, related slope failures, trigger landslides
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Eruptive hazards lahars
Mudflows result when water moves Ash, dense like concrete, can carry everything away
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Eruptive hazard earthquakes
Moving magma causes earthquakes, can cost slope failure, and damage to structures
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Eruptive hazard tsunamis
Island arc eruptions create giant waves
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Eruptive hazard threat of gas and aerosols
Causes respiratory problems, can be posinous
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Recurrence interval
Average time between eruptions
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Active
Erupting, recently erupted, or likely to erupt
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Dormant
Hasn’t erupted in hundreds of thousands of years
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Extinct
Not capable of erupting, tectonics can shut off magma, then erosion takes over
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Warning signs of eruption
Earthquake activity, heat flow, changes in shape, emission increases
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Mitigating volcanic eruptions
Planning, evacuations, diverting flows
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2 styles of flow
Effusive and explosive
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Effusive
Produce lava flows, vast and out pouring, common with mafic
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Explosive
Eruptions blow up,release pressure catastrophically, mostly andesitic and rhyolitic in composition
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4 explosive types
Strombolian, vulcanian, plinian, surtseyan
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Strombolian eruptions
Regular burps of magma, every 20 to 10 minutes, shoots out lapilli and blocks, basaltic pyroclastic eruption
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Vulcanian eruptions
Modertly sizes and explosive, pyroclastic eruptions
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Plinian eruptions
Huge explosive eruptions, eject a lot of materials, often destroy parts of stratovolcano
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Surtseyan eruptions
Vent erupts in shallow seawater, creates large amount of steam that carries ash out of water
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Super volcanos
Some past irruption‘s have been huge
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Fault
Fractured surface on which sliding takes place
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Seismicity
Earthquake activity
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Most common cause of earthquakes
Fault slip
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Hypo center
Place where fault slip occurs, usually on fault surface
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Epicenter
Land surface right above the hypocenter
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Most faults have a
Slope
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Foot wall
Block below the fault
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Hanging wall
Block above the fault
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Normal fault
Hanging wall moves down relative to the foot wall results from extension
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Reverse fault
Hanging wall moves up relative to the foot wall, results from compression
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Thrust fault
Special kind of reverse fault, slope is much less steep, common fault type in compressional mountain belts
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Strike-slip fault
One block slides laterally pass the other block, no vertical motion across the fault, fault surface is nearly vertical
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Displacement
Amount of movement across a fault, accumulates over time
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Active faults
Ongoing stressors produce motion
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In active faults
Motion occurred in the geologic past
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Blind faults
Invisible, don’t reach the surface
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Energy creating earthquakes originate when
Rocks break to form a new fault, pre-existing fault is reactivated
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Faults remain
A Zone of weakness
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Tech tonic forces stresses to rock
Push pull or sheer
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Fault motion is arrested by
Friction, force that resists sliding on a surface and due two bumps along the fault
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Faults move in
Jumps, stops quickly due to friction, strain builds up
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Stick
Friction prevents motion
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Slip
Friction is briefly overwhelmed by motion
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Foreshocks
Small tremors indicating crack development in rock, forewarn before large earthquake
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Aftershock
Follow a large earthquake, maybe weeks or years afterward
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How much does a fault slip during an earthquake
Depends on the size of the earthquake, larger earthquakes have larger areas of slip
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Displacement is greater near
The hypocenter
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Fault slip is
Cumulative , offset rocks by hundreds of kilometers given geologic time
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Can fault slip without earthquakes
Faulting is brutal D formation, rocks deform in ductile fashion that does not create earthquakes
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Two body waves pass through earths interior
P waves and S waves
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P waves
Primary are compressional waves, material moves back-and-forth apparel, fastest, travels through solids, liquids, and gases, travel by compressing and expanding
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S waves
Secondary or shear waves travel by material Moving up and down, material moves S perpendicular to waves, slow, only solids
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To surface waves along earths exterior
L waves and R waves
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L waves
Love waves, S waves that intersect land surface, movieland like a snake
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R waves
Rayleigh waves, P waves that intersect land surface, ground ripples up and down like water
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Seismometers
Instruments that record ground motion, waited pan on a spring traces movement on the frame
135
P waves always
Arrive first
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Time delay is used to establish
Distance from epi center
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Earthquake measurements
Intensity and magnitude
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Mercalli intensity scale
Degree of shaking damage with Roman numerals
139
Magnitude
Maximum amplitude of says Magrath motion, normalize to remove the influence of distance
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Richter magnitude
Useful near the Epicenter
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Moment magnitude
Most accurate measure
142
Shallow earthquakes
Divergent and transform boundaries
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Intermediate and deep earthquakes
Convergent boundaries
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Divergent plate boundary
Mid ocean ridges, normal fault, strike slip fault
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Convergent plate boundary
Shallow subdirectory slab an overriding plate, normal faults form down going slab Bends, large thrust faults accurate contact of two plates
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Wadati- Benioff zone
Earthquakes trace the sending slab
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Transform plate boundary
Plates slide past each other, most link mid ocean ridges or Cutthrough crust, large transform earthquakes are major disaster
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Continental rifts
Stretching creates normal faults, similar to mid ocean ridges, impacts people
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Collision zones
Orogenic crustal compression, continental lithosphere compresses along thrust faults, large earthquakes, landslide hazard
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Intraplate earthquakes
5% of earthquakes are not near plate boundaries
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Induced seismicity
People influence says make events, changing ground water pressure, adding pressure of damned reservoir
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Surface waves are delayed traveling along the
Exterior
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Severity of shaking and damage depends on
Magnitude, distance from hypocenter, intensity and duration of vibrations, nature of sub surface material
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Which plate tectonic boundaries would you expect to see shallow earthquakes
Divergent, convergent, transform, continental rift, collision zones, intraplate
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Liquefaction
Waves liquefy H2O filled sediments such as quicksand a quick mud
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Liquified soil
Loses strength, structure slump and flow
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Frequently realized earthquake hazard
Fire, fire fighters may be powerless
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Geologic processes that manifest mountains
Uplift, Deformation, metamorphism
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Mountain belt
Elongate/linear belt
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Orogenesis
Mountain building process
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Constructive processes
Build mountains up
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Destructive processes
Tear mountains back down again
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Orogenesis applies force to rocks, causing deformation
Bending, breaking, shortening, stretching, shearing
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Strain
Change in shape from deformation
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Joints
Fractures that have no offset
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Folds
Layers that are bent by slow plastic flow
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Faults
Fractures that are offset
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Foliation
Planar metamorphic fabric
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Undeformed rocks
Unstrained, horizontal beds, spherical sand grains, no folds or faults
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Deformed rocks
Strained, tilted beds, metamorphic alteration, folding, and faulting
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Deformation results in
Displacement, rotation, distortion
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Displacement
Change in location
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Rotation
Change in orientation
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Distortion
Change in shape
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Several types of strain
Stretching, shortening, shear
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Stretching
Pulling apart
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Shortening
Squeezing together
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Shear
Sliding past
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Two major Deformation types
Brittle and ductile
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Brittle
Rocks break by fracturing, occurs in the shallow crust
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Ductile
Rocks to form by flowing and folding, occurs at high pressure and temperature in deep crust
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What causes strain
Stress
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Stress
Force applied across a unit area
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Types of stress
Compressional, tensioner, sheer
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Compressional
Squeezing
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Tensional
Pulling apart
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Shear
Sliding past
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Tectonic collision produces
Horizontal compression
189
Joints
Planar rock fractures without any offset, result from tension, groundwater flows through
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Joints filled with minerals
Veins
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Strike
Horizontal intersection with a tilted surface
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Dip
Angle of the surface down from the horizontal
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Fault geometry varies
Vertical, horizontal, and dipping
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Dip slip
Blocks move parallel to the depth of the fault
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Strike slip
Blocks move parallel to fault plane strike
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Oblique slip
Components of both dip slip and strike slip
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hinge (fold axis)
line along which the curvature is the greatest
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limbs
less curved sides of a fold
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axial plane
connects hinges of successive layers
200
anticline
fold that looks like an arch
201
syncline
fold that opens upward like a trough
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dome
circular fold with the appearance of an overturned bowl, old rocks
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basin
circular fold shaped like an upward bowl, young rock
204
open fold
large angle between limbs
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tight fold
small angle between limbs
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folds develop in 2 ways
flexural slip and passive flow
207
passive flow
folds form in hot, soft, ductile rock at high temperature
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foliation develops via
compressional deformation or shearing
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orogenesis creates
igneous, metamorphic, and sediment
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igneous rocks
intrusive and extrusive
211
metamorphic rocks
regional or contact
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sediment
orogenesis generates a large amount
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rock characteristics control erosion
resistant layers form cliffs, easily eroded rocks form slopes
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craton
crust that has not been deformed in 1 Ga, shields and platforms
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shields
precambrian igneous and metamorphic rocks
216
platforms
shields covered by layers of phanerozoic strata
