Geology Exam Vocab
Terms
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- lava
- molten rock that has extruded onto the earth's surface
- lava flows
- moving masses of molten lava
- viscosity
- resistance to flow
- basaltic lava flow
- mafic lava that has low viscosity (fast moving)
- lava tube
- an insulated tunnel like conduit within a flow through which lava moves
- flows with warm pasty surfaces wrinkle into smooth glassy rope like ridges
- pahoehoe (pa-hoy-hoy)
- jumble of sharp angular fragments creating a rubbly flow
- a'a'
- fracturing that creates hexagonal columns
- columnar jointing
- andesitic lava flows
- medium viscosity lava flow, it forms a mound and then slides down the sides /\
- rhyolitic lava flows
- Most viscous (slowest) flow, accumlates into a dome like mass/ lava dome
- lava that accumulates in to a dome like mass
- lava dome
- volcanic ash is composed of ____
- tiny glass shards
- all fragmental material erupted from a volcano
- pyroclastic debris
- finest pyroclastic debris, powered sized glass shards
- lapilli
- apple to refrigerator sized pieces of pyroclastic debris
- blocks (or) bombs
- unconsolidated deposits of pyroclastic grains (regardless of size)
- tephra
- ash or ash mixed with lapilli, when lithified becomes
- tuff
- avalanches of hot ash and lapilli that rush down the side of a volcano
- pyroclastic flow/ nuee ardente("glowing cloud")
- a sheet of tuff formed from a pyroclastic flow
- ignimbrite
- fluid fast moving volcanic debris flows - ash and water
- lahar
- composed of water, CO2, SO2, and hydrogen sulfide
- volcanic gas
- cone shaped piles of tephra
- cinder cones
- "composite volcanoes", large and cones shaped and consist of alternating layers of lava and tephra
- Stratavolcanoes
- eruptions that produces lava flows
- effusive eruptions
- eruptions that produce clouds and avalanches of pyroclastic debris
- explosive/ pyroclastic eruption
- eruption involving water and magma
- phreatomagmatic eruption
- low viscosity lava spread over large areas
- flood basalts
- time between eruptions
- recurrence interval
- volcanoes that are erupting or likely to erupt soon
- active volcanoes
- volcanoes that have not erupted in hundreds to thousands of years
- dormant volcanoes
- volcanoes that were active in the past but have stopped forever
- extinct volcanoes
- a map that delineates areas that lie in the path of potential lava flows, lahars, debris flows or pyroclastic flows
- volcanic danger assessment map
- earthquake activity
- seismicity
- a fracture on which sliding occurs
- fault
- the place in the earth where rock ruptures and slips
- hypocenter/focus
- the point on the surface of the earth that lies directly above the hypocenter
- epicenter
- hanging wall block goes down relative to the footwall due to crustal stretching
- Normal fault
- hanging wall slips diagonally
- Oblique slip fault
- hanging wall goes up due to crustal shortening
- thrust fault
- no vertical motion, sideways motion
- strike-slip fault
- the amount of slip on a fault
- displacement
- the intersection between a fault and the ground surface
- fault trace/ fault line
- the small step that is created when a normal fault is created
- fault scarp
- a change in the shape of an object that disappears when stress is removed is called...
- elastic strain
- the start stop movement on a fault
- stick-slip behavior
- smaller earthquakes that precede a major earthquake
- foreshocks
- smaller earthquakes that follow a major earthquake
- aftershocks
- the instant a earthquake appears at a seismograph station
- arrival time
- the lines that record an earthquake
- seismogram
- the instrument that records an earthquake
- seismograph
- the waves that arrive first
- P waves
- the waves that arrive second
- S waves
- the waves that arrive last
- surface waves/ rayleigh and Love waves (r and l waves)
- first scale to characterize an earthquake. described by roman numerals
- Mercalli intensity scale
- the number that indicates the earthquakes relative size as determined by measuring the maximum amplitude of ground motion recorded by a seismograph
- magnitude
- earthquake magnitude is measured by this scale
- Richter scale
- calculates the EXACT magnitude of an earthquake
- moment magnitude
- area where earthquakes occur
- seismic belts
- earthquakes that occur on the interior of plates
- intraplate earthquakes
- seismic events that are caused by the actions of people
- induced seismicity
- waves that move the ground upwards
- P waves
- waves that move the ground side to side
- S waves
- waves that makes the ground move like a snake
- L(ove) waves
- waves that move the ground like waves
- R(ayleigh) waves
- the movement of water within a bay or lake caused by an earthquake
- seiche
- the abrupt loss of stregth of a wet sediment
- liquefaction
- average time between successive events (earthquakes)
- recurrence interval
- where a know active fault has not slipped for a long time
- seismic gap
- designing buildings that can withstand earthquakes
- earthquake engineerings
- determine where land is stable and where it might collapse
- earthquake zoning
- boundary between the rock through which a wave has passed and the rock through which it has not yet passed
- wave front
- changing position of an imaginary point on wave front as the front as the front moves through rock
- seismic ray
- time it takes for a wave to travel from the focus to a seismograph
- travel time
- between 100 and 200 km deep in the mantle beneath the oceanic lthosphere seismic velocities are slower than the lithospheric mantle
- low velocity zone
- when the seismic ray is disjointed as it moves through different layers
- seismic velocity discontinuities
- 3d image of seismic wave velocities within the earth
- seismic tomography
- rocks squash, stretch, bend and break
- deformation
- cracks
- joints
- fractures on which one body of rock slides past another
- faults
- bends or wrinkles
- folds
- layering resulting from alignment of mineral grains or the creation of compositional bands
- foliation
- mountain belts
- orogens
- mountain building event
- orogeny
- material breaks into 2 ore more pieces
- brittle deformation
- material changes shape without breaking
- ductile deformation
- when a rock is pulled apart
- tension
- one side of a rock is moved sideways past the other side
- shear stress
- special stress condition in which the same push acts on all sides of an object
- pressure
- the rock above the fault plane
- hanging wall block
- rock below the fault plane
- footwall block
- sliding occurs up or down the slop of the fault
- dip-slip fualts
- one block slides past another
- strike slip faults
- sliding occurs diagonally on the fault plane
- oblique-slip faults
- polished fault surfaces
- slickenslides
- linear grooves on fault surfaces
- slip lineations
- faults in which moment occured ductilely
- shear zones
- the portion of the fold where curvature is greatest
- hinge
- sides of the fold that show less curvature
- limbs
- folds that an arch like shape in which the limbs dip away from the hinge
- anticlines
- folds with a trough like shape in which the limbs dip toward the hing
- synclines
- the shape of a carpet draped over a stairstep
- monocline
- layering created by the alignment of deformed and or reoriented grains
- tectonic foliation
- condition when the buoyancy force pushing lithopshere up equals the graviational force pulling lithosphere down
- isostacy/ isostatic equilibrium
- asymmetric ridge
- cuesta
- when geds dip steeply and forma narrow more symmetrical ridge
- hogback
- mountains collapsing because of own weight
- orogenic collapse
- blocks that attach to a convergent margin
- exotic terranes
- orogens that grow laterally by the attachment of exotic terranes
- accretionary orogens
- when the continent is pushed tightly against a subduction zone ___ this is generated
- fold-thrust belt
- crust that has not been affected by orogeny for at least 2 billion years
- craton
- where precambrian metamorphic and igneous rocks crop out of the ground
- shields
- relatively thing layer of sediment covers the precambrian rocks
- cratonic platform
- the broad vertical movement that grenerate huge but gentle mid continent domes and basins
- epeirogeny