Chapter 14 Flashcards
Continental Drift
Alfred Wegner
old theory that continental landmasses were “drifting” across the earth (Pangea)
evidence: similar fossils and glaciated continents fit
Plate Tectonics Theory
lithospheric plates move as a result of slow convection in Earth’s mantle; plates float on the asthenosphere
Evidence of plate tectonics
paleomagnetism: iron cooled magma orients itself with the magnetic poles of earth; this is used to verify age of ocean floor rock and seafloor spreading
Divergent Boundaries
plates move away from each other
- midocean ridges; earthquakes and volcanoes; seafloor spreading
Oceanic-continental convergent boundaries
oceanic plate sinks bc it is more dense (SUBDUCTION)
- forms oceanic trenches and continental mountains
- earthquakes and volcanoes along this boundary
- forms metamorphic rocks
Oceanic-Oceanic convergent boundaries
results in an undersea trench formation
- deep shallow earthquakes
- Pacific Ring of Fire (75% of volcanoes are here)
* SO MUCH SUBDUCTION HERE
continental-continental convergent boundaries
NO SUBDUCTION bc plates are highly buoyant
- builds huge mountain ranges
- shallow earthquakes
- no volcanoes
Transform boundaries
two boundaries slip past each other laterally
- transform faults (san andres fault)
- produces earthquakes
Mantle Plumes
localized hot areas NOT associated with plate boundaries
- move with the plate so eventually become inactive
- explains anomalous volcanoes
Accreted Terranes
piece of lithosphere carried by a plate that eventually collides and fuses with another plate
Extrusive Volcanism
occurs on Earth’s surface; lava cools quickly->no time for atoms to bond->fine igneous rocks
Intrusive volcanism
occurs below the surface; plutonic activity; lava cools slowly->atoms have time to bond-> coarse-grained igneous rocks
viscosity
resistance to flow
high silica: high viscosity: SLOW FLOW
low silica: low viscosity: FAST FLOW
Explosive Eruptions
high silica, high viscosity, pyroclastic, granite
Gentle Eruptions
low silica, low viscosity, basalt
Volcanic HAZARDS
volcanic gases: can cause acid rain, alter global climate
eruption clouds: gas and ash material clouds
pyroclastic flows: avalanche of hot gases
volcanic mudflows (LAHARS): result from heavy rain and or snow melt during an eruption
Volcanic POSITIVES
- much of earth’s water originates from water vapor from volcanoes
- magma contains elements required for plant growth
- provides soil fertility
Flood Basalt
A vast accumulation of lava build up; correlated with mass extinctions
Shield Volcanoes
layer upon layer of solidified lava flows; little pyroclastic material; not steep (Hawaiian islands)
Composite Volcanoes
emit higher silica lava (andesite lava); form symmetric, steep sided volcanoes; pyroclastics from explosive lava flows alternate with nonexplosive lava; pyroclastic flow produces steep slopes, lava holds it together
Lava Domes
masses of viscous lava that does not flow far; lava bulges from the vent, done grows by expansion from below and lava within; some domes form inside composite volcanoes
Cinder Cones
baby volcanoes; grow on big volcanoes; basaltic magma is common; slopes form from pyroclastic materials
Calderas
result from a volcano that explodes, collapses, or both; immense basin-shaped depression; larger than original crater
volcanic necks
pipe or throat of an old volcano that filled with solid lava
Diatrophism
the deformation of earth’s crust through two processes (folding and faulting)
Folding
when rock is subjected to lateral compression
- anticline/upfold: can be forced to have reverse orientation, an overturned fold (upside down U)
- syncline/downfold: overthrust fold (U)
Faulting
occurs when rock breaks accompanied by displacement
- occurs along zones of weakness in the crust, fault zones
- begin as sudden ruptures, end in big faults
Normal fault
going away from each other
Reverse fault
going towards each other
thrust fault
older rocks are pushed towards younger rocks
strike slip fault
blocks move horizontally; create linear fault troughs; sag ponds; offset drainage channels; shutter ridge
Earthquakes
vibration in Earth resulting from sudden displacement along a fault; the ground above the origin (the epicenter) experiences strongest jolt
P waves vs S waves
P waves go from long to short to long
S waves stay at a consistent cycle
Hazards of Earthquakes
damage from ground shaking
liquefaction of moist sediments
landslides
tsunamis
