04.plate tectonics
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this ppt contains all details about Plate Tectonics.TRANSCRIPT
Theory of Plate Theory of Plate Tectonics – an Tectonics – an
overviewoverview
Geo 100N Geo 100N
Spring 2005Spring 2005
Plate Tectonics -OverviewPlate Tectonics -Overview
1.1. The Lithosphere and CrustThe Lithosphere and Crust
2.2. Basic Concepts of Plate TectonicsBasic Concepts of Plate Tectonics
3.3. Plate Movements and BoundariesPlate Movements and Boundaries
4.4. SummarySummary
Inside the EarthInside the Earth
USGS
The LithosphereThe Lithosphere
http://volcano.und.edu/vwdocs/vwlessons/plate_tectonics/part1.html
Basic Concepts of Plate Basic Concepts of Plate TectonicsTectonics
The Earth’s surface is covered by The Earth’s surface is covered by about 12 lithospheric platesabout 12 lithospheric plates
USGS
The plates move slowly (a few The plates move slowly (a few cm/year).cm/year).
USGS
Most Most endogenicendogenic geological activity geological activity occurs at or near plate boundaries.occurs at or near plate boundaries.
Mt St Helens, 1980
Endogenic = process that originates within the Earth’s interior
Plate interiors are relatively quiet Plate interiors are relatively quiet geologicallygeologically
Plate Movements and Plate Movements and BoundariesBoundaries
Divergent boundariesDivergent boundaries
Plates move apartPlates move apart
Volcanic activity is always presentVolcanic activity is always present
Earthquakes are shallowEarthquakes are shallow
Two types of boundaries:Two types of boundaries:1.1. OceanicOceanic
2.2. ContinentalContinental
Oceanic Divergent BoundaryOceanic Divergent Boundary Sea-floor spreading of oceanic lithosphere Sea-floor spreading of oceanic lithosphere examples: Mid Atlantic Ridge, East Pacific examples: Mid Atlantic Ridge, East Pacific
RidgeRidge
USGS
Sea-floor spreading of oceanic Sea-floor spreading of oceanic lithospherelithosphere
USGS, Digital elevation model
Mid Atlantic Rift at IcelandMid Atlantic Rift at Iceland
Þingvellir (Thingvellir), Iceland
Continental Divergent BoundaryContinental Divergent Boundary
Continental rifting Continental rifting
Eventually, oceanic crust is formed and Eventually, oceanic crust is formed and divergence becomes oceanic typedivergence becomes oceanic type
Modern Example: East AfricaModern Example: East Africa
East African Rift ZoneEast African Rift Zone
Oldoinyo Lengai, Kenya
Convergent boundariesConvergent boundaries
Plates move toward each otherPlates move toward each other
Volcanic activity commonVolcanic activity common
Deep, medium, and shallow Deep, medium, and shallow earthquakes earthquakes
Three types of Convergent BoundariesThree types of Convergent Boundaries1.1. Ocean-oceanOcean-ocean
2.2. Ocean-continentOcean-continent
3.3. Continent-continentContinent-continent
Ocean-ocean convergenceOcean-ocean convergence
SubductionSubduction – one oceanic plate subducts – one oceanic plate subducts (dives) beneath the other(dives) beneath the other
Volcanic island arcVolcanic island arc is formed is formed Example: Aleutian Islands Example: Aleutian Islands
Aleutian Islands, AlaskaAleutian Islands, Alaska
Kanaga
Ocean-continent convergenceOcean-continent convergence
During ocean-continent convergence, During ocean-continent convergence, oceanic lithosphere oceanic lithosphere alwaysalways subducts subducts beneath continental lithosphere beneath continental lithosphere
Continental volcanic arcContinental volcanic arc formed formedExample: Andes mountains Example: Andes mountains
Continent-continent convergence Continent-continent convergence
Subduction does not occur (continental crust Subduction does not occur (continental crust is is too buoyanttoo buoyant to be subducted) to be subducted)
Mountain building occurs without volcanismMountain building occurs without volcanism
Example: Himalayas, AlpsExample: Himalayas, Alps
India-Asia CollisionIndia-Asia Collision
Collision of India Collision of India with Eurasian plate with Eurasian plate caused uplift of the caused uplift of the Himalaya, the Himalaya, the highest mountains highest mountains on Earth.on Earth.
Transform boundariesTransform boundaries
Plates slide past Plates slide past each othereach other
Little or no volcanic Little or no volcanic activityactivity
Shallow earthquakesShallow earthquakes
Example: oceanic Example: oceanic transform faults; transform faults; San Andreas FaultSan Andreas Fault
San Andreas FaultSan Andreas Fault
Pacific plate is Pacific plate is moving NW moving NW relative to the relative to the North American North American PlatePlate
As plates move, As plates move, transform fault transform fault slips, and slips, and earthquakes occurearthquakes occur
Summary Summary
1.1. Earth’s surface is covered by about Earth’s surface is covered by about 12 lithospheric plates. 12 lithospheric plates.
2.2. The plates move slowly (2.5-15 The plates move slowly (2.5-15 cm/year). cm/year).
3.3. Most volcanism and earthquake Most volcanism and earthquake activity occurs at or near plate activity occurs at or near plate boundaries. boundaries.
4.4. Plate interiors are relatively quiet Plate interiors are relatively quiet geologically (some exceptions). geologically (some exceptions).
Geo 100- Useful InformationGeo 100- Useful Information
Course Homepage:Course Homepage: http://mercury.atmos.albany.edu/geo100/
For SKN, email your name to instructor For SKN, email your name to instructor atat
[email protected]@albany.edu