plate tectonics. overview: the lithosphere and the crust basic concepts of plate tectonics plate...
TRANSCRIPT
Plate Tectonics
Overview:
• The Lithosphere and the Crust
• Basic Concepts of Plate Tectonics
• Plate Movements and Boundaries
Inside the Earth:
The Lithosphere:
The Basic Concepts:
- the earth is covered by several large lithospheric plates
These plates move slowly (about a few cm./yr)
• Due to convection cells in the asthenosphere
Convection movement driven by heat from the core:
Mantle convection produces lateral forces at the boundary between the
mantle and the crust
Theory of Plate Tectonics:
Plate Movement and Boundaries
• Divergent Boundarieso Plates move aparto Volcanic activityo Earthquakes shallowo Two types of boundaries
OceanicContinental
Oceanic divergent boundary
• Sea-floor spreading of ocean platesMid-Atlantic Ridge
Page 43, Worrall
Continental Divergent Boundary
• Continental Rifting,
eventually oceanic
crust is formedModern example ; East African Rift
Convergent Boundaries
• Plates move towards each other• Volcanic activity common• Deep, medium and shallow earthquakes• Three types;
Ocean to oceanOcean to continentContinent to continent
Ocean to Ocean- convergence
• Subduction - process which one plate slides under the other (subducts)
• Volcanic arc islands are formed
Ocean to Continent Convergence
• Ocean lithophere subductssubducts under continent
•Most tectonic activity occurs at or near these boundaries
Continent to Continent - Convergence
• Subduction does not occur
• Mountain building occurs without volcanic activity
• Collision of India with Eurasia
• Height is still increasing
Transform Boundaries
• Plates slide past each other
• Little or no volcanic activity
• Shallow but strong earthquakes
• Example: San Andreas Fault
West Coast: unstable -subduction zone and transform fault zone
A
Divergent
B
Convergent
C
Transform
•plates are moving apart
•new crust is created
•Magma is coming to the surface
•plates are coming together
•crust is returning to the mantle
•plates are slipping past each other
•crust is not created or destroyed
A
Divergent
B
Convergent
C
TransformContinental crust
rift valley
Oceanic crust mid-ocean ridge
2 continental plates mountain range
Plates move against each other
Stress builds up
Stress is released
earthquake
2 oceanic plates oroceanic + continental subduction
The Big Picture