Download tectonics for lab-short version

Tectonic plates “float” on the higher density mantle.
The driving mechanism of
plate tectonics is mantle
convection. Hot mantle
material rises at ridges and
cooler mantle material sinks
at subduction zones.
Major Tectonic Plates
There are several large tectonic plates and a number of much smaller
plates. The Earth’s continents sit on plates composed of both oceanic
and continental crust.
The huge Pacific plate is composed almost entirely of oceanic crust, and
is being subducted around almost its entire western boundary.
Eurasian
North
American
Pacific
Phillipine
Caribbean
Pacific
African
Nazca
South
American
Antarctic
Australian-Indian
The contacts along which plates meet are called boundaries.
Individual plates move relative to each other in one of three ways:
Convergent - moving toward each other.
Divergent - moving away from each other
Transform - moving past each other
Plate
Boundaries
convergent
divergent
transform
The different kinds of boundaries have different properties:
Convergent – old oceanic crust destroyed through subduction
Divergent – new oceanic crust accreted at mid-ocean ridges
Transform – crust neither created or destroyed
convergent
divergent
transform
Convergent Boundaries
Oceanic-Continental
http://geo.lsa.umich.edu/~crlb/COURSES/270/
Subduction leads to orogeny
A sinking slab of oceanic crust will partially melt as it
heats up, creating pockets of magma that rise through the
crust, forming volcanoes.
Convergent Boundaries
Oceanic-Oceanic
http://geo.lsa.umich.edu/~crlb/COURSES/270/
When oceanic crust converges with oceanic crust, the denser
plate (usually the oldest and coldest) generally subducts. An arc
of volcanic islands forms from upwelling magma.
Convergent Boundaries
Continental-Continental
http://geo.lsa.umich.edu/~crlb/COURSES/270/
Since continental crust is buoyant, it does not subduct
easily. While the edge of a plate can be dragged under by
the weight of attached oceanic crust, it does not go far.
Divergent Boundaries
Divergent Boundaries
Mid-Ocean Ridges
Mid-ocean ridges are long
mountains formed parallel to
oceanic rifts.
The plates on either side of the
ridge grow as new crustal material
is added at the spreading center.
Rifts are characterized by relatively
shallow earthquake foci along the
length of the rift.
http://wwwneic.cr.usgs.gov/
Divergent Boundaries
Spreading Centers
http://geo.lsa.umich.edu/~crlb/COURSES/270/
upwelling magma causes bulge
Divergent Boundaries
Spreading Centers
http://geo.lsa.umich.edu/~crlb/COURSES/270/
upwelling magma causes bulge
rift valley forms as plates pull apart
Divergent Boundaries
Spreading Centers
http://geo.lsa.umich.edu/~crlb/COURSES/270/
upwelling magma causes bulge
rift valley forms as plates pull apart
oceanic crust accretes to continental crust as ridge forms
Divergent Boundaries
Spreading Centers
http://geo.lsa.umich.edu/~crlb/COURSES/270/
upwelling magma causes bulge
rift valley forms as plates pull apart
oceanic crust accretes to continental crust as ridge forms
continents continue to move apart, opening ocean
Divergent Boundaries
http://pubs.usgs.gov
Transform Boundaries
Most transform boundaries are associated with mid-ocean ridges (they
form perpendicular to the rifts). This movement resolves stresses
caused by different rates of spreading along the divergent boundary.
Transform Boundaries
Transform Boundaries
The San Andreas fault system is part
of a system of strike-slip faults caused
by the relative motion of the North
American and Pacific plates.
http://pubs.usgs.gov
http://www.ingv.it/~roma/cultura/ingescuola/terremotopagina/SanAndreas.html
http://wwwneic.cr.usgs.gov/
Boundary Type Volcanoes Mountains Earthquakes
Convergent
yes
yes
shallow-deep
Divergent
yes
yes
shallow
Transform
no
no
varies