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Plate Tectonics
Brigitte Steinmetz
John Adams Middle School
Disclaimer
The images, maps and diagrams in this
presentation were taken from the public
domain on the world wide web.
Permissions were granted where possible.
Any privately owned images not available
for this non-commercial, educational
project will gladly be removed.
E-mail: [email protected]
Earth’s Interior
Oceanic Crust
Oceanic
B.
Crust
C.
Asthenosphere
A.
Continental
Crust
Lithosphere
D.
E.
Mantle
Outer Core
Inner Core
The Mantle
• Upper part = hot &
rigid (hard)
– part of the
lithosphere.
• Middle part =
hotter & soft
(asthenosphere)
• Lower part =
hottest & solid
http://pubs.usgs.gov/publications/text/inside.html - 12/7/2004
The Earth is HOT
• Review Heat Transfer
– Radiation =
• Energy transferred through
an empty space
(i.e. sun energy).
– Conduction =
• Energy transferred directly from one object to
another (i.e. burning feet at the beach).
– Convection =
• Energy transferred through the movement of a
heated fluid.
Convection inside Earth
http://pubs.usgs.gov/publications/text/unanswered.html - 12/7/2004
Convection inside Earth
• Convection in the mantle causes the
crust’s plates to move!
http://www2.nature.nps.gov/geology/usgsnps/animate/A08.gif - 12/7/2004
Continental Drift
• Alfred Wegener:
– Hypothesis:
• About 300 MYA all
continents were
once joined
together forming a
SUPER continent!
– He named it
PANGEA!
• Pangaea begins to break apart and
continents move to present day locations
• Occured tens of millions of years ago
http://www.mpm.edu/reef/pt-gif.html - 12/7/2004
Continental Drift Theory
Evidence of Drift
• Continents fit together like a puzzle
• Land forms similar on different
continents (like mountain ranges)
Evidence of Drift Continued
• Fossils found in
unlikely places
– For example:
• Reptiles were
found in
Antarctica.
• Tropical plants
found in ice
covered places.
http://www.soc.soton.ac.uk/CHD/classroom@sea/carlsberg/images/f
ossil_correlation_lge.jpg - November 27, 2005.
What about the FUTURE?
Plates on the Move
• Plates move 1-10cm/year.
• Moving apart.
• Moving plates
cause:
–Earthquakes
–Volcanoes
http://pubs.usgs.gov/publications/text/Krafla.html - December 13, 2004.
Plate Boundaries
• Place where two plates meet and
interact.
• Three Types:
–Transform
–Divergent
–Convergent
http://pubs.usgs.gov/publications/text/ridge.html - December 13, 2004.
Convergent Boundaries
• Occurs when two plates collide (run into
each other).
• Two types:
Continental
Oceanic
http://pubs.usgs.gov/publications/text/understanding.html - December 13, 2004.
Continental Convergence
• Two plates collide and buckle upwards
forming mountains and cause earthquakes!
Oceanic Convergence
• When two plates collide, one goes under
the other called subduction!
• Causes volcanoes.
Divergent Plate Boundaries
• When two plates move apart.
• Occurs at two places:
Mid-Oceanic Ridge
Land – Rift Valley
http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0006339.html - December 13, 2004
Sea Floor Spreading
• Magma comes up forming new rock and
pushes old rock to sides.
http://www.uwsp.edu/geo/faculty/ritter/glossary/S_U/sea_flr_spread.html - December 13, 2004.
Which Rock is Older?
• The older rock
is closer to the
continents.
• New rock is at
the mid-oceanic
ridge.
http://www.soc.soton.ac.uk/CHD/classroom@sea/carlsberg/sci
ence/oceanic_constr.html - December 13, 2004.
Where are Mid-Ocean Ridges?
Pacific vs. Atlantic Oceans
Pacific Ocean is
getting smaller –
continents are
coming together.
Oceanic crust is
moving under them.
Atlantic Ocean
is getting
bigger – USA
and Europe
are moving
apart!
http://www.soc.soton.ac.uk/CHD/classroom@sea/carlsberg/science/oceanic_constr.html - December 13, 2004.
Transform Boundary
• Plates slide past each other in opposite
directions.
• Causes a lot of earthquakes.