Download The Structure of Earth - Mrs. wolfe`s 6th grade​ science classroom

Plate Tectonics
Mr. Q and Mrs. Wolfe
6th Grade Earth Science
What is Plate Tectonics?
• Theory that earth’s crust is broken into
plates that float on the upper part of the
mantle.
What causes plate
tectonics?
• Convection Currents in the mantle
Continental drift – theory that the
continents were at one or more
times a single landmass that
broke apart and eventually moved
into the positions they are in
today.
Quick Review
• Plate Tectonics: The Earth’s Crust is
Broken into plates that Float on the mantle
• Continental Drift: The earth’s Continents
were once one piece that have floated
away.
• Alfred Wegener – Scientist who
came up with the Theory of
Continental Drift.
Pangaea – The name of the First single
landmass created by Alfred Wegener.
http://www.youtube.com/watch?v=ryrXAGY
1dmE
• Evidence for Continental Drift
1. Earth’s continents look like puzzle pieces.
2. Fossils (remember Mesosaurus?)
3. Mountain ranges on different continents
appear to match-up.
4. Rocks – of one continent match those
along another continent.
• There are two (2) kinds of crust:
• Oceanic Crust (ocean)
• Continental Crust (land)
• Mid-Ocean ridge: ocean-floor feature
resembling a mountain. (New Sea Floor)
• Rift valley: flat area between two ridges
that is formed by spreading plates.
• Seafloor spreading: process that forms
new sea floor. (happens at Mid ocean
Ridge)
http://www.youtube.co
m/watch?v=ryrXAGY1
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• New Seafloor is close to the MidOcean Ridge…older floor is
Farther away. (DUH!)
• Subduction Zone: A place where
old oceanic crust is forced back
down into an ocean trench and
back into
the mantle
• A TRENCH is a deep ocean
canyon. ( Subduction zones are
found here)
• Many volcanoes and earthquakes
are found near subductions
zones. (ring of fire)
Evidence of Seafloor Spreading
• Fossils
• Magnetic strips
What are some
effects of Plate
Tectonics?
Earthquakes
Earthquakes
1906 and 1989 San Francisco
earthquake was caused by the
movement of tectonic plates at the San
Andreas Fault.
Mountain Building
• When two plates collide such a collision
can cause the continental plate to
crumble, and rise upwards – thus forming
mountains.
Volcanoes
• At subduction zones, oceanic plates dip
back down into the hot mantle.
• Heat from the mantle melts the rocks in
the plate, forming magma.
• Magma collects in underground pockets
called magma chambers.
• Hotter than the surrounding rock, the
magma rises to the surface.
Volcanoes
Volcanoes
Hot Spot – place where magma
reaches the surface of a tectonic
plate. The Hawaiian islands
were formed this way.
• THE END (for now)