Plate Tectonics earth
Visit our website: http://www.sliderbase.com/
Free PowerPoint Presentations for teaching and learning
Plate Tectonics
Evolution of the Earth
How do we know anything about the Earth
Interior structure
Volcanoes and hotspots
Earthquakes
Tectonic plates
Tectonic motion
Reconstruction of the Earth’s history
Volcanoes
Volcanoes are the result of hot spots within the crust or mantle of the earth.
The hot, liquid rock will break through weak spots in the surface and form volcanoes or flood basalts.
Many volcanoes do not release lava, instead they spit ash and small bits of lava called lapilli.
Some eruptions are quiet with very fluid (low viscosity) lava flows while others are explosive
Flood basalts
Basalt is a type of rock that is
produced from the mantle
Earthquakes
Earthquakes are a result of motion within the earth.
This only occurs where the earth is solid and therefore can only occur within about 100 miles of the surface
Earthquakes provide the best evidence regarding the interior structure of the Earth.
Tectonic Plates
Today plate boundaries are determined by examining
the location of volcanoes and earthquakes.

Volcanoes result from the friction (heat) of the plates
motion.

Earthquakes occur where plate rub against one another
Plate Types
Oceanic plates: basalt
Dark (black) and dense rock type composed of silicates, iron and magnesium

Continental plates – granite and andesite
Light colored (pink, white and gray) and low density rock type composed almost entirely of silicates.
Plate Boundaries
Convergent – plates move toward one another

Divergent – plates move away from each other

Transform – plate moves sideways from each other
Why do the Plates Move?
No single idea explains everything but we can identify several forces that contribute to the movement of the plates.
Slab pull
The sinking of the cooled dense oceanic plates pulls on the rest of the plate
Ridge rises
The material deposited on the top of the ridge slides downs from the rise pushing on the plate
Convection
Movement within the mantle could be part of the driving force behind the motion of the plates.
Pangea
What is Pangaea?
Pangaea was a super continent at one time.
Scientists use the similarity of rock types and fossil types that date to the same age to support their theory that the continents were connected to form a super continent.
The map below give just one example of areas on different continents that show the same fossils and rock types.
Where are we going?
We appear to be headed for another
super continent as North America,
South America, Asia and Australia converge in the
ever shrinking Pacific Ocean