plate tectonics. tectonic plates plate tectonics greek – “tektonikos” of a builder pieces of...
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Plate tectonics
Tectonic Plates
Plate Tectonics
• Greek – “tektonikos” of a builder• Pieces of the lithosphere that move around• Each plate has a name• Fit together like jigsaw puzzles• Float on top of mantle similar to ice cubes
in a bowl of water
Continental Drift
http://members.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml
Alfred Wegener 1900’sContinents were once a single land mass that drifted apart.
Fossils of the same plants and animals are found on different continents
Called this supercontinent Pangea, Greek for “all Earth”
245 Million years ago
Split again – Laurasia & Gondwana 180 million years ago
Evidence of Pangea
Sea Floor Spreading
Sea Floor Spreading
• Mid Ocean Ridges – underwater mountain chains that run through the Earth’s Basins
• Magma rises to the surface and solidifies and new crust forms
• Older Crust is pushedfarther away from the ridge
Why do plates move?
Convection currents
Convection currents• What are they?• How do they make plates move?• When mantle rocks near the radioactive core are heated, they
become less dense than the cooler, upper mantle rocks. These warmer rocks rise while the cooler rocks sink, creating slow, vertical currents within the mantle (these convection currents move mantle rocks only a few centimeters a year). This movement of warmer and cooler mantle rocks, in turn, creates pockets of circulation within the mantle called convection cells. The circulation of these convection cells could very well be the driving force behind the movement of tectonic plates over the athenosphere.
Subduction
• What is it?• One plate sinks underneath the other because
it is more dense.
How Plates Move
http://pubs.usgs.gov/gip/dynamic/unanswered.html
Convection currents
• Destructive vs. Constructive forces• Define both of the terms below:• Constructive forces- builds the Earth up• Destructive forces- Breaks the Earth down
Destructive or constructive?type destructive constructive both
Erosion
Weathering
Deposition
Volcano
earthquake
Different Types of Boundaries
http://pubs.usgs.gov/gip/dynamic/understanding.html
Plate boundaries
• Transform• Plates slide past each other• Earthquakes form
Plate boundaries
• Divergent• Plates divide• In ocean- will be mid-ocean ridges• On land- rift valleys• Why? As plates spread apart, magma rises
through the gap and forms new crust
Divergent Boundary – Arabian and African Plates
Arabian Plate
African Plate
Red Sea
Divergent Boundary – Iceland
http://pubs.usgs.gov/gip/dynamic/understanding.html
Convergent Boundary – Indian and Eurasian Plates
Indian Plate
Eurasian Plate
Convergent Boundary – Oceanic & Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Plate boundaries
• Convergent• Plates collide (go together)• When ocean plates meet continent plates, an
ocean trench forms with volcano on the land• Why? Ocean plate is more dense than
continental and sinks under it into mantle (subduction)
Convergent Boundary – Oceanic & Oceanic
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
NOTE – PLATES ARE REVERSED
Plate boundaries
• Convergent• Plates collide (go together)• When ocean plates meet ocean plates, an
ocean trench forms with magma forming islands
• Why? The ocean plate that is more dense will sink under the other (subduction)
Convergent Boundaries - Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Plate boundaries
• Convergent• Plates collide (go together)• When continent plates meet continent plates, mountains form Why? Continental plates buckle up as they
push together
Plate tectonic animations
• http://www.nature.nps.gov/geology/usgsnps/animate/pltecan.html
Additional activities:
• Plate tectonics www.brainpop.com• Volcanoes
http://www.brainpop.com/science/earthsystem/volcanoes/
• Earthquake http://www.brainpop.com/science/earthsystem/earthquakes/
• Pangaea activity worksheet• Plate boundary prediction worksheet