plate tectonics
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Plate Tectonics. Liz LaRosa for use with my 5 th Grade Science Class http://www.middleschoolscience.com 2009 . Earth’s Layers. The Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed. - PowerPoint PPT PresentationTRANSCRIPT
Plate TectonicsLiz LaRosa for use with my 5th Grade Science Class
http://www.middleschoolscience.com 2009
Earth’s LayersThe Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed.
This crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle.
The Crust
• Outermost layer• 5 – 100 km thick• Made of Oxygen, Silicon, Aluminum
The Mantle• Layer of Earth between
the crust and the core• Contains most of the
Earth’s mass• Has more magnesium
and less aluminum and silicon than the crust
• Is denser than the crust
The Core• Below the mantle
and to the center of the Earth
• Believed to be mostly Iron, smaller amounts of Nickel, almost no Oxygen, Silicon, Aluminum, or Magnesium
earth's layers
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
plate tectonics
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
continental drift
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
sea floor spreading
How Plates Move
http://pubs.usgs.gov/gip/dynamic/unanswered.html
Different Types of Boundaries
http://pubs.usgs.gov/gip/dynamic/understanding.html
plate boundaries
Divergent Boundary
• Plates move apart• Constructive plate boundaries – where new
oceanic lithosphere is created• Forms oceanic ridges in oceans• Forms rift vallies in continents
Divergent Boundary – Arabian and African Plates
Arabian Plate
African PlateRed Sea
Divergent Boundary – Iceland
http://pubs.usgs.gov/gip/dynamic/understanding.html
Convergent boundary
• Destructive plate margins• Leading edge of one plate is bend downward
and slides beneath the other• subduction zones are where one oceanic plate
slides beneath a second plate
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
Oceanic plate is more dense and sinks below the continental plate which is less dense and floats on top.
Denser oceanic plate sinks to asthenosphere and begins to melt.
Magma is less dense than surrounding rock and rises, sometimes causing volcanic eruptions.
Convergent Boundaries - Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Continental lithosphere is buoyant and doesn’t sink to great depth.
Complex mountain ranges are formed.
Appalachian, Alps, Himalayas, and other mountain ranges were formed this way.
Convergent plates - oceanic
• One plate sinks beneath the other causing volcanic activity similar to oceanic – continental plate margins
• Volcanic island arcs are newly formed land masses forming arc shaped volcanic islands.
Transform boundary
• Plates grind past each other without destroying the lithosphere
• Most are located within ocean basins.• A few, like the San Andres Fault, cut through
continental crust
Slab Pull• Slab pull- old oceanic crust, which is cool and
dense, has sunk under another plate into the asthenosphere which pulls the trailing lithosphere along.
Ridge Push
• Ridge push- results from elevated oceanic ridge system and causes oceanic lithosphere to slide down the sides of oceanic ridge.
Convection• Hot plumes of rock are flowing upward in
mantle convection.• Hot plumes sometimes show themselves on
earth’s surface as hot spots and volcanoes.
Review
• Name the 3 main layers of the Earth• What is a tectonic plate?• What was Pangea?• What is Sea-Floor spreading?• Name the three different types of plate
boundaries and one location on Earth for each one
Resources
• This powerpoint was adopted from middleschoolscience.com by Ms. Glass on 9/07/12
• Video clips were found on youtube and incorporated