Post on 11-Jul-2015
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
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 Pangaea, Greek for “all Earth”
245 Million years ago
Split again – Laurasia & Gondwana 180 million years ago
Evidence of Pangea
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
• http://www.youtube.com/watch?v=1-HwPR_4mP4• (7min 40 sec)
How Plates Move
http://pubs.usgs.gov/gip/dynamic/unanswered.html
How Plates Move
• Convection current – movement in a fluid or air due to uneven cooling1. the denser plate moves below into the earth
2. heated to liquid
3. decreases in density
4. rises to surface again
5. it cools and increases in density.
Different Types of Boundaries
http://pubs.usgs.gov/gip/dynamic/understanding.html
Divergent Boundary
• Regions where two tectonic plates are moving apart
• Occurs between oceanic plates, continental plates, and a combination of the two
Divergent Boundary – Arabian and African Plates
Divergent Boundary – Iceland
http://pubs.usgs.gov/gip/dynamic/understanding.html
Divergent Features
• Rift valley – a long, narrow depression that forms when continental crusts begins to separate
Divergent: 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
http://www.youtube.com/watch?v=GyMLlLxbfa4
Convergent Boundary
• Border formed from by the direct collision of two plates
Convergent Boundary – Indian and Eurasian Plates
Convergent Boundary – Oceanic & Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Convergent Boundary – Oceanic & Oceanic
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Convergent features
• Subduction zone – one plate moves under the other – Oceanic is more dense and moves below
continental crust at subduction zones
• Ocean trench - an elongated, sometimes arc-shaped depression in the seafloor that can extend for thousands of kilometers and is the deepest part of the ocean basin as continental and oceanic plates converge
Convergent features
• Island arc – chain of volcanic islands formed along an ocean trench
Convergent Boundaries - Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Transform (fault) Boundary
• Boundary formed where two plates slide past each other
Transform Boundary – San Andreas Faulthttp://mass.pbslearningmedia.org/resource/ess05.sci.e
ss.earthsys.thrustfault/earthquakes-los-angeles/
www.geology.com
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