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Copy of Plate Tectonics
Transcript of Copy of Plate Tectonics
For billions of years plates have been moving around on earth’s surface because of forces known as “plate tectonics” http://geochemist.files.wordpress.com/2009/07/plate-tectonics.jpg http:/www.youtube.com/watch?v=GYVS_Yh6dTk - Plates move upon the mantle, the layer of partially molten rock.
- They move because nuclear reactions in the core that produce heat
- The heat causes the mantle material to expand and rise toward the surface.
- When it reaches the surface, it cools and moves downward due to gravity
- This cycle of the convection currents and the effect of the gravitational forces cause the plates to move. Recap... so now we know... the crust of the earth is divided into plates these plates "float" on the partially melted mantle (asthenosphere) over a long period of time these plates have moved around the earth creating the land masses we have today Interactions between plates There are 3 ways that plates can interact with each other moving together - converging moving apart - diverging and moving past one another - transforming http://blue.utb.edu/paullgj/physci1417/Lectures/Conv_Cont_Ocean.JPG http://www.teleseismic.net/aboutearthquakes/aboutearthquakes_files/image007.jpg so now we know... ~ The crust of the earth is divided into plates
~ These plates "float" on the partially melted mantle (asthenosphere)
~ Over a long period of time these plates have moved around
the earth creating the land masses we have today
~ There are 3 ways that plates can interact with each other
moving together - converging
moving apart - diverging
moving past one another - transforming
~ The plates move because of strong convection currents in the mantle Subduction Zones Plates move toward each other
The heavy, oceanic plate descends below the lighter continental plate Google: "plate tectonics evidence fossils" first website result http://www.visionlearning.com/library/module_viewer.php?mid=65 What is a Plate? The earth’s surface is made up of about 20 large “plates” and a number of smaller ones. Together, these plates cover earth’s entire surface.
Theories on Plate Tectonic Movement Continental Drift Theory (1915)
By Alfred Wegener
Wegener’s came up with 4 pieces of evidence to support his theory:
1.He saw a jigsaw fit between South America and Africa
2.He found fossils of the same plants and animals on both sides of the Atlantic (in South America and Africa)
3.He found similar rocks and mountains on both sides of the Atlantic (Appalachian Mountains in Canada and Caledonian Mountains in the British Isles)
4.He found evidence of ice sheets in tropical countries (Africa, India, Australia and South America) Proof of Wegener’s Theory Theory of Plate Tectonics (1960)
By John Tuzo Wilson Wegener proposed the theory of continental drift but couldn’t explain what was powerful enough to move huge pieces of land
Wilson supported Wegener’s idea with technological proof
Wilson argued that:
•Earth’s outer shell is made up of about 20 plates
•The plates are floating on a layer of hot rock (mantle)
•It is the unequal distribution of heat within Earth’s core that creates convection currents which cause the plates to move 200 million years ago this super-continent started to break up and the pieces that broke apart evolved into the seven continents we know and see today 300 million years ago all land masses collided to form a super-continent called Pangaea (“all land”) The earth is over 4.6 billion years old.
The differences in the physical shape of our landscape are the result of the Earth’s geological development.
Tectonic plates can move in 4 different ways. (spreading) Convergent (spreading) Plates move apart from each other
As they pull apart, magma rises o fill the space
The magma cools and hardens, forming new crust Plate Actions: Plates move towards each other
Rock is forced upward Plate Actions: •Fold mountain ranges
•Volcanic activity Effects: •Constructs new crust
•Volcanic activity Effects: Plate Actions: •Creates trenches
•Young, active mountain ranges
•Earthquake activity (deep & powerful) Plates slide past one another
This sliding causes friction Plate Actions •Creates faults
•Earthquake activity on the surface Effects: Effects: Ex: Mid Atlantic Ridge Ex: Himalayas Ex: Pacific Ring of Fire Ex: San Andreas Fault