1. In this presentation you will:
Plate Tectonic Theory
In this presentation you will:
explore historical development that supports plate tectonic theory
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2. Continents fit together like puzzle pieces.
Pangaea (1 of 1)
Continents fit together like puzzle pieces.
Pangaea is a large supercontinent that split into several pieces, These pieces became Earth's current continents.
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3. Alfred Wegener and Theory of Continental Drift (1 of 1)
In 1912 a scientist named Alfred Wegener theorized that the continents had once been joined together and drifted over millions of years.
This was called the theory of Continental Drift
Unfortunately he had no scientific proof, and could not explain what moved the continents
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4. Evidence of Continental Drift (1 of 1)
Fossils of the same species of plants and animals were found across different continents.
This supported Wegener’s theory that the continents had once been joined together.
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5. Plate Tectonic Theory (1 of 1)
Continental drift was disputed by scientists for many years. However, as more evidence was found, it became universally accepted.
With the discovery of fossils and seafloor spreading scientists came up with the Theory of plate tectonics
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6. Indo-Australian plate
Tectonic Plates (1 of 1)
The outer layer of the Earth is broken up into a different tectonic plates and fit together like a puzzle.
Eurasian plate
Pacific plate
Indo-Australian plate
South American plate
North American plate
North American plate
African plate
Indian plate
Nazca plate
Caribbean plate
Cocos plate
Philippine plate
Antarctic plate
Juan De Fuca plate
Arabian plate
Scotia plate
The tectonic plates are constantly moving at a very slow speed, and this movement can change the Earth’s surface.
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7. Lithospheric and Asthenosphere Plates (1 of 1)
The plates of the outer layer of Earth made of the crust, and the solid part of the upper mantle are the called the Lithospheric Plates.
The Asthenosphere is a semi liquid that the lithosphere floats on. It allows the lithosphere and plates to move
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8. What Causes Plate Motion? (1 of 2)
Imagine you are cooking an egg in a pot of water. As the water is heated and the temperature increases, the egg floating at the surface begins to move.
The hot particles rise to the surface, when they cool they sink back down. This cycle is called a convection current.
The movement in the hot water causes the egg to move.
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9. This convection takes millions of years.
What Causes Plate Motion? (2 of 2)
Convection currents within the Earth’s mantle cause the plates floating above to move.
Mantle
Plates
This convection takes millions of years.
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10. Plate Movement (1 of 2)
The plates collide, pull apart or scrape against each other depending on their relative directions.
The effects of the plate motion can be seen at the edges (boundaries) of the plates.
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11. Plate Movement (2 of 2)
Plate movement can cause volcanic eruptions, earthquakes, and mountain formation.
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12. Types of Plate Boundary (1 of 1)
There are three types of boundaries between plates:
Convergent – The boundary between two plates that are moving towards each other.
Divergent – The boundary between two plates that are pulling apart.
Transform – The boundary between two plates that are sliding past each other horizontally.
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13. When two plates collide, one plate is forced below the other.
Convergent Boundaries (1 of 1)
When two plates collide, one plate is forced below the other.
Crust is destroyed
On the ocean floor, a trench is formed. Trenches are narrow, deep cuts.
Creates: volcanoes, folded mountains, Ocean trenches, subduction zones,
Trench
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14. Types on Convergent boundaries (1 of 1)
Oceanic – Continental
An oceanic plate slides under (subduction) a continental plate. The continental plate is pushed up and a volcano is created
Oceanic – Oceanic
Two oceanic plates converge and the oldest crust is pushed under (subduction). Oceanic trench , under water volcanoes, and volcanic islands are formed.
Continental – Continental
Two continents converge and are pushed up. High mountains are created

15. Oceanic Trenches (No notes on this page)
Probably the most famous trench (for being so deep) is the Mariana trench in the Pacific Ocean.
Its deepest point is about 11,000 m (36,000 ft) below sea level.
That’s 2,000 m deeper than Mount Everest is tall!
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16. Divergent Boundaries (1 of 1)
Plates pull apart and cause cracks to appear on the surface. Magma escapes through the cracks onto the surface. The magma then hardens to form new rock.
Creates:
Mid ocean ridges, rift valleys, new crust, sea floor spreading
Magma hardens to form rock
Magma escapes
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17. Transform Boundaries (1 of 1)
Or Sliding boundaries two plates slide past each other
Lots of stress is put on the rocks causing them to deform and form a crack or fault.
Creates: Earthquakes, deforms crust
San Francisco earthquake 1906
San Andreas Fault, California
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