1. What Goes On Beneath Our Feet
Plate Tectonics
What Goes On Beneath Our Feet

2. Pull out your colored plates map
Bellwork
Alfred Wegener
Harry Hess
John Tuzo Wilson
What were their contributions to the study of plate tectonics?
Pull out your colored plates map
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3. The Beginning Of Time Time when the earth was born - Precambrian Era.
During this time the continents were joined together in one huge island called Pangea
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4. Alfred Wegener – 1930
In 1910, Noticed the matching coastlines of the Atlantic continents -- they looked on maps like they had once been fit together.
He first spoke on the topic in January of 1912, where he put forth the idea of "continental displacement" or what later was called continental drift.
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5. Harry Hess
Proved Wegener's basic idea correct and clarified the mechanism that broke the once-joined continents into the seven continents.
IMPORTANT - The continents are attached to the plates and do not move independently of them. The plates themselves shift and change shape, carrying the continents along.
In 1960 he hypothesized that the seafloor was spreading from vents in the Rift, where hot magma oozed up.
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6. John Tuzo Wilson
1960's - Refined and the theory of plate tectonics.
Introduced the idea of "hot spots" which remain stationary under the moving plates and produce chains of islands like Hawaii and Japan
First to identify "transform faults" which link trenches (where the plates collide) and rifts (where the plates pull apart)
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7. Know the 7 Major Tectonic Plates of the World
PLATE TECTONICS
Know the 7 Major Tectonic Plates of the World
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8. “Plate Tectonics”. There are about 20 oceanic and continent plates.
Plates float across a layer of soft rock like rafts in a stream, their motions driven by forces generated deep in the Earth.
In addition to the continents drifting, large blocks of heavier ocean floor are also being pushed about the surface of the earth.
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9. Close to Home – Example
The North American and the Eurasian Plates are made of rigid mantle and oceanic and continental crust.
The Mid-Atlantic Ridge is the boundary between the two plates. New oceanic crust is created at the ridge.
The Mid-Atlantic Ridge is an example of a divergent plate boundary. Because the plates are diverging, the distance between North America and Europe is increasing.
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10. Overview - Importance
Here, new land (crust) is born and old land is consumed.
Geologically active: Hot springs spew out mineral-rich waters, volcanoes erupt, and earthquakes tremble -- resulting in devastating tsunamis, floods, and mudslides.
At their boundaries, the plates spread apart, converge, and slide past one another.
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11. Convergent Plate Boundaries
Convergent Plate Boundaries - Regions where plates are pushing together
Oceanic crust toward continental crust
Oceanic crust toward oceanic crust
Continental crust toward continental crust
Compression
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12. Subduction at Converging Boundaries
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13. Ring of Fire (Subduction Zone) found in the basin of the Pacific Ocean
Scraping of one plate on another generates powerful earthquakes
Heating of the plate within the depths of the mantle produces molten rock (magma) that surface as volcanoes.
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14. Volcanoes
Volcanoes are formed when magma makes its way to the surface, accumulates a mountain as it cools and then is a giant mountain of cold magma.
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15. Trenches
Trenches are formed when two plates push toward each other and there is a valley in between the plates.
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16. Mountains
Mountains are formed when two plates collide into each other and cause the land to crinkle and fold.
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17. Divergent Plate Boundaries
The lithospheric plates interact with the neighboring plates in several ways.
Boundaries between plates moving apart:
Divergent oceanic crust – for example, the Mid-Atlantic Ridge
Divergent continental crust - for example, the Rift Valley of East Africa.
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18. Valleys Formed during divergent plate movement How?
Two plates collide together but are not pushed leaving a leaving a depression called a valley
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19. Ridges – Volcanic Mountains
Ridges are formed when the pulling apart of a fault in the ocean floor causes magma or “lava” to ooze through and form a bump on the ocean floor.
Over time looks like a dirt bike track, except its on the bottom of the ocean floor.
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20. Ridge System
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21. Translation at transform boundaries causes shear.
Plate Boundaries
Transform plate boundary: slide past each other.
Example: The San Andreas fault in California (Pacific Plate slides past the North American Plate).
Translation at transform boundaries causes shear.
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22. EARTHQUAKES – Transform Faults
Earthquakes, too, can occur outside of the plate boundaries.
Within the interior of a plate, stresses -- from buckling, stretching, or compression of the rock -- can build up, until the rock finally breaks creating an Earthquake.
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23. Partner Quiz Number your paper 1-20 (Write both names on the paper)
You may use your notes on this quiz.
Partner Quiz
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