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Plate Tectonics
EQ: How do lithospheric plates move and how do they affect the Earth’s surface?
An Idea Before its Time
 In 1912, _____Alfred Wegener______ proposed the idea of _____Continental Drift________
 He suggested that all of the _________continents___________ were once ___joined_________ together to
form a _______supercontinent____
Pangaea
 Wegener called this super landmass _______Pangaea__________ and believed that it broke apart
___200 million____ years ago
 Pangaea means “_______all land____”
 At first, his theory was ________accepted__________________________

___Unable____ to explain how the continents drifted apart
Evidence down the Road
 Years later came important observations that supported Continental Drift
1. ______Fossil Clues____- similar fossils found in South America and Africa and others found in
Africa, Australia, India, South America, and Antarctica.
2. Rock evidence- similar rock structures are found on different continents, such as this
_____mountain belt_________ that end at one coastline, only to ______reappear______ on a
landmass across the _____ocean______.
3. Climate Clues- ______glacier deposits_______ and rock surfaces shows that parts of South
America, Africa, India, and Australia were once covered with _________glaciers_____________
Quick Check:
1. What is Continental Drift? _____The idea that all of the continents were once joined together_______
_______________________________________________________________________________________________________________
2. What 3 pieces of evidence support the idea of Pangaea? _Fossils, Rock Clues (mountains), Glaciers_
_______________________________________________________________________________________________________________
A New Theory Emerges
 Wegener could not provide an __explanation__ of exactly what made the continents move.
 New _____technology______ lead to findings which then lead to a ____new theory__ called __plate
tectonics__
This New Evidence…
 With new technologies, scientists discovered a _______mountain chain_____ on the ____ocean floor___
known as the ___Mid-Ocean Ridge_______
 Mid-ocean ridges are underwater chains that run through Earth’s ocean basin
Seafloor Spreading
 Mid-ocean ridges are places where the _____________sea floor spreads___________________
 As tectonic plates__________ rises to fill in the gaps
 The hot magma contacts ocean water, cools and hardens becoming new____rock_____
 This process is known as _________Seafloor Spreading_______
Plate Tectonics
 The Theory of Plate Tectonics was developed in 1960s and
combines
_Continental Drift________ and ______Seafloor Spreading________.
the theories of
 Scientist believe the Earth’s __crust___ and part of the __upper mantle___ is broken into 13 sections that
make up the plates which move on top of the ___asthenosphere____
Convection Currents
 Convection currents, originating
drives plate tectonic
deep within the mantle
provides the ______energy___ that
 These currents rotate in ______curricular patterns____, ______carrying heat upward__________
Plate Boundaries
 _____Divergent boundaries_______ are the place where two plates move __apart_.
 ___Convergent boundaries____ form where two plates move _together__.
 ____Transform____ fault boundaries are where two plates _slide___ past each other without the
production or destruction of the lithosphere.
Plate Tectonic Discussion Questions:
1. Explain why Wegener’s theory of Continental Drift was not accepted at first.
2. Explain what is Plate Tectonics and what causes the movement of plate tectonics.
3. What are the 3 plate boundaries and describe them.