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
- ______Fossil Clues____-similar fossils found in South America and Africa and others found in Africa, Australia, India, South America, and Antarctica.
- 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______.
- Climate Clues-______glacier deposits______and rock surfaces shows that parts of South America, Africa, India, and Australia were once covered with ______glaciers______
Quick Check:
- What is Continental Drift? _____The idea that all of the continents were once joined together____________
- 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 the theories of _Continental Drift______and ______Seafloor Spreading______.
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 deep within the mantle provides the ______energy___ that drives plate tectonic
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:
- Explain why Wegener’s theory of Continental Drift was not accepted at first.
- Explain what is Plate Tectonics and what causes the movement of plate tectonics.
- What are the 3 plate boundaries and describe them.