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Lab 06 ONLINE LESSON. If viewing this lesson in Powerpoint Use down or up arrows to navigate. If viewing this lesson in Flash Use the control bar to navigate. Do take notes as we peruse through this lesson…. Plate Tectonics.
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Plate Tectonics is a geologic idea that states the surface of the planet is covered by a series of rigid plates that move…
Plate Tectonics is driven by heat within the interior of the planet…
A current theory suggests that radioactive materials are the source for the earth’s internal heat…
Melted rock (magma) rises to the surface and pushes the plates…
A divergent boundary is also referred to as a spreading center, such as the Mid Atlantic Ridge…
A divergent boundary is a part of the earth’s surface where new crust is formed…
Subduction is the process of pushing seafloor crust into the interior of the planet…
A convergent boundary is where crust is destroyed and massive earthquakes occur…
A transform boundary is also known as a fracture zone or fault…
The San Andreas Fault is a well known transform fault in this area…
Earthquakes occur at all of these boundaries because solid rock is moving against solid rock…
The bigger earthquakes occur at the convergent and transformboundaries…
But small and shallow earthquakes can occur at transform and divergentboundaries…
Shallow earthquakes occur at divergentboundaries because the crust is thin… 5 -10 km thick…
The following is a map of many divergent, convergent and transformboundaries…
Plate Tectonics can be thought of as a grand unifying theory in geology…
Meaning that many geologic phenomena are associated with Plate Tectonics
At convergent boundaries …volcanoes, earthquakes and mountains and deep sea trenches can be formed…
Also at convergent boundaries …the deepest earthquakes occur
Subducted seafloor is pushed into the interior of the planet….
At divergent boundaries …heat, volcanoes, earthquakes and new seafloor can be formed…
Since new seafloor is formed at the divergentboundaries…the notion of seafloor spreading can also be observed…
Seafloor crust is made primarily of iron rich (MAFIC) minerals
These MAFIC minerals are subject to the earth’s magnetic field…
The newly formed MAFIC crust can record the prevailing magnetic field
The earth’s magnetic field has changed direction over the course of the life of the planet