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Plate Tectonics - Types of Movement
Transcript of Plate Tectonics - Types of Movement
Types of Plate Movement at Plate Boundaries To Supplement "Plate Tectonics Rocks"
A Lesson by Mary Curtis and Brittany Heller So, the Earth has plates and they...MOVE?!? That's right! There are currently seven major plates and many minor plates that make up the lithosphere (or top layer of the Earth's crust) of the Earth. Take a look... http://www.windows2universe.org/earth/images/earth_plates_usgs_L_2_jpg_image.html So, how do they move? Any ideas? Simply put, the top layer of the Earth's crust (or lithosphere) "glides" over the underlaying asthenosphere (the upper part of the mantle). Now, you can imagine that if each plate is gliding over the asthenosphere individually, there would be collisions, right? Yes! When plates collide with one another, the result is usually some type of tectonic activity. Tectonic activity is a fancy term for volcanoes, earthquakes, mountain-building, mid-ocean ridges, and oceanic trenches. Collisions happen at plate boundaries - The composition of each plate and the direction in which each plate is moving will determine what the end result will be when two plates collide. Now, get your pencils... The three types of movement are:
Transform Let's start with convergent boundaries:
Continental-Continental convergence Oceanic-Oceanic Convergence
One plate is subducted under the other
A Deep oceanic trench is formed (Example: Marianas trench)
Under-sea volcanoes form island arcs
Over millions of years, the volcano will surface to form a volcanic island Oceanic-Continental Convergence
Oceanic Plate is subducted under continental plate due to age and density
overriding continental plate is lifted up and a volcanic mountain range is created
Example: The Andes Continental-Continental Convergence
Neither plate is subducted - Relatively same composition, density, and age
Crust tends to buckle and be pushed upward or sideways creating enormous mountain ranges
Example: The Himalayas Now, let's talk about Divergent Plate Boundaries...
Diverging Plate Boundary (Oceanic)
New crust is created
Oceans are born and grow wider
Oceanic ridge is created
Example: Mid-Atlantic Ridge Divergent Plate Boundary (Continental)
When two or more plates diverge on land, a rift forms
Land will eventually break apart
Oceans will fill the gaps between the broken apart land masses
Example: African Rift Valley So, who remembers the last type of plate boundary?
...It starts with a T... Good! Transform Plate Boundary
Occurs when two plates slide horizontally past one another in opposite directions
Also known as Transform Fault boundaries or more commonly, just simply Faults
Most are found on the ocean floor
Often accompanied by shallow earthquakes
Example: San Andreas Fault Graphic courtesy of USGS.org Graphic courtesy of USGS.org Graphic courtesy of USGS.org Graphic courtesy of USGS.org Graphic courtesy of USGS.org http://www.gweaver.net/techhigh/projects/period1_2/Yellowstone/Plate%20Tectonics.html So, let's review...
What are the three types of plate boundaries?
Are you able to provide examples for each?
Do you have any questions about what was presented?