7.3 Plate Tectonics
Dec 13, 2015
7.3 Plate Tectonics
The Theory of Plate Tectonics Plate Tectonics – the theory that explains
how large pieces of the Earth’s outermost layer called tectonic plates, move and change shape.
Tectonic Plate Boundaries
Boundary – a place where tectonic plates touch.
There are three different types of boundaries: Convergent Divergent Transform
Convergent Boundaries
Convergent Boundary – the boundary formed by the collision of two lithospheric plates.
There are three different types of convergent boundaries: Oceanic – Oceanic Oceanic – Continental Continental - Continental
Oceanic – Oceanic Plate Boundaries http://geology.com/nsta/convergent-boun
dary-oceanic-oceanic.gif
Oceanic – Oceanic Convergent Boundary Normally one of the oceanic plates will
subduct below the other. The older plate is usually the one that gets
pushed down because it has a greater density. Eventually magma is formed because of the
increased pressure causing volcanoes to form over the top of the layer. Eventually the volcanoes will peak out of the
water and if they continue to grow the will form island chains. Ex. Japan
Oceanic – Oceanic Plate Boundary
Continental – Oceanic Plate Boundaries “Mt. Adams” http://geology.com/nsta/convergent-boun
dary-oceanic-continental.gif
Continental – Oceanic Plate Boundaries When the two plates collide the less
dense continental plate will rise up on top of the more dense oceanic plate. The subducted plate will become molten
due to the increase in temperatures. The magma will then rise because it is less
dense than the mantle that is surrounding it. As the magma rise it will cause volcanic and
earthquake activity.
Continental – Oceanic Plate Boundaries
Continental – Continental Plate Boundaries http://geology.com/nsta/convergent-boun
dary.gif
Continental – Continental Plate Boundaries The process in which two land masses
collide together. Normally the landmass that is the least dense will subduct only slightly below the other. Mountains will form because the two
colliding plates are very light in comparison to the mantle.
Divergent Plate Boundaries
Divergent Boundary – the boundary between two tectonic plates that are moving away from each other. New Sea floor forms at divergent
boundaries. Mid-ocean ridges is the most common type
of divergent boundary.
Divergent Plate Boundaries
Transform Boundaries
Transform Boundary – The Boundary between tectonic plates that are sliding past each other.
Ex. San Andreas Fault in California. One of the few faults that can be visibly
seen. One of the major causes of Earthquakes.
Output: Pushing and Pulling Mountains Draw an example of the five different
plate boundaries. Label and describe what happens at
each different plate boundary.
Transform Plate Boundaries
Plate Summary
Possible Causes of Tectonic Plate Motion Asthenosphere flows very slowly. This movement occurs because of the
change in density within the asthenosphere. Density changes because of the outward
flow of energy within the Earth. Hot rock expands and rises.(Less Dense) Cool rock contracts and sinks. (More Dense)
Possible Causes of Tectonic Plate Motion
Tracking Tectonic Plate Motion Tectonic plates move roughly 5cm per
year. The rate is so slow that it cannot be seen
nor felt except during an Earthquake. Plate movement is tracked by GPS.