Subduction and plate movement

Subduction and plate movement

5.2 and 5.3 -

plate tectonics and plate boundaries

​Bill Nye explains what we have discussed so far....

• ​Next up --- understanding the process of subduction

• ​sea-floor spreading makes new crust!

• ​subduction destroys old crust!

​Subduction

​A subduction zone is the biggest crash scene on Earth.

​

​It is when two tectonic plates collide.

​What causes subduction?

​If the sea-floor is spreading at mid ocean ridges, and this is ultimately what pushes the continental crust around, then it only makes sense that continental crust will collide at some point.

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​Sometimes continental crust collides with other continental crust.

​

​Other times continental crust may collide with ocean crust.

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​Sometimes ocean crust collides with ocean crust.

​Subduction Zones!

Where two tectonic plates meet at a subduction zone, one bends and slides underneath the other, curving down into the mantle. (The mantle is the hotter layer under the crust.) 

​

​Oceanic crust is denser than continental crust. At a subduction zone, the oceanic crust usually sinks into the mantle beneath lighter continental crust.

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​Where the ocean crust is pulled beneath a deep ocean trench is formed. This is different than a mid ocean ridge.

​Subduction

​* As rock cools it

​becomes more

​dense. Dense rock

​sinks.

​

* ​Old ocean crust is

​more dense than

​young ocean crust.

Multiple Choice

What feature is found at A? 

• deep ocean trench

• mid-ocean ridge

Multiple Choice

What process is occuring at B?

• Subduction

• The sea-floor is spreading

• no process is happening

• I am so confused by all of this.

Open Ended

What results from the process occuring at B ?

Open Ended

What process occurs at C and why does it occur?