Plate Tectonics The Theory of. What are tectonic plates?
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Transcript of Plate Tectonics The Theory of. What are tectonic plates?
Plate TectonicsPlate TectonicsThe Theory of
What are tectonic plates?What are tectonic plates?
What are tectonic plates?What are tectonic plates? lithosphere- the crust and rigid upper
layer of the mantle, broken up into blocks called tectonic plates
3 types of tectonic plates (a.k.a. crust)1) Continental crust = low-density silicate
rock (granite)2) Oceanic crust = dense, Iron/Mg rich
rock (basalt)3) A combination of continental and
oceanic
Where are tectonic plates found?Where are tectonic plates found?
The plates are Earth’s shell; but unlike an eggshell, these pieces are always being created, destroyed, or moved
How is plate movement explained?How is plate movement explained? The theory of plate tectonicsThe theory of plate tectonics- How - How
ttectonic plates move around on a plastic layer of the mantle called the asthenosphere
“Plastic”- like nacho cheese, pudding, or syrup
Where is plate movement Where is plate movement happening?happening?
Where is plate movement Where is plate movement happening?happening?Where one plate ends and another plate
begins; cracks in the lithosphere mark plate
boundaries
What are the 3 plate boundaries? What are the 3 plate boundaries? There are 3 kinds of boundaries:Divergent
= spreading boundaries
Convergent
= colliding boundaries
Transform
= sliding boundaries
What are mid-ocean ridges?
What are mid-ocean ridges?Divergent = spreading boundaries Mid-ocean ridge- An undersea mountain
range with a rift valley running through the center of it
Hot magma rises to the surface, cools as rock, and the new crust spreads out
60 foot-wide60 foot-wideboundaryboundaryof the N. Americanof the N. Americanand Eurasian platesand Eurasian plates
Mid-ocean ridges = rift zones
Rift- cracks in the center of a ridge where magma, which is less dense than rock, flows upward
Mid-ocean ridges = rift zones Rifting causes new crust to push the older crust Rifting causes new crust to push the older crust
aside; they are divergent, or spreading, boundariesaside; they are divergent, or spreading, boundaries
What is paleomagnetism?Iron inside the Earth makes Earth a giant
magnet
When hot magma cools off, the bits of iron in the crust will point to the poles like a compass needle
Paleomagnetism = Earth’s magnetic memory
Iron in new crust pushes the older crust aside; they Iron in new crust pushes the older crust aside; they record their polar-charge for thousands of yearsrecord their polar-charge for thousands of years
The magnetic poles have reversed in the past, and the rocks on the sea-floor show this change
Proof for the Theory of Plate Tectonics:
Recording movement at plate boundaries Recording movement at plate boundaries (earthquakes)(earthquakes)
Studying how magma forms new crust at rift valleys Studying how magma forms new crust at rift valleys and mid-ocean ridges (rifting)and mid-ocean ridges (rifting)
Observing that many volcanoes are occurring near Observing that many volcanoes are occurring near plate boundaries, such as, the Ring of Fireplate boundaries, such as, the Ring of Fire
What is the Ring of Fire?
What is the Ring of Fire?A zone of active volcanoes and earthquakes A zone of active volcanoes and earthquakes
that marks the Pacific Plate boundary that marks the Pacific Plate boundary Deep- point that goes very far down into the
crust Trench- steep, narrow valley where a plate ends
For your summary answer…
What are tectonic plates made of?What are tectonic plates made of? What are the 3 types of boundaries?What are the 3 types of boundaries? What is paleomagnetism?What is paleomagnetism?
ResourcesResources WikipediaWikipedia http://images.google.com/imgres?http://images.google.com/imgres?imgurl=http://mensa-barbie.com/imgurl=http://mensa-barbie.com/bloggerimages/MB_Leif_luck_bridge_tectonbloggerimages/MB_Leif_luck_bridge_tecton%2520copy.JPG&imgrefurl=http://mensa-%2520copy.JPG&imgrefurl=http://mensa-barbie.blogspot.com/barbie.blogspot.com/2007_03_01_archive.html&usg=__AjtDMB4aNJ2007_03_01_archive.html&usg=__AjtDMB4aNJNetWXC-NetWXC-b0hnRWFnrM=&h=272&w=425&sz=33&hl=eb0hnRWFnrM=&h=272&w=425&sz=33&hl=en&start=3&um=1&itbs=1&tbnid=Gm8U8eb0n&start=3&um=1&itbs=1&tbnid=Gm8U8eb0aJOB-M:&tbnh=81&tbnw=126&prev=/imagesaJOB-M:&tbnh=81&tbnw=126&prev=/images%3Fq%3DBridge%2Bacross%2Bthe%2B%3Fq%3DBridge%2Bacross%2Bthe%2B%25C3%2581lfagj%25C3%25A1%2Brift%25C3%2581lfagj%25C3%25A1%2Brift%2Bvalley%26um%3D1%26hl%3Den%26sa%2Bvalley%26um%3D1%26hl%3Den%26sa%3DN%26rlz%3D1R2GWYE_en%26%3DN%26rlz%3D1R2GWYE_en%26tbs%3Disch:1
What is the Ring of Fire?A zone of active volcanoes and earthquakes A zone of active volcanoes and earthquakes
that marks the Pacific Plate boundary that marks the Pacific Plate boundary Deep- point that goes very far down into the
crust Trench- steep, narrow valley where a plate ends
Warm up
1) Describe one part of this figureor, describe a part that you do not understand.
2) What do you think is a good title for this figure?3) How many plate boundaries do you see?