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?