Constructive Force Constructive Force 11A Plate TectonicsA Plate Tectonics

1)Alfred Wegener hypothesized 1)Alfred Wegener hypothesized that all of the continents were that all of the continents were once connected to form one once connected to form one large land mass called Pangaea. large land mass called Pangaea.

Evidence of Continental drift Evidence of Continental drift 22

a)a)As a student, and scholar As a student, and scholar he saw the globe as a he saw the globe as a broken jigsaw puzzle.broken jigsaw puzzle.

Evidence for Continental Drift Evidence for Continental Drift 33 b)b)as a scholar, he collected samples of as a scholar, he collected samples of fossils from all over the world. What he fossils from all over the world. What he found was that a fossil found on one found was that a fossil found on one continent could also be found on continent could also be found on another continent usually near the another continent usually near the shore .shore .

Evidence for Continental Drift Evidence for Continental Drift 44

c) c) he discovered deep he discovered deep scratches in rock on the scratches in rock on the shores of South Africa. He shores of South Africa. He identified these as caused by identified these as caused by glaciers.glaciers.This shows Climate changeThis shows Climate change

More evidence More evidence 55

d) d) Alfred also discovered coal Alfred also discovered coal deposits at exactly the same deposits at exactly the same depth and type located near the depth and type located near the same latitude but across the same latitude but across the ocean from each other.ocean from each other.

What Wagoner couldn’t What Wagoner couldn’t 6 6answeranswer

What force is large enough What force is large enough to split and move to split and move continents apart from each continents apart from each other?other?

Advances in Technology Allow Advances in Technology Allow 77 More Accurate ObservationsMore Accurate Observations

Sonar developed in WWII is used in Sonar developed in WWII is used in 1950 to continue mapping the ocean 1950 to continue mapping the ocean floor. floor.

An underwater ridge is discovered that An underwater ridge is discovered that that encompasses the Earth. that encompasses the Earth.

A new question is asked. A new question is asked.

What is this underwater ridge? What is this underwater ridge? 88

More observations were More observations were needed before a hypothesis needed before a hypothesis could be formed.could be formed.

Drilling begins Drilling begins 99

Scientists begin to drill into the ocean Scientists begin to drill into the ocean floor near the ridge to study rock floor near the ridge to study rock samples to see if they could learn samples to see if they could learn anything about the ocean floors and the anything about the ocean floors and the ridge that ran through them.ridge that ran through them.

What is learned through What is learned through 1010drilling and rock samplesdrilling and rock samples

The ocean floor is made of basalt!The ocean floor is made of basalt! The farther away from ridge the older The farther away from ridge the older

the rock!the rock! What does this tell you ?What does this tell you ? What is this underwater ridge?What is this underwater ridge? HypothesizeHypothesize ModelModel

Three types of heat transfer Three types of heat transfer 1111Which of these three types of heat transferWhich of these three types of heat transfer

can cause the plates to move?can cause the plates to move?

ExplainExplain RadiationRadiation ConductionConduction ConvectionConvection

However this can’t be the only force. Can you findHowever this can’t be the only force. Can you find

other forces that would cause the plates toother forces that would cause the plates to

move?move?

2) Plate movements 2) Plate movements 1212 a)Translationa)Translation- - When two plates slide past each When two plates slide past each

each-other in opposite directions.each-other in opposite directions. 1) The place where these plates 1) The place where these plates

meet are called a transform meet are called a transform boundaryboundary

IE. The San Andreas Fault in CA.IE. The San Andreas Fault in CA.

b) Converging plates b) Converging plates 1313Where the two plates are Where the two plates are

collidingcollidingThe boundary where the two The boundary where the two

plates meet is called a plates meet is called a convergent boundaryconvergent boundary

IE. The island of Japan and the IE. The island of Japan and the country of Icelandcountry of Iceland

c) Subduction c) Subduction 1414When one plate moves When one plate moves

underneath another plate. This underneath another plate. This happens because one plate is happens because one plate is denser and therefore heavier denser and therefore heavier than the other. This is most than the other. This is most likely to happen when an likely to happen when an oceanic plate collides with a oceanic plate collides with a continental plate.continental plate.

d)Spreading- d)Spreading- 15 15Spreading is when two Spreading is when two plates move apart from plates move apart from each-othereach-other

1)divergent boundaries is 1)divergent boundaries is the point at which the two the point at which the two plates are moving away plates are moving away from each -other.from each -other.

Example of spreading Example of spreading 1616

Africa’s Great Rift Africa’s Great Rift Valley (on land)Valley (on land)

Mid-Oceanic Ridge Mid-Oceanic Ridge (under the ocean)(under the ocean)

Plate movements below Plate movements below 1717 create landforms abovecreate landforms above

Diverging platesDiverging plates

Continental crust away from continentalContinental crust away from continental

crust crust = Rift valley= Rift valley

Oceanic crust away from oceanic crust Oceanic crust away from oceanic crust ==

Mid ocean ridgeMid ocean ridge

Plate movements below Plate movements below 1818 create landforms abovecreate landforms above

Converging platesConverging plates

Continental crust into continental crust Continental crust into continental crust ==

Fault block mountains, folded mountainsFault block mountains, folded mountains

Continental crust into oceanic crust Continental crust into oceanic crust ==

Coastal and Volcanic mountains, ocean trenchCoastal and Volcanic mountains, ocean trench, ,

Plate movements below Plate movements below 1919create landforms abovecreate landforms above

Translating platesTranslating plates

Folded hills, riverbed offsets.Folded hills, riverbed offsets.

No new crust is created or No new crust is created or destroyed.destroyed.

Final slideFinal slide

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