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Earths Major Roles

Plate Tectonics

According to the plate tectonicstheory,

the uppermost mantle, along with the

overlying crust, behaves as a strong, rigidlayer. This layer is known as the

lithosphere. A plate is one of numerous rigid sections of the

lithosphere that move as a unit over the material

of the asthenosphere.

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Three Types of

Plate Boundaries

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Spreading Center

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Divergent Boundaries

Actions at Plate Boundaries

Continental Rifts

When spreading centers develop within a

continent, the landmass may split into two

or more smaller segments, forming a rift.

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East African Rift Valley

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Magmatisme Zona Pemekaran

Magma berasal dari lapisan mantle (astenosfer)

Magma muncul melalui rekahan yang dibentuk oleh

pemekaran lantai samudera

Pada suhu yang dingin (pada lantai samudera),magma cair menjadi cepat membeku membentuk

lapisan basalt berstruktur bantal

Zona pemekaran yang telah tertutup lava basalt

menjadi sangat keras sehingga zona pemekaranmencari zona lemah lain secara transform

Magma asal mantel yg tidak mampu ke permukaan

membeku membentuk dike2 peridotit, lapisan gabro

dan dunit

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Transform Fault Boundaries

Actions at Plate Boundaries

At a transform fault boundary, plates grind

past each other without destroying the

lithosphere.

Transform faults

Most join two segments of a mid-ocean ridge.

At the time of formation, they roughly parallel thedirection of plate movement.

They aid the movement of oceanic crustalmaterial.

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Transform Fault Boundary

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Evidence for Plate Tectonics

Testing Plate Tectonics

Paleomagnetismis the natural remnant

magnetism in rock bodies; this permanent

magnetization acquired by rock can beused to determine the location of the

magnetic poles at the time the rock became

magnetized.

Normal polaritywhen rocks show the samemagnetism as the present magnetism field

Reverse polaritywhen rocks show theopposite magnetism as the present magnetism

field

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Paleomagnetism Preserved

in Lava Flows

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Evidence for Plate Tectonics

Testing Plate Tectonics

The discovery of strips of alternating

polarity, which lie as mirror images across

the ocean ridges, is among the strongestevidence of seafloor spreading.

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Polarity of the Ocean Crust

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Evidence for Plate Tectonics

Testing Plate Tectonics

Earthquake Patterns

Scientists found a close link between deep-focus

earthquakes and ocean trenches. The absence of deep-focus earthquakes along

the oceanic ridge system was shown to beconsistent with the new theory.

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Evidence for Plate Tectonics

Testing Plate Tectonics

Ocean Drilling The data on the ages of seafloor sediment

confirmed what the seafloor spreadinghypothesis predicted.

The youngest oceanic crust is at the ridge crest,and the oldest oceanic crust is at the continentalmargins.

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Evidence for Plate Tectonics

Testing Plate Tectonics

Hot Spots A hot spotis a concentration of heat in the

mantle capable of producing magma, which risesto Earths surface; The Pacific plate moves overa hot spot, producing the Hawaiian Islands.

Hot spot evidence supports that the plates moveover the Earths surface.

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Hot Spot