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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
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