Download Figure 01-04 Origin Solar System

Plate Tectonics
• A geological theory that states that pieces of
Earth’s crust are in constant, slow motion,
driven by convection currents in the mantle
• The plates of the lithosphere float on the top of
the asthenosphere
• Convection currents rise in the asthenosphere
and spread out beneath the lithosphere
• Geologists believe this causes plate movement
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Essentials of Geology, 1b–1
Convection Currents: The movement of a fluid,
caused by differences in temperature, that
transfers heat from one part of the fluid to
another
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Essentials of Geology, 1b–2
• Plates are a section of the lithosphere that
slowly moves, carrying pieces of continental
and oceanic crust
• As plates move, they collide, pull apart, or grind past
each other producing spectacular changes in the
earth’s surface.
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Essentials of Geology, 1b–3
Transform Boundary
• A plate boundary where two plates move past
each other in opposite directions
• Crust is neither created nor destroyed
• Fault lines are usually created in which
earthquakes happen
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Essentials of Geology, 1b–4
Figure 1-13 Transform Motion
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Essentials of Geology, 1b–5
Geology at a
Glance
Plate Boundaries
(cont'd)
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Essentials of Geology, 1b–6
Convergent Boundaries
• A plate boundary where two plates move
toward each other
• Collisions can occur between:
– oceanic crust and oceanic crust (subduction)
• deep ocean trenches
– oceanic crust and continental crust
• volcanic eruptions
– continental crust and continental crust
• mountain ranges
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Essentials of Geology, 1b–7
Geology at a Glance Plate Boundaries (cont'd)
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Essentials of Geology, 1b–8
Figure 1-12a Continental Collision
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Essentials of Geology, 1b–9
Figure 1-12b Continental Collision (cont'd)
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Essentials of Geology, 1b–10
Figure 1-11 Plate Subduction
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Essentials of Geology, 1b–11
Divergent Boundaries
• A plate boundary where two plates move away
from each other
• Most divergent boundaries occur at the midocean ridge
• Divergent boundaries that occur on land are
called rift valleys
• Ocean Basins are usually the result of this type
of movement
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Essentials of Geology, 1b–12
Geology at a Glance Plate Boundaries (cont’d)
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Essentials of Geology, 1b–13
Summary of Boundaries
• Transform
– Plates slip past each other (grind)
• Convergent
– Plates come together (collide)
• Divergent
– Plates move apart (pull apart)
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Essentials of Geology, 1b–14
Geology at a Glance Plate Boundaries
Major Plates
• Six major plates:
–
–
–
–
–
–
Eurasian
African
Indo-Australian
Pacific
North American
South American
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Essentials of Geology, 1b–16
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Essentials of Geology, 1b–17