8th Grade

1
8th Grade

• Social Studies
• Plate Tectonics

2

• Geologists are scientists who study the forces
  that make and shape the planet Earth.
• Geologists study the Earths interior through
  seismic waves.

3

• Geologists discovered the Earth has three
  layers-the crust, the mantle, and the core.
• Continental crust consists of less dense rock
  like granite.
• The upper mantle and crust make up the
  lithosphere.

4

• Heat is transferred in the mantle through
  radiation, conduction, and convection.
• Radiation is the transfer of heat through empty
  space.
• Conduction is heat transfer by direct contact of
  particles of matter.
• Convection is heat transfer by the movement of
  heated liquid.

5

• Alfred Wegener first proposed the theory of
  continental drift.
• Continental drift is Wegeners theory that all
  continents had once been joined together in a
  single landmass and have drifted apart since.
• Wegener named this supercontinent Pangaea.
• Wegeners theory was rejected by scientists
  because he could not explain what force pushes
  or pulls continents.

6
Fossils of tropical plants found on an island
in the Arctic Ocean are evidence for the theory
of continental drift.
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• The mid-ocean ridge is the longest chain of
  mountains.
• Most of the mountains in the mid-ocean ridge lie
  hidden under hundreds of meters of water.
• Hess proposed that the ocean floors move,
  carrying the continents along with them. The
  movement begins at the mid-ocean ridge.
• At the mid-ocean ridge, molten material rises
  from the mantle and erupts.

8
The process that continually adds new material to
the ocean floor is called sea-floor spreading.
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• The lithosphere is broken into separate sections
  called plates.
• The geological theory that states that pieces of
  Earths lithosphere are in constant, slow motion,
  driven by convection currents in the mantle is
  plate tectonics.

10
Faults are breaks in the Earths crust where
rocks have slipped past each other.
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• The place where two plates move apart or diverge
  is called a divergent boundary.
• A transform boundary is a place where two plates
  slip past each other, moving in opposite
  directions.

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• When a divergent boundary develops on land, two
  of Earths plates slide apart.
• A deep valley called a rift valley forms along
  the divergent boundary.
• A convergent boundary is where two plates come
  together, or converge. The result of the plates
  hitting together is called a collision.