6th Grade

1
6th Grade

• Science
• 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.
• The oceanic crust beneath the ocean consists
  mostly of dense rock like basalt.
• Continental crust consists of less dense rock
  like granite.
• The upper mantle and crust make up the
  lithosphere.
• The asthenosphere is a soft layer that can bend
  like plastic.

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.

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The process that continually adds new material to
the ocean floor is called sea-floor spreading.
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• The ocean floor plunges into deep underwater
  canyons called deep-ocean trenches.
• Subduction takes place in deep-ocean trenches.
• Subduction is the process by which the ocean
  floor sinks beneath a deep-ocean trench and back
  into the mantle.

10

• 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.

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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.

13

• 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.