The Earth in Motion

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The Earth in Motion
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• Our lithosphere is made up of many large plates
  Oceanic and Continental
• The plates are moving several cm/yr.
• As the plates move, the continents also move or
  drift, over Earths surface.
• German Scientist, Alfred Wegener , used fossil
  evidence to prove the continents were drifting
  and once formed a massive supercontinent called
  Pangea.

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Continued

• The idea that the plates are in constant slow
  motion (drifting) is known as continental drift.

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Rock Stress

• The movement of Earths plates creates powerful
  forces that squeeze or pull the rock in the
  crust.
• These forces cause a stress on the rock.
• Shearing, tension, and compression work over time
  to change the shape and volume of rock.

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Plate Tectonics

• The motion of the plates also explains how they
  interact producing
• mountain ranges (uplift), earthquakes, volcanoes,
  and features on the ocean floor.

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Uplift

• The forces of plate movement can build up Earths
  surface. Over millions of years, fault movement
  can cause uplift, changing a flat plain into a
  towering mountain range or plateau.

Mt. Everest in the Himalayas
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• Earthquakes are a reminder that the Earths crust
  is in constant motion.
• An earthquake is what happens when two blocks of
  the earth suddenly slip past one another.  The
  surface where they slip is called the fault or
  fault plane.

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Volcanoes

• During a volcanic eruption, the gases dissolved
  in magma rush out, carrying the magma with them.
  Once magma reaches the surface and becomes lava,
  the gases bubble out.

• An erupting volcano can trigger tsunamis,
  flashfloods, earthquakes, mudflows and rock
  falls.

website
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Volcano Hazards

• During a quiet eruption, lava flows pour from
  vents, setting fire to and then burning
  everything in their path.
• During an explosive eruption, a volcano can belch
  out hot, burning clouds of volcanic gas, ash,
  cinders, and bombs.

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Stages of a Volcano

• An active, or live, is one that has erupted
  recently or volcanologists see the possibility of
  an eruption soon. Active volcanoes are watched
  very closely!

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• A dormant, or sleeping, volcano is like a
  sleeping bear it has been quiet for a long time,
  but still has signs it may erupt again. A volcano
  becomes dormant when the vent is blocked by
  hardened lava, called a plug, or if the magma
  seeps back under the earths crust.

Mt. St. Helens after 5/18/80
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• An extinct, or dead, volcano is unlikely to erupt
  again. It has not erupted for thousands of years.
  Sometimes it is hard to tell if a volcano is
  dormant or extinct. They will be listed as
  dormant until volcanologists are sure there will
  no more eruptions.

Shiprock, the erosional remnant of the throat of
an extinct volcano. (NM)
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• There are more than 500 active volcanoes in the
  world. More than half of these volcanoes are part
  of the "Ring of Fire."

Kilauea volcano in Hawaii.
Sicily, Italy
Volcanic cone
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• Zone of frequent earthquakes and volcanic
  eruptions that circles the basin of the Pacific
  Ocean. It is associated with a continuous series
  of oceanic trenches, island arcs, volcanic
  mountain ranges and plate movements.