Earth

1
Earths Movement

• Plate Tectonics and Faults

2
Pangaea

• Approximately 200 million years ago Earth's land
  was grouped together in one large super-continent
  named Pangaea.

http//pubs.usgs.gov/gip/dynamic/historical.html
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Jurassic Cretaceous Periods

• Pangaea began to break apart during the Jurassic
  Period.

http//pubs.usgs.gov/gip/dynamic/historical.html
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Present Day
http//pubs.usgs.gov/gip/dynamic/historical.html
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Notice the shape of South America and Africa. Can
you picture how these two land masses fit
together like a puzzle?
6
Evidence

• Scientists have found evidence that the
  continents are moving in fossils. For example,
  fossils of tropical plants were found in
  Antarctica which led to the conclusion that this
  frozen land had previously been closer to the
  equator.

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Fossil Evidence
http//pubs.usgs.gov/gip/dynamic/continents.html
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Plate Tectonics

• Plate Tectonics is a theory that was developed in
  the 1960's. This theory states that Earth's top
  layer called the crust is divided into plates
  that are moving at a speed of 1 to 10 cm per
  year.

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Tectonic Plates
http//pubs.usgs.gov/gip/dynamic/slabs.html
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Another Picture of the Tectonic Plates
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Fault

• The breaks in the Earths crust where the plates
  meet (push together, pull apart, and slide beside
  each other) are called faults.

12
Plate Movement

• The plates move in three ways
• Divergent Plate Movement ?  ?
• Convergent Plate Movement  ?  ?
• Transform Plate Movement or Lateral Slipping
  Plate Movement ??

13

• Divergent Plate Movement ?  ?
• Convergent Plate Movement  ?  ?
• Transform Plate Movement or
• Lateral Slipping Plate Movement ??

14
Mid-Ocean Ridges

• Mid-Ocean Ridges are places where the Earth's
  tectonic plates are gradually moving apart. As
  the plates move apart, magma rises up to fill the
  gap. This can cause undersea volcanic eruptions.
• This shallow magma provides a heat source that
  creates many seafloor hot springs along the
  ridges which transport heat and chemicals into
  the ocean.

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Mid-Ocean Ridge
http//pubs.usgs.gov/gip/dynamic/baseball.html
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Activity

• You will be given a piece of waxed paper. On
  the wax paper spread a spoonful of icing about a
  half of a centimeter thick. The icing represents
  the magma that is under the Earths crust. Next
  you will be given two squares of fruit rollups.
  Place the two squares of fruit rollup onto the
  frosting right next to each other. These
  represent oceanic plates. Press down slowly on
  the fruit rollups because oceanic plates are
  dense and will sink a bit. Slowly push the
  plates apart about half a centimeter. Notice
  how the frosting is exposed and pushed up where
  the plates are separated. This is how magma comes
  to the surface where real plates are moving apart
  at divergent plate boundaries.

17
Volcanic Activity

• The black dots represent volcanic activity.
  Notice that most of these are along the edges of
  the plates. These are called fault lines.

http//pubs.usgs.gov/gip/dynamic/zones.html
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Earth Gains New Crust

• On divergent plate boundaries new crust is being
  formed as magma escapes from the Earth's core. In
  other locations under the ocean are deep
  trenches.

19
Earth Loses Old Crust

• Scientist believe these deep trenches are where
  the old crust is being lowered back into the
  Earths core.
• This cycle is known as the Wilson Cycle, named
  after John Tuzo Wilson.

20
Wilson Cycle

• The cycle, beginning with new crust being formed
  to the old crust returning to the Earth's core,
  takes approximately 100 million years.

21

• Continents do not fall back into the Earth's
  core, so land masses are much older than the
  Earths crust beneath the ocean.

22
Points to Remember

• When plates move apart, volcanoes may form.
• ?  ?

23
? Divergent ?

• 2 Oceanic Plates
• Submarine mountain ranges
• Volcanic activity
• Earthquakes
• New seafloor
• 2 Continental Plates
• Rift valley
• Earthquake activity
• Volcanic activity sometimes occurs

24
Convergent Plate Movement  ?  ?

• Convergent boundaries are where plates are moving
  toward each other.
• The outcome of convergent plate movement varies
  depending on the types of plates that meet
• OceanicOceanic
• Oceanic-Continental (Land)
• Continental-Continental or (Land-Land)

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Vocabulary

• Lithosphere - outermost layer of the earth's
  crust is broken up into large solid plates
  called tectonic plates - about 40 - 250 miles
  deep
• Asthenosphere - part of the earth just below the
  lithosphere - not liquid but there is a small
  amount of melted rock there - 250 - 435 miles
  thick
• Subduction - the process that takes place at
  convergent boundaries ?  ? in which one tectonic
  plate moves under the other

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Oceanic-Oceanic Convergence

• When two oceanic plates collide, one is pushed
  under the other and magma from the mantle rises,
  forming volcanoes.

http//pubs.usgs.gov/gip/dynamic/understanding.htm
l
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Lava Flow

• In some cases the magma calmly erupts. The lava
  emerges and cools forming new crust.

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Violent Eruption

• In other cases the volcano erupts violently
  sending dust and ash into the sky.

29
Calderas

• In other cases the area above the volcano has
  cracks which release gases usually during a
  volcanic eruption. As the gases release the
  emptied chamber can no longer support the weight
  of the earth above it. The earth falls into this
  void leaving deep craters called calderas.

30
Crater Lake

• One famous example of a caldera is North
  Americas Crater Lake located in Southern Oregon.
  Around 7,000 years ago a massive volcanic peak
  reaching 12,000 feet in elevation set in this
  location. A powerful eruption blasted the top
  4,000 feet away, leaving a deep bowl shaped
  caldera. Since that
• time, a new dome has begun to form in the
  center of
• the caldera.

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• The factor that determines the type of eruption
  is the amount of silica that is in the lava.
  Silica is a very common mineral composed of
  silicon and oxygen (SiO2). Silicates makes up
  about 95 of the Earths crust. Volcanoes rarely
  change the type of eruption that occurs.

32
Activity

• Slide the two pieces of fruit rollups
  together. Notice that one piece slides under the
  other. A hump forms where the two pieces hit.
  Volcanic mountain building occurs when two
  oceanic plates meet.

33
Oceanic-Continental Convergence

• When an oceanic plate pushes against a
  continental plate, the oceanic plate moves under
  the continental plate.

http//pubs.usgs.gov/gip/dynamic/understanding.htm
l
34
Activity

• Remove one of the fruit rollups from the
  frosting. (You may eat it.) Place one of the
  graham cracker halves lightly onto the frosting
  next to the remaining fruit rollup piece. The
  graham cracker represents the continental crust,
  which is thicker and less dense than oceanic
  crust (fruit rollup). It floats high on the
  asthenosphere (upper mantle of the Earth) so
  don't push it down. Gently push the continent
  (graham cracker) towards the ocean plate (fruit
  rollup) until the two overlap, and the graham
  cracker is on top. The oceanic plate is subducted
  below the continental one.

35

• When an oceanic plate meets a continental (land)
  plate usually an oceanic trench will develop on
  the ocean side and a mountain range on the
  continental side.

36
Continental-Continental Convergence

• When two continental plates collide, mountain
  ranges are created as the crust is pushed
  upwards. You can feel this movement through
  earthquakes.

http//pubs.usgs.gov/gip/dynamic/understanding.htm
l
37
Activity

• Remove both the cracker and fruit roll up
  from the frosting asthenosphere. Place one edge
  of both crackers into the glass of water for just
  a few seconds. Place the crackers onto the
  frosting with wet edges next to each other.
  Slowly push the graham crackers towards each
  other. Notice how the wet edges crumple. This is
  how mountains are made at convergent plate
  boundaries! When continents move towards each
  other there is nowhere for the rock to go but up!

38
Point to Remember

• When two plates move towards each other mountains
  form.
• ?  ?

39
? Convergent ?

• Oceanic and Continental Plates
• Earthquake activity
• Sometimes ocean trench
• Volcanoes
• Destruction of oceanic lithosphere
• 2 Oceanic Plates
• Earthquakes
• Oceanic trench
• Destruction of oceanic lithosphere
• 2 Continental Plates
• Folding and faulting
• Mountain ranges
• Earthquake activity
• Shortening of plates

40
Transform Plate Movement or Lateral Slipping
Plate Movement ??

• When two plates move sideways against each other,
  there is a tremendous amount of friction which
  makes the movement jerky. This is known as an
  earthquake.

41
Activity

• Pick the two crackers up off the frosting and
  turn them around so that two dry edges are next
  to each other.
• Push one cracker past the other to simulate a
  transform plate boundary like the San Andreas
  fault!

42
Point to Remember

• When two plates move past each other earthquakes
  are likely to happen.
• ? ?

43
?Transform Boundary?

• Recurring earthquake activity
• Volcanic activity

44
Review

• Divergent Plate Movement ?  ?
• Convergent Plate Movement  ?  ?
• Transform Plate Movement or Lateral Slipping
  Plate Movement ??

45
http//pubs.usgs.gov/gip/dynamic/Vigil.html
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http//pubs.usgs.gov/gip/dynamic/world_map.html
47
Ring of Fire

• The Ring of Fire is a chain of volcanoes and
  oceanic trenches. Seventy-five percent of Earths
  volcanoes are in the Ring of Fire.

http//pubs.usgs.gov/gip/dynamic/fire.html
48
http//pubs.usgs.gov/gip/dynamic/Farallon.html