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Movements of the Earth

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... Molten Rock, from the asthenosphere, move up to fill the gaps between the 2 plates and form new crust. ... Plates float along this heated flowable material. – PowerPoint PPT presentation

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Title: Movements of the Earth


1
Movements of the Earths Crust

2
Continental Drift
  • Alfred Wegener proposed the hypothesis of
    continental drift
  • The idea the continents were all together at one
    point and drifted to their present locations
  • Pangaea Name of all land masses
  • Panthalassa Water surrounding Pangaea

3
Pangaea

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What is the Evidence?
  • Similarities of the coastlines
  • Fossils of plants and animals in parts of Pangaea
    that had been joined
  • Types of rocks and rock layers on the coastal
    region of formerly adjoined parts
  • Changes in climate patterns
  • Glacier Records

6
Fossil Evidence

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Rock Similarities



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Coastline Similarities


9
Theory of Plate Tectonics

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Plate Tectonics
  • There are two types of crust- oceanic and
    continental
  • There are 30 plates on the earths surface
  • The plates are chunks of lithosphere that float
    on the asthenosphere
  • Lithosphere Crust and the upper mantle
  • Asthenosphere Layer of plastic rock

11
Rules of Plate Tectonics
  • 1. Continental crust is less dense, or lighter,
    than Oceanic crust so it doesn't sink. It is
    never destroyed and is permanent.
  • 2. Oceanic crust is heavier so it can sink below
    Continental crust. It is constantly being formed
    and destroyed at ocean ridges and trenches.
  • 3. Continental crust can carry on beyond the
    edges of the land and finally end far below the
    sea. This explains why the edges of all the
    continents don't have deep trenches right up
    against their coastlines.
  • 4. Plates can never overlap. This means that they
    must either collide and both be pushed up to form
    mountains, or one of the plates must be pushed
    down into the mantle and be destroyed.

12
Rules of Plate Tectonics Continued
  • 5. There can never be gaps between plates, so if
    two plates move apart, as in the middle of the
    Atlantic, new rock will be formed to fill the
    space.
  • 6. We know the Earth isn't getting bigger or
    smaller, so the amount of new crust being formed
    must be the same as the amount being destroyed.
  • 7. Plate movement is very slow. This is partly
    why Wegener's original ideas were ignored. Nobody
    could 'see' the continents moving. When the
    plates make a sudden movement we call it an
    Earthquake, and it's the only time we are
    directly aware of the plates moving.

13
Plates of the World
14
Types of Crust
  • Crust very thin outer layer of the earth
  • Oceanic crust is more dense, heavier, and younger
    than continental crust

15
Types of Plate Boundaries

Draw these pictures in your notes
16
Diverging Plate Boundary
  • In most cases, there is seafloor spreading
    occurring at this type. Two plates moving away
    from each other,
  • Molten Rock, from the asthenosphere, move up to
    fill the gaps between the 2 plates and form new
    crust.
  • Rift Valley Narrow valley formed when plates are
    separating

17
Diverging Boundary


18
Seafloor Spreading

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Rift Valley

20
Convergent Plate Boundaries
  • Two plates colliding and one is being
    subducted under another.
  • Subduction Zone one plate moving under another
  • Ocean Trench generally forms along a
    subduction zone
  • Mountain Ranges
  • Island Arc chain of volcanic islands

21
Converging Boundary


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Oceanic-Oceanic Converging

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Oceanic-Continental Converging

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Continental-Continental Converging

25
Transform Plate Boundary
  • Two plates grinding past each other.
    Earthquakes occur here.

26
Transform Plate Boundary

27
What Causes Plate Motion?
  • Most think that the major reason for plate
    movement is due to convection.
  • Convection Current formed by hot rock formed in
    the asthenosphere rising and the cold material at
    the surface falling to replace the rising
    material.
  • Plates float along this heated flowable material.

28
Convection Currents
29
Compositional Layers of the Earth
  • Crust
  • Mantle
  • Outer Core
  • Inner Core

30
Mechanical Layers of the Earth
  • Lithosphere
  • Asthenosphere
  • Mesosphere
  • Outer Core
  • Inner Core

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Earthquakes
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  1. When rock fragments move, they release energy in
    the form of seismic waves.
  2. The point where the earthquake occurs is called
    the focus.
  3. The point on the surface that is directly above
    the focus is the epicenter.
  4. Most earthquakes have a shallow focus because
    other focuses loose energy before it reaches the
    surface.

40
ANSS Recent Earthquakes in the US
41
Three major earthquake zones

42
Pacific Ring of Fire
  • West coast of north/south America
  • Along here, most plates are being subducted or
    scrape past each other.

43
  • Mid-Oceanic Ridge
  • Spreading motion creates stress in the rocks
    along the mid-oceanic ridges.
  • Seafloor spreading
  • Mid-Atlantic Ridge under sea mountain range
    with a steep narrow valley running down the
    center.
  • Part of a mid-oceanic ridge that winds its way
    around earth.
  • New rock is forming at the oceanic ridges and
    is called seafloor spreading.

44
  • Eurasian-Melanesian Belt
  • Formed with the collision of Eurasian and
    Africa and Indian plates.
  • The mountains are being produced at these
    boundaries.

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Potential Earthquakes in US
48
Recorded Earthquakes Around The World

49
Earth/ Env Sci
  • Please get your notes out and something to write
    with.
  • You should ALL be in your seats, ready to go when
    the bell rings.
  • We have notes to take first, then a guided
    worksheet, then our test review.
  • TEST MONDAY!!!

50
Fault Zones
  • Created when the plates separate, collide,
    subduct, and slide past each other.
  • Example San Andres fault in California.
  • Earthquakes can also occur along former fault
    lines in the middle of current plates.

51
What is a Fault?
  • Faults are fractures in Earth's crust where rocks
    on either side of the crack have slid past each
    other

52
3 Types of Faults
  • Strike-slip faults indicate rocks are sliding
    past each other, with little to no vertical
    movement. Both the San Andreas and Anatolian
    Faults are strike-slip.
  • Normal faults create space. Two blocks of crust
    pull apart, extending the crust. The Basin and
    Range Province in North America and the East
    African Rift Zone are two well-known regions
    where normal faults are spreading apart Earth's
    crust.
  • Reverse faults, also called thrust faults,
    squeeze the crust, pushing two blocks of crust on
    top of each other. These faults are commonly
    found in mountain ranges such as the Himalayas
    and the Rocky Mountains.

53
Faults
54
Recording Earthquakes
  • Earthquakes are recorded by an instrument called
    a seismograph
  • Every earthquake is going to give off three
    different seismic waves
  • To find the location of an earthquake readings
    from three different locations are needed

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Types of Seismic Waves
  • P Waves the fastest moving wave and can travel
    through solids and liquids
  • S Waves Can only travel through solids and are
    the second wave to arrive
  • L Waves Slowest moving seismic wave, but causes
    the most damage

62
Richter Scale
  • The Richter scale measures magnitude of an
    earthquake
  • Magnitude is a measurement of the energy released
    by an earthquake
  • Each whole number increase in magnitude is an
    increase of 31.7 times more energy

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Mercalli Scale
  • A measurement of the intensity of an earthquake

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Volcanoes

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Parts of a Volcano
  • Volcano vent and the lava material that builds
    up around the vent
  • Crater Funnel shaped pit at the top of a
    volcanic pit
  • Caldera Large basin shaped depression at the top
    of a volcano. Usually due to a violent eruption

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Magma
  • Volcanism Any activity that includes the
    movement of magma toward or onto the surface
  • Magma Liquid rock
  • Most magma is formed at a subduction boundary
  • Lava Magma that reaches the earths surface

73
There Are Three Major Volcanic Zones
  • Subduction Zones
  • Mid-oceanic ridges
  • Hot spots

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Subduction Zones
  • Plate being subducted is turned into magma
  • Some magma will erupt to form volcanoes
  • EX. The Pacific Ring of Fire

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Mid Oceanic Ridge
  • Greatest amount of magma surfaces here
  • Diverging boundary
  • Emerging lava forms new ocean floor
  • EX. Mid-Atlantic Ridge

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Hot Spots
  • Areas of volcanism within a plate
  • Generally hot spots are shield volcanoes
  • Ex. Hawaii

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There are Two Different Types of Lava
  • Mafic lava is dark in color when cooled and
    usually produced from oceanic crust
  • Felsic lava is lighter in color and usually
    produced from continental crust

86
Mafic Lava
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Felsic Lava
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There are Three Different Types of Volcanoes
  • Sheild Cone- Broad base and gently sloping sides
  • Cinder Cone- Very steep slopes, not to tall
  • Composite Cone- Develops into high volcanic
    mountains

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Sheild Cone
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Cinder Cone
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Composite Cone
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Mt. Rainer
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