Movements of the Earth

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Movements of the Earths Crust

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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

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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

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Fossil Evidence

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Rock Similarities

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Coastline Similarities

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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

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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.

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Rules of Plate TectonicsContinued

• 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.

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Plates of the World
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Types of Crust

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

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Types of Plate Boundaries

Draw these pictures in your notes
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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

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Diverging Boundary

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Seafloor Spreading

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Rift Valley

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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

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Converging Boundary

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Oceanic-Oceanic Converging

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Oceanic-Continental Converging

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Continental-Continental Converging

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Transform Plate Boundary

• Two plates grinding past each other.
  Earthquakes occur here.

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Transform Plate Boundary

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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.

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Convection Currents
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Compositional Layers of the Earth

• Crust
• Mantle
• Outer Core
• Inner Core

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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.

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ANSS Recent Earthquakes in the US
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Three major earthquake zones

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Pacific Ring of Fire

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

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• 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.

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• 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
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Recorded Earthquakes Around The World

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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!!!

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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.

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What is a Fault?

• Faults are fractures in Earth's crust where rocks
  on either side of the crack have slid past each
  other

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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.

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Faults
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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

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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

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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

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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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