Earth Systems

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Earth Systems

• Earths Layers and Plate Tectonics

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How many layers is the Earth dived into?

• The earth has four main layers and those layers
  are divided even further into sub-layers.
• Scientists have learned about the structure of
  the Earth through deep drilling and seismic
  evidence.

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How many layers is the Earth dived into?

• The earth has four distinct layers
• Crust (continental and oceanic)
• Mantle (upper asthenosphere and lower)
• Outer Core
• Inner Core

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Layers of Earth
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What is the Crust?

• The crust or thin shell that covers the globe
  is the first layer.
• 60-70 covered water
• 30-40 seven continental continents

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What is the difference between Continental Crust
and Oceanic Crust?

• The continental crust is the rigid and brittle
  layer of igneous, sedimentary, and metamorphic
  rocks which form the continents. The age of these
  rocks varies from between 4 billion to 600
  million years. Even though it has all types of
  rocks the majority is granitic rock, so
  continental crust has a density of about 2.7
  g/cm3 .
• It ranges in thickness of 20-70 km. The thickest
  crust is found in mountain ranges.

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What is the difference between Continental Crust
and Oceanic Crust?

• Oceanic crust is the layer of mostly basalt found
  under the oceans.
• The average density of the oceanic crust is 3.3
  g/cm³. It ranges in thickness of 5 -10 km.
• Oceanic crust is created at the mid-oceanic
  ridges and destroyed at the oceanic trenches.
  Oceanic crust is relatively young age and is
  being created even today at mid-oceanic rift
  zones. Maximum age is about 200 million years.

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Mid Ocean Ridge
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Oceanic Trench
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Is the crust one big piece or multiple pieces?

• The Theory of Plate Tectonics (1960) states that
  the Earths crust is made up of about a seven
  major plates on which the continents and oceans
  rest and that these plates are in constant slow
  motion.

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What are the seven major plates?

• North American Plate, Eurasian Plate, Pacific
  Plate, Nazcan Plate, South American Plate,
  Indo-Australian Plate, and African Plate.

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Are there any combined regions?

• The crust and the upper part of the mantle is
  called the lithosphere. This is a solid, rigid
  area.

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Crust and Lithosphere
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Where is the mantle and what are its features?

• The mantle is located below the crust and it
  contains mostly Fe, Mg, Si, Al, and O.
• The mantle has an upper portion and a lower
  portion.
• The asthenosphere is the molten, ductile, upper
  portion of the earth's mantle and it reaches a
  depth of about 250 km.
• The asthenosphere is a solid but it flows like a
  liquid this is known as plasticity.

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Where is the mantle and what are its features?

• The rest of the mantle extends to 2900 km. The
  mantle has convection currents which result from
  differential temperatures (2800 ?C to 3200 ?C)
  in mantle materials.
• Convection currents are the vertical (rising and
  falling) movement of rock within the mantle.
  Convection currents are the driving force that
  causes tectonic plates to move around the Earth's
  surface.

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Convection Currents
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Where is the core and what are its features?

• The core is broken up into two sections (inner
  and outer core).

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Outer Core Features

• The outer core is less dense than the inner core
  and it is about 2,200 km thick.
• The temperatures reach between 4000 ?C 5000 ?C.
  
• Due to the great temperature, the outer core made
  of LIQUID iron (Fe) and nickel (Ni).

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Inner Core Features

• The inner core is about 1,250 km thick.
• The inner core is denser and has temperatures
  reaching 6000 ?C.
• Even though it is hotter than any other part of
  the layers of the earth, it is NOT liquid. The
  inner core is SOLID because of the intense
  pressure applied on it from all the layers above.
  
• The material in the core is mostly iron (Fe).

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Magnetic Field

• The currents of the outer core, cause the inner
  core to spin. It spins at a faster rate than the
  rest of the planet. This leads to the creation
  of the Earths magnetic field.

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Part II Plate Tectonics
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Layers of Earth
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How did Alfred Wegner come up with his idea?

• In 1911 Alfred Wegner (German geophysicist/meteoro
  logist) began his quest to prove that the
  continents were once connected due to what he
  called continental drift. It all started when
  Wegner was browsing in the university library
  when he came across a scientific paper that
  listed fossils of identical plants and animals
  found on opposite sides of the Atlantic.

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Alfred Wegner Continued

• Intrigued by this information, Wegner began
  to look for, and find, more similar cases of
  similar organisms separated by great oceans.
  Alfred Wegner also noticed that the different
  large landmasses of the Earth almost fit together
  like a jigsaw. America fit closely to Africa and
  Europe and Antartica, Australia, India, and
  Madagascar fit next to the tip of Southern Africa.

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What did Alfred Wegner propose?

• In 1912, he proposed the theory of continental
  drift which hypothesized that the continents were
  slowly drifting around the Earth. He claimed
  that millions of years before present Earth, the
  continents were all connected. He called this
  huge landmass Pangaea.

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Comparison

• Pangaea (100 mya)

• Present

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What evidence helps to support his theory of
Pangaea?

• Geologist have discovered that the geological
  structures of rocks in South West Africa and
  South East Brazil were distinctively identical,
  and the age of the two rocks were the same.
• Fossils of the same species were found on several
  different continents. Wegner proposed that
  species dispersed were together and later carried
  to their present position as continents drifted.

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What evidence helps to support his theory of
Pangaea?

• Coal can be found underneath the cold and dry
  Antarctic ice cap, though coal can only form in
  warm and wet conditions.
• Glossopteris, a fern, was found on the continents
  of South America, Africa, India, and Australia.
• Mesosaurus, an early freshwater reptile, fossils
  are both found in Africa and South America. Since
  this animal inhabited freshwater habitats, it
  could not have swam in the ocean with is
  salt-water.

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Evidence
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Mesosaurus and Glossopteris
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Is there proof that the plates move?

• Even though the crust is solid rock, it sits on
  top of a hot, soft, semi-solid material located
  in the mantle. As the material in the upper
  mantle moves, it drags the overlying plates
  across the Earths surface. The plates are moving
  about 1 centimeter to 15 centimeters per year in
  different directions. GPS (Global Positioning
  Units) and satellites are used track this
  movement.

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What is the name of the area between the crust
tectonic plates?

• The border between two tectonic plates is called
  a boundary.

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What types of boundaries are there?

• Convergent boundaries are areas under pressure
  that either result in subduction which is the
  lithosphere plates are driven down and destroyed
  in the molten magma OR in crustal uplifting that
  leads to mountain building.

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Convergent Boundary-Subduction
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Island Formation
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Convergent Boundary-Mountain
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Convergent Plates
EURASIAN PLATE
INDIAN PLATE
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Divergent Boundary

• Divergent boundaries are areas under tension
  where plates are pushed upward by magma uprising
  from the mantle.

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Divergent Boundary
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Divergent Plates
ARABIAN PLATE
AFRICAN PLATE
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Seafloor Spreading
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Transform Boundary

• Transform boundaries are areas that are moving
  laterally past one another and creating a
  shearing force.

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Transform Boundary
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San Andreas Fault
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When the plates move and interact, can this
cause natural events on Earth?

• When plates interaction through collisions,
  plates sliding past each other, plates splitting
  from each other, it can lead to the formation of
  mountains, volcano eruptions, sea-floor spreading
  and earthquakes.

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When do mountain chains form?

• Mountain chains form when continental landmasses
  that have the same rock density converge. Since
  they have similar density, one plate cant be
  subducted under the other. The pressure of the
  impinging plates can only be relieved by
  thrusting skyward forming mountain peaks. For
  example, the Himalayas, which stretch 2900km
  along the border between India and Tibet formed
  between 40-50 mya when India and Eurasia, driven
  by plate movement collided.

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Himalayan Mountains
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 When do earthquakes occur?

• Earthquakes occurs along faults. Faults are
  large cracks in the Earths crust. Rocks on
  either side of a fault are under pressure and get
  locked together. When too much pressure builds
  up, the rocks suddenly slide past each other and
  release the pressure. The result is an
  earthquake (violent shaking on the Earths
  crust). The San Andreas Fault is a transform
  boundary that connects the Pacific plate with the
  N.A. plate.

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San Andreas Fault
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How do volcanoes form?

• Volcanoes form when material from inside the
  Earth reaches the surface. In convergent
  boundaries one plate can submerge under another
  and the heat and pressure turn rock into magma,
  which can rise through the cracks in the crust.
  In divergent boundaries, where plates pull apart,
  magma rises through cracks and forms volcanoes.

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Parts of a volcano
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Types of Volcanoes
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Is this the only way that volcanoes form?

• The Hawaiian Islands, which are entirely of
  volcanic origin, have formed in the middle of the
  Pacific Ocean more than 3,200 km from the nearest
  plate boundary. These volcanoes form due to a hot
  spot (a constant up flow of magma in a stationary
  location).

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Hot Spot
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Hawaii Island Formation