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Earth Systems

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Title: Earth Systems


1
Earth Systems
  • Earths Layers and Plate Tectonics

2
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.

3
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

4
Layers of Earth
5
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

6
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.

7
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.

8
Mid Ocean Ridge
9
Oceanic Trench
10
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.

11
What are the seven major plates?
  • North American Plate, Eurasian Plate, Pacific
    Plate, Nazcan Plate, South American Plate,
    Indo-Australian Plate, and African Plate.

12
Are there any combined regions?
  • The crust and the upper part of the mantle is
    called the lithosphere. This is a solid, rigid
    area.

13
Crust and Lithosphere
14
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.

15
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.

16
Convection Currents
17
Where is the core and what are its features?
  • The core is broken up into two sections (inner
    and outer core).

18
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).

19
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).

20
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.

21
Part II Plate Tectonics
22
Layers of Earth
23
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.

24
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.

25
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.

26
Comparison
  • Pangaea (100 mya)
  • Present

27
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.

28
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.

29
Evidence
30
Mesosaurus and Glossopteris
31
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.

32
What is the name of the area between the crust
tectonic plates?
  • The border between two tectonic plates is called
    a boundary.

33
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.

34
Convergent Boundary-Subduction
35
Island Formation
36
Convergent Boundary-Mountain
37
Convergent Plates
EURASIAN PLATE
INDIAN PLATE
38
Divergent Boundary
  • Divergent boundaries are areas under tension
    where plates are pushed upward by magma uprising
    from the mantle.

39
Divergent Boundary
40
Divergent Plates
ARABIAN PLATE
AFRICAN PLATE
41
Seafloor Spreading
42
Transform Boundary
  • Transform boundaries are areas that are moving
    laterally past one another and creating a
    shearing force.

43
Transform Boundary
44
San Andreas Fault
45
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.

46
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.

47
Himalayan Mountains
48
  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.

49
San Andreas Fault
50
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.

51
Parts of a volcano
52
Types of Volcanoes
53
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).

54
Hot Spot
55
Hawaii Island Formation
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