Inside the Earth

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Inside the Earth
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Composition of the Earth

• The Earth is divided into three layers based on
  compounds that make up each layer
• Crust
• Mantle
• Core

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The Crust

• The outermost layer of the Earth
• 5 to 100 km thick in places
• Thinnest layer of the Earth
• Two Types of Crust
• Continental
• Oceanic

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Continental Crust

• Continental crust is less dense than oceanic
  crust
• Contains the elements oxygen, silicon

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Oceanic Crust

• Oceanic crust is more dense than continental
  crust
• Contains the same elements but has about twice as
  much which makes is more dense
• Moho discontinuity divides crust and mantle

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The Mantle

• The layer of the Earth between the crust and the
  core
• Contains most of the Earths mass
• No one has ever been to the mantle
• In some places mantle rock pushes through to
  Earths surface so scientists are able to study
  it there

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The Mantle

• Scientists also look for clues about the mantle
  at the ocean floor
• Magma from the mantle flow out of underwater
  volcanoes
• Scientists are able to find clues about the
  mantles composition by studying earthquakes
• Gutenburg discontinuity divides mantle and core

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The Core

• Layer that extends from below the mantle to the
  center of the Earth
• Made up of mostly iron and small amount of nickel
• Makes up 1/3 of the Earths mass

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Physical Structure of the Earth

• Another way to look at the Earth is to examine
  the physical properties of its layers.
• Lithosphere -crust and upper mantle
• Asthenosphere- lower mantle and core

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Lithosphere

• The outermost, rigid layer of the Earth
• Made up of two parts
• The crust
• Rigid upper part of the mantle
• Divided into pieces called tectonic plates

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Asthenosphere

• A plastic layer of the mantle on which pieces of
  the lithosphere float
• Made up of solid rock that flows very slowly

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Lithosphere and asthenosphere
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Outer Inner Core

• The Outer Core is the liquid layer that lies
  beneath the mantle and surrounds the Inner Core.
• The Inner Core is the solid, dense center of our
  planet that extends from the bottom of the outer
  core to the center of the earth
• About 6,380 km beneath the surface

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Tectonic Plates

• Pieces of the lithosphere that move around on top
  of the asthenosphere
• There are 10 major tectonic plates
• They vary in size
• They fit together like a jigsaw puzzle
• Some plates have continental crust some have
  oceanic and some have both

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Tectonic Plates

• Continental Plates are the thickest
• Displace more of the asthenosphere
• Oceanic Plates are the thinnest
• Displace less of the asthenosphere

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Mapping the Earths Interior

• How do we know what the interior of the Earth is
  like?
• Earthquakes produce seismic waves which travel at
  different speeds through the earth
• Their speed depends on the density and
  composition of the material they travel through

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Mapping the Earths Interior

• Seismographs are instruments that pick up seismic
  waves
• It can then determine how far away the earthquake
  happened
• Scientists can then use these distances to figure
  out the density and thickness of the layers of
  the Earth

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Seismic Waves

• P waves- primary waves, first to leave focus,
  travel the fastest, travel through solids, and
  liquids. Reach seismograph 1st.
• S waves- secondary waves, second to leave focus,
  slower traveling, travel through solids only.
  Reach seismograph 2nd.
• L waves or surface waves- do most damage, rolling
  motion.
• Need 3 reading to locate epicenter above focus

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Question 1

• What are the three main layers of the Earth?

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Answer

• The three layers of the Earth are the crust,
  mantle, and core

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Question 2

• What is the difference between the lithosphere
  and the asthenosphere?

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Answer

• The lithosphere is the outermost layer of the
  Earth and it is made up of plates and the
  asthenosphere is the plastic layer of the mantle
  on which the lithospheric plates float

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Question 3

• What type of plates are the thickest?
• Continental
• Oceanic

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Answer

• Continental Plates are the thickest