journey to the center of the earth topic 12 regents earth science
TRANSCRIPT
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Journey to the Center of the Earth
Topic 12
Regents Earth Science
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Objectives
• Describe the Earth’s internal structure.• Explain the changes in P and S wave
velocities in the Earth.• Describe the shadow zone and explain its
significance.• Use the ESRT to describe various
properties of the Earth’s interior such as pressure, temperature, and density.
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The study of seismic waves allows scientists to “see” inside the earth.
Scientists have discovered that seismic waves
• refract
• reflect
• change velocity
• and become absorbed by various parts of the Earth’s interior
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Changes in the speed of seismic waves were used to determine the location of the Earth’s different layers
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Layers of the Earth
• Crust
• Mantle
• Outer Core
• Inner Core
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Crust
• This is the layer that we live on
• The thickness ranges from 8 km under the oceans to 40 km under the continents
• Continental crust is thickest beneath high mountains
• It is the thinnest layer of the earth
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Comparing Oceanic and Continental Crust
Oceanic Crust• Composition is
“basaltic”• Density about 3.0
g/cm3
• Younger (180 my old or less)
Continental Crust• Composition is
“granitic”• Density about 2.7
g/cm3
• Older (4 by old)
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Mohorovicic Discontinuity
• Called Moho
• Is the boundary between the crust and mantle
• Was discovered in 1909 by Andrija Mohorovicic
• He found that seismic waves increase in speed at an average depth of 40 km.
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The Mantle
• Is divided into 2 regions
• It consists of magnesium, iron, and silicon
• It is 3000 km wide
• It is more rigid closer to the surface
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The Upper Mantle
Rigid Mantle• Cool and brittle• The rigid mantle and
crust make up the lithosphere
• Divided into sections called plates
• 15-300 km thick
Plastic Mantle• Partially molten - the
rock in this layer has the ability to flow.
• Also known as the asthenosphere
• Magma originates here• About 200 km thick
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The Outer Core
• liquid
• 2100 km wide
• consists of nickel and iron
• flow of iron creates the Earth’s magnetic field
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How do we know the outer core is liquid?
• S-waves do not pass through this zone
• Shadow zone - no p-waves or s-waves received here
• 103° to 143° from focus
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At the outer core
• Thers is a sudden decrease in p-wave velocity and
• S-waves disappear
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The Inner Core
• solid
• consists of the metals nickel and iron
• temperature is 6,000° C
• width = 2,100 km
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The Earth’s Interior
ESRT page 10
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Selected Poperrties of the Earth’s Interior
• The x-axis shows the depth from bottom to top.
• As depth increases, pressure increases.
• 1 atmosphere = 14.7 psi or “normal” air pressure at sea level
• As depth increases, density increases.
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Melting Point and Temperature
• As depth increases, temperature increases.
• What evidence can you see for a liquid outer core?