Download journey 05 - Auburn High School

Journey to the Center of the
Earth
Topic 12
Regents Earth Science
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.
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
Changes in the
speed of seismic
waves were used to
determine the
location of the
Earth’s different
layers
Layers of the Earth
•
•
•
•
Crust
Mantle
Outer Core
Inner Core
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
Comparing Oceanic and
Continental Crust
Oceanic Crust
Continental Crust
• Composition is
“basaltic”
• Density about 3.0
g/cm3
• Younger (180 my old
or less)
• Composition is
“granitic”
• Density about 2.7
g/cm3
• Older (4 by old)
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.
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
The Upper Mantle
Rigid Mantle
Plastic Mantle
• Cool and brittle
• The rigid mantle and
crust make up the
lithosphere
• Divided into sections
called plates
• 15-300 km thick
• Partially molten - the
rock in this layer has
the ability to flow.
• Also known as the
asthenosphere
• Magma originates here
• About 200 km thick
The Outer Core
•
•
•
•
liquid
2100 km wide
consists of nickel and iron
flow of iron creates the Earth’s magnetic
field
How do we know the outer core
is liquid?
• S-waves do not
pass through this
zone
• Shadow zone - no
p-waves or swaves received
here
• 103° to 143° from
focus
At the outer
core
• Thers is a sudden
decrease in p-wave
velocity and
• S-waves disappear
The Inner Core
•
•
•
•
solid
consists of the metals nickel and iron
temperature is 6,000° C
width = 2,100 km
The Earth’s Interior
ESRT page 10
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.
Melting Point and Temperature
• As depth increases,
temperature increases.
• What evidence can
you see for a liquid
outer core?