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Layers of the Earth and Seismic Waves
Transcript of Layers of the Earth and Seismic Waves
Thinnest Layer = 6 to 70 Km thick
Composition - various types of minerals and all types of rocks
~Continental Crust - all the continents and major islands (thickest)
~Oceanic Crust - ocean floors (thinnest);
does not include the oceans themselves
2900 Km thick
More dense than the crust
Composition = various types of minerals
Upper Mantle is cool and solid.
Just below the Upper Mantle, the rock is hot and soft (molten) enough to move like a thick paste.
Lithosphere is a cool, solid layer made of the
CRUST AND UPPER MANTLE.
The lithosphere is broken into sections, called tectonic plates.
Astenosphere is the part of the mantle, just below the lithosphere, that is molten and moves like a thick paste.
The astenosphere is what moves the tectonic plates.
Iron and Nickel
Outer core is 2300 Km thick.
More dense than the mantle, but less dense than the inner core.
The outer core is a layer of liquid metal.
Pressure and temperature of the outer core is lower than that of the inner core.
Inner core is 1200 Km thick.
Inner core is the most dense layer.
The inner core is hot, solid metal.
The inner core is hotter than the outer core, but it
remains solid because of the intense pressure.
Layers are separated by temperature and density.
How Do Scientists Know What the Inside of the Earth Looks Like?
A seismic wave is a form of energy that travels as a wave and is generated by an earthquake.
Seismic waves help scientists understand the
composition and density
of the Earth by studying how the waves move through the Earth.
Waves travel through the Earth to various
is the actual record of the seismic waves, recorded at each seismograph station.
The different densities of material will cause the seismic waves to change their
speed and direction.
Primary waves are the
first and fastest
waves to leave the earthquake and arrive at the seismograph station.
, meaning they move
in and out
(like an inch worm).
They can travel through
all types of matter
(solids, liquids and gases)
so they can go through
all layers of the Earth
Secondary waves are the
to leave the earthquake and to arrive at the seismograph station. S-waves travel
shearing (or transverse)
up and down
(like a rolling hill).
They can only travel through solid material. They
, so they
Surface waves are the
to leave an earthquake and arrive at the seismograph station.
side to side
(like a snake).
They are the
Density and Convection Currents
Density = mass/volume (d=m/v)
That means density is determined by how much mass an object has divided by the amount of space it takes up.
Convection currents within the asthenosphere move molten rock in a circular pattern.
Less dense material rises and more dense material sinks.
Bulk of the mantle.
Transfers heat energy from the core to the upper mantle.
P & S wave shadow zone
P & S wave shadow zone
Together the core is Earth's thickest layer at 3500Km.
Interpreting the chart
WAVES TRAVEL FASTEST THROUGH SOLIDS.
7 to 8 Km/s
4 to 4.5 Km/s
11 to 14 Km/s
6 to 7.5 Km/s
10 to 11 Km/s