Download Earth`s Layers

Earth’s Layers
The Structure of the Earth
Layers of the Earth
• The layers of the Earth in order from the center
out are.
– Inner core
– Outer core
– Mantle
• lower
• Middle
• upper
– Asthenosphere
– Lithosphere (crust)
The Crust
• The crust is the
outermost layer of the
Earth
• Most widely studied and
understood
• Made up primarily of
silicon and oxygen
• Very thin when compared
to the other layers
– 3-5 miles or 8 km thick
under the oceanic crust
– 32 km or 25miles thick
under the continental crust
The Crust
• The crust is the thinnest
layer of the earth.
– Oceanic crust
• The mantle is the
thickest layer of the
Earth
– Stretches from the
lithosphere to the outer
core
Continental Crust
• Composed mainly of
granite
• Thicker than oceanic
crust (30-50 km)
• Makes up only 25% of
Earth’s surface
• Less dense than oceanic
crust
Oceanic Crust
• Oceanic crust is composed
of primarily basalt
• Basalt is much denser than
the granite.
– The less dense continents
ride on the denser oceanic
plates
• Covered by water
• Makes up 75% of Earth’s
crust.
• Thinner than the
continental crust (5-10km)
The Lithosphere
• The crust and the upper
layer of the mantle
together make up a
zone of rigid, brittle
rock called the
lithosphere.
Lithospheric Plates
• The crust of the Earth is
broken into many
pieces called
(lithospheric) plate.
• The plates “float” on
the soft, semi rigid
asthenosphere
Mohorovicic Discontinuity
• The imaginary line of
discontinuity that separates
the brittle crust of the earth
from the mantle is the
Mohorovicic Discontinuity
or MOHO for short.
• Boundary between
the crust and the mantle in
the earth.
• Depth where seismic waves
change velocity and there is
also a change in chemical
composition
MOHO
The Mantle
• The mantle is the thickest
layer of Earth.
• 2,885 km thick, the
mantle is 82% of Earth’s
volume.
– Upper mantle
– Middle mantle
• Asthenosphere
– Lower mantle
• Mesosphere (middle layer)
• Mantle composition is an
ultramafic rock called
peridotite.
• Solid rock layer between
the crust and the core.
The Upper Mantle
• The uppermost mantle
is connected to the
crust and forms the
asthenosphere, which
composes Earth's
tectonic plates.
• Part of the lithosphere
The Asthenosphere
Middle Mantle
• The asthenosphere is
the semi-rigid part of
the middle mantle that
flows like hot asphalt
under a heavy weight
• The movement of the
middle mantle,
asthenosphere, is the
reason that the crustal
plates of the Earth
move.
Convection Currents
• The middle mantle "flows"
because of convection
currents.
• Convection currents are
caused by the very hot
material at the deepest
part of the mantle rising,
then cooling and sinking
again
• The cycle repeats over and
over.
• The molten rock below
Earth’s surface is known as
magma
The Lower Mantle
• Called the Mesosphere
because it is the middle
layer of Earth.
– “middle” sphere
• 2,250 km thick
• lowest part of mantle
The Outer Core
• 1400 miles thick
• It is so hot that the
metals in it are all in the
liquid state.
• Composed of the
melted metals of nickel
and iron.
• The flow of the inner
core creates Earth’s
magnetic field
Earth’s Magnetic Field
• The flow of the fluid outer core around the
solid inner core creates the Earth’s magnetic
field
The Inner Core
• The inner core of the Earth
has extremely high
temperatures and pressures
– 4,000 - 5,000 °C
– 3 million atmospheres
• Pressure is so great that the
metals are squeezed together
and are not able.
– forced to vibrate in place like a
solid.
– A ball of very hot metals.
• Inner core dimensions
– 3,248 km radius
• Composed of a sphere of hot,
dense nickel and iron
• 1/3 of the Earth’s mass
Proof of Earth’s Structure
• Seismic Waves: the waves
that travel through the
Earth’s interior during an
earthquake.
• Altered by the type of
material that it travels
through.
• Timing and strength of
seismic waves gives us a
picture of Earth’s interior
Using the diagram which seismic wave travels
through what type of substance?
Seismic Waves
• P-Waves
– Travels through any substance
– Compression wave
– Any substance can be compressed
– Solid, liquid, gas
• S-Waves
– Transverse, shear waves
– Travels through solid only
Seismic Shadow Zone
• 104 -140 degrees from the epicenter
– No direct P-waves
– S-Waves are stopped entirely by the liquid core
– P-Waves are bent
Think, Pair, Share
• Write down the following
question on a sheet of
paper.
– Have we ever seen part of
the Mantle? Explain.
– Include an illustration of
the explanation.
• Discuss the question with
your partner and write
the answer down.
• Sit quietly until I say time
is up