Transcript Earth Layers notes

Journey to the
Center of the
Earth
Hang on!
It’s going to be
a WILD RIDE!
Imagine if you will…..
You are a Geologist* and have been given the task of
traveling to the center of the Earth. You have a
specially designed Earthship that will take you to the
core. Your Earthship, Gaia One, is equipped with
instruments that will record changes in temperature and
pressure as you travel through the crust, the mantle,
and finally, the core.
So strap yourself in….
It’s going to get very,
very HOT!
*A scientist who studies the physical and chemical properties of rocks,
and the processes and forces that make and shape the Earth.
First stop – the CRUST
The first layer that Gaia One will travel through is the crust…
The crust is a layer of rock
that forms the outer skin of the Earth
Earth's crust is made up of several elements: 32% iron, 30% oxygen, 15% silicon,
14% magnesium, 3% sulfur, 2% nickel, and trace amounts of calcium, aluminum and
other elements.
2 types of crust:
Oceanic crust – thinnest part of crust, composed mostly of
dense igneous rock known as basalt.
Continental crust - thicker than oceanic crust, especially
beneath high mountains, made up mostly of a less
dense igneous rock called granite.
First stop – the CRUST
Temperature in the crust…
First 20 meters rock is cool
After that, temperature rises one degree Celsius for every 40
meters in depth. Continues for several kilometers.
Temperature rise slows down to a more steady rate.
At the crust – mantle boundary, temperature is approximately
870 degrees Celsius
The deeper you go into the Earth, the hotter it
gets (temperature increases with depth)
First stop – the CRUST
Less Pressure in the crust…so it is the least dense.
Pressure - the force pushing on a surface or area
• Pressure increases with depth, caused by the
weight of the rock above.
• This pressure increase changes the density of the
layers of Earth as you move toward the core.
Next stop – the MANTLE
At a depth between 5 and 40 kilometers beneath the surface,
you cross a boundary called the Mohorovicic Discontinuity.
• Above you - the oceanic and continental crust
• Below you lies the mantle, a layer of hot rock
• The crust & uppermost part of the mantle are very similar
• Together they form a rigid layer called the lithosphere
(lithos = ‘stone’)
• The lithosphere averages about 100 kilometers in thickness
• Lithosphere broken into sections called tectonic plates
Next stop – the MANTLE
• Beneath the lithosphere, the rock begins to change
• Hotter and under increasing pressure (more dense)
• Like in the crust, temperature, pressure, & density increase
with depth in the mantle
• Here, with this heat and pressure, rock is less rigid
• More like road tar softened by the heat of the sun
• It can bend like plastic
• This layer is called the asthenosphere (asthenes = ‘weak’)
Next stop – the MANTLE
• The lithosphere floats on top of the asthenosphere.
• It is between 400 and 700 kilometers thick.
• Below the asthenosphere, the mantle continues for almost
another 3000 kilometers before reaching the solid iron
core.
Final stop – the CORE
FINALLY! The CORE!
• Core = the innermost part of the Earth.
• Composed of the metals iron and nickel.
• Two Parts - liquid outer core and solid inner core.
• The outer core is a layer of molten metal that surrounds the
inner core.
• This layer is under extreme pressure, but still behaves like a
thick liquid.
Final stop – the CORE
• The inner core is a dense ball of solid metal.
• The pressure is so great here that atoms of iron and nickel
are squeezed so much that they cannot spread out to
form a liquid.
• The inner core spins, which generates the Earth’s
magnetic field
• Together, the inner and outer core make up about one-
third of Earth’s mass, but only about 15 % of
its volume.
Easy Peasy – Can you do it?
The Earth’s structure can be divided
up two different ways.
The first is based on the chemical
properties of the layers. As we go
deeper toward the core, the chemical
elements that make up those layers
increase in density. For example, the
crust is made mainly of silicate
minerals, whereas the core is made
of iron and nickel. The silicates are
much less dense than the metals.
This separation occurred in the very
early stages of the Earth’s formation,
as heavier elements were pulled by
gravity towards the center, and the
lighter elements rose to the surface.
The second way we divide up the Earth is by
the physical properties of the layers, which is
controlled by the effects of heat and pressure
with depth.
The inner core is solid. Even though the
temperatures are greatest there, the intense
pressure keeps the inner core solid.
The outer core, with less pressure, behaves as
a liquid due to the intense heat.
The mesosphere, or mantle, acts as a highly
viscous solid, which means it is capable of flow.
Heat from the core rises, causing convection
movement in the mantle. More on that later.
On top of the mantle is the asthenosphere, a
relatively low-viscosity layer on which the
lithosphere rides. The asthenosphere behaves
like a hot plastic or road tar. The outer
component, the lithosphere, is solid and
includes the oceanic and continental crust,
along with the very uppermost part of the rigid
mantle. Imagine a graham cracker on top of
pudding. That is similar to how the lithosphere
moves on the asthenosphere.
“Moho”
Snapshots
from your
trip…
Snapshots from your trip…
“Moho”
Snapshots from your trip…
Moving the plates….
The engine behind plate tectonics
Divergent boundary
Convergent
boundaries
Ocean - Continent
Ocean - Ocean
Continent - Continent