Download Earth`s Layered Interior - Donovan

Earth’s Layered Interior
 Earth formed about 4.5 billion years ago from the accumulation of
dust and rocks
o Over time, heat and gravity layered the elements
o Denser ones sinking towards the middle (iron, nickel)
o Lighter ones flowing outward (Al, Si, O, …)
 Discovering Earth’s Layers
o Density of Earth (D=m/v)
o Density of the layers
o Behavior of seismic waves
o Composition of sun
o Samples
o Balance of location of elements
o Magnetic field
 3 main layers
o Core – 16% of the total mass
o Mantle – 83% of the total mass
o Crust – 1% of the total mass
 Pressure and temperature increase as you go down to the center
Crust
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Thin sheath surrounding the planet
Density less than the density of the Mantle
High portion silicon, aluminum, Ca, Na, K
Total thickness of 30-45 km
2 kinds of crust: Oceanic and Continental
o Oceanic = thin, 5 km in thickness, composed mostly of basalt,
contains dark colored minerals, greater density than continental
o Continental = thick, 30 – 40 km in thickness, low density, lots
of silica, quartz and feldspar and is a by-product of mountain
building, lots of granite
Mantle
 Thickest layer of the Earth
 Has 3 layers of its own
o Very thick lower layer (lower mantle, mesosphere)
o Middle ooey-gooey layer (asthenosphere)
o Top solid layer (very similar to the Crust) (lithosphere)
 The Mantle has more than one consistency, composed mostly of a
rock known as peridotite which is dark in color and made of iron and
magnesium
 Middle layer is plastic-like in consistency and allows for the
convective flow of materials
o Heat rises to the surface, cools and drops back down
 2,800 km in thickness and varies in temperature
 boundary between crust and mantle is known as the MOHO or the
Mohorovicic Discontinuity named after a Croatian seismologist who
discovered it
The Core
 The Core is divided into 2 parts – inner and outer core
 Inner Core
o About 1200 – 1400 km in thickness, very solid and dense and
composed mostly of iron with a small percentage of nickel;
temperatures here may be as high as 7200 degrees Celsius
which should melt iron but the pressure is too high to allow that
to happen
o Since this layer sinks to the middle, it is assumed it has the
greatest density
 Outer Core
o Mostly iron but has other elements (10%) because it can be
assumed to have a smaller density than the inner core
o Liquid in consistency, lower temperature than inner core, about
2,200 km in thickness
o The movements of the outer core may be responsible for our
magnetic field