Transcript Earth`s layered structure notes

EARTH’S INTERNAL
STRUCTURE
And processes
What Was Early Earth Like?
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Describe what Earth was like right as the Solar
System was forming?
Why did earth get hot?
What do fluids do when they are hot?
At first there were no layers, where did they come
from?
Early Earth
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Early Earth was homogeneous (uniform)
Composed of mostly silicates, iron and magnesium
oxides
Temperature increased because of:
 Meteorite
impacts
 Gravitational Compression
 Radioactive Decay
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When Iron and Nickel melted everything changed.
Earth’s Differentiation
Differentiation = segregated into a series of
concentric layers of differing composition and
density
 Molten iron and nickel
sank to form the core
 Lighter silicates flowed
up to form mantle
and crust
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Distinct Layers
Compositional Layers
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Crust
Mantle
Core
Mechanical Layers
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Lithosphere
Asthenosphere
Lower Mantle
Outer Core
Inner Core
Crust
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2 types
 Continental
 Density
 Oceanic
 Density
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Crust 20km ~ 90km thick (12~56miles)
of 2.7g/cm3
Crust 5km ~ 10km thick (3~6miles)
of 3g/cm3
If the earth were an inflated balloon, the crust
would be the skin!
What element do you think makes up most of the
crust?
Crust
Oxygen is the most common element in the crust!
 Oxygen bonds
with the other
elements to make
minerals of the
crust.
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The crust is not
just oxygen!
Crust
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Continental crust is made up of all rock types.
 In
general it is where you find less dense minerals
 More pores (spaces) in the rocks further decrease
density
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Oceanic crust made of more dense rocks.
 The
minerals have a higher amounts of iron and
magnesium
 Smaller pores means higher density
Mantle
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Mantle is about 2,885km thick! About 1800miles.
The mantle is SOLID ROCK, it is not a liquid!
Has a density from about 3.5g/cm3 to 5.5g/cm3
Lets think about that for a second!!!
Mantle
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But, if the mantle is SOLID how can it flow?
 At
about 100km – 150km it is hot enough to flow very
slowly.
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The mantle makes up about 83% of earth’s total
volume.
It is made up almost entirely by a iron and
magnesium rich, dark colored rock, called Peridotite.
Core
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The core is made up of iron alloy (iron mixed with
small amounts of other elements)
Outer core is about 2255km thick. About 1400miles
 Outer
core is liquid because temperature is so high that
not even the high pressure can force it to become solid.
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Inner core is about 1220km thick. About 758miles.
 Even
though it is hotter than the outer core, the pressure
is so high that the atoms get forced together to make a
solid.
Core
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The swirling convective flow in the outer core
creates earth’s magnetic field.
The Inner core actually spins slightly faster than the
rest of the planet due to the force of earth’s
magnetic field.
Lithosphere and Asthenosphere
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So far we have broken the layers down by
composition and density. (Crust, Mantle, Core)
 We
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can also divide them up by how they “behave”
The upper most layer is called the lithosphere
 It
is rigid, meaning it can bend slightly but not flow at
all.
 This layer extends down from the surface about 100150km.
 What two compositional layers does this include?
 Do lithosphere and crust mean the same thing?
Lithosphere and Asthenosphere
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Below the lithosphere you have the asthenosphere
 The
asthenosphere is entirely upper mantle rock
 It is NOT A LIQUID!
 But it is hot enough, 1280°C or 2330°F, that it can flow
very slowly.
 Even at that temp. it can only flow about 10cm – 15cm
per year.
Earth’s Interior Layers
• Lithosphere
– solid upper mantle
and crust
– broken into plates that
move over the
asthenosphere
• Asthenosphere
– part of upper mantle
– behaves plastically
and slowly flows
Plate Tectonic Theory
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Lithosphere is broken into individual pieces or
plates
• Plates move over the asthenosphere
– as a result of underlying convection cells
Modern Plate Map
Summary
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Earth has layers because of density.
As you go towards the center temp and pressure
increase.
You can refer to earths Compositional Layers –orits Mechanical Layers