Transcript Inside the Earth

Inside the Earth
Review of Density…
Density is an expression of the relative
heaviness of a substance

mass per unit volume

grams per cubic centimeter (g/cm3)


The density of pure water is 1g/cm3.
Granite rock is about 2.7 times denser at
2.7g/cm3.

Formation of the Earth
• The most dense material (Iron and Nickel) settled
to the core (center)
• Less dense matter (Silicates) formed the vast
interior of the Earth (mantle).
• The least dense material (Granite and Basalt)
formed the Earth’s solid stony crust.
– Volcanic eruptions continued through the crust.
Formation of the Earth
Continued…
• With each eruption, gases, water vapor,
ash and lava (molten material) were
brought to the surface.
• The water vapor and gases formed the
atmosphere.
• As the Earth cooled the water vapor turned
to water and the rains started.
• The oceans formed from runoff. This also
supplied the ocean with the mineral
content it has today.
IGNEOUS ROCKS
• Formed from molten
material including
volcanic lava, ash,
or bombs as well as
magma below
Earth’s surface
TYPES OF IGNEOUS
ROCKS
GRANITE
BASALT
Composition (What it is made of)
• Crust
• Mantle
• Core
Earth’s Layers
• How are the earth’s
layers similar to an
egg?
The Crust
• Outer layer
• 5-25 miles thick
• Broken into pieces plates
• 2 types of crust
– Oceanic
• more dense – 2.9g/cm3
• made of basalt
– Continental
• least dense – 2.8g/cm3
• made of granite
Oceanic and Continental Crust
The Mantle
• Middle layer
• Very thick
• Largest layer
Upper Mantle –
“Floats on plastic”
3.3 g/cm3
Plastic Mantle –
3.5 g/cm3
Lower Mantle –
The Core
•
•
•
•
•
Made mostly of iron
1/3 of the earth’s mass
Very hot
The most dense
Divided into 2:
– The outer core
• made up of liquid iron and nickel
• density of 11.8g/cm3
– The inner core
• made up of solid iron and nickel
• density of 16.0g/cm3
Physical Structure of the Earth
•
Crust (less than 1% of the total volume of the Earth)
– Continental Crust
• 2.7 g/cm3
• granite
– Oceanic Crust
• 2.9 g/cm3
• basalt
•
Mantle (83% of the total volume of the Earth)
– Lithosphere (lower crust and upper mantle)
• Plate in the “plate tectonic theory”
• Floats on upper mantle like water
• 3.1 g/cm3
– Asthenosphere
• solid rock that flows slowly (like hot asphalt)
• “Plastic” layer
• 3.3 g/cm3
– Mesosphere
• 4.5 g/cm3
•
Core (16% of the total volume of the Earth)
– Outer Core
• liquid iron and nickel
• density of 11.8g/cm3
– Inner Core
• Solid iron and nickel
• density of 16.0g/cm3
Subduction Zone
Ocean trench
Ocean
Continental Crust
Oceanic crust
Continental Crust
Solid Mantle
Solid Mantle
Plastic Mantle
Solid mantle=
Lithosphere
Plastic mantle =
Asthenosphere
Label the
following:
-Continental Crust
-Ocean
-Oceanic Crust
-Solid Mantle
-Plastic Mantle
-Original Subduction
Zone
-New Subduction
Zone
Density Layering
• The overall density of the Earth is
5.5g/cm3
• The crust changes continually to
balance the amount of lighter and
denser material.
– Erosion and glacial melting decreases
the density of the crust.
– Volcanic eruption will increase the
density.
Seismic waves
• Evidence of distinct layers in the Earth with different
densities comes from the observations of seismic
waves (the vibrations generated by earthquakes and
explosions)
• As seismic waves move through the Earth, wave
patterns may change indicating the waves were:
– Reflected: bounced back due to extreme density
– Refracted: directional change
• Measuring the changes in the velocity of these waves
as they travel through the Earth provides information
on the number of layers and the thickness and
composition of the layers.