Download Earth`s Interior

Chapter 12
Earth’s Interior
Mount Etna, Italy
Earth’s Internal Structure
 Earth’s
interior is divided into 3 major
layers based on chemical composition
 Crust,
Mantle & Core
 These layers are further divided based on
physical properties
Layers of the Earth
Gravity and Layering
 The
most dense material (iron) sinks
to the center of the planet
 The
least dense material makes up
the outer layers
Seismic Waves & the Earth’s
Interior
 We
learn about the earth’s interior by
studying seismic waves
 Velocities of P & S waves vary as they
travel through the earth
 Travel
faster through stiff (rigid) rocks
Possible Paths of Seismic Waves
The Earth’s Crust
 Oceanic
 Forms
Crust
at mid-ocean ridges
 Averages 7 kilometers thick
 Comprised of basalt and gabbro
 Average density of 3.0 g/cm3
The Earth’s Crust
 Continental
Crust
 Lots
of granite
 Averages 40 km thick
• Thickest ~70 km at mountains
• Thinnest ~20 km Basin & Range regions
 Average
density of 2.7 g/cm3
The Mohorovicic Discontinuity
 The
“Moho” is the
boundary between
the crust & mantle
P
wave velocities
abruptly increase at the
“Moho”
The Mantle
 ~80%
of earth’s
volume
 Solid
rocky layer?
 Convection Cells
 Peridotite
 The “D” layer
The Core-Mantle Boundary
(Guttenberg Discontinuity)
The Outer Core
 Is
a liquid (absence of S waves)
 Density of 9.9 g/cm3
 Mostly iron with some nickel
The Inner Core
 Is
a solid
 Density of 13 g/cm3
 Growing as the Earth cools
 Rotates faster than other layers
The Earth’s Temperature
 Heat
flows from hotter to colder areas
 Earth’s
core is 5500° C (10,000° F)
 Earth’s surface is 0° C (32° F)
 Heat flows from the core to the surface
How Did our
Earth Get Hot?
 Accretion
 Radioactive
Decay
 Asteroid collision
 Forming
our moon
Types of Heat
Transfer
 Conduction
 Molecular
Activity
 Convection
 Movement/Circulation
 Radiation
 Subatomic
Movement
Mantle Convection
& Plate Tectonics
Temperature
Profile
 Geothermal
 Crust
Gradient
is 30° C/km
 Mantle is 0.3°C/km
 Except the “D” layer
Earth’s Magnetic Field
 Convection
of iron in outer core
 Random reversals throughout history
 During reversals earth is unprotected
End of Chapter 12