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What’s inside the Earth?
Is there really another world
at the center?
What is the
energy for surface
features?
Our Dynamic Earth
 Earth
is constantly changing
 How do we know it’s dynamic??

Earthquakes (and tsunamis)

Volcanic eruptions

Surface Features:
– Mountain Ranges; Mid-Ocean
Ridges; Deep-Sea Trenches
Topography of the Ocean Floor
Topography of the Ocean Floor
Topography of the Ocean Floor
Topography of the Ocean Floor
Elevated
Continents
Elevated
Continents
Submerged
Ocean Basins
Questions:
How are the ocean basins formed?
How permanent are these features?
What is the age of the ocean floor?
What’s the age of the continents?
Why are the ocean basins deep and
the continents high?
The Surface of the Earth
2 levels:
– elevated continents
– submerged ocean basins
 What causes these surface features?
 We must know what goes on inside the Earth

What’s going on inside the
Earth?
Early Ideas
 Jules
Verne
“Journey to
the Center of
the Earth”
Entered in Iceland
 Exited in Italy

Information about the Earth’s
Interior comes from:
 Meteorites
 Volcanoes
 Seismic
Waves (“sound images”)
 Tremendous pressure
enormous heat (from natural
radioactivity)
Meteor Crater (Arizona)
Willamette Meteorite
Found 1902,
in West Linn
 Largest in
the U.S.A.
 Sold and now
resides in
NYC

Volcanoes
E.g., Hawaiian “hotspot”
 Windows into the
Earth
 Samples 200km down
(e.g., diamonds!)

Seismic Waves

Sound energy
from earthquakes
and large
explosions
DEPTHS

Top of Mantle
– 10 to 70 km (5 to 30
miles)

Top of Core
– 2,900 km (2000
miles)

Center of Earth
– 6,300 km (4,000
miles)

Mt. Everest  9 km high.
 Marianas Trench  11
km deep.
How do we know what’s inside
the Earth?
How do we know what’s inside the Earth?
Direct Observations:
Exposures on surface up
from  50 km (30 miles)
depth
 Drilling to  15 km (10
miles)
 Volcanic Material up
from  200 km (120
miles) depth

How do we know what’s inside
the Earth?
How do we know what’s inside
the Earth?
Indirect Observations:
Magnetic Field
Iron core.
 Gravity Field
 Densities:
– Crust: 2 - 3 g/cm3
– Mantle: 3.3 - 5.8g/cm3
– Core: 10.8 g/cm3
 Earthquake Seismic Waves
 Physical state of crust,
mantle, core.


Interior of Earth by Strength

LITHOSPHERE
– rigid outer shell
– crust and upper mantle (~ 50 to 200
km thick)
– somewhat brittle, breakable
– cold (like butter out of fridge)

ASTHENOSPHERE
– warmer, plastic layer under
lithosphere
– mantle from ~ 150 to 700 km
– squishy, plastic
– warm (like softened butter)

LOWER MANTLE
– Solid, but can flow over time!
– ~700 to 2900 km

OUTER CORE
– liquid

INNER CORE
Elevated
Continents
Submerged
Ocean Basins
Swimming Pool
Earth’s Mantle
Continental
Crust
Earth’s Mantle
Types of Crust
 Continental
Crust
– 20 to 70 km (10 to 30 miles) thick.
– Composed of highly evolved rocks,
like granite (igneous), and
metamorphic rocks, squeezed and
heated under mountain ranges
Continental
Crust
Earth’s Mantle
Oceanic Crust
Types of Crust
 Continental
Crust
– It is less dense, but thicker than oceanic
crust
 Oceanic
Crust
– It is thinner, but more dense than
continental crust, so it sits lower than
continental crust.
– Composed of basalt (volcanic).
Thick, Buoyant
Continental Crust
Thin, Less-Buoyant
Oceanic Crust
Thick Continental Crust Floats Higher
Thick Continental Crust Floats Higher
Thin Oceanic Crust Floats Lower
Water Fills in
the Low Areas
And Hides
Features on the
Ocean Floor!
Water Fills in
the Low Areas
PLATE BOUNDARIES
PLATE TECTONICS
Tectonics:
 From the Greek “tecton”

builder

“architect”
 The study of large features on Earth’s
surface and the processes that formed
them.

PLATE TECTONICS:
Large features:
– continents, mountain ranges
– ocean basins
 and processes:
– earthquakes
– volcanic eruptions
 These are due to movement of plates of
Earth’s outer shell.


All resulting from mantle convection
Cracked Egg Shell!