Planet Earth:
An Owner’s Manual
Earth’s Interior Machine
What phenomena are produced by the Earth’s
complex internal structure?
Earth’s magnetic field
•Generated
by movement of
currents in liquid outer core
around solid inner core.
•Shields the Earth from the
solar wind
•Prevents the atmosphere from
being slowly stripped away by
the solar wind.
•Causes the aurora borealis
magnetic force lines
and aurora australis.
around a bar magnet
•
•
•
•
Aurora Borealis (Australis)
Northern (Southern) Lights
Caused by solar wind particles trapped in the lines of
Earth’s magnetic field.
Charges particles flow downward toward the poles,
collide with gases in the atmosphere.
Ionized gas glows red, green, and blue.
Aurora Borealis
Pattern of aurora
activity around
the north pole.
Questions for Discussion
What is the Solar
Wind? What are the
potential dangers of
the solar wind?
LR
What will happen
to the Earth’s
atmosphere after the
core solidifies?
RR
What will happen
to the Earth’s
magnetic field when
the outer core
solidifies?
LF
What will happen
to the temperature
of the Earth’s
surface after the
core solidifies?
RF
Planetary Atmospheres
• 96% CO2
3% N2
•
• Sulfuric Acid
• trace H2O
• 90 atm at
surface
78% N2
•
21% O2
•
H2O
•
• < 1% CO2, CH4
• 1 atm at surface
•
•
•
•
95% CO2
4% N2
.13 % O2
.01 atm at
surface
Question for Discussion
Mars is half the diameter and 1/10th the
mass of the Earth.
Mars has no magnetic field.
Based on these observations, construct a
hypothesis to explain the extremely thin
atmosphere on Mars.
What observations could be collected to test
your hypothesis?
What phenomena result from the
peculiar structure of the Earth?
Plate Tectonics
• Lithosphere
is broken up into tectonic
plates that “float” on the weaker
underlying asthenosphere.
• Plate
move as they form on one side are
are recycled on the other side.
• “Continental
Drift”
• Plate
collisions cause earthquakes,
volcanoes, and mountain building
Mafic (Ma / Fe)
Plate
Sialic (Si / Al)
shallow
intermediate
deep
Global Distribution of Earthquakes
shield volcanoes
Divergent Plate Boundary
stratovolcanoes
Convergent Plate Boundary
Trench
Hot Spot
MidOcean
Ridge
Trench
Rift
Zone
Plate Tectonics
Volcanic eruption in Iceland
Basaltic lava
Shield Volcano
Basaltic Lava
High volume magma
eruptions
Relative size
Stratovolcano
Andesitic Lava
Explosive ash eruptions
Shield Volcano
Sierra Negra (Isabela / Galápagos Islands)
Eruption on the north rim of the Sierra Negra
caldera, October 2005.
photo is courtesy of Aksel Voigt
Video by Karen Harpp, Colgate University
Shield Volcano and
Aa lava flow
Fernandina, Galápagos
Physical Geology - Rock Cycle and Isostasy
Lava flow on the island of Hawaii
Stratovolcanoes
Mt. Saint Helens prior to 1980.
Stratovolcanoes
Mt. Saint Helens erupting
Stratovolcanoes
Mt. Saint Helens after 1980 eruption.
Cotopaxi Stratovolcano
Ecuador
Volcanic ash and
pumice deposit
Otavalo, Ecuador
Physical Geology - Rock Cycle and Isostasy
Decompression
Melting
Flux
Melting
Thermal
Melting
Production of Magma
Melting can be induced in rock by increasing
temperature or decreasing pressure.
decompression
melting
Thermal Melting
from Mantle Plumes
Rock in the Earth’s
mantle flows via
convection, driven
upward by the flow of
interior heat and
pulled downward by
gravity.
Mantle plumes deliver
heat to the base of
the lithosphere and
cause melting.
le
Mant
Core
Iceland
Galapagos
Hawaii
Mt. St. Helens
Cotopaxi
Shield Volcano
Volcanism
Stratovolcano
Volcanism
Decompression Melting
Subduction
Subduction
Questions for Discussion
Why are there
volcanoes at divergent
plate boundaries?
LR
What might cause
shield volcanoes and
stratovolcanoes to
erupt so differently?
LF
Why are there
volcanoes at
convergent plate
boundaries?
RR
Besides rock, what
else descends into
the mantle when a
tectonic plate is
subducted?
RF
Flux Melting at Convergent Plate Boundaries
Flux melting
of the
asthenosphere
due to the
addition of
water from the
descending
plate.
Melting
of dry
mantle
rock
Partial melting of rock due
to mixing with water
Silica
Density
3.01
2.77
Seafloor
What is the origin of
continental crust?
What is the origin of
oceanic crust?
2.69
Continents
Why is the elevation of Earth’s surface
bimodal, while Mars and Venus are unimodal?