Earth’s Interior Machine
Magnetic Field and
Plate Tectonics
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
and aurora australis.
magnetic force lines
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.
Pattern of aurora
activity around
the north pole.
Questions for Discussion
What is the Solar
Wind? Why is it a
potential problem?
What causes the
aurora borealis /
australis
What will happen
to the Earth’s
magnetic field when
the core freezes?
What will happen
to the Earth’s
atmosphere after the
core freezes?
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 - all groups
Mars is a smaller planet than 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
• Movement
and recycling of the Earth’s
oceanic lithosphere.
• Production of continental crust.
• “Continental Drift”
• Plate collisions and mountain building
• Volcanism and Earthquakes
Mafic (Ma / Fe)
Plate
Sialic (Si / Al)
Rock in the Earth’s
mantle flows via
convection, driven
upward by the flow of
interior heat and
pulled downward by
gravity.
shield volcanoes
Divergent Plate Boundary
stratovolcanoes
Convergent Plate Boundary
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.
Video by Karen Harpp, Colgate University
photo is courtesy of Aksel Voigt
Lava flow on the island of Hawaii
Shield Volcano and
Aa lava flow
Fernandina, Galápagos
Physical Geology - Rock Cycle and Isostasy
Stratovolcanoes
Mt. Saint Helens prior to 1980.
Stratovolcanoes
Mt. Saint Helens after 1980 eruption.
Cotopaxi Stratovolcano
Ecuador
Volcanic ash and
pumice deposit
Otavalo, Ecuador
Physical Geology - Rock Cycle and Isostasy
Questions for Discussion
Why are there
volcanoes at divergent
plate boundaries?
Why are there
volcanoes at
convergent plate
boundaries?
What might cause
shield volcanoes and
stratovolcanoes to
erupt so differently?
Besides rock, what
else descends into
the mantle when a
tectonic plate is
subducted?
Why is the
asthenosphere
melting above
the subducting
ocean 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
oceanic crust?
What is the origin of
continental crust?
2.69
Continents
Why is the elevation of Earth’s surface
bimodal, while Mars and Venus are unimodal?