Planet Earth: How it Works

1

• Module V
• Tectonic Activity of a Dynamic Planet
• (volcanoes, earthquakes, orogeny)

2

• Lesson 16
• Volcanoes

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The products of volcanic eruptions
? Lava flows Pyroclastic debris Volcanic gas
4
The products of volcanic eruptions
Lava flows
? The character of a lava flow will depend on
the viscosity of the lava
? Basaltic lava flow (very fluid low
viscosity) Andesitic lava flow (viscous ? more
silica) Rhyolitic lava flow (very viscous
felsic)
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Crystalline igneous rocks
6
The products of volcanic eruptions
Basaltic (mafic) lava flow
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The products of volcanic eruptions
Andesitic lava flow
? Slow moving cools faster Viscous enough to
form a dome
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The products of volcanic eruptions
Andesitic lava flow
9
The products of volcanic eruptions
Rhyolitic lava flow
? Very viscous cools very fast Lava do not
travel far (highly pyroclastic)
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The products of volcanic eruptions
Rhyolitic lava flow
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The products of volcanic eruptions
Rhyolitic lava flow
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The products of volcanic eruptions
? Lava flows Pyroclastic debris Volcanic gas
13
The products of volcanic eruptions
Pyroclastic debris
? All fragmental material erupted from a volcano
? Pieces of solid rock shattered/ejected from
vent Lava drops that solidify in the
air Glass shards (volcanic ash)
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The products of volcanic eruptions
Pyroclastic debris
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The products of volcanic eruptions
Pyroclastic debris
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The products of volcanic eruptions
Pyroclastic debris
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The products of volcanic eruptions
Pyroclastic debris water lahars
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The products of volcanic eruptions
Pyroclastic debris water lahars
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The products of volcanic eruptions
? Lava flows Pyroclastic debris Volcanic gas
20
The products of volcanic eruptions
Volcanic gas
? Most magma contains dissolved gases (up to 9
of magma composition) water vapour (H2O),
hydrogen sulfide (H2S), carbon dioxide (CO2),
and sulfur dioxide (SO2) Gas come out of
solution as pressure decreases (soda pop)
21
The products of volcanic eruptions
Volcanic gas
? Generally, felsic lavas contain more gases The
gas expansion in a felsic magma (as it rises to
the surface) can cause explosive pressures to
build up
22
The architecture and shape of volcanoes
Magma chamber
? Magma accumulates underground in a magma
chamber
If magma solidifies ? intrusive igneous rock If
it rises through an opening ? extrusive rock
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The architecture and shape of volcanoes
Magma chamber
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The architecture and shape of volcanoes
Volcanic cone
? In some volcanoes, the conduit has the shape
of a vertical pipe solid products of eruption
(lava pyroclastic debris) accumulates around
a conduit to form a Volcanic cone
25
The architecture and shape of volcanoes
Volcanic cone
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The architecture and shape of volcanoes
Volcanic fissure
? In some volcanoes, the conduit is a vertical
crack called Volcanic fissure
27
The architecture and shape of volcanoes
Volcanic fissure
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The architecture and shape of volcanoes
Volcanic fissure
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The products of volcanic eruptions
Volcanic crater
? At the top of the cone, a circular depression
develops (1) material from the eruption
accumulates around the vent or (2) the summit
collapses, after eruption, into the drained
conduit
30
The products of volcanic eruptions
Volcanic crater
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The products of volcanic eruptions
Volcanic crater
Mt. Erebus (Antarctica)
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The products of volcanic eruptions
Volcanic crater
Capulin national monument (New Mexico)
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The products of volcanic eruptions
Volcanic caldera
? After a major eruption, the center of the
volcano may collapse into the empty magma
chamber, creating a caldera
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The products of volcanic eruptions
Volcanic caldera
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The products of volcanic eruptions
Volcanic caldera
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The products of volcanic eruptions
Volcanic caldera
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The products of volcanic eruptions
Volcanic caldera
Quilotoa, Ecuador
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Volcanoes and Plate Tectonics
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Volcanoes and Plate Tectonics
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Volcanoes and Plate Tectonics
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Volcanoes and Plate Tectonics
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Volcanoes and Plate Tectonics
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Volcanoes and Plate Tectonics
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Volcanoes and Plate Tectonics
Iceland a mantle plume on a ridge
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Questions?
46
Lesson 16 review questions
1. What are the products of volcanic eruptions?
2. What are the 3 types of lava flow? Explain
their differences.
3. What are pyroclastic debris? Give examples.
4. When pyroclastic material mix with water,
they form a type of mudflow called
5. Which type of lava contains more volcanic gas
felsic or mafic? Explain why?
6. What is a magma chamber?
7. What is the difference between a volcanic cone
and a volcanic fissure?
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Lesson 16 review questions
8. What is the difference between a volcanic
crater and a volcanic caldera?
9. What type of plate boundary is associated
with the formation of island arc volcanoes? Give
examples.
10. What type of plate boundary is associated
with the formation of continental arc volcanoes?
Give examples.
11. What type of plate boundary is associated
with the formation of rift volcanoes? Give
examples.
12. What type of plate boundary is associated
with the formation of mid-ocean ridge volcanoes?
Give examples.
13. What type of plate boundary is associated
with the formation of hot-spot volcanoes? Give
examples.
48

• Lesson 17
• Earthquakes

49
What are earthquakes?

• ?
• Earthquakes are ground-shaking episodes
• resulting from (major natural causes)
• Sudden formation of a fault
• Sudden slip of an existing fault
• Movement of magma inside a volcano
• Giant landslides

Fault formation movement causes the vast
majority of destructive earthquakes
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What are faults?
Faults are fractures on which slip or sliding
occurs
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Types of faults
Normal fault
Faults are fractures on which slip or sliding
occurs
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Types of faults
Reverse fault
Faults are fractures on which slip or sliding
occurs
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Types of faults
Thrust fault
Faults are fractures on which slip or sliding
occurs
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Types of faults
Strike-slip fault
Faults are fractures on which slip or sliding
occurs
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Types of faults
Oblique slip fault
Faults are fractures on which slip or sliding
occurs
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How faulting generates earthquakes?
Earthquakes result from vibrations (energy
pulses) caused by the sudden break of rock in
faulting
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How faulting generates earthquakes?
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Earthquake focus hypocenter X epicenter
Hypocenter (focus)
? The place (point) in the Earth where the
earthquake occurred
Epicenter
? The place (point) in the Earths surface that
lies directly above the quake focus
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Earthquake focus hypocenter X epicenter
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Earthquake focus hypocenter X epicenter
Epicenters of earthquake events in late 2002
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Foreshocks and Aftershocks
Foreshocks
? Small earthquakes preceding a major
one (smaller cracks before rock breaks)
Aftershocks
? Smaller earthquakes that follows a major
one (resulting from new stress created by the
major earthquake)
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The San Francisco earthquake (1906)
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The San Francisco earthquake (1906)
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The San Francisco earthquake (1906)
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The San Francisco earthquake (1906)
Strike-slip fault
Faults are fractures on which slip or sliding
occurs
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The Alaska earthquake (1964)
Alaska 1964 (thrust fault)
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The Alaska earthquake (1964)
Thrust fault
Faults are fractures on which slip or sliding
occurs
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The Alaska earthquake (1964)
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The Alaska earthquake (1964)
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The amount of slip on faults (displacement)
The amount of slip decreases toward the edge of
the slipped area It depends on the distance to
the quake focus
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The amount of slip on faults (displacement)
Depends on the size of the earthquake
San Francisco 1906 (strike-slip fault)
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How earthquake energy is transmitted?
? Like other kinds of energy, earthquake energy
travels in the form of waves called seismic
waves
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Seismic waves
Types of seismic waves
?
Body waves (pass through the interior of
Earth) Surface waves (travel along the
Earths surface)
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Seismic waves
Types of wave behaviour
?
Compressional waves back and forth parallel to
the direction of wave propagation Shear waves
back and forth perpendicular to the direction
of wave propagation
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Seismic waves
Wave behaviour compressional wave
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Seismic waves
Wave behaviour shear wave
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Seismic waves
Seismic waves used by geophysicists
?
P-waves compressional body waves S-waves
shear body waves R-waves surface waves (ripple
up down) L-waves surface waves (ripple
sideways)
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Seismic waves
P-waves compressional body waves
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Seismic waves
S-waves shear body waves
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Seismic waves
R-waves surface waves (ripple up down)
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Seismic waves
L-waves surface waves (ripple sideways)
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Seismic waves
Relative speed of seismic waves
?
Which is faster P-waves or S-waves???
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Seismic waves
Recording seismic waves in a seismograph
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Seismic waves
Relative speed of seismic waves
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Seismic waves
Relative speed of seismic waves
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Seismic waves
Using seismic waves to find the epicenter
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Seismic waves
Using seismic waves to find the epicenter
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Seismic waves
Using seismic waves to find the epicenter
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Damage from earthquakes
Mostly caused by ground shaking displacement
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Ground shaking and displacement
P-waves compressional body waves
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Ground shaking and displacement
S-waves shear body waves
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Ground shaking and displacement
R-waves surface waves (ripple up down)
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Ground shaking and displacement
L-waves surface waves (ripple sideways)
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Ground shaking and displacement
Failing built structures
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Ground shaking and displacement
Landslides and avalanches
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Ground shaking and displacement
Landslides and avalanches
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Ground shaking and displacement
Sediment liquefaction
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Ground shaking and displacement
Sediment liquefaction
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Ground shaking and displacement
Sediment liquefaction
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Ground shaking and displacement
Tsunami
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Ground shaking and displacement
Tsunami
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Ground shaking and displacement
Tsunami (Indian Ocean 2004)
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Damage from earthquakes
Disease and distress
?
(1) Earthquakes cut water and sewer lines,
destroying clean water supplies and exposing
the public to disease-causing microbes
(2) Earthquakes cut transportation lines,
preventing food and medicine from reaching the
affected area
104
Earthquakes and Plate Tectonics
deep
shallow
105
Earthquakes and Plate Tectonics
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Earthquakes and Plate Tectonics
Where do earthquakes occur?
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Earthquakes and Plate Tectonics
Intraplate earthquakes
?
Earthquakes that occur in the interior of plates
and are not associated with plate boundaries,
active rifts or collision zones
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Earthquakes and Plate Tectonics
Intraplate earthquakes
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Earthquakes and Plate Tectonics
Intraplate earthquakes
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Earthquakes and Plate Tectonics
Intraplate earthquakes
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Earthquakes and Plate Tectonics
Intraplate earthquakes
112
Questions?
113
Lesson 17 review questions
1. The vast majority of destructive earthquakes
result from
2. What are faults?
3. What are the (5) types of faults?
4. What is the difference between normal and
reverse faults?
5. What is the difference between reverse and
thrust faults?
6. What is the difference between strike-slip
and oblique faults?
114
Lesson 17 review questions
7. Explain how fault formation generates
earthquakes.
8. What is the difference between an earthquake
focus and its epicenter?
9. What is the difference between foreshocks and
aftershocks? What causes them?
10. What type of fault caused the big San
Francisco earthquake of 1906?
11. What type of fault caused the big Alaska
earthquake of 1964?
12. The amount of slip on faults during an
earthquake is called
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Lesson 17 review questions
13. How is earthquake energy transmitted?
14. What are the (2) types of seismic waves?
15. What is the difference between body waves
and surface waves?
16. What is the difference between compressional
waves and shear waves?
17. What are the (2) body waves used by
geophysicists to determine the earthquake focus
and epicenter?
18. Describe the movement (behaviour) of P-waves.
19. Describe the movement (behaviour) of S-waves.
116
Lesson 17 review questions
20. Which wave is faster P-waves, S-waves, or
surface waves?
21. Which wave causes more damage P-waves,
S-waves, or surface waves?
22. What type of ground movement (vibration) is
caused by the arrival of P-waves?
23. What type of ground movement (vibration) is
caused by the arrival of S-waves?
24. What type of ground movement (vibration) is
caused by the arrival of surface waves?
25. Give examples of damage from earthquakes.
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Lesson 17 review questions
26. What are the only places on Earth where you
can find deep-focus earthquakes?
27. Where can you find shallow earthquakes?
28. The only earthquakes that are not associated
with plate boundaries, active rifts or collision
zones occur at ____________________ and are
called
29. Earthquakes that happen in Ohio are called
30. Where is the most tectonically active place
in the US midwest?
31. Where is the most tectonically active place
in Ohio?