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Slide 1
Visualizing Physical Geography
by Timothy Foresman and Alan Strahler
Chapter 9
Volcanic and Tectonic Landforms
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 2
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Chapter Overview
Plate Tectonics
Tectonic Activity and
Earthquakes
Volcanic Activity and
Landforms
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 3
Plate Tectonics
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Major and minor lithospheric plates of the globes
• Plate tectonics = The theory of tectonic activity, which deals
with lithospheric plates and their motions
• Movement of these plates is driven by heat from Earth’s core
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
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Slide 4
Plate Tectonics
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Types of Plate Boundaries
• Extensional tectonic activity
•Spreading boundary
•Plates pulled apart
• Compressional tectonic activity
•Converging boundary
•Plates pushed together
• Plates move past each other
•Transform boundary
•Transform faults
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 5
Plate Tectonics
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Converging boundaries
• A boundary where two
lithospheric plates move apart
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• Mid-ocean ridge
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 6
Plate Tectonics
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Transform boundaries
• Plates slide past each other without colliding
• The Dead Sea Fault marks the transform boundary
between the African Plate on the west and the Arabian
Plate on the east.
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 7
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Plate Tectonics
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 8
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Plate Tectonics
Convergent boundaries
• Subduction zones = Descent of
the edge of a lithospheric plate
under an adjoining plate and
into the asthenosphere
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A
B
• Oceanic trenches
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• Mariana Trench
• Japan Trench responsible
for Great Tohoku earthquake
of 2012
• Andes mountains
Which letter represents
the mid-ocean ridge
and subduction?
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 9
Plate Tectonics
Convergent boundaries
B
C
A
D
• Subduction zones
• Associated with volcanoes
and earthquakes
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Which letter is associated with
volcanoes, ocean trench,
oceanic crust, and continental
crust?
Which way does the
oceanic plate move?
Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
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Slide 10
Plate Tectonics
B
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A
Collision zones
• Continental plates collide
Which letter is an anticline and
which one is a syncline?
• Folds
• Orogeny is a mountain
building process
C
• Himalayas
• Appalachian
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D
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• Synclines
• Anticlines
• Overthrust faults
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 11
Plate Tectonics
Differential erosion of
strata
• The ways fold areas erode to
form sequential landforms
depends on the rock
strengths of different strata
• Weaker formations (shale
and limestone) erode away
to leave long, narrow ridges
of hard strata (sandstone or
quartzite)
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 12
Plate Tectonics
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Continental suture
• Two continents can converge to eliminate an ocean
between them
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• A continental
suture permanently
unites the two plates,
so that there is no
further tectonic
activity along that
collision zone
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• Appalachian and
Ural mountains
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 13
Tectonic Activity and Earthquakes
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Faults and fault landforms
• Faults occur when a sharp break
associated with a slippage
of the crustal block on one
side of a tectonic plate with
respect to another
• Depth can be several kilometers
• Fault slippage varies (1 cm to 15 m)
• Four main types of faults
• Normal
• Strike-slip
• Reverse
• Overthrust
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 14
Tectonic Activity and Earthquakes
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Faults and fault landforms
• Normal faults occur when the
crust on one side of normal
fault drops down relative to the
other side.
• Strike-slip faults are produced
when tectonic plates move
past each other horizontally
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 15
Tectonic Activity and Earthquakes
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Faults and fault landforms
• Reverse faults are produced
by compression in the crust
• Overthrust faults involve
mostly horizontal movement.
One slice of rock rides over the
adjacent ground surface.
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 16
Tectonic Activity and Earthquakes
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Faults and fault landforms
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• Grabens = a crustal block is
dropped down between two
normal faults.
• Horst = A crustal block
pushed up between
two normal faults.
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• Fault scarps
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 17
Tectonic Activity and Earthquakes
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Earthquakes
• Earthquakes = A trembling or
shaking of the ground
produced by movements along
a fault.
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• Focus = Location where fault
slipped
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• Epicenter = The location on the
Earth’s surface directly above
where a fault slipped to
produce an earthquake
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 18
Tectonic Activity and Earthquakes
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Earthquakes
• P-waves
• S-waves
• Epicenters are calculated by
triangulating the readings
from three different
seismometer reading
centers (A, B, and C), using
the difference in travel times
for P and S waves.
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
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Slide 19
Tectonic Activity and Earthquakes
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Earthquakes
• Magnitude = the amount of
energy released by an
earthquake
• Richter scale
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 20
Tectonic Activity and Earthquakes
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Tectonic environments of earthquakes
• Pacific Ring of Fire
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 21
Tectonic Activity and Earthquakes
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Earthquakes
• Subduction zone
•Greatest earthquakes,
including those in Japan,
Alaska, North America,
Central America, and
Chile
•Java Trench 9.0
earthquake and resulting
tsunami (2004)
•Tohoku 9.0 earthquake
and tsunami (2012)
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
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Slide 22
Tectonic Activity and Earthquakes
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Earthquakes
• Transform boundaries
• San Andreas Fault in
California
• 1906 San Francisco
Quake
• 1989 Loma Prieta
Quake
• 1992 Landers Quake
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
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Slide 23
Tectonic Activity and Earthquakes
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Earthquakes
• California
earthquakes,
identified as circles
with size proportional
to the earthquake
magnitude, are
overlaid on top of
delineated and
mapped fault lines.
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 24
Tectonic Activity and Earthquakes
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Earthquakes
• Spreading center
earthquakes mostly
occur along mid-ocean
ridges
• The New Madrid
earthquakes of 1811 is
an example of quakes
away from plate
boundaries
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
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Slide 25
Tectonic Activity and Earthquakes
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Earthquakes along blind faults
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Barn, Iran
2003 Quake
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 26
Tectonic Activity and Earthquakes
Space-based instruments imaging Earth movements
(InSAR)
Landform deformation
of tectonic stresses
after the Northridge,
California earthquake
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 27
Volcanic Activity and Landforms
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• Volcano = conical, circular
structure built by
accumulation of lava flows
and tephra (volcanic ash)
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• Magma
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
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Slide 28
Volcanic Activity and Landforms
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Volcanic activity
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Many volcanoes are
located on subduction
boundaries or rift zones
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 29
Volcanic Activity and Landforms
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Volcanic activity
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•Hot spots = A center
of volcanic activity
thought to be located
over a rising mantle
plume.
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
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Slide 30
Volcanic Activity and Landforms
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Volcanic eruptions
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•When lava is forced out of a volcano
violently, in the form of a volcanic
eruption, it is a severe hazard
• Various impacts from
eruptions
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• Mt. Pelée on the
island of Martinique in
1902
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
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Slide 31
Volcanic Activity and Landforms
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Volcanic eruptions
• Atmospheric impacts
from volcanic ash and
gases have been
shown to affect global
weather and surface
temperatures for
months or years after
an event
• Mt. Tambora in 1815
was the year without a
summer
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Based on this graph, what can
you conclude about the role of
volcanoes in global warming?
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 32
Volcanic Activity and Landforms
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Volcanic eruptions
• Monitoring
• Green is for the
least hazardous
• Red is for the most
hazardous
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 33
Volcanic Activity and Landforms
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Volcanic eruptions
• Types of Volcanoes
• shape, size, and
explosiveness depend
on the type of magma
• Magma comes from
two main types of
igneous rocks: felsic
and mafic
• Two most common
volcanoes:
• Stratovolcano
• Shield
Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
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Slide 34
Volcanic Activity and Landforms
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Volcanic eruptions
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•Stratovolcano = volcano
constructed of multiple layers
of lava and tephra (volcanic
ash)
•Felsic lavas
•Rhyolite, andesite
•Thick, resistant to flow
•Builds steep slopes
around volcanic vents
•Tall, steep cone, with
crater
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 35
Volcanic Activity and Landforms
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Volcanic eruptions
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•Stratovolcano
• Most active
stratovolcanoes on
circum-Pacific
mountain belt
• Associated with
subduction zones
• Felsic lavas produce
explosive eruptions
• Caldera
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 36
Volcanic Activity and Landforms
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Volcanic eruptions
•Stages of stratovolcano erosion
1
3
2
4
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 37
Volcanic Activity and Landforms
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Volcanic eruptions
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• Shield Volcano = low, often
large, dome-like
accumulation of basalt lava
flows emerging from long ,
radial fissures on flanks
• Mafic lava (basalt) is thin,
not viscous
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• Holds little gas
• Usually quiet eruptions
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 38
Volcanic Activity and Landforms
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Volcanic eruptions
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Shield Volcanoes
•Lava travels long
distances, spreads out in
thin layers
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•Shield volcanoes are
rounded domes, with
gentle slopes
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Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
Slide 39
Volcanic Activity and Landforms
Volcanic eruptions
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1
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•Erosion of shield Volcanoes
2
3
Mauna Kea, Hawaii
Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
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Slide 40
Volcanic Activity and Landforms
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Other volcanic landforms
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• Flood basalts
• Cinder cones
• Wizard Island in Crater Lake
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Continental flood basalts,
Columbia Plateau, U.S.
Visualizing Physical Geography
Copyright © 2012 John Wiley and Sons Publishers Inc.
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