Chapter 14 discusses volcanic and tectonic processes, as well as the resulting landforms, emphasizing processes such as weathering, erosion, and tectonics. It details various types of igneous eruptions and their landforms, including shield and composite cones, as well as the effects of tectonic forces on rock structures leading to earthquakes. The chapter also covers the measurement of earthquakes and the associated hazards from significant historical events.

1. Chapter 14: Volcanic and Tectonic
Processes and Landforms
Physical Geography
Physical Geography
Ninth Edition
Ninth Edition
Robert E. Gabler
James. F. Petersen
L. Michael Trapasso
Dorothy Sack

2. Volcanic and Tectonic Processes and
Landforms

3. Volcanic and Tectonic Processes and
Landforms
• Topography: distribution of landscape
(mountains, plains, hills, valleys, plateaus)
• Landforms: surface terrain features
• Geomorphology
– Understanding landforms and landscapes
– Seek explanations for the shape, origin,
spatial distribution, and development of terrain
features
– Igneous processes and tectonic processes

4. 14.1 Landforms and Geomorphology
• Relief
– Low relief (e.g. western Utah)
– High relief (e.g. Great Basin, Rockies, Himalayas)

5. 14.1 Landforms and Geomorphology
• Geomorphic Processes
– Endogenic processes: originate within earth and
result in an increase in surface relief
– Exogenic processes: originate at Earth’s
surface, tend to decrease relief
• Examples:
– Weathering
– Erosion
– Transportation
– Deposition
– Geomorphic agent (e.g. flowing water or ice)

6. 14.1 Landforms and Geomorphology
• Rising Relief:
– Endogenic processes
greater than exogenic
processes
– Grand Tetons, Wyoming
• Punctuated Equilibrium
– Examples:
• Earthquakes
• Volcanic eruption
• Exogenic processes (e.g.
flood)

7. 14.1 Landforms and Geomorphology
• Punctuated Equilibrium
– Mt. Vesuvius

8. 14.2 Igneous Processes and
Landforms
• Landforms resulting from
igneous processes are
related to:
– Volcanism (extrusive)
• Volcanoes
– Plutonism (below Earth’s
surface)

9. 14.2 Igneous Processes and
Landforms
• Volcanic Eruptions
– Natural processes
– Large eruptions can be
devastating
– Vary greatly in size and
character
– Resulting landform varies
– Two main types of Eruptions:
• Explosive
• Effusive

10. 14.2 Igneous Processes and
Landforms
• Nature of Volcanic Eruption
dependent on:
– Mineral composition
• Silica rich felsic (cool, thick,
resistant to flowing)
• Mafic (very hot, flows readily)
• Silica rich magmas with rhyolite
(violent eruption)
• Basaltic (effusive)
– Pressure
– Pyroclastic materials (ash and
tephra)

11. 14.2 Igneous Processes and
Landforms
• Volcanic Landforms
– Depends primarily on explosiveness
– 6 major kinds (least explosive to most explosive)
• Lava flows
• Shield Volcanoes
• Cinder Cones
• Composite Cones
• Plug Domes
• Calderas

12. 14.2 Igneous Processes and
Landforms
• Lava Flows
– Basalt is the most
common
– Small potential for
explosive eruption
– Joints and columnar-
jointed basalt flows
– Pahoehoe

13. 14.2 Igneous Processes and
Landforms
• Lava Flows
– Aa
– Fissures
– Flood basalts
– Basalt plateaus
• Columbia plateau
• Deccan plateau in
India

14. 14.2 Igneous Processes and
Landforms
• Shield Volcanoes
– Numerous basaltic
lava flows piling up
– Gently sloping, dome
shaped cone
– Hawaii
– Not very explosive,
but still damaging

15. 14.2 Igneous Processes and
Landforms
• Shield Volcanoes
Q: Why do Hawaiian volcanoes erupt less explosively than
volcanoes of the Andes or Cascades?

16. 14.2 Igneous Processes and
Landforms
• Cinder Cones
– Smallest type of
volcano
– Rhyolite composition
– Steep, straight sides
and a large crater in
the center
– Examples:
• Craters of the Moon,
ID
• Sunset Crater, AZ

17. 14.2 Igneous Processes and
Landforms
• Composite Cones
– Effusive or explosive
– Composite of lava and
pyroclastic
– Stratovolcanoes
– Pyroclastic flows
– Concave slopes that are
gently near the base and
steep near the top
– Fujiyama, Vesuvius,
Rainer, Mt. St Helens

18. 14.2 Igneous Processes and
Landforms
• Composite Cones
Q: Could other volcanoes
in the Cascade Range,
such as Oregon’s Mount
Hood, erupt with the kind
of violence that Mount St.
Helen’s displayed in
1980?

19. 14.2 Igneous Processes and
Landforms
• Composite Cones
– Examples:
• Krakotoa (1883 and
subsequent tsunami)
• Mount Pinatubo
(1991)
• Many died in both
events above.
– Mexico City is
threatened

20. 14.2 Igneous Processes and
Landforms
• Plug Domes
– Viscous silica-rich
magma pushed into a
vent
– Dome shaped summit
and jagged blocks
make up cone on
steep sloping sides
– Lassen Peak, CA

21. 14.2 Igneous Processes and
Landforms
• Calderas
– Large
depression
– Crater Lake
– Yellowstone

22. 14.2 Igneous Processes and
Landforms
• Plutonism and
Intrusions
– Igneous intrusions
(plutons)
– Classified by size,
shape, and
relationships to
surrounding rocks
– Stock
– Laccolith

23. 14.2 Igneous Processes and
Landforms
• Examples of
Laccoliths
– Henry and La Sal
Mountains in S. Utah
• Sill
– Palisades along
Hudson River, NY

24. 14.2 Igneous Processes and
Landforms
• Dike
– New Mexico
• Volcanic Neck
– Shiprock, New
Mexico

25. 14.3 Tectonic Forces, Rock Structure,
and Landforms
• Rock Structure
– Nature
– Orientation
– Inclination
– Arrangement of
affected rock layers
– Strike
– Dip

26. 14.3 Tectonic Forces, Rock Structure,
and Landforms
• 3 Principal Tectonic
Forces:
– Compressional
– Tensional
– Shearing

27. 14.3 Tectonic Forces, Rock Structure,
and Landforms
• Compressional
Tectonic Forces
– Folding (e.g.
Appalachians,
Rockies)
– Anticlines
– Synclines
– Recumbent folds

28. 14.3 Tectonic Forces, Rock Structure,
and Landforms
• Compressional
Tectonic Forces
– Faulting
– Reverse Fault
– Fault
– Thrust fault
– Overthrust

29. 14.3 Tectonic Forces, Rock Structure,
and Landforms
• Tensional Tectonic
Forces
– Fault blocks
– Normal faults
– Graben and Horst
(e.g. Great Basin)

30. 14.3 Tectonic Forces, Rock Structure,
and Landforms
• Tensional Tectonic
Forces
– Tilted fault blocks
(e.g. Death Valley)
– Rift valleys
• Rift Valley of east
Africa
• Rio Grande rift

31. 14.3 Tectonic Forces, Rock Structure,
and Landforms
• Tensional Tectonic
Forces
– Escarpment (scarp)
– Fault scarp
• Eastern Sierra
Nevada
• Grand Tetons
– Piedmont fault
scarps

32. 14.3 Tectonic Forces, Rock Structure,
and Landforms
• Shearing Tectonic
Forces
– Dip-slip faults
– Strike-slip faults
– Lateral fault
• San Andreas Fault
• 1906 san Francisco
Earthquake

33. 14.3 Tectonic Forces, Rock Structure,
and Landforms
• Relationship between Rock Structure and
Topography

34. 14.4 Earthquakes
• Earthquakes
– Evidence of present-
day tectonic activity
– Ground motions of
Earth caused when
accumulating tectonic
stress is suddenly
relieved
– Seismic waves
– Epicenter
– Aftershocks

35. 14.4 Earthquakes
• Measuring
Earthquake Size
– Size of the event
– Degree of its impact
on humans
– Earthquake
magnitude
– Moment magnitude

36. 14.4 Earthquakes
• Measuring Earthquake Size
– Earthquake intensity
– Modified Mercalli scale

37. 14.4 Earthquakes
• Earthquake Hazards
– 2004 Sumatra-
Andaman
Earthquake in quake
and ensuing tsunami
• Killed 300,000
• 9.1 magnitude
– Pakistan (7.6)
– Kobe, Japan (7.2)
– Mojave Desert (7.5)

38. 14.4 Earthquakes
• Earthquake Hazards
– Loma Prieta (San
Francisco Bay) in
1989
– Northridge
earthquake (1994
6.7 magnitude)
– Mexico City (1985
8.1 magnitude)

39. 14.4 Earthquakes
• Earthquake Hazards
Q: what is the earthquake hazard where you live,
and what does that level of intensity mean
according to the Mercalli scale?

40. Physical Geography
End of Chapter 14: Volcanic and
Tectonic Processes and Landforms