This chapter discusses volcanic and tectonic landforms and processes. It describes different types of volcanic eruptions and the resulting landforms such as lava flows, shield volcanoes, cinder cones and composite cones. It also discusses tectonic forces that shape the landscape, including folding, faulting and rifting. Earthquakes are examined as evidence of present-day tectonic activity, and methods for measuring their magnitude and intensity are outlined. Hazards posed by large earthquakes are also highlighted.

1. Chapter 14: Volcanic and Tectonic Processes and Landforms Physical Geography 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