1. Chapter 12 Tectonics, Earthquakes, and Volcanism
Geosystems 6e
An Introduction to Physical Geography
Robert W. Christopherson
Charles E. Thomsen

2. Tectonics, Earthquakes, and Volcanism
Earth’s Surface Relief Features  
Crustal Formation Processes  
Crustal Deformation Processes  
Orogenesis (Mountain Building)  
Earthquakes  
Earthquakes and the San Andreas Fault  
Volcanism  

3. Earth’s Surface Relief Features
Relief – vertical elevation differences in the landscape
Topography – the characteristics of the Earth’s surface
Crustal Orders of Relief 
First Order – continental landmasses and ocean basins
Second Order – mountain chains, plains, lowlands, mid-ocean ridges, oceanic trenches 
Third Order – individual mountains, cliffs, valleys, hills

4. Earth’s Surface Relief Features
Earth’s Topographic Regions 
Plains
High tablelands
Hills and low table lands
Mountains
Widely spaced mountains
depressions

5. Crustal Formation Processes
Continental Shields  - region where a craton is exposed at the surface
Craton – the heart of continental crust
Terranes – slowly migrating crustal pieces which have become part of a plate
Appalachian Mountains
Folding – convergent plate boundary where rocks are compressed and deformed

6. Continental Shields
Figure 12.4

7. Crustal Formation
Figure 12.5

8. Faults
Rocks on either side of a fracture in Earth’s crust displace relative to the other side in a process known as faulting.
Earthquakes occur at the moment of fracture and represent a sharp release of energy
The basic types of faults: normal fault, reverse (thrust) fault, and strike-slip fault

9. Normal Fault
Figure

10. Reverse Fault
Figure

11. Strike-slip Fault
Figure

12. San Andreas Fault
Figure

13. Orogenesis: Oceanic-continental Collision
Figure

14. Oceanic-oceanic Collision
Figure

15. Continental-continental Collision
Figure

16. The Appalachian Mountains
Figure 12.18

17. Earthquakes Forecasting earthquakes Land uplift and tilting
tiltmeter
Increasing minor tremors
Changes in magnetic field
Previously undetected faults
Radon monitoring
Carbon dioxide
Foreshocks – tremor preceding the main shock

18. Earthquakes
Focus – subsurface area along a fault plane where the motion of seismic waves is initiated
Epicenter – area at surface directly above the focus

19. Anatomy of an Earthquake
Figure

20. Volcanism
Volcano – form at the end of a central vent or pipe that rises from the astenosphere and upper mantle through the crust into a volcanic mountain
Geothermal energy – boiled groundwater
Lava – molten rock
Pyroclastics – pulverized rock and clastic materials ejected during an eruption

21. Where to find volcanoes
Subduction zones, Sea-floor spreading, and Hot spots

22. Volcanoes
Effusive eruption – gentler eruptions that produce enormous volumes of lava
Hawaii and Iceland
Shield volcanoes
Explosive eruptions – volcanic activity inland from subduction zones
Composite (strato) volcanoes

23. Composite Volcanoes
Figure

24. Shield and Composite Volcanoes
Figure

25. White’s Isle, New Zealand
Figure 12.31

26. Calderas
Large depression formed when a volcanic mountain collapses after erupting
Long Valley Caldera, California
Carbon dioxide

27. Geosystems 6e An Introduction to Physical Geography
End of Chapter 12
Geosystems 6e
An Introduction to Physical Geography
Robert W. Christopherson
Charles E. Thomsen