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Chapter 9 Earthquakes and Volcanism I. Earth’s Earth s Surface Relief II. Orogenesis III. Earthquakes A. What is an earthquake B. Anatomy of an Earthquake C. Measuring Earthquakes D. Tsunamis Earth’s Hypsometry Figure 9.2 1 I. Earth’s Surface Relief Features Crustal Orders of Relief Crustal Orders of Relief 1. First order relief – refers to the coarsest level of landforms, including continental platforms and ocean basins. 2. Second order relief – intermediate level of landforms, including mountain masses, plains, and lowlands 3. Third order relief – most detailed order of relief includes things like mountains, cliffs, valleys, hills, and other small scale landforms. I. Earth’s Surface Relief Features Cratons and Continental Shields Craton – Continental nucleus of ancient crystalline rock on which the continent grows with the addition of crustal fragments and sediments. A continental shield occurs where a craton is exposed at the surface. Figure 12.4 2 I. Earth’s Surface Relief Features Building Continental Crust Figure 12.5 I. Earth’s Surface Relief Features North American Terranes Terrane: A migrating piece of Earth’s crust, dragged about by processes of mantle convention and plate tectonics. Figure 12.6 3 I. Earth’s Surface Relief Features North American Terranes Figure 12.6 I. Earth’s Surface Relief Features Crustal Deformation Processes Folding: Rock bends as a result of stress. F lti R k fractures f t lt off stress t th t is i greater t Faulting: Rock as a result that than the internal strength of the rock. 4 Crustal Deformation Processes A. Folding Figure 12.11 Folding Figure 9.8 5 Crustal Deformation Processes A. Folding Figure 12.11 6 Normal Fault Figure 9.11 Reverse Fault Figure 9.11 7 Strike-Slip Fault Figure 9.11 Crustal Deformation Processes B. Faulting San Andreas Fault Figure 12.12 8 Figure 12.11 II. Orogenesis A. Definitions Orogenesis refers to the building of mountains. 9 II. Orogenesis (Mountain Building) A. Types of Orogenies 1 Oceanic plate1. continental plate collision 2. Oceanic plateoceanic plate collision 3. Continentalcontinental plate collision III. Earthquakes A. Definitions An earthquake is a sudden vibration or trembling in the Earth The motion caused by the quick release of stored potential energy into the kinetic energy of motion. Focus is the subsurface area along a fault plane where the stress is released. Epicenter is the area at the surface of the earth directly above the focus. 10 III. Earthquakes A. Definitions Types yp of Seismic Waves: 1. Body Waves: Waves that travel through the lithosphere. P-waves = primary waves S-waves = secondary waves 2. Surface Waves: Travel at or near the Earth's surface. f Th These waves produce d a rolling lli or swaying motion causing the Earth's surface to behave like waves on the ocean. III. Earthquakes San Andreas Fault: 11 III. Earthquakes B. Anatomy of an Earthquake III. Earthquakes B. Anatomy of an Earthquake 12 Impacts of Earthquake Prediction Figure 9.22 II. Earthquakes B. Anatomy of an Earthquake Where do earthquakes occur? 1. Faults 2. Tectonic plate boundary zones 3. Mid-ocean ranges Earthquakes with magnitude greater than 7.0 Earthquakes with magnitude less than 5.0 13 III. Earthquakes C. Measuring Earthquakes A seismograph is an instrument that measures the energy contained in seismic waves from an earthquake or other type of ground displacement. The standard unit of measurement for wave energy is the Richter scale or the moment magnitude scale. Figure 12.22 III. Earthquakes C. Measuring Earthquakes Magnitude in Richter Scale Energy Released in Joules 2 6.3 x 10 5 2.0 x 10 6.7 7.1 x 10 7 2.0 x 10 7.4 7.9 x 10 7.6 1.6 x 10 8.3 1.8 x 10 8.6 5.0 x 10 7 12 Comment Smallest earthquake detectable by people. Energy released by the Hiroshima atomic bomb. 14 Northridge, California earthquake 1994. 15 Major earthquake. Turkey earthquake August 17, 1999. More than 12,000 people killed. Deadliest earthquake this century. Tangshan, China, 1976. About 250,000 people died. San Francisco earthquake of 1906. 700 died. Most powerful earthquake recorded in the last 100 years. Southern Chile 1960. Claimed 5,700 lives 15 16 17 17 14 Tsunami III. Earthquakes Tsunamis 15 III. Earthquakes (CSUN parking lot, 1994) Figure 12.22 (Fishing boat beached from a tsunami caused by the 1964 earthquake in the Gulf of Alaska.) III. Earthquakes Figure 12.22 16