© 2007, John Wiley and Sons, Inc. Physical Geography by Alan Arbogast Chapter 13 Tectonic Processes and Landforms Lawrence McGlinn Department of Geography State University of New York - New Paltz

© 2007, John Wiley and Sons, Inc. Tectonic Processes and Landforms Plate Tectonics Types of Plate Movement Plate Convergence Earthquakes Volcanoes

© 2007, John Wiley and Sons, Inc. Plate Tectonics Theory that Earth’s crust consists of plates that move individually & collectively Helps explain location of mtn ranges, earth- quakes, volcanoes & other landforms First theorized by Wegener in early 1900s Pangaea – supercontinent that existed 300 my ago – continents spread by Continental Drift Theory ignored through 1950s – validated in more recent research

© 2007, John Wiley and Sons, Inc. Fossil Evidence for Pangaea

© 2007, John Wiley and Sons, Inc. Continental Drift Since Pangaea Continental Drift

© 2007, John Wiley and Sons, Inc. Crustal Movements Figure 11.14

© 2007, John Wiley and Sons, Inc. Mechanisms of Continental Drift Convection within Earth Magma Plume pushes plates apart

© 2007, John Wiley and Sons, Inc. Seafloor Age Red youngest through green & yellow to blue, oldest

© 2007, John Wiley and Sons, Inc. Current Locations & Movement of Plates

© 2007, John Wiley and Sons, Inc. Magnetic Reversals Figure 11.15

© 2007, John Wiley and Sons, Inc. Types of Plate Movements Passive Plate Margins Transform Plate Margins Plate Divergence Plate Convergence Collision Subduction

© 2007, John Wiley and Sons, Inc. Passive Plate Margins Where continental crust and bordering oceanic crust are on the same tectonic plate – tectonically stable Example of East Coast of US on North American Plate

© 2007, John Wiley and Sons, Inc. Transform Plate Margins Boundaries where plates slide past each other horizontally

© 2007, John Wiley and Sons, Inc. Plate Divergence Lithospheric plates moving away from each other Magma plumes move up & out through plate fractures, plates spread in process called Rifting As plates spread, Mid-Oceanic Ridge forms from rifting Active and Passive Margins

© 2007, John Wiley and Sons, Inc. Rifting in East Africa

© 2007, John Wiley and Sons, Inc. Plate Convergence Collision – two plates of continental crust meet Crust crumples causing folding of horizontal bedrock layers Monocline – 1-sided slope rock beds inclined in one direction over large area Anticline – upward arc of folded rock Syncline – downward dip in folded rock Overthrust fault – intense compression shoves one part of rock mass over the other

© 2007, John Wiley and Sons, Inc. Collision and Folding Folding

© 2007, John Wiley and Sons, Inc.Subduction Process in which one converging plate is forced beneath another, usu. oceanic plate under continental Plate Boundary Relationships

© 2007, John Wiley and Sons, Inc. Orogenesis: Oceanic-continental Collision Figure 12.16

© 2007, John Wiley and Sons, Inc. Oceanic-oceanic Collision Figure 12.16

© 2007, John Wiley and Sons, Inc. Continental-continental Collision Figure 12.16

© 2007, John Wiley and Sons, Inc. Ridge and Valley Evolution The Folded Appalachians

© 2007, John Wiley and Sons, Inc. The Appalachian Mountains Figure 12.18

© 2007, John Wiley and Sons, Inc.Earthquakes Sudden release of tectonic stress creates movement in Earth’s crust & shockwaves through lithosphere Fault – fracture between adjoining plates along which plates can move Focus – point in lithosphere where fault breaks Epicenter – point on surface directly above focus

© 2007, John Wiley and Sons, Inc. Earthquake Processes

© 2007, John Wiley and Sons, Inc. Earthquake Energy Waves released by an earthquake: P-waves – primary, compressional waves that travel km/sec S-waves – secondary, vertical waves that travel 60-70% slower than P waves Difference in arrival time of p-waves and s- waves, helps estimate distance to epicenter Known distance to 3 stations yields location

© 2007, John Wiley and Sons, Inc. Triangulation to Locate ‘Quake Known distance to stations A, B and C shows location of epicenter

© 2007, John Wiley and Sons, Inc. Seismograph Records vertical & horizontal motion of Earth, & magnitude of motion

© 2007, John Wiley and Sons, Inc. Measuring Earthquakes Richter Scale – logarithmic measure where each whole number represents 10X the shaking of the next smaller number

© 2007, John Wiley and Sons, Inc.Faulting Earthquakes occur along faults – cracks in Earth’s crust where rocks or plates are displaced Fault Types: Normal – vertical fault, diverging force Reverse – vertical fault, compressional force Strike-Slip – horizontal fault, blocks slide past one another – larger scale called Transform Overthrust – upthrown block slides over downthrown block

© 2007, John Wiley and Sons, Inc. Fault Types Earthquake

© 2007, John Wiley and Sons, Inc. Normal Fault Figure 12.11

© 2007, John Wiley and Sons, Inc. Reverse Fault Figure 12.11

© 2007, John Wiley and Sons, Inc. Strike-slip Fault Figure 12.11

© 2007, John Wiley and Sons, Inc. San Andreas Fault (Transform Fault) Movement

© 2007, John Wiley and Sons, Inc. Basin and Range Province Horst & Graben Formation From Satellite In Landscape