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Slide 1 Visualizing Physical Geography by Timothy Foresman and Alan Strahler Chapter 9 Volcanic and Tectonic Landforms ___________________________________ ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 2 ___________________________________ Chapter Overview Plate Tectonics Tectonic Activity and Earthquakes Volcanic Activity and Landforms ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 3 Plate Tectonics ___________________________________ Major and minor lithospheric plates of the globes • Plate tectonics = The theory of tectonic activity, which deals with lithospheric plates and their motions • Movement of these plates is driven by heat from Earth’s core ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. ___________________________________ Slide 4 Plate Tectonics ___________________________________ Types of Plate Boundaries • Extensional tectonic activity •Spreading boundary •Plates pulled apart • Compressional tectonic activity •Converging boundary •Plates pushed together • Plates move past each other •Transform boundary •Transform faults ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 5 Plate Tectonics ___________________________________ Converging boundaries • A boundary where two lithospheric plates move apart ___________________________________ • Mid-ocean ridge ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 6 Plate Tectonics ___________________________________ Transform boundaries • Plates slide past each other without colliding • The Dead Sea Fault marks the transform boundary between the African Plate on the west and the Arabian Plate on the east. ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 7 ___________________________________ Plate Tectonics ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 8 ___________________________________ Plate Tectonics Convergent boundaries • Subduction zones = Descent of the edge of a lithospheric plate under an adjoining plate and into the asthenosphere ___________________________________ A B • Oceanic trenches ___________________________________ • Mariana Trench • Japan Trench responsible for Great Tohoku earthquake of 2012 • Andes mountains Which letter represents the mid-ocean ridge and subduction? ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 9 Plate Tectonics Convergent boundaries B C A D • Subduction zones • Associated with volcanoes and earthquakes ___________________________________ ___________________________________ Which letter is associated with volcanoes, ocean trench, oceanic crust, and continental crust? Which way does the oceanic plate move? Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. ___________________________________ ___________________________________ Slide 10 Plate Tectonics B ___________________________________ A Collision zones • Continental plates collide Which letter is an anticline and which one is a syncline? • Folds • Orogeny is a mountain building process C • Himalayas • Appalachian ___________________________________ D ___________________________________ • Synclines • Anticlines • Overthrust faults ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 11 Plate Tectonics Differential erosion of strata • The ways fold areas erode to form sequential landforms depends on the rock strengths of different strata • Weaker formations (shale and limestone) erode away to leave long, narrow ridges of hard strata (sandstone or quartzite) ___________________________________ ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 12 Plate Tectonics ___________________________________ Continental suture • Two continents can converge to eliminate an ocean between them ___________________________________ • A continental suture permanently unites the two plates, so that there is no further tectonic activity along that collision zone ___________________________________ • Appalachian and Ural mountains ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 13 Tectonic Activity and Earthquakes ___________________________________ Faults and fault landforms • Faults occur when a sharp break associated with a slippage of the crustal block on one side of a tectonic plate with respect to another • Depth can be several kilometers • Fault slippage varies (1 cm to 15 m) • Four main types of faults • Normal • Strike-slip • Reverse • Overthrust ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 14 Tectonic Activity and Earthquakes ___________________________________ Faults and fault landforms • Normal faults occur when the crust on one side of normal fault drops down relative to the other side. • Strike-slip faults are produced when tectonic plates move past each other horizontally ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 15 Tectonic Activity and Earthquakes ___________________________________ Faults and fault landforms • Reverse faults are produced by compression in the crust • Overthrust faults involve mostly horizontal movement. One slice of rock rides over the adjacent ground surface. ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 16 Tectonic Activity and Earthquakes ___________________________________ Faults and fault landforms ___________________________________ • Grabens = a crustal block is dropped down between two normal faults. • Horst = A crustal block pushed up between two normal faults. ___________________________________ • Fault scarps ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 17 Tectonic Activity and Earthquakes ___________________________________ Earthquakes • Earthquakes = A trembling or shaking of the ground produced by movements along a fault. ___________________________________ • Focus = Location where fault slipped ___________________________________ • Epicenter = The location on the Earth’s surface directly above where a fault slipped to produce an earthquake ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 18 Tectonic Activity and Earthquakes ___________________________________ Earthquakes • P-waves • S-waves • Epicenters are calculated by triangulating the readings from three different seismometer reading centers (A, B, and C), using the difference in travel times for P and S waves. ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. ___________________________________ Slide 19 Tectonic Activity and Earthquakes ___________________________________ Earthquakes • Magnitude = the amount of energy released by an earthquake • Richter scale ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 20 Tectonic Activity and Earthquakes ___________________________________ Tectonic environments of earthquakes • Pacific Ring of Fire ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 21 Tectonic Activity and Earthquakes ___________________________________ Earthquakes • Subduction zone •Greatest earthquakes, including those in Japan, Alaska, North America, Central America, and Chile •Java Trench 9.0 earthquake and resulting tsunami (2004) •Tohoku 9.0 earthquake and tsunami (2012) ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. ___________________________________ Slide 22 Tectonic Activity and Earthquakes ___________________________________ Earthquakes • Transform boundaries • San Andreas Fault in California • 1906 San Francisco Quake • 1989 Loma Prieta Quake • 1992 Landers Quake ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. ___________________________________ Slide 23 Tectonic Activity and Earthquakes ___________________________________ Earthquakes • California earthquakes, identified as circles with size proportional to the earthquake magnitude, are overlaid on top of delineated and mapped fault lines. ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 24 Tectonic Activity and Earthquakes ___________________________________ Earthquakes • Spreading center earthquakes mostly occur along mid-ocean ridges • The New Madrid earthquakes of 1811 is an example of quakes away from plate boundaries ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. ___________________________________ Slide 25 Tectonic Activity and Earthquakes ___________________________________ Earthquakes along blind faults ___________________________________ Barn, Iran 2003 Quake ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 26 Tectonic Activity and Earthquakes Space-based instruments imaging Earth movements (InSAR) Landform deformation of tectonic stresses after the Northridge, California earthquake ___________________________________ ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 27 Volcanic Activity and Landforms ___________________________________ • Volcano = conical, circular structure built by accumulation of lava flows and tephra (volcanic ash) ___________________________________ • Magma ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. ___________________________________ Slide 28 Volcanic Activity and Landforms ___________________________________ Volcanic activity ___________________________________ Many volcanoes are located on subduction boundaries or rift zones ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 29 Volcanic Activity and Landforms ___________________________________ Volcanic activity ___________________________________ •Hot spots = A center of volcanic activity thought to be located over a rising mantle plume. ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. ___________________________________ Slide 30 Volcanic Activity and Landforms ___________________________________ Volcanic eruptions ___________________________________ •When lava is forced out of a volcano violently, in the form of a volcanic eruption, it is a severe hazard • Various impacts from eruptions ___________________________________ • Mt. Pelée on the island of Martinique in 1902 ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. ___________________________________ Slide 31 Volcanic Activity and Landforms ___________________________________ Volcanic eruptions • Atmospheric impacts from volcanic ash and gases have been shown to affect global weather and surface temperatures for months or years after an event • Mt. Tambora in 1815 was the year without a summer ___________________________________ ___________________________________ Based on this graph, what can you conclude about the role of volcanoes in global warming? ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 32 Volcanic Activity and Landforms ___________________________________ Volcanic eruptions • Monitoring • Green is for the least hazardous • Red is for the most hazardous ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 33 Volcanic Activity and Landforms ___________________________________ Volcanic eruptions • Types of Volcanoes • shape, size, and explosiveness depend on the type of magma • Magma comes from two main types of igneous rocks: felsic and mafic • Two most common volcanoes: • Stratovolcano • Shield Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. ___________________________________ ___________________________________ ___________________________________ Slide 34 Volcanic Activity and Landforms ___________________________________ Volcanic eruptions ___________________________________ •Stratovolcano = volcano constructed of multiple layers of lava and tephra (volcanic ash) •Felsic lavas •Rhyolite, andesite •Thick, resistant to flow •Builds steep slopes around volcanic vents •Tall, steep cone, with crater ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 35 Volcanic Activity and Landforms ___________________________________ Volcanic eruptions ___________________________________ •Stratovolcano • Most active stratovolcanoes on circum-Pacific mountain belt • Associated with subduction zones • Felsic lavas produce explosive eruptions • Caldera ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 36 Volcanic Activity and Landforms ___________________________________ Volcanic eruptions •Stages of stratovolcano erosion 1 3 2 4 ___________________________________ ___________________________________ ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 37 Volcanic Activity and Landforms ___________________________________ Volcanic eruptions ___________________________________ • Shield Volcano = low, often large, dome-like accumulation of basalt lava flows emerging from long , radial fissures on flanks • Mafic lava (basalt) is thin, not viscous ___________________________________ • Holds little gas • Usually quiet eruptions ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 38 Volcanic Activity and Landforms ___________________________________ Volcanic eruptions ___________________________________ Shield Volcanoes •Lava travels long distances, spreads out in thin layers ___________________________________ •Shield volcanoes are rounded domes, with gentle slopes ___________________________________ Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. Slide 39 Volcanic Activity and Landforms Volcanic eruptions ___________________________________ 1 ___________________________________ •Erosion of shield Volcanoes 2 3 Mauna Kea, Hawaii Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. ___________________________________ ___________________________________ Slide 40 Volcanic Activity and Landforms ___________________________________ Other volcanic landforms ___________________________________ • Flood basalts • Cinder cones • Wizard Island in Crater Lake ___________________________________ Continental flood basalts, Columbia Plateau, U.S. Visualizing Physical Geography Copyright © 2012 John Wiley and Sons Publishers Inc. ___________________________________