Class Note for GEO 101 with Professor Hooks at UA
Class Note for GEO 101 with Professor Hooks at UA
Popular in Course
Popular in Department
This 32 page Class Notes was uploaded by an elite notetaker on Friday February 6, 2015. The Class Notes belongs to a course at University of Alabama - Tuscaloosa taught by a professor in Fall. Since its upload, it has received 17 views.
Reviews for Class Note for GEO 101 with Professor Hooks at UA
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 02/06/15
Introduction to Geology a GEO101004 Class 3 Plate Tectonics University of Alabama gical Sciences Last Classes Question of the Day What was Pangea Answer Pangea was a single superconcontinent that existed about 200 million years ago It broke up to form the current continents Question of the Day Name the three major plate boundary types and define the process that occurs at each A scientific revolution begins Transform aults PeruChile Trench Copygh 2005 Pearson Prenticall Inc Paleomagnetic reversals recorded in oceanic crust Reverse Normal Copyright 2005 Pearson Prentice Hall Inc The Last Piece of the Puzzle The 1960 s were a period of chaos for geoscientists Some geoscientists even still believed in the expanding Earth hypothesis In 1965 J Tuzo Wilson suggested that large faults connected the global mobile belts into a continuous network that divides the Earths outer shell into several rigid plates Wilson de ned three types of plate boundary Oceanic ridges plates are moving apart Deep ocean trenches plates are moving together Transform faults Plates slide past one another By the 1968 the concepts of continental drift and sea oor spreading were united into the theory known as plate tectonics copyncu a 205 Pearson P39annze raw lnc A scientific revolution begins Geomagnetic reversal Paleomagnetism was the most convincing evidence set forth to support the concepts of continental drift and sea oor spreading Plate tectonics The new paradigm Earth s major plates 0 Associated with Earth39s strong rigid outer layer Known as the lithosphere Consists of uppermost mantle and overlying crust Lithosphere thickness ranges from a few km 7 I under spreading ridges to 100 km in y the deep ocean basins to 100150 km thick WW l earso tr HIL no Plate tectonics The new paradigm The lithosphere Overlies a weaker region in the mantle called the asthenosphere In the upper asthenosphere the pressuretemperature regim is such that the rocks are near their melting point allowing the asthenosphere to detach from the lithosphere The lithospheric plates can thus move over the asthenosphere Crust 5 70 km Copyrighl 2005 Pearson Premise Hall Inc 0202 The lithosphere is 1 the central portion of the Earth below 2900 km depth 2 the weaker portion of the Earth below about 100 km depth on which the plates move the upper 740 km of the Earth the strong and rigid outer shell of the earth Plate tectonics The new paradigm Earth s major plates Seven major lithospheric plates Plates are in motion relative to one another and continually changing in shape and size North America South American Paci c African Eurasian AustraliaIndian Antarctic Largest plate is the Paci c plate Several plates include an entire continent plus a large area of sea oor Earth 395 plates Copyright 2005 Pearson Prentice Hall Inc Ju n de Fuca plate 39 39 San Andreaquot Fgul i A Divergent boundary y B Convergent boundary X c Transform fault boundary y Copyright 2005 Pearson Prentice Hall Inc Plate tectonics The new paradigm Earth s major plates Plates move as coherent units Some small internal deformation Plates move relative to each other at a very slow but continuous rate About 5 centimeters 2 inches per year Cooler denser slabs of oceanic lithosphere descend into the mantle Driven by unequal distribution of heat in the Earth that causes convection which in turn drives plate tectonics Movement of continents causes earthquakes to occur volcanoes to form Plate tectonics The new paradigm Plate boundaries 39 New Interactions among individual plates occur along their boundaries Types of plate boundaries Pacific plate Divergent plate boundaries constructive margins Convergent plate boundaries destructive margins Transform fault boundaries A Divergent boundary X Copyright 2005 Pearson Prentice Hall Inc margins B Convergent boundary X C Transform fault boundary Plate tectonics The new paradigm Plate boundaries Each plate is bounded by a combination of the three types of boundaries New plate boundaries can be created in response to changing forces The total surface area of Earth does not change one plate grows at the expense of another or itself Africa and Antarctica are getting larger the boundaries are moving away from the center of the continents The Pacific is shrinking quotX Pacific plate NorthArnerican plate Canadian Shield quot ast Fri 786 Chlle Ridge A Dlvergenl boundary Copyright 2005 Pearson Prentice Hall Inc Eurasian plate B Convergent boundary X C Transform fault boundaryEquot Divergent plate boundaries Most are located along the crests of oceanic ridges Oceanic ridges and sea oor spreading Along welldeveloped divergent plate boundaries the sea oor is elevated forming oceanic ridges Fractures that form as the plates separate are filled with molten rock that wells up from the hot mantle below These boundaries are occas10nally found on continents oupyngmo 2005 Pearson Prentice Hall Inc Divergent plate boundaries The crest of the ridge is typically 23 km higher than the surrounding sea oor Hotter rock is less dense As it cools it becomes more dense and therefore subsides Takes about 80 million to cool completely The ridges range in Width from 10004000 km Many ridges have a central rift valley Spreading rates are typically about 5 cm per year but do Vary Cnpyrigh1 2005PearscnPrentice Haumc Divergent plate boundaries A an is Spreading rates and ridge topography Ridge systems exhibit topographic differences 15m mo we was mo woo mpquot 1m Southern East Pam c Fuse 137235 These differences are controlled by spreading rates andor the thermal regime From httpoceanridgeIdeocolumbiaedugeneraIhtmIhomehtml flybymw From httpooeanridgeIdeocolumbiaeduOtherstuffPARMovieparmoviehtml Divergent plate boundaries Continental rifting Splits landmasses into two or more smaller segments along a continental rift Examples include the East African rift valleys and the Rhine Valley in northern Europe Produced by extensional forces acting on lithospheric plates If the continent is stretched enough sea oor spreading can start examples of Where this is happening today are the Red Sea Gulf of Aden Gulf of California and the Woodlark Basin Continental rifting 2 2 O O The modernday Red Sea IS explained by plate tectonics theory because it is 1 a tiny remnant of a once immense ocean that was closed as Africa moved Asia 2 the site of a transform fault along which Arabia is moving away from Africa a rift zone that may eventually open into a major ocean if Arabia and Africa continue to separate 4 a rare example of a two continent subduction zone where the African continental plate is sinking under the Arabian continental plate Convergent plate boundaries The Earth is not growing larger to balance the addition of new lithosphere older parts must be subducted at destructive plate boundaries Older portions of oceanic plates are returned to the mantle in these destructive plate margins As the leading edge of one plate approaches another one plate is bent down allowing it to slide under the other Surface expression of the descending plate is an ocean trench Trenches may be thousands of kilometers long 50100 km wide and 810 km deep Also called subduction zones Average angle of subduction 45 Volcanic island are 1 an 41 39 iv Trench r Oceanic crust Copyright 2005 Pearson Prentice Ha boun Convergent plate boundaries Types of convergent daries Oceaniccontinental convergence Denser oceanic slab sinks into the asthenosphere Along the descending plate partial melting of mantle rock generates magma Resulting volcanic mountain chain is called a continental volcanic arc Andes and Cascades Volcanoes sit about 100 km above the subducting slab How does cool oceanic lithosphere cause mantle rocks to melt Voltiles water lower the melting temperature of the asthenosphere Oceanic crust iTrench Continental Volcanic arc a re Convergent plate boundaries Types of convergent Volcanlc Island are Oceanicoceanic convergence When two oceanic slabs converge one descends beneath the other Volcanoes grow up from the ocean floor Copyrigm 2005 Pearson Prennce Hall inc If the volcanoes emerge as islands a volcanic island arc is formed Japan Aleutian islands Tonga islands Convergent plate boundaries Types of convergent boundaries Continentalcontinental convergence Continued subduction can bring two continents together Less dense buoyant continental lithosphere capyngnxoams Pearson Prentice HalHnm Resulting collision between two continental blocks produces mountains Himalayas Alps Appalachians Continental volcanic arc imalayas C Copyright 2005 Pearson Prentice Hall Inc L O PPFPFPP N Largest Earthquakes in the World Since 1900 Location Chile Prince V lliam Sound Alaska Andreanof Islands Alaska Kamchatka Off the West Coast of Northern Sumatra Off the Coast of Ecuador Rat Islands Alaska Assam Tibet Kamchatka Banda Sea Indonesia Kuril Islands Date UTC 1960 05 22 1964 03 28 1957 03 09 1952 11 04 2004 12 26 1906 01 31 1965 02 04 1950 08 15 1923 02 03 1938 02 01 1963 10 13 Magnitude 95 92 91 90 90 88 87 86 85 85 85 Coordinates 3824 8 6102 N 5156 N 5276 N 330 N 10 N 5121 N 285 N 540 N 505 S 449 N 7305 W 14765 W 17539 W 16006 E 9578 E 815 W 17850 E 965 E 1610 E 13162 E 1496 E From httpneicusgsgovneiseqlists 0mapswordhtml Transform fault boundaries Plates slide past one another and no Inactive Transform fault Inactive acx v on new lithosphere is created or destroyed In 1965 J Tuzo Wilson proposed that transform faults connect the active belts convergent divergent and transform boundaries into a continuous network that divides the unaware Earth into plates 39 Transform faults Most join two segments of a midocean ridge along breaks in the oceanic crust known as fracture zones approximately 100 km spacing A few the San Andreas fault Iquot 7 alld Copyrighl 2005 Pearson Prenlice Hall Inc Zealand cut through continental crust Spreading Daniels America Mendocino Fault PACIFIC PLATE San FranCIsco l Relative motion of Pacific plate California Copyright 2005 Pearson Prentice Hall Inc
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'