Lecture #4 Week #2. A.K. Morris, Ph.D. Fullerton College ESC 130F, Lecture #4. Chapter 3

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1 Fullerton College ESC 130F, Lecture #4 Chapter : Dutch map maker Abraham Ortelius Postulated that the Americas were torn from Europe and Africa by earthquakes and flood 1620: Sir Francis Bacon also noted continents on opposite Atlantic coasts fit like puzzle pieces The idea was ridiculed in those days Ortelius Theatrum Orbis Terrarum 3 Hondius-Jansson 1629 world map 4 A fixed Earth Continents and Oceans don t move! Topography results from divine guidance 1858 Antonio Snider Pellegrini French geographer Chose to ignore the critics La Création et ses mystères dévoilés Found identical plants in Europe and N. America Postulated that the continents were connected in the past Breaking from dogma is hard Separation was due to the Noah flood and eruptions of material out of Earth s interior along cracks 5 6

2 1908 Frank Bursley Taylor First proposed continental drift by Crustal Movement great world belt of Tertiary fold mountains almost encircling the earth. Explained mountain formations Cites the mid Atlantic ridge as the original place of the great fracture Alfred Wegener the man who history officially associates with continental drift German meteorologist. Made key observations: Identical fossil flora and fauna in N. America and Europe. Anomalies? Identical snail species in Scandinavia and New England Marsupials in Australia. World continents must ve been together in the geologic past 1915 Published The Origin of Continents and Oceans Called the landmass Pangaea. But he was an obscure crackpot American 7 8 Wegener s s Pangaea Triassic 250 mya This explained the fossil anomalies 9 10 Also explained the presence of tropical fossils near the poles Still downplayed among scientists! WHY??? Continental Drift had no MECHANISM Fossil conifer from Antarctica, I. Poole, 1999 Fossil beech wood from Antarctica, R. Hunt,

3 Recall sonar developed in WW II Could now see beneath ocean Late 1940s 1950s HUGE advances in seafloor mapping Harry Hess Princeton professor and Navy captain. Fathometer used for landing maneuvers. Hess never turned it off! Ocean NOT covered thickly with sediment. Huge mountain range down the Atlantic with a canyon in the middle. Earth is splitting apart! He wrote it up and WAS IGNORED! At the same time as Hess Robert Dietz Scripps oceanographer Described the geology of mid-ocean ridges 1960s core samples: young rock at rift, gets older further away ! Vine and Mathews on the Carlsberg Ridge Morley in the NE Pacific. Mobile crust finally an accepted concept. Magnetic Polar Reversal Named the moving masses plates. Vine-Mathews-Morley Hypothesis Plate Tectonics is born! 17 18

4 Magnetic Polar reversal even debuts in a movie!!! Waterworld video clip Polar Wandering Polar Reversal 2050? Oldest rock furthest from ridges Mid Atlantic ridge runs through the center of Iceland

5 Crust & upper mantle = rigid Lithosphere: crust & mantle km layer Forms several plates that cover earth surface Floats on asthenosphere, upper mantle fluid Plates move on top of asthenosphere Spread at spreading zones Crust Fig

6 Even more evidence has emerged Similarities in: 1. Geology 2. Fossils of extinct spp Fig. 3.5 All crusts contain oceanic and continental Different proportions E.g. Pacific plate vs. Eurasian plate Dimensions change. E.g. Indo Australian plate split 8-12 larger plates 20 or so smaller plates Fig. 3.8.a Edges of plates interact in 3 main ways Divergent Boundaries (separating) Convergent Boundaries (coming together) Transform Boundaries (sliding past) 35 36

7 Fig. 3.8.b We ve got sea floor spreading Is the earth getting bigger? What must be occurring elsewhere? As new lithosphere created, old destroyed at trenches Formed when two plates collide and one dips below (subduction) Trenches = subduction zones Depends on density. Why? Explains why never get REALLY old rock in ocean Breaks up Earthquakes Gets hot and melts Volcanoes 41 42

8 A collision causes development of continental volcanoes Forms deep trenches May form coastal mountain ranges (Andes of south America). Fig Chilean Trench LEFT OFF HERE 1/29/10 Causes quakes & volcanoes. Volcanoes may rise to create chains of volcanic islands. (Aleutian & Mariana Islands) Aleutian Islands Fig Mariana Trench 47 48

9 Both plates float and neither is subducted b/c of low density. Causes folding and upward pushing of earth India & Asia collide to produce Himalayas Himalaya Mountain Range Fig Plates can t spread evenly on spheres Northridge Earthquake, January 17, 1994 (4:30am) A.K. Morris

10 So what is actually moving the plates? No one knows for sure. A few plausible explanations: Convection Model Ridge Push, Slab Pull Model Plate Driven Plate Tectonics Model Gravity is the important force Combination of forces Fig Fig Trench suction

11 Fig

12 I am Archean from the Planet Cratons Pangaea (from Wagener) 250 mya Reeeeally old Earth Crust (>2.5 bya) Pieces all over the world Implies there may have been one originally Fig mya 150 mya 2,500 mya 540 mya mya mya today 71 72

13 Fig Fig Bordering on Sci-Fi proposed in 1990 based on paleomagnetic and geochemical data 1,100 1,000 mya came together mya broke up Super Sci-Fi Science proposed in 1996 by UNC Prof John Rodgers 3,000 mya supercontinent cycle worked only with craton fragments Fig a-c Genesis and elimination of oceans Oceans form by a rifting of a continent Ocean destroyed by subduction zone Fig d 200 m.y. the vast Pacific will close Fig d-g 77 78