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Supercontinent

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Supercontinent

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Supercontinent

  1. 1. 1"”. V ". ___f'—. ___ ‘, ‘ I, ’ IV , - 3 ( I. -’ AFRICA In Q9 K ‘ARABIA/ 4;" -. / " ‘ V. -1"" ‘ " N EW M —, /' ‘-7) /1; E GUINEA , ~‘ ; { 0;’ INDIA , .r~A «L soum AMERICA )/ _lJ! %/‘S3-: .._», ff__, J l»*’ K K II“: J’ _. ‘ V“ ? ( ‘~ I _w-_' )1 ,4 ANTARCTICA ({ AU5'fR, :}-{IA - " . / ' I E _/ I “Q / ... .~m/ ~. _-. _‘, » ‘-, 7 ‘I ‘ ,1 . _ X ‘—L - II ' , I ‘I ‘—‘7 "" / ) '. ;;1’/ 5/
  2. 2. In geology, a supercontinent is the assembly of most or all of the Earth's continental blocks or eratons to form a single large landmass.
  3. 3. Many tectonicists such as Hoffman (1999) use the term "supercontinent" to mean "a clustering of nearly all continents". E This definition leaves room for interpretation when labeling a continental body and Is easier to apply to Precambrian timesfl Using the first definition provided here, Gondwana (aka Gondwanaland) is not considered a supercontinent, because the landmasses of Baltica, Laurentia and Siberia also existed at the same time but physically separate from each other.
  4. 4. , _ . . . _. 7. an Isle of Ma
  5. 5. The landmass of Pangaea is the collective name describin all of these continental masses when they were in a close proximity to one another. This would classify Pangaea as a supercontinent. According to the definition by Rogers and Santosh (2004), a supercontinent does not exist today, Supercontinents have assembled and dispersed multiple times in the geologic past (see table). The positions of continents have been accurately determined back to the early duraeeie. However, beyond 200 lllla, continental positions are much less certain.
  6. 6. SUPERCONTINENT CYCLES A supercontinent cycle is the break-up of one supercontinent and the development of another, which takes place on a global sca| e.1'11 Supercontinent cycles are not the same as the Wilson 93%, which is the opening and closing of an individual oceanic basin. The Wilson cycle rarely synchronizes with the timing of a supercontinent cycle. IZ1 However, supercontinent cycles and Wilson cycles were both involved in the creation of Pangaea and Rodinia. l§l Secular trends such as carbonatites, granulites, eclites, and greenstone belt deformation events are all possible indicators of Precambrian supercontinent cyclicity, although the Protopangea-Paleopangea solution implies that Phanerozoic style of supercontinent cycles did not operate during these times. Also there are instances where these secular trends have a weak, uneven or lack of imprint on the supercontinent cycle; secular methods for supercontinent reconstruction will produce results I-[st-5} lnu rnI: Ill nvrInnnI>:4n ant-I nank nvnlnnnfiinn ‘Far I‘! *l'l'lI'l
  7. 7. CONTINENTAL DRIFT Laurasia and Modern Gondwana world Pangaea
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  9. 9. iPangaea Laurasia L, I, Gondw’ana 4 PANGAEI 200 million yeam ago LAURASIA & GONUWANA 1 20 million years ago __ _é, . South Vrgs‘ America i ‘ . (,'b’~' C - 69 {$0 .53’ . ;s %% North_ America c-, <a if’ A <¢§"’ . ¢z> V South {S5 America _. ‘(:5 _, ° <> '1? <3?"
  10. 10. VOLCANISM The causes of supercontinent assembly and dispersal are thought to be driven by processes in the mantle. I3-1 Approximately 660 km into the mantle, a discontinuity occurs, affecting the surface crust through processes like plumes and "superplumeg". When a slab of crust that is subducted is denser than the surrounding mantle, it sinks to the discontinuity. Once the slabs build up, they will sink through to the lower mantle in what is known as a "slab avalanche". This displacement at the discontinuity will cause the lower mantle to compensate and rise elsewhere. The rising mantle can form a plume or superplurne.
  11. 11. ISLAND ARC PLATE HOT-SPOT CONTINENTAL PLATE PLATE SUBDUCTION DIVERGENCE VOLCANISM SUBDUCTION Mafic to intermediate Basaltic extrusives Basaltic extrusives Mafic to felsic intrusives I intrusives (plutonism) : Basalticintrusives ; Basalticintrusives 1 Mafic to felsic extrusives Mafic tointerlrrrecliate H°t_spotv0kano Efitrlglves lg/ obcgnzln) Midmean ridgeE : / Subduction Continental | - 53" 3"‘ “ " '°"- I . . I , - zone margin volcano- : volcano zone ; I -, ./ AV, ; : I r I I I a 1‘ I . g __ L’ ‘ ' ' V’; /3’ ‘V I. I‘-_ ‘T i ; Partial melting Oceanic crust "90; Ir” I C‘ 3/c I of upper mantle / /.(/70%. ” *1/3, , _ _ l / Mantle plume °‘p/ ,e"¢2/ I; -I Rising magma (hoispot) , ,, 9'9 . .' 8’ ‘. ;, ‘ Oceanic , lithosphere "; ¢ Mantle / . » V ‘r
  12. 12. PLATE TECTONICS Global paleogeography and plate interactions as far back as Pangaea are relatively well understood today. However, the evidence becomes more sparse further back in eoloic history. Marine magnetic anomalies, passive margin match-ups, geologic interpretation oforogenic bglts, paleomagnetism, paleobiogeography of fossils, and distribution of cllmatlcally sensitive strata are all methods to obtain evidence for continent locality and Indicators of environment throughout time.
  13. 13. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display , // / /(/ P P K _ Jl Convergent Transform Divergent Convergent Continental rift zone plate boundary plate boundary plate boundary plate boundary (young divergent plate boundary) ‘? O?oi¢9,)/ . 7. as . P I II J lLithosphere «: ::'3: I rs: ‘ ‘[“lI| Il. lll'lOSpl'l9l'6 «mfg ‘r-, .’«= - I; Asthenosphere
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