Hypothetical Orogeny: An Illustration of Tectonic Cycles and Mountain Building


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    Table of Contents

    Hypothetical Orogeny: An Illustration of Tectonic Cycles and Mountain Building

    1. initial rifting of large continental block

    2. continent rifts into three blocks

    3. plates (blocks) separate; new oceans formed

    4. new rifts form and split off new small blocks

    5. five separate plates; all passive margins

    6. new oceans continue to widen

    7. oceans continue to widen

    8. two incipient subduction zones form

    9. arcs build on two continental blocks adjacent to subduction zones

    11. north oceans narrow while south ocean continues to expand

    12. initial collision about to occur

    13. ophiolite obduction marks final phase of north oceans

    14. continent-continent collisions initiating

    15. orogeny begins to north along oblique collision

    16. orogeny spreads southward as continents sissor together

    17. climax of orogeny as new subduction established at south margin of accreted continents

    18. last remnants of southern ocean ridge subducted

    19. new continental block rifts off southern continent; new ocean formed

    20. old south ocean being subducted below north continent; back arc spreading developes to SW edge of north continent

    21. new plate and subduction appear at NW margin of map; new rifting along southern continent

    22. subduction on south margin of north continent closes ocean

    23. oceans close in northern part of map; continue to spread in south

    24. two collisions about to occur at margins of north continent

    25. ophiolites obducted as old south ocean closes

    26. initial collision at south margin of north continent

    27. subduction begins to jump south of accreted block as orogeny developes

    28. redeveloped southern subduction zone consumes new south ocean; ocean to NW closing

    29. obduction of ophiolites in NW ocean as arc-continent collision begins; new south ocean closing

    30. arc-continent orogeny underway

    31. remnant ocean forms south of colliding arc between subduction zones; collision about to occur to south

    32. oceanic plateaus and south continent about to collide with north megacontinent; ophiolites obducted

    33. collision underway; note two remnant oceans

    34. major continent-continent orogeny; note subduction zone has jumped to NW of accreted arc

    35. subduction swings down around accreted continent; subduction zone to east reorganizing around accreted oceanic plateaus

    36. several remnant oceans close resulting in more ophiolites

    37. subduction expands to SE as major plate reorganization occurs; rifts forming to north

    38. supercontinent bounded by several active and passive margins; rifts continue in several areas

    39. rifts expand as supercontinent about to break up

    40. break up underway as subduction zones continue to reorganize. LAST SLIDE