GoConqr has a new look! Let us know what you think.

Sign up free

Flashcards

plate tectonic theory

niamh bergin Geography - physical A level English 76 cards

Cards in this deck (76)

  1. 1what are the 7 major plate tectonics ?1. pacific plate
    2. eurasian plate
    3. indo-australian plate
    4. north american plate
    5. south american plate
    6. african plate
    7. nazca plate
  2. 2what is a well used example of a destructive subduction plate boundary ?the nazca plate and south american plate
  3. 3as soon as maps of the atlantic ocean were produced, people began to notice what ?that the continents either side seemed to fit together remarkably well - bulge of south america fitting into the indent in west africa
  4. 4who noticed this fit as early as the 17th century but it didnt attract any serious attention as no one thought that continents could move ?Francis Bacon
  5. 5in 1912, who published their theory of 'continental drift' stating that there was only a single continent 300 million years ago - named PangaeaAlfred Wegener
  6. 6WEGENER: this single continent eventually split into two and then into what ?the continents we know today
  7. 7WEGENER: what was the geological evidence for the theory ?- the fit of South America and West Africa
    - evidence of a late carboniferous glaciation deposits are found in south america, antartica and india this can only be explained if they were once connected
    - the same rock sequences are found in Canada and scotland
  8. 8WEGENER: what is the biological evidence for the theory ?- fossils found in indian limestone are comparable with similar fossils in Australia
    - reptile fossil remains found in both south america and match those in south africa
  9. 9WEGENER: wegener's theories were unable to explain how continental movement could have taken place and thus what ?his ideas gained little ground
  10. 10from 1940s onwards evidence began to accumulate to show how wegener could have been correct - what was discovered ?the mid-atlantic ridge
  11. 11examination of the ocean crust either side of the mid-atlantic ridge suggested what ?that sea-floor spreading was occurring
  12. 12SEA FLOOR SPREADING: what was the evidence to suggest this was occurring ?the alternating polarity of the rocks that form the ocean crust -
  13. 13SEA FLOOR SPREADING: iron particles in lava erupted on the ocean floor are what ?aligned with the earth's magnetic field
  14. 14SEA FLOOR SPREADING: as the lavas solidify what happens ?these particles provide a permanent record of the earth's polarity at the time of the eruption
  15. 15SEA FLOOR SPREADING: the earths polarity reverses at regular intervals (approx every 400,000 years) - what is the result ?a series of magnetic strips with rocks aligned alternately towards the north and south poles
  16. 16SEA FLOOR SPREADING: the striped pattern, is mirrored exactly on either side of a mid ocean ridge, suggests what ?the oceanic crust is slowly spreading away from this boundary
  17. 17SEA FLOOR SPREADING: does oceanic crust get older or younger the further away from the mid-atlantic ridge ?older
  18. 18SEA FLOOR SPREADING: sea floor spreading implies that the earth must be what ?getting bigger
  19. 19SEA FLOOR SPREADING: as the earth is not getting bigger, then plates must be destroyed somewhere to accommodate the increase in their size at mid-oceanic ridges - what evidence of this was found ?the discovery of oceanic trenches where large areas of ocean floor were being pulled downwards in process of subduction
  20. 20GRAVITATIONAL SLIDING (RIDGE PUSH AND SLAB PULL): at what margins does upwelling of hot material at ocean ridges generate a buoyancy effect which produces the ocean ridge?constructive
  21. 21GRAVITATIONAL SLIDING (RIDGE PUSH AND SLAB PULL): this ocean ridge stands how many km above the ocean floor ?2-3
  22. 22GRAVITATIONAL SLIDING (RIDGE PUSH AND SLAB PULL): oceanic plates experience a force that acts away from ridge - known as ridge push or grav sliding- what is this a result of ?gravity acting down the slope of the ridge
  23. 23GRAVITATIONAL SLIDING (RIDGE PUSH AND SLAB PULL): what happens at a destructive margin ?the downward gravitational force of the dense, cold descending plate pulls the slab into the mantle, this gravity generated force pulls the plate down as a result of negative buoyancy
  24. 24CONVECTION CURRENTS: hot spots around the core of the earth generate thermal convection currents within where ?the asthenosphere
  25. 25CONVECTION CURRENTS: these currents cause magma to rise towards the crust then spread before cooling and sinking - this circulation of magma is what ?a vehicle upon which the crustal plates move
  26. 26CONVECTION CURRENTS: the crust can be thought of as 'floating' on the denser asthenosphere - this is a continuous process where what is happening ?new crust is being formed at divergent boundaries and older crust being destroyed at convergent boundaries
  27. 27CONVECTION CURRENTS: where convection currents move away from each other = what margin ?constructive
  28. 28CONVECTION CURRENTS: where convection currents move towards each other = what margin ?destructive
  29. 29CONVECTION CURRENTS: where convection currents cause plates to slide past each other = what margin ?conservative margin
  30. 30PLATE MARGINS: what is a constructive (divergent) plate margin ?when two plates separate (diverge) - move away from each other
  31. 31PLATE MARGINS: CONSTRUCTIVE (DIVERGENT) : there are two types of divergence - what are these ?oceanic areas = sea-floor spreading occurs on either side of mid-ocean ridges
    continental areas = stretching and collapsing of the crust creates rift valleys
  32. 32PLATE MARGINS: CONSTRUCTIVE (DIVERGENT) : what is an example of divergence in oceanic areas ?mid-atlantic ridge
  33. 33PLATE MARGINS: CONSTRUCTIVE (DIVERGENT) : what is an example of divergence in continental areas ?the Great African Rift Valley
  34. 34PLATE MARGINS: CONSTRUCTIVE (DIVERGENT) : what landforms are associated with divergent plate movements ?- mid-ocean ridges
    - rift valleys
    - volcanoes
    - earthquakes
  35. 35PLATE MARGINS: CONSTRUCTIVE (DIVERGENT) : OCEAN RIDGES: ocean ridges are the longest continuous uplifted features on earths surface - how are ocean ridges formed?when plates move apart in oceanic areas the space is filled with basaltic lava upwelling from below to form a ridge
  36. 36PLATE MARGINS: CONSTRUCTIVE (DIVERGENT) : OCEAN RIDGES: volcanic activity also occurs along these ridges forming what ?submarine volcanoes which sometimes rise above sea level
    i.e. Surtsey in mid atlantic ocean
  37. 37PLATE MARGINS: CONSTRUCTIVE (DIVERGENT) : OCEAN RIDGES: regular breaks that cut across ridges are called what?transform faults
  38. 38PLATE MARGINS: CONSTRUCTIVE (DIVERGENT) : OCEAN RIDGES: transform faults occur at rights angles to the plate boundary, they may widen at different rates which leads to what ?frictional stresses building with shallow focus earthquakes releasing tension
  39. 39PLATE MARGINS: CONSTRUCTIVE (DIVERGENT) : RIFT VALLEYS: how are rift valleys formed ?they are formed in continental areas when the lithosphere stretches causing it to fracture into sets of parallel faults, the land between these faults collapses into deep wide valleys
  40. 40PLATE MARGINS: CONSTRUCTIVE (DIVERGENT) : RIFT VALLEYS: wide valleys are separated by upright blocks of land - known as what ?horsts
  41. 41PLATE MARGINS: CONSTRUCTIVE (DIVERGENT) : RIFT VALLEYS: why is the Great African Rift Valley seen as important ?as it may eventually mark the formation of a new ocean as eastern africa splits away from the rest of the continent
  42. 42PLATE MARGINS: CONSTRUCTIVE (DIVERGENT) : it is at constructive plate margins that what are to be found ?some of the youngest rocks on earth
  43. 43PLATE MARGINS: CONSTRUCTIVE (DIVERGENT) : what plates form a constructive margin ?- south american plate moving away from the african plate
    - the north american plate moving away from the eurasian plate
    - the pacific plate moving away from the nazca plate
  44. 44PLATE MARGINS: DESTRUCTIVE (CONVERGENT) : there are 3 types of convergence possible what are these ?1. oceanic plate meeting continental
    2. oceanic plate meeting oceanic plate
    3. continental plate meeting continental plate
  45. 45PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : this is the colliding of what plates ?oceanic and continental
  46. 46PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : as the oceanic plate is denser than the lighter continental plate what happens when they collide ?the oceanic plate subducts underneath the continental plate
  47. 47PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : the point of collision is marked by the bending of the oceanic plate to form what ?a deep ocean trench
  48. 48PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : as the two plates converge what happens to the continental land mass ?it is uplifted, compressed, buckled and folded into chains of fold mountains i.e. the ANDES
  49. 49PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : as compression continues what can happen to these fold mountains ?the simple folding can become asymmetrical then over-folded making a recumbent fold
  50. 50PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : the descending oceanic plate starts to melt at depths beyond ???100km
  51. 51PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : the oceanic plate is completely destroyed by how many km ?700 km
  52. 52PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : the zone of melting is called the benioff zone, melting is caused how ?by both increasing heat at depth and friction
  53. 53PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : the friction between the plates can cause what ?intermediate or deep focus earthquakes
  54. 54PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : what then happens to the melted oceanic plate ?it creates magma which is less dense than the surrounding asthenosphere and as a result rises in great plumes
  55. 55PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : these magma plumes then do what ?pass through cracks / faults in the continental plate, it may eventually reach the surface to form explosive volcanic erruptions
  56. 56PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : what landforms are associated with this margin ?- deep sea trenches
    - island arcs
    - fold mountains
    - volcanoes
    - earthquakes
  57. 57PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : give examples of a destructive subudction plate margin ?- the nazca plate subducts under the south american plate
    - the pacific plate subducts under the eurasian plate
    - the oceanic pacific plate subducts under the north american plate
  58. 58PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : DEEP SEA TRENCHES: how is a deep sea trench formed ?where oceanic and continental plate meet, the denser oceanic plate is subducts underneath the lighter continental - the downwarping of the oceanic plate forms a very deep part of the ocean known as a trench
  59. 59PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : DEEP SEA TRENCHES: give an example of a deep sea trench at this margin ?off the western coast of south america the nazca plate is subducted under the south american plate forming the Peru-Chile trench
  60. 60PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : ISLAND ARCS: how are island arcs formed ?during subduction the descending plate encounters hotter surroundings + heat generated from friction = plate begins to melt
    as material is less dense than the surrounding asthenosphere, it begins to rise towards the surface as plutons of magma
    eventually these reach surface and form complex, composite and explosive volcanoes.
    if eruptions take place offshore, a line of volcanic islands forms
  61. 61PLATE MARGINS: DESTRUCTIVE SUBDUCTION (CONVERGENT) : ISLAND ARCS: give an example of an island arcJapanese archipelago
  62. 62PLATE MARGINS: DESTRUCTIVE (CONVERGENT): OCEANIC + OCEANIC: when two oceanic plates collide what happens ?one plate (the faster or denser) subducts beneath the other, this leads to the formation of a deep ocean trench and melting - the resulting rising magma from the benioff zone forms crescents of submarine volcanoes along the plate margins which may grow to form island arcs
  63. 63PLATE MARGINS: DESTRUCTIVE (CONVERGENT): OCEANIC + OCEANIC: what landforms are associated with this margin ?- island arcs
    - deep see trench
    - volcanic eruptions
    - earthquakes
  64. 64PLATE MARGINS: DESTRUCTIVE (CONVERGENT): OCEANIC + OCEANIC: give example of landformsthe Mariana Trench and Marianas islands where the pacific plate is subducted beneath the smaller philippine plate
  65. 65PLATE MARGINS: DESTRUCTIVE (CONVERGENT): OCEANIC + OCEANIC: give an example of plate margins- pacific plate subducts under the philippine plate
  66. 66PLATE MARGINS: DESTRUCTIVE (CONVERGENT): CONTINENTAL + CONTINENTAL : continental plates are of lower density then the asthenosphere beneath them - this means what ?subduction doesnt occur
  67. 67PLATE MARGINS: DESTRUCTIVE (CONVERGENT): CONTINENTAL + CONTINENTAL : what happens when two continental plates collide ?the colliding plates and any sediments deposited between them, are forced up/ are uplifted and buckle to form high fold mountains, material is also forced downwards to form deep mountain roots
  68. 68PLATE MARGINS: DESTRUCTIVE (CONVERGENT): CONTINENTAL + CONTINENTAL : give an example fold mountains formed from this process ?the Himalayas
  69. 69PLATE MARGINS: DESTRUCTIVE (CONVERGENT): CONTINENTAL + CONTINENTAL : volcanic activity does not occur at these margins because there is no subduction but what can happen ?shallow-focus earthquakes can be triggered
  70. 70PLATE MARGINS: DESTRUCTIVE (CONVERGENT): CONTINENTAL + CONTINENTAL : give an example of this margin- indo-australian into the eurasian
  71. 71PLATE MARGINS: CONSERVATIVE: what happens at conservative plate margins ?when two plates slide past each other crust is neither being destroyed or made - there is no volcanic activity
    friction between the moving plates when they slide past each other leads to stresses building up whenever 'sticking' occurs - eventually these stresses will be released suddenly as a powerful shallow-focus earthquake
  72. 72PLATE MARGINS: CONSERVATIVE: give examples of earthquakes at this margin ?Los Angeles and San Francisco - san andreas fault
    Haiti
  73. 73PLATE MARGINS: CONSERVATIVE: give an example of a plate marginnorth american and pacific
  74. 74MAGMA PLUMES : what is a magma plume ?a magma plume = vertical column of extra-hot magma that rises up from the mantle
  75. 75MAGMA PLUMES : most volcanic activity occurs at plate margins but there are some areas of intense volcanic activity that aren't near any plate margins - these are caused by magma plumes how ?volcanoes form above magma plumes which remain stationary over time, the crust however moves above it, volcanic activity in the part of the crust that was above the magma plume decreases as it moves away. New volcanoes form in the part of the crust that is now above the magma plume - as crust continues to move, a chain of volcanoes is formed
  76. 76MAGMA PLUMES : the chain of islands where was formed by magma plumes ?hawaii

Information

Description
A level Geography - physical (hazards) Flashcards on plate tectonic theory, created by niamh bergin on 28/04/2018.
Created by
niamh bergin
Views
0
Rating

Feedback

What is it about?

What do you think of the new look?

How do you like it?