Features of Plate Margins

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  • Features Of Plate Margins
    • Constructive features
      • Oceanic ridges
        • Mid-Atlantic Ridge
        • volcanic activity also occurs along the ridge, forming submarine volcanoes, which sometimes rise above sea leve eg Surtsey, Iceland
        • the parts of the diverging plates may move at different rates producing friction and ultimately earthquakes
      • Rift valleys
        • brittle crust fractures as sections of it move apart. areas of the crust drop down between parallel faults to form Rift Valleys
        • African Rift Valley extends 4000km from Mozambique to the Red Sea
        • often marked by a series of step faults
    • Destructive features
      • oceanic-continental convergence
        • the denser oceanic plate if forced under the lighter continental plate (subduction)
        • Forms ocean trenches
        • Peru-Chile Trench
        • the uplifting of the continental plate results in fold mountains such as the Andes
        • Composite explosive volcanoes - Island Arc can appear
      • Continental-continental
        • fold mountains
        • no volcanic activity
        • shallow focus earthquakes
        • Himalayan Range - Mt Everest
      • oceanic-oceanic
        • pcean trenchs and island arcs
        • Eg pacific plate is being subducted beneath the smaller Philippine plate- forming the Marianas trench and a line of volcanic islands
    • conservative features
      • shallow focus earthquales
      • San Francisco 1906 and 1989
      • San Andreas fault California, where the pacific and north americanplates are moving parallel to each other, in the same direction but at different speeds


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