1. 3 Tectonic Plates

BORN 

• Plate tectonics combines the ideas of Continental Drift and Seafloor Spreading  

Types of boundaries 

• Divergent boundaries 

  • Divides the land; spreads and creates new lands 

  • Properties: 

    • Most of them are mid ocean ridges aka underwater mountain ranges 

    • Rifts: divergent plate boundaries on land 

      • Rift > valley > seaway > new ocean 

      • Tears > sinks > new ocean crust > newer ocean crust 

    • Adds new crust to the rocks 

    • Volcanic activity, only shallow quakes along plate boundaries 

    • Examples: Iceland and East Africa 

  • This is the way earth creates new baby rocks 

• Convergent boundaries  

  • Collision between plates: they converge 

  • Destroys old crust 

  • Three scenarios possible depending on the type of crusts involved 

    • Oceanic vs oceanic converge 

      • Subduction: process where the older, colder plate is forced beneath the younger, hotter plate 

        • The older one is more dense 

        • The colder is more bouyant 

      • Magma forms creating chain of volcanic islands 

      • Largest earthquakes 

      • Deep ocean trenches 

      • Ex: japan, aleutian islands 

    • Continent vs oceanic converg 

      • Oceanic is subducted beneath continent 

      • Volcanic mountains 

      • Large eartquakes 

      • Deep ocean trenches 

      • Ex: andes mtns, cascade mtns 

    • Continent vs continent converg 

      • NO subduction 

        • Continients are bouyant 

      • No volcanoes 

      • Very high mountains as the materials are being pushed together making it higher and higher 

      • Deformed rocks 

      • Large earthquakes 

      • Ex: himalayas, alps 

  • Can a convergent plate rid and oceanic-continent to continent to continent? 

    • Yes, the further they converge, the more the oceanic subducts, eventually it subducts entirely below the lithosphere, leaving a continent vs continent and creating tall mountains  

• Transform boundaries 

  • Horizontal motion,  

  • Common in ocean where they link offset divergent boundaries 

  • Large earthquakes 

  • Ex: san andreas fault, dead sea 

• Hybrid boundaries 

  • Oblique divergent 

    • Transform + divergent 

      • Move away and to the side 

        • Ex: gulf of california 

  • Oblique convergent 

    • Transform + convergence 

      • Move together yet sideways 

        • Ex: alpine fault in new zealand and san andreas fault in S. CA is actually a little big oblique, produces high mountains in Southern California