Tectonics 2

Tectonics 2

1. Constructive margins

   • lithosphere spreads apart
     • magma escapes + makes new crust material
   • e.g Mid Atlantic Ridge
     • Iceland; Surtsey, Heimey formed along it
     • 1,000km wide with central rift valley
   • shallow focus earthquakes and volcanic activity

2. Destructive margins

   • oceanic continental
     • e.g The Andes
     • denser oceanic is subducted beneath lighter continental
       • creates ocean trenches, batholiths, volcanic mountain chains
       • shallow-intermediate focus earthquakes
         • e.g Chile 2010
           • Subduction of Nazca under South American
   • oceanic oceanic
     • two oceanic plates converge
       • makes volcanic island arcs + ocean trenches + earthquakes
         • e.g Ryukyu Islands
           • The Phillipines plate and the Eurasian
             • Volcanic activity led to formation
       • subduction leads to melting (Benioff Zone)
   • continental continental
     • continental crust doesn't subduct
       • creates fold mountains (oregeny)
         • not much earthquake and no volcanic activity
         • intense folding, faulting + uplifting
     • e.g Himalayas
       • Indo-Australian Plate and Eurasian
         • Mount Everest

3. Conservative margins

   • Plates slide laterally against eachother
     • friction creates shallow focus earthquakes, no volcanic activity
   • e.g San Andreas Fault
     • Pacific Plate (faster) than North American