booklet 4 - plate margins

• divergent (constructive) plate margin


  where 2 plates separate (diverge) they form a constructive margin
• divergent margin - oceanic + oceanic

  - magma rises between gap left by 2 plates separating, forming new land when it cools
• divergent margin - continental + continental


  - any land in the middle of separation is forced apart causing a rift valley
• destructive plate margin - CONVERGENT

  - when two plate collide

  - denser plate subducts

  oceanic + continental - oceanic subducts leaving an ocean trench

  oceanic + oceanic - denser plate subducts
• collision plate margin - CONVERGENT

  - 2 plates move towards eachother

  continental + continental - collide causing uplift + form fold mountains
• conservative plate margin


  - two plates slide past eachother

  - no melting of rock and crust isn't destroyed

  - no volcanic activity / new land

  - extremely active

  - friction occurs causing earthquakes
• fold mountains


  - found at collision boundaries

  - plates are lower density + as they move towards eachother, they're forced up to form fold mountains
• volcanoes


  form at constructive + destructive boundaries
• ocean ridges


  - oceanic divergence overtime forms chains of submarine mountain ridges
• rift valleys


  - constructive plate boundaries

  - develop over hot spots

  - weaknesses in crust that flood

  - two sides are moving apart, will eventually flood

  - rising magma causes region to uplift
• deep sea trenches


  - denser oceanic plate subducts under continental crust

  - downward displacement of plate forms a deep sea trench - parallel to plate boundary
• island arcs


  - line of volcanic islands appear

  - where denser crust subducts beneath the less dense crust
• hotspots


  - area moved by abundant magnetic activity

  - hot magma plumes from mantle rise + burn through weaker parts of the crust

  - can create volcanoes and islands