3.1.1.2 Tectonic hazards (part a) GapFill

Earthquakes and volcanoes typically occur along  Pacificplatecontinentalcentre margins. These are at the  centrePacificedgesHaiti of the plates. For example, they can be seen as a so-called 'ring of fire' around the  conservativeshallowIndianPacific. Plate margins can be categorised according to type: Some are termed  shallowvolcanomantleconstructive. Here, the plates are forced apart by convection currents in the  corelavamantleIceland. There can be  corecontinentalshallowdeep focus earthquakes, which occur as the plates move.  ConservativeCoreLavaMagma rises to fill the gaps between plates. This forms basic lava volcanoes such as Surtsey, off the coast of  AzorescontinentalIcelandcrust. Some margins are termed destructive. Here, the plates are pushing into each other. There can be  deepshallowIndianbigger focus earthquakes in the subduction zone where the  biggerMontserratcrustdenser oceanic plate is forced under the lighter continental plate. In the subduction zone, the  mantleIndianoceaniccontinental plate melts and magma rises to the surface. This process forms explosive volcanoes such as Soufrière Hills,  shallowMontserratIcelandCrust.