types of volcanoes

• shield volcanoes are found at divergent boundaries

  they are low with gentle sloping sides

  they are formed by eruptions of thin, runny lava

  eruptions tend to be frequent but relatively gentle
• composite volcanoes formed of sticky (viscous) acidic lava, ash and cinders

  found at convergent boundaries

  e.g. Mt St Helens in the USA

  composite volcanoes may have several cones rather than just a single cone
• supervolcanoes erupts 1000km³ of material forms depression called caldera has a ridge of higher land around it erupts rarely, eruptions hundreds of thousands years apart