Types of volcano

Composite:

• Pyroclastic flows common in larger eruptions

• The most explosive eruptions containing ash first and then followed by lava. Large amounts of tephra ejected. VEI up to 8

• Examples include Mt Pinatubo, Philippines, Krakatoa, Indonesia and Vesuvius in Italy

• Steeply sided, symmetrical cones of large dimensions built from the alternate layering of ash and lava on the sides

• Highly viscous, andesitic lava which is cooler than basaltic lava and high in silica. Hardens and cools quickly

Shield

• Basaltic lava, low in silica with a low viscosity flows out of a central vent. The larva flow is often referred to as pahoehoe (ropy) or a’a (blocky and thick)

• Frequent, non-explosive (effusive) eruptions. VEI 4 and below

• Flat shape, gently sloping sides made of layers of lava only

• Gas release is rare- least explosive

• Examples include Mauna Loa, Hawaii, USA and Sierra Negra in the Galápagos Islands

Cinder

• Fine ash and cinder build up into symmetrical cones volcanoes

• Examples include Paricutin in Mexico and Cerro Negro in Nicaragua

• Basaltic lava, more viscous than that from shield volcanoes and contains more trapped gas. This gas results in small explosions during eruptions

• Lava is ejected but it cools very quickly in the air becoming cinder, which falls from the air and settles only short distances from the vent