14.2 Types of volcanic eruption Flashcards
What is viscosity?
An indication of how well a substance flows
What causes volcanic eruptions to produce diverse landforms?
- Where the eruption occurs
- The type of lava
- Variety of materials produced eg ash, gases
- How the eruption takes place
What are the two types of volcanic eruption?
Effusive and explosive
Effusive eruptions: where do they occur?
Divergent plate boundaries
Effusive eruptions: what type of lava?
Basalt
Effusive eruptions: characteristics of the lava?
Basic (low % silica), low viscosity, higher temperature at eruption
Effusive eruptions: style of eruption?
Gas bubbles expand freely, limited explosive force
Effusive eruptions: materials erupted?
Gas, lava flows
Effusive eruptions: frequency?
Tend to be more frequent and can continue for many months
Effusive eruptions: shape of volcano?
Gently sloping sides, shield volcanoes
Explosive eruptions: where do they occur?
Convergent plate boundaries
Explosive eruptions: type of lava?
Rhyolite (more acid), andesite (less acid)
Explosive eruptions: characteristics of the lava?
Acid (high % silica), high viscosity, lower temperature at eruption
Explosive eruptions: style of eruption?
Violent bursting of gas bubbles when magma reaches the surface, highly explosive, vent and top of cone often shattered
Explosive eruptions: materials erupted?
Gas, dust, ash, lava bombs, tephra
Explosive eruptions: frequency of eruption?
Long periods with no activity
Explosive eruptions: shape of volcano?
Steep-sided stratovolcanoes, caldera
What type of eruptions does Iceland owe itself to?
Effusive eruptions
Two products of explosive eruptions?
Calderas and stratovolcanoes
What are stratovolcanoes?
Also known as composite cone volcanoes – made up of layers of ash and acid lava with concave symmetrical profiles – associated with explosive eruptions