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What is an example of flooding resulting from lava flows?

Spirit Lake rose 80m after the eruption of Mount St Helen's


What are the benefits of volcanoes?

- hot rocks allow the development of geothermal power
- lava flows create new land
- igneous rocks make good building materials
- lava and ashes= fertile soils
- tourist attractions e.g. geysers and hot springs
- extinct = defensive sites
- volcanic sulphur= pharmaceutical manufacturing processes
- valuable mineral deposits


Example of geothermal power



Example of extinct volcano as a defensive site

Edinburgh Castle


Example of valuable mineral deposits

Gold silver and diamonds in Java


What is the type of magma at constructive?

Basaltic magma
Above 1000 degrees C


What is the type of magma at destructive?

Up to 1000 degrees C


What are the characteristics of magma at constructive?

- low in silica
- thin and runny (less viscous)
- gas can escape
- hotter


What are the characteristics of lava at destructive

- high in silica
- viscous and thick
- traps gas
- cooler


What is the type of eruption at constructive?

Low on VEI scale e.g. Hawaiian
not very explosive as gases are able to escape, lava


What is the type of eruption at destructive?

High on VEI e.g. Vulcanian, Plinian
can be extremely explosive with ash, dust and lava


What is the eruption height at constructive?

2km and less


What is the eruption height at destructive?

55km and below, can be way over 20km


What are the materials produced at constructive?

mainly lava


What are the materials erupted at destructive?

- pyroclastic material
- ash and dust
- lava bombs
- tephra


What is the frequency at constructive

Eruptions are regular but can be continuous


What is the frequency at destructive?

less frequent, often have long dormant periods


What is the form of volcano at constructive?

- basic shield volcano or lava plateau
- made of only lava


What is the form of volcano at destructive?

- composite cone or acid lava dome
- layers of ash and lava
- very viscous lava


What are the hazards of volcanoes?

- ash falls ruin crops/machinery, disrupts transport, breathing
- lava flows burn and bury crops
- dust emissions create rainstorms; dangerous lahars
- dust absorbs solar energy and lowers atmospheric temps
- pyroclastic flows; life and property
- flooding results from lava flows/debris blocking rivers
- submarine eruptions= tsunamis


What are the two types of volcanic landforms?

1. Extrusive igneous rock formation (volcano)
2. Intrusive igneous rock formation (not a volcano)


What happens to intrusive rock forms?

- lava cools quickly when in contact with air
- this creates crystals so rock is finer grained
- e.g. basalt


What are the solid material coming from volcanoes?

- dust
- glassy cinders
- ash


What are the gases released by volcanoes?

- chlorine
- carbon monoxide
- hydrogen sulphide
- sulphur dioxide


What are the liquids released by a volcano?

- surface lavas e.g. acid, basic
- lava bombs e.g. tephra or pyroclasts; solidify in mid air e.g. Forming pumice, fine hairlike trails of magma called lapili


What are the three types of lava?

1. Basic lava
2. Andesitic (intermediate) lava
3. Rhyolithic lava (acidic) lava


Characteristics of basic lava

- upward movement of mantle material at constructive margins
- along spreading ridges and hot spots
- low in silica, mostly fluid lava which allows gas bubbles to expand and pop so it isn't explosive


Characteristics of andesitic lava

- destructive plate margins
- high in silica; very viscous (acidic)
- often solidifies before reaching surface; build of pressure creates violent eruptions
- gas can't escape so eruptions are explosive


Characteristics of rhyolithic

- destructive and collision
- same characteristics as andesitic


Why do intrusive volcanic landforms form?

- magma intrudes into the crust and solidifies
- can be exposed at the surface later due to lateral erosion
- magma in the intrusive landforms crystallises and solidifies at plutonic depths
- forms large crystals creating rocks e.g. granite, dolerite
- more resistant than extrusive such as basalt because the cooling process is longer and the crystals have taken more time to grow