The Process of aVolcanic Eruption
- At a destructive plate boundary the oceanic plate moves towards the continental plate, but as the oceanic plate is heavier it sinks.
- The oceanic plate is pushed further under and melts in the hot temperatures of the mantel, and the extra magma increases pressure.
- As the melted rock is lighter it forces its way to the surface creating a volcano. Further eruptions build up layers of rock.
- Red hot lava flows down the side of the volcano. Gases in the volcano can cause explosions as more magma forces its way upwards, releasing thousands of volcanic bombs and pyroclastic flows. The lava can also mix with water to form Lahas (a type of mudflow which causes more deaths than the lava alone)
If volcanoes are so dangerous, why do we live near them?
- Fertile soils – the physical breakdown and chemical weathering of rocks over thousands of years forms fertile soil (e.g. Hawaii)
- Geothermal energy – water in permeable rocks is heated by the magma beneath to form steam. It can be used to drie turbines for electricity, for spas or for space heating. It is an environmentally-friendly and limitless source of enerfy. (e.g. in Iceland 70% of homes are heated by geothermal energy)
- Minerals – lava can crystallise into gold/silver/diamonds etc. meaning dormant volcanoes provide good mining oppurtunities, which could lead to job creation and the development of near-by towns.
- Tourism – Hot springs/geysers are huge tourist attractions and provide additional revenue for the country (e.g. Old Faithful in Yellowstone park)
- Science – Close study of volcanoes could lead to a better understanding of them and help to develop new prediction techniques
- Other – local inhabitants often think an eruption won’t happen in their lifetime so it is safe to live there and as it has always been their home they are often reluctant to leave, particually as many jobs are based near volcanoes e.g. logging
Case Study – Mt. St. Helens
A detailed account of the eruption and its affects can be found here, but here is a rather informative and at the same time commical song about the eruption: