Tectonics- Volcanoes Flashcards
Volcanoes
Formed when vents spew lava onto the surface
Shield volcanoes
Eject basalt lava which is runny due to its low silicon content
Found above mantle hotspots and constructive plate boundaries
Runny lava flows far and wide which results gently sided volcanoes
Eruptions are non-violent
Strato/composite volcanoes
Eject rhyolite lava and ash which is very thick due to its high silicon content
Found at destructive plate boundaries
Thick lava does not easily flow, causing it to build up a steep sided volcanoe
Volcano produces violent pyroclastic flow eruptions
Primary effects of volcanoes
Ash clouds - making breathing difficult
Volcanic gases poison the atmosphere
Property destroyed
Secondary effects of volcanoes
Acid rain
Suffocation due to poison in atmosphere
Ash clouds block sun and reduces earths temperature
Damage of lungs
Hospitals overwhelmed
Homelessness
Loss of jobs
Increase in crime rate
Outwards migration
Pyroclastic flow
Heavy cloud of scorching gas, dust, ash and rock collapses and rushes like a flow down a slope - can reach 200km/h
Why do people live in volcanic areas
Geothermal power
Minerals
Fertile soil
Agriculture
Tourism
How to predict eruptions
Gas emissions
Earthquakes- when lava moves around underground it causes little earthquakes
Bulges
Rising ground temperatures
How damaging effects of volcanoes can be reduced
Evacuation orders
Eruptions can be diverted away from settlements using channels/ earth walls
Planning policies to avoid high risk areas or making hazard maps
Montserrat, 1997 - case study
Caribbean island sits on a destructive boundary where the North American plate sinks under the Caribbean plate
Sub ducting plate melts due to friction and heat from mantle and magma rises to the surface to create eruptions which have built the soufriere hills volcano and the island itself
Magma is very thick and so built up to create a lava dome which collapsed June 1997, resulting in devastating pyroclastic flows
Effects of Montserrat eruption
Destroyed villages, farmland and the capital
Killed 19 people that’s failed to follow the evacuation order
Inhabitants left the island to surrounding islands
Millions of dollars spent on building new schools, hospitals, ports and airports
