Tectonics- Volcanoes

Question 1

Volcanoes

Answer 1

Formed when vents spew lava onto the surface

Question 2

Shield volcanoes

Answer 2

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

Question 3

Strato/composite volcanoes

Answer 3

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

Question 4

Primary effects of volcanoes

Answer 4

Ash clouds - making breathing difficult

Volcanic gases poison the atmosphere

Property destroyed

Question 5

Secondary effects of volcanoes

Answer 5

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

Question 6

Pyroclastic flow

Answer 6

Heavy cloud of scorching gas, dust, ash and rock collapses and rushes like a flow down a slope - can reach 200km/h

Question 7

Why do people live in volcanic areas

Answer 7

Geothermal power

Minerals

Fertile soil

Agriculture

Tourism

Question 8

How to predict eruptions

Answer 8

Gas emissions

Earthquakes- when lava moves around underground it causes little earthquakes

Bulges

Rising ground temperatures

Question 9

How damaging effects of volcanoes can be reduced

Answer 9

Evacuation orders

Eruptions can be diverted away from settlements using channels/ earth walls

Planning policies to avoid high risk areas or making hazard maps

Question 10

Montserrat, 1997 - case study

Answer 10

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

Question 11

Effects of Montserrat eruption

Answer 11

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