Tectonics Case Studies


Soufriere Hills, Montserrat

  • Destructive plate boundary
  • North American plate being subducted beneath the Caribbean plate - Peurto Rico Trench; Antilles volcanic island arc
  • 1995 - continual
  • 19 people died in 1997
  • W H Bramble airport closed and the port closed
  • 50% of population evacuated after erutpions began - many left with no return
  • Valleys were blocked with ash which led to floods and lahars e.g. Tar River Valley
  • Pyroclastic flows caused forest fires
  • Acid rain destroyed vegetation and farmland; streams and lakes were polluted
  • Plymouth submerged in 12m of ash
  • £41 million given in aid by British government
  • Montserrat Volcano Observatory set up as a result to study the volcano and provide future warnings - deformaton monitoring, environmental monitoring, volcanological monitoring
  • £6.5 million spent on emergency housing schemes
  • Hospital upgraded to cope with future incidents
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Mount Etna, Sicily

  • Stratovolcano with 4 summit craters
  • Active fault between African plate and Ionian microplate - both being subducted beneath Eurasian plate
  • Andesitic and basaltic lava - eruptions can be gentle and explosive
  • Erupted in 2001 as a result of 6 fissures opening on the flank of the volcano
  • All 4 summit craters produced activity ranging from strombolian to high energy explosive episodes
  • Main eruption lasted for 24 days, beginning in July 2001
  • Valle del Bove provided channel for lava - low viscosity meant lava travelled at even faster speeds, increasing potential to cause damage
  • One of the vents was the site of vigorous phreatomagmatic activity as the dike cut through a shallow aquifer, during both the initial and closing stages of the eruption
  • Concrete and earth dams used to divert lava flows away from major settlements
  • Airport cllosed, people evacuated
  • Blocks dropped into lava flows in attempt to cool and slow its movement
  • Heavy ash falls as result of ash plume
  • Forest fires as a result of lava flows
  • Less snow settled later that year which affected tourism - skiing is source of income in Italy
  • 77 deaths can be attributed to Mount Etna.
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Mt Nyiragongo, Congo

  • January 2002 - associated with the African Rift Valley
  • Main crater 250m deep and 2km wide
  • Warnings of lava flows enabled most people to flee from their effects
  • A fissure 13km long opened on southern flank of volcano - lava flows 2m deep
  • Destroyed at least 1/3 of Goma; a town with over 200,000 inhabitants
  • CBD was destroyed, along with water and power supplies
  • Death toll reached 147
  • More than 350,000 fled the area, many to Rwanda
  • Sulphurous lava entered Lake Kivu, polluting the waters which were major source for drinking
  • Increased temperature of Laka Kivu allowed toxic gases to be released from river bed
  • Earthquakes accompanied eruption, one measuring ver 5 on the richter scale
  • Thousands required medical attention
  • Looting of abandoned homes became a serious problem
  • UN began to bring humanitarian aid 2 days after the eruption
  • Congo was entirely reliant on the UN and other foreign aid as a response to the eruption
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Mt Pinatubo, Luzon

  • Destructive boundary between Eurasian and Philippine plates - Philippine plate being subduced beneath Eurasian plate
  • Erupted in 1991 and killed 847 - 300 from collapsing roofs, 100 from lahars and the rest from disease
  • 650,000 workers lost jobs
  • $700 million in damages
  • 1.2 million left homeless
  • Electricity cut off, water contaminated, road links destroyed, telephone links cut
  • Typhoon Yang exacerbated effects - strong winds combined with ash and rainfall produced lahars, despite the fact that the volcano was no longer erupting
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Mt St Helens, Washington

  • Cascade mountains located at destructive boundary where Juan de Fuca plate being subducted beneath the North American plate 
  • Composite volcano
  • 1980 - warning signs of iminent eruption e.g. M5.1 earthquake 
  • Followed by massive eruption of volcanic material - pyroclastic flows, lahars, floods, phreatic activity
  • $1.1 billion worth of damage
  • 200 homes destroyed
  • 27 bridges destroyed, 24km of railways and 300km of roads
  • 57 people killed
  • Unemployment levels increased dramatically
  • 240km2 of forest destroyed - wildlife severely effected - 12 million young salmon were killed
  • Sediment dumpe in Spirit Lake raised the lake bed by 90m and water levels by 60m
  • Face masks distributed to limit those breathing in ash
  • Emergency shelters set up, ash clean up organisations created
  • USGS started round the clock monitoring following beginning of earthquakes - gathered seismic data, gas emissions etc
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Eyjafjallajokull, Iceland

  • Divergent plate boundary - North American plate is moving west and Eurasian plate is moving East 
  • Mid-Atlantic Ridge - palaeomagnestism used as evidence for plate tectonics theory
  • Moving apart at rate of 1-5cm per year
  • Created chain of volcanoes along SE Rift zone of Iceland
  • Eyjafjallakokull is a small volcano within the chain of volcanoes
  • Most southernly volcano in Iceland - elongated ice-covered stratovolcano; 2.5km wide summit caldera
  • Fissure eruptions travel down East and West flanks of the volcano
  • 2010 eruption caused global disruption
  • Ash plume reached 11,000m into the stratosphere; distributred by high velocity jet streams between troposphere and stratosphere
  • Fine grained ash closed global airspace as when it enters engines it can turn into a glassy substance
  • Britain had fine anticyclonic weather for a lot of the time that the ash cloud existed
  • Glacier covered the summit - caused a flood (jokulhlaups - glacier led flood) - 700 people evacuated
  • Lava emitted from 500m long fissure; VEI of 4
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Haiti, Hispaniola

  • January 2010 - Strike slip failt that runs off a destructive margin to the north of Hispaniola - Caribbean and North American plates - Peurto Rico Trench - ENRIQUILLO-PLANTAIN GARDEN
  • Magnitude 7.0 on Richter scale; Japanese Tsunami of 2011 had bigger fore and aftershocks - lasted 30-40 seconds
  • Epicentre 15 miles WSW from Port-au-Prince and focus 13km deep - SHALLOW
  • 200 years since last major earthquake; big earthquakes reasonably rare
  • Struck close to the nation's capital of 2 million people; geology of area did not help - built on many unstable soils; seismic waves amplified causing liquefaction
  • Haiti is the poorest country in the Western Hemisphere - 38% of population are under 14
  • 80% of population lived below the poverty line in 2009, with only 53% literate
  • Haiti doesn't have the resources to heed warnings
  • Poor building quality - concrete roofs collapsed and killed thousands, walls not properly reinforced; 50% collapsed
  • Very few 'reserves' (money, food) - limited safety net
  • Haiti was reliant on international aid for over 30% of national GDP before the earthquake
  • 316,000 people died and more than 1 million made homeless - before rainy season beginning in April and storm season later in June
  • 3 million people affected in total - 30,000 commercial buildings collapsed or damaged
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