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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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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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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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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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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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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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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