Tectonics case studies Flashcards
Example of a deep ocean trench
Peru-Chile trench, Pacific ocean
Example of fold mountains
Andes
Example of oceanic meeting oceanic plate-destructive margin
Pacific plate subducts beneath smaller Philippine plate
Example of a mid ocean ridge formed at constructive plate margin
Mid Atlantic Ridge
Example of rift valley
Great African Rift Valley
Example of a volcanic island
Surtsey
Example of a conservative plate margin
Pacific plate moving past the North American plate (Causing powerful shallow focus earthquakes such as Los Angeles 1994 and San Francisco 1906)
Example of a constructive plate margin
Eurasian meets North American
Example of a destructive oceanic to continental plate margin
Nazca and South American plate
Example of a destructive continental to continental plate margin
Indo Australian and Eurasian
Example of where and when lava flows killed people
1977 Nyirangongo volcano, Congo killed 72
Example of where pyroclastic flows killed a large number of people
Mount Pelee,Caribbean, 1902
Election meant government stopped evacuation
Lead to all but 2 of the 29000 inhabitants being killed in pyroclastic flows
Example of where volcanic gases killed people
Nyos, California 1986 1700 people died as CO2 was released quickly and in great quantities
Example of lahars killing people
1985 Nevada del Ruiz, Columbia, lacking hazard salience as focus on narcotics
Town of Armero was buried in 8m of mud and killed 22000 people from lahars
Example where sea water sprays were successfully used to cool lava
Eldafell, Heimaey 1973 to protect harbour
Example where explosives were used to divert lava
Mount Etna
Example where artificial mounds are used to enable villagers to escape to higher ground
Indonesia
Example where hazard resistant design is used
Hawaii
Houses with steep sloping roofs designed to shed ash
Example where evacuation was successful
The Gallungung eruption of 1982 evacuated 75000 people with small fatality of 68
Example where bottom up approach is used to educate people to basic warning signs
PHIVOLVS
Philippines
Sulphur odours, strange animal behaviour, steam releases and crater glow
Example where a volcanic eruption was predicted a week before using satellites
Pacaya Guatemala
Example where land use planning is in place
Hawaii
Volcanoes MEDC case study
Mount Etna, Sicily, Italy
Background information on Mount Etna
GDP per capita $20000
25% of Sicily’s population live on slopes
Has experienced several caldera collapses and erupted every year since 2001
Subduction of African plate beneath Eurasian plate
Composite statovolcano erupts basaltic lava
Prominent feature of Valle del Bove
Information of 1991-93 eruption of Mount Etna
December 91- lava pouring from Valle del Bove, threatening village of Zafferana (8700 people)
Eruption lasted for 473 days and was most volumous eruption in over 300 yrs
What protective measures were put in place on Mount Etna?
Earth barriers to hold back lava-buy time.
Spring 1992 lava breached barrier heading for Zafferana,decided to block feeder channel by dropping concrete blocks.
May 1992- made a new direction of flow
Lead to protection of Zafferana
Reasons for the success of Etna’s management
Low effusion rates, high elevation of vents, diversion from inhabited areas, different groups involved e.g. Italian army, local council and volcanologists
Only 77 deaths attributed to Etna’s eruptions
Other times where Etna’s eruptions weren’t successfully managed
2002- Ski station Piano Provenzana completely destroyed in lava flows and ash clouds closed Catania airport
Impacts of 91-93 Etna eruption
Destroyed springs which provided water supply to the town of Zafferana (8000ppl)
Thousands of insurance claims made bc of damage to property.
Ppl who lost homes on Valle del Bove blamed the government for not acting soon enough.
Residents interviewed weren’t fearful of another event and they knew it would be diverted.
What monitoring and management occurs on Etna?
INGV monitor using seismic, geodetic, magnetic and gravimetric remote sensors.
Data continuously recorded by permanent stations and discrete observations, surveys and laboratory analysis to evaluate activity level.
Geochemical monitoring programmes.
SO2 plum flux has been routinely measured by correlation spectrometry.
Warning systems, land use planning and preparation of civil defence.
GPS to examine slope angle changes.
Government sponsored insurance, international aid, evacuation plans, traditional rural society suffer still.
Italian government pledged immediate financial assistance of over $8million and tax breaks for villagers.
LEDC case study
Montserrat 1995-97 Soufriere hills Chances Peak
Background information on Montserrat and 95 eruption
Chances Peak is a composite volcano
North American plate subducts under Caribbean plate
After lying dormant for many centuries, July 1995, began to erupt- ash, steam and numerous earthquakes
March 96- ash cloud, dome growth, small pyroclastic flows
June 97- large explosion, extensive pyroclastic flows
Effects of Montserrat 95 eruption
40km squared deemed safe out of the 100km squared
Islands capital Plymouth buried under 10m of ash and mud, airport and docking facilities destroyed, south rendered uninhabitable
17 died In 600 degC pyroclastic flows
9000 moved abroad
Respiratory diseases such as Silicosis
PTSD
8/35 staff from school left
Ruined fertile land
Animals become feral kill endangered species
2/3 houses buried or flattened
Top heavy population as young didn’t see economic potential
Attraction of 1500 due to construction opportunities
British Government assistance for Montserrat
Set up exclusion zones
7,000 ppl moved to Antigua, USA, North or UK
Temporary shelters set up in the north
Moving capital to Salem
Setup of Montserrat Volcano Observatory run by British Geological Society
£100million spent assisting mitigation and restoration
A new airport called Geralds
Development of Port facilities at Little Bay
£17 million emergency aid sent for temp buildings and water purification
£5 million grant from UK for capacity building
3 yr redevelopment plan funded by UK
(Warning systems set up- sirens, speaker systems, media
Troops from USA and Britain to aid evacuation)
Management of Montserrat
MVO
Records of how the eruptions tend to take place
Zoning of island
Search and rescue infrastructure
Mass casualty plan
Off and on island evacuation
Construction of air tight underground bunkers for shelter from pyroclastic flows
Rebuilding house roofs with steep slopes
Education by local paper, internet and newsletter
Sustainable development plan 2008-2020
What are the worried about management for Montserrat?
Ppl become complacent if warnings are given too often
Destruction of infrastructure
Damage to monitoring equipment
Mount Merapi 2010
Monitored by CVGHM
Indonesian government raised highest alert in 2010- evacuation of 20km
Javanese beliefs- spiritual guardian and 13 other died in pyroclastic flow as refused to evacuate.
Heavy rain triggered lahars.
Previous eruptions of a different nature.
JALIN merapi set up- in 2010: radio, twitter, website, fb, phone hotline.
Mount Pinatubo, Philippines 1991
Philippine plate subducted beneath Eurasian.
Monitored by PHIVOLCS and USGS
US Clark Air Base located here so vested interest
Successful evacuation meant death toll was 350 initially due to pyroclastic flows
Typhoon Yunga caused lahars increasing death toll
Tribal Aetas died-some refused evacuation, others died in evacuation camps due to lacking immunity and reluctance to take medicine and eat unfamiliar diet. 94% of camp deaths were Aetas
2 million ppl affected
$711 million in losses
Iceland 2010
Eyjafjallajokull
Eruption melted 150m of ice cap
Released thick clouds of ash into atmosphere
International impact on flights
European airspace fell to around 5,000 a day compared to a normal level of over 25,000- 6 day shut down
Cost London £102 million
Serious flash flooding but Iceland was well prepared- trenches dug
Chaiten,Chile 2008
First time in 9400 yrs.
Subduction of Nazca beneath S. American.
Rhyolitics-pyroclastic flow
USGS monitoring team flew to help observatory in Chile and to find out more about rhyolitic eruption
Widespread ash fall, rainfall triggered lahars, flooding 90% of Chaiten
4000 evacuated 50km exclusion zone set up
Monthly disaster stipend $1200-$2200 per month per family given
90 day freeze on existing loans
Financial aid to small companies granted
Casualties low and one death toll from stress
Remote location and lack of activity- wasn’t considered high priority
Mt St Helens USA 1980
Subduction zone Juan de Fuca subducts beneath N.American plate.
Lateral blast pyroclastic material
57ppl died
Swelling of north flank was noted and so it was constantly monitored two months prior to the eruption
Low pop dens
