Mt St Helens
Signals
 Earthquakes
 Ground deformation
 Steam explosions
 Swelling bulge on the northern flank
 Erupted 18 May 1980
Impacts
 Landslides triggered by the collapse of the bulge on the northern flank
 Pyroclastic flows
o Collapse of northern flank suddenly exposed pent-up gas and gas-rich
magma underneath to much lower pressure, causing gases to expand rapidly,
resulting in huge lateral explosion
o When burning flow encountered water in its path, they were immediately
turned into steam
o Searing gas and pyroclastic flows rapidly melted glacial ice and snow, mixing
together to form huge mudflows
 Mudflows
o Destroyed 27 bridges, 185 miles of roads, 15 miles of railway and about 200
homes
 Ash eruption and fallout
o Clouds of gas and ashes generated lightning strikes, setting surrounding
forests ablaze
o Turned day into night in nearby towns
o Blanketed town of Ritzville with nearly 5cm of ash
o Ash shot into upper atmosphere, drifted around the globe within 2 weeks
 Damage survey
o Most victims died from inhalation of hot volcanic gases and other related
injuries
o Extensive damage to land and property
o Cost nearly US $1.1b
o Unemployment
o Tourism affected with cancellation or postponing of conventions, meetings
and social gatherings
 But due to the reawakening of Mt St Helens, the area regained its
appeal and visitor centers are opened for firsthand views
Mitigation
 Closure of areas around the volcano and beyond its immediate slopes
 Large-scale volcanic hazard map drawn up and released
 Access to further areas at risk closed and residents evacuated
Response
 1.8 million m³ of ash removed from highways and airports in Washington
 Granted funding for mental health programs to assist residents suffering stress and
emotional problems
 Mt St Helens National Volcanic Monument set up in 1982, preserving sites affected
by volcanic events for scientific studies, education, recreation and first-hand views
 Ongoing monitoring
Nevado Del Ruiz, Colombia
Eruption
 Exploded on Nov 13, 1985
 Citizens of Armero remained calm as they were placated by reassuring messages
from the mayor over the radio, and from a local priest over the church public
address system
 Red Cross ordered an evacuation, but was called off once ash stopped falling
 Then molten rock began to erupt from summit crater, but a storm obscured the
summit area so most citizens were unaware of the pyroclastic eruption
 Melted water mixed with pyroclastic fragments to form lahars
 25 000 people and 15 000 animals were killed
 4 500 people were injured, 8 000 people homeless
 Estimated cost: $1000m, 1/5 of Colombia’s Gross National Product
Prediction and Mitigation
 Few measures were taken
 Minor earthquakes and steam eruptions for 51 weeks prior to eruption, but not
enough to convince authorities that the volcano was a real threat
 No equipment to monitor the volcano, or expertise to do so
 Money obtained from the Unified Nations to help map areas thought to be at
greatest risk, but only 10 copies distributed
 Some government officials dismissed the report as too alarming and did not want to
evacuate people till they were assured of the necessity
 A group of scientists visited the crater, saw nothing to suggest eminent danger and
did not recommend and evacuation
 No emergency plans were made to evacuate people
Response
 Researchers assessed the scientific, technical and management capabilities needed
to limit the effects of volcanic eruptions, existing capabilities of local government
and inhabitants, and made policy recommendations
 Created video aimed at educating communities at risk
 Identified ways to share expertise and resources throughout the region
 Need to establish better links between the scientific community and the mass media
 Need for equipment and political will to implement permanent monitoring of highrisk volcanoes
 Encourage international organisations to support this capacity in developing
countries
Montserrat
Eruption
 Erupted on 18 July 1995
Impacts
 Death and injuries
o 19 people killed by pyroclastic flows and surges, but they were all in the
Exclusion Zone which was supposed to be evacuated except for authorized
people
o 7 people suffered severe burns due to walking on hot ash deposits,
inhalation injuries and burns to the nostrils and mouth
 Damage to homes
o Entire villages (eg. Farms and Trant’s) buried by block and ash flow deposits
 Damage to infrastructure
o W.H. Bramble Airport closed as debris from pyroclastic flow came within 50m
of it
 Destruction and loss of farmlands
o Land in the south of the island and close to the volcano had been used for
farming, even though it was in the Exclusion Zone
o This is because there was not enough food to go around, especially to feed
the evacuees
o Trees broken and flattened
o In some areas, vegetation completely stripped away
o Soil baked hard
 Damage to the economy
o Dearth of customers due to evacuation led to closure of several businesses
and banks
o Total tourist arrivals declined by 24%
o Exports dropped by 40%
o Concerns whether it Montserrat will continue to be a viable and functioning
place to reside in
Prediction
 Montserrat Volcano Observatory (MVO) set up to monitor developments of the
Soufriere Hills Volcano
 14 seismometers set up close to the volcano to record ground movements 24h a day
 GPS system and 5 electronic tiltmeters measuring ground deformation and lava
dome growth
Mitigation
 Evacuation plans devised
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
British Government funded temporary infrastructure in north of island that included
a jetty, roads, water, electricity and shelters
o But development slow and housing conditions not up to standards
o British Government reluctant to build permanent housing with improved
conditions as that would require greater funding
Voluntary evacuation scheme to allow evacuees to move to the UK for 2 years
Response
 Emergency Support Unit activated and search and rescue teams deployed quickly to
pick up survivors
 MVO issued advice to the public about ash fall
 British government finally agreed to fund development in the north of the island
Mount Pinatubo
Eruption
 Erupted in June 1991 in the Philippines
 More than 5b m³ of ash and pyroclastic debris ejected
 Eruption columns 18km wide at the base and heights reaching 30km above volcano’s
vent
 Typhoon Yunya struck on the same day, mixed with the ash deposits and caused
massive lahars
 Successful predictions led to many lives being saved and has been hailed as a great
success for volcanology and eruption prediction
Effects
 Short term
o 300 – 800 people killed, mostly by roofs collapsing under weight of
accumulated wet ash
o Roads and communications damaged or destroyed by pyroclastic flows and
lahars
o Cost $3.8b pesos
o Commercial and industrial operations temporarily suspended
o 650 000 workers forced out of work due to destruction of their farms, shops,
factories and work places
o Ninoy Aquino International Airport closed for 4 days
o Public buildings converted into evacuation centers
 Long term
o Poor sanitation and spread of illnesses, damage of healthcare facilities led to
soaring death rates
o Arable land rendered infertile, destroying livelihoods of farmers
o Education disrupted due to destruction of schools
o Hampered economic development
o Eruption injected large amount of aerosols into the stratosphere, causing
global temperatures to drop by 0.5°C
Prediction
 Remote sensing tools to monitor rainfall and ground vibration
 Seismometers
 Series of earthquakes
 Aerial survey showed that magma intrusion was very near surface as evidenced by a
dome forming near its summit
 Evacuated 50 000 people from within 16km perimeter
Mitigation
 Philippine Institute of Volcanology and Seismology (PHIVOLCS) and the Pinatubo
Lahar Hazards Taskforce (PLHT) began to provide general public education about
lahars
 Instruction of news media provided in the course of day-to-day interviews and field
trips
 Education posters, videos, leaflets, booklet prepared on lahars
 Residents with mental preparation about how to react in times of crisis
Response
 Evacuations to mainly Manila and Quezon City
 Volcanic alerts issued daily stating the alert level and associated danger area, and
information announced in major national and local newspapers, radio and television
stations, non-governmental organisations
Mt Vesuvius
Eruption
 Erupted on 16th December 1631 in Naples, Italy
 Preceded by a series of earthquakes, lasting for 6 months, and gradually increasing
in magnitude
 Sightings of smoke and fire coming out from fractures in the mountain
 Water wells became muddy
 Decrease of height of water table
 Uplift of bottom of crater
 Pyroclastic flows followed by mudflows, landslides, floods
Impacts
 Lands destroyed and covered with ash
 Hundreds of houses and buildings in towns on the slope of Somma and around it
collapsed
 Deposited 12 inches of tephra in Naples
 More than 3 500 inhabitants killed
 Skies darkened for days as ash fell as far as Constantinople (Istanbul) over 1 000
miles away
Response
 People affected relieved from paying high taxes previously imposed on them by the
Spanish empire in power
 During the restoration, workers discovered the ruins of Pompeii
 Scientific study of the volcano only began in the late 18 th century and first
observatory opened in 1845
Lake Nyos, Cameroon
Eruption
 21st August 1986, 1.24m tones of CO2 was released due to eruption into nearby
villages of Lake Nyos
 Waters supplied with a source of CO2 from a magma chamber beneath it, CO2
percolates through the lake bed, causing Lake Nyos waters to be saturated with it
 CO2 normally stays in the bottom layers of the lake but brought to surface due to
eruption
 Expulsion of great masses of CO2 caused clouds of gas to form and spread into the
neighbouring region
 CO2 denser than air, so it sinks to the ground and drives oxygen up
 Living things suffocated
 Caused asphyxiation of approximately 1 800 people and 2 500 livestock within 27km
of lake
Prediction and Mitigation
 Gas detection systems installed to produce warnings
 Experts predict the frequency of outgassings
 Lake Nyos and Monoun Degassing Project initiated by the Government of Cameroon
to ensure lake stability, supported by an International Advisory Committee
consisting 8 scientists and sources of funding
o Further logistical support required in forms of modes of transport to and fro
the stations
o Government support needed for local engineers to be given training overseas
by foreign technicians
o Inter-Ministerial Committee formed to ensure proper training and logistics,
coupled with the education of locals on the hazards and remediation
 Natural dam wall of Lake Nyos has shown signs of weakening
o Most of CO2 should be removed before lowering lake levels to decrease
pressure on wall
o Strengthen the dam before the gas is removed
o Construct a barrier in the lake to reinforce the dam
o But all short term measures only
 Investigations have begun on other African lakes to prevent the disaster of Lake
Nyos happening again
Human response
 Survivors sent to resettlement camps
 Insufficient supply brought to some camps due to inadequate rationing and
corruption
 Limited schools available, teachers scarce



Lack of road links makes transportation of surplus crops and search for better
healthcare facilities difficult
Need to have a long-term solution to allow the displaced to claim back their homes
without having their lives endangered
Buabua-Kimbi Lake Nyos Survivors Cultural and Development Association and the
Nyos Cultural and Development Association offered assistance in the form of
humanitarian pledges
Unzen
Eruption
 Dormant volcano which erupted in May 1991 in Japan
 Volcano averaged 35 flows a day but flows were small yet destructive
 June 3, much larger dome collapsed and explosion produced a large pyroclastic flow
and ash cloud
 Lava domes continued to build up towards east flank of volcano and toward the end
of July, an elongated dome was created which generated 10 small pyroclastic flows
daily on average
 1992, pyroclastic flows covered larger section of volcano and lahars became more
common
 After 4 years of volcanic hazard, total of 15 000 people evacuated, 43 people died
and $2 billion worth of property destroyed
Prediction and Response
 Scientists paid attention towards the monitoring of the dome’s active margin to
predict which part of the volcano was at risk from pyroclastic flows
o Successful prediction in 1993, when officials ordered residents to evacuate
the area near the Nakao River valley
 Unzen Scientific Drilling Project is a joint project undertaken by the Japan Ministry of
Education, Culture, Science, Sports and Technology and the International
Continental Scientific Drilling Program
o Drill a hole towards the conduit of Unzen, geologists can then sample the
conduit and improve interpretation of premonitory signals
 Monitoring hot springs
o Monitor concentration of carbonic acid which usually increases gradually
before an eruption is about to occur but decreases as the summit crater
beings to open
Mitigation
 Efficient warning system and strategic evacuation plan
 Minimise damage from lahars
o 3 sediment basins lined with interlocking concrete blocks
o Series of discontinuous dikes along both sides of main channel along the
Mizunashi River
o Trap sediment and channel lahar flows
Sakurajima
Eruption
 Erupted in January 1914 in Japan
 After 5 strong earthquakes and 250 other earthquakes, people immediately
evacuated on boats even without orders from the government
 Japanese army and navy then arrived to help with the evacuation
 Few people died
Prediction
 On upper flanks of volcano, tunnel drilled into the mountain for more than 200 yards
o Equipment placed at the mouth to measure changes in movement, tilt and
seismic activities
 Seismic detectors to monitor seismic activity directly related to the movement of
magma beneath the earth’s surface
 Observation of magma activity detected by seismometer, tiltmeter and
extensometer
Mitigation
 Large drainage channels built to channel lahar flow safely into sea
 CCTVs installed near the channels monitored at all times by scientists
 Evacuation drills carried out annually on 12th Jan
 Japanese education system integrated volcanoes into their curriculum at the
developmental age
 Publishing of volcano hazard maps
 Constantly reviewed evacuation system and plan
Mount Tambora
Eruption
 Experienced centuries of dormancy prior to eruption
 Enormous magma chamber took 100s of years to refill
 Erupted in April 1815 in Indonesia
 11 000 – 12 000 killed directly by explosion, 60 000 – 100 000 additional deaths
Direct effects
 Explosion heard on Sumatra (>2 000km away)
 Pyroclastic flows which were largely responsible for the extinction of the Tambora
population
 Tsunamis created by volcanic material displacing sea water
 Whirlwind swept property and people out into sea
 Tephra and gases ejected
o Ash blanketed land up to 250km away, sometimes up to 60cm thick
 Caldera collapse caused earthquakes felt up to 500km away
Geographical impacts
 Global cooling: drop in temperatures globally by 0.5C to 3.0C
o Sulphur dioxide released mixed with water to form sulphuric acide, reducing
the amount of sunlight reaching the earth
o Northern hemisphere experienced snow and frost in summer
 Monsoon season disrupted, leading to flooding in China and famine in India
 Some areas covered with ash took up to 5 years for vegetation to grow back
Economic impacts
 Massive crop failure in the Northern hemisphere due to cold
 Food prices inflated
 Livestock killed to make up for crop losses
Social impacts
 Population of Tambora wiped out
 Indonesians sold themselves into slavery to escape islands, children sold for food
 Riots started in Britain and France by starving citizens breaking into store houses
 State of emergency declared in Switzerland
 Mass migration to the US
 Epidemics in Indonesia, Typhus outbreak in Europe, Cholera outbreak in India and
Europe
Response
 Soup kitchens set up in Europe
 Britain suspended income taxes
Krakatoa
Eruption
 Erupted on 27 August 1883 in Indonesia
 Sudden land slump provided opening for magma from highly pressurized chamber to
burst out
 36 400 deaths in total
Direct effects
 Loudest known sound in history, atmospheric shock waves detectable after 5 days
 Pyroclastic flows reached the Sumatran coast (40km)
 Tsunamis formed by displacement of several cubic km of water rushing in to fill
caldera
 Tephra and gases ejected propelled to 80km into the atmosphere, blocked out the
sun for 2 days, affected the weather for 5 years
Geographical impacts
 Disappearance of 2/3 of the island
 Incoming solar radiation dropped by 10%
 Global temperatures dropped by up to 1.2C
 Acid rain and other chaotic weather phenomena experienced
Economic impacts
 Some areas devastated not been repopulated up till today
Social impacts
 Population of Sebesi (13km from Krakatoa) wiped out
 Numerous settlements wiped out
 Human bodies washed up coasts
Paricutin
Eruption
 Eruption occurred 1943 – 1952
 Marks the first time scientists were able to observe the complete life cycle of a
volcano, from birth to extinction
Impacts
 No one died directly from the eruption
 3 people died after being struck by lightning generated by the pyroclastic eruptions
 2 nearby villages: Paricutin and San Juan were overrun by the lava flow
Prediction and mitigation
 3 weeks before eruption, Paricutin villagers heard rumbling noises that resembled
thunder
 A farmer and his wife were burning shrubbery in their cornfield when they observed
the earth in front of them swell upward and crack to form a fissure 2-2.5m across
o Heard hissing sounds and later described the rise of ‘smoke’ from the fissure
Response
 People began to evacuate the day after a lobe of lava began to advance toward
Paricutin village
 Larger village of San Juan evacuated a few months later
Popocatepetl
Eruption
 3 major plinian eruptions, the most recent took place about 800 AD
 Became active just before Christmas 1994 after 5 decades of quiet
Impacts
 On morning of Dec 21 a gray ash cloud was visible over the top of the volcano and
ash fell on Puebla
 20m Mexican people live close enough to the volcano to be threatened by its
eruptions
 Ash from eruption could endanger aircraft using Mexico City international airport
Prediction and mitigation
 United States Geologic Survey sent a team of volcano experts to Mexico to help
Mexican scientists evaluate what the volcano may do in the near future
 Monitoring of ash plume dispersion using Geostationary Operational Environmental
Satellites (GOES) imagery
Responses
 Because most of the ash was blowing to the east, civil defense authorities evacuated
19 villages east of Popo