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Volcanic Hazards (workbook 3) (secondary hazards (Lahars happens when…
Volcanic Hazards (workbook 3)
Types of magma
BASALTIC- hotspots and constructive margins, low viscosity, 1000 degrees +, less hazardous
ANDESITIC- destructive plate margins, sticky viscosity, 800 degrees, very hazardous
RHYOLITIC- continental hotspots, collision boundaries, high viscosity, 700 degrees, very hazardous
magnitude measured on VEI, volcanic explosivity index
primary hazards
Lava Flows
flows of magma extruded from the volcano vent
less dangerous as people can move out of the way
economic impacts
Volcanic Gases
includes carbon dioxide, carbon monoxide, hydrogen sulphide, sulphur dioxide and chlorine
e.g Lake Nyos, Cameroon
Pyroclastic fallout
64mm = volcanic bombs
2-64 mm = lapilli
<2mm = ash
if ash lands on buildings it can cause them to collapse or it can suffocate crops and clog rivers
Nuee Ardente/ Pyroclastic Flows
'glowing cloud'
occurs when lava dome collapses
over 800 degrees
700 km/h
most explosive volcanoes/ most dangerous
Mt Vesuvius, 79 AD
secondary hazards
Lahars
happens when volcanic ash combines with water e.g rain or a typhoon
travels at up to 50 km/h
can include melted snow and ice
1985 Nevado del Ruiz
Flooding
the melting of glacial sources (Jokulhlaup)
e.g Grimsvotn volcanic eruption in Iceland 1996
Volcanic Landslides
mass movement occurs on the side of a volcano
e.g Mt St Helens in 1980
Tsunamis
debris from volcanic landslides can cause water displacement
e.g Krakatoa Indonesia 1883- killed 36,000 people
Acid Rain
volcanoes emit sulphur which combines with atmospheric moisture
caused damage to vegetation and corrodes buildings
Climate Change
the debris ejected can reach the troposphere (upper layer of atmosphere)
reduce temperatures by deflecting incoming solar radiation (insolation)
Management
mitigation
diverting or cooling lava flows
risk assesments
prepardness
monitor changes in the relief of the land to identify the swelling of a volcano
examine the changes in the level or the chemical composition of groundwater
monitor seismic activity to see whether magma is moving towards the surface
issue warnings to evacuate and enforce
prevention
sea water sprayed onto lava to cool it
dig diversion channels and concrete blocks dropped in the lava
build barriers to stop the lava flow
alarms and drills
build resistant structures
adaptation
inform land use planning so that buildings do not take place in high risk areas
Eyjafjallajokull
Mid-Atlantic Ridge
North American and Eurasian Plate
constructive plate margin
moves at 23mm per year
located above a hotspot
Hazards
volcanic bombs
small ash particles
gases ( water vapour, carbon dioxide, sulphur dioxide)
social
800 local people were evacuated
drinking water was poisoned
flights delayed
health problems (eye irritations and dry throats)
asthma
tourism
no fly ban
decline in air and noise pollution
economic
tourism (travel agents in the UK lost an estimate of £6 million each day)
increase in tourism (10,000 people visited by end of March)
car rental firms and taxi companies increase in business
channel tunnel and ferries got extra business
environmental
flooding due to ice cap melting
ash fall more than 10cm
nutrients released into the soil
fresh fish imports badly affected
2.8 million tonnes less of co2 emitted during the period
management
short term
evacuation
emergency services
cancelling and redirecting flights
preparing airports across Europe
Breathing masks handed out
water supplied in tankers
ash was tracked by many countries
long term
predict and forecast monitor (GPS sensoring)
preparing airports across Europe
Icelanders become more aware of the issues
further research into the effects of ash on aircrafts
new Futurevolc project set up