Volcanic Hazards Flashcards
formation of a volcano
plates subducts
friction causes plate to melt into magma
this is less dense so rises
breaks through crust to form volcano
types of volcanic hazard
primary
- lava flow
- gas
- ash fallout
- pyroclastic flow
- tephra
secondary
- lahars
- acid rain
pyroclastic flow
explosion of ash, has and volcanic rock that flow down side of volcano
- high speeds - 200m/s
- long way - up to 15km
- little warning
eg Mount Pelee
lava flow
flow of Laval from vets
distance depends on
- viscosity
- steepness of volcano
often slower so people can evacuate
but very destructive, cause fires
volcanic gases
releases CO2 and sulphur dioxide
into atmosphere
can be harmful to humans and animals if inhaled
eg Mammouth Lakes, California
CO2 released causing suffocation
ash fallout
tephra and material ejected in eruptions fall back down
large pieces fall closer
larger can damage buildings and people
smaller particles can travel thousands of kilometres, damage agriculture and hinders transport
eg Eyjafjalllajokull
nuees ardentes
dense, rapid moving clouds of hot gases, ash
a type of pyroclastic flow
- denser so doesn’t move as far
eg Mount Pelee
tephra
solid material ejected in an eruption
larger pieces fall closer
eg Pompeii
lahars
when volcanic material mixes with water from rainfall or ice melt
- moves fast, over 80km/h
- travel far, tens of km
bury or destroy habitats and infrastructure
eg Nevado del Ruiz, Colombia
acid rain
volcanic gases can react with water vapour
fall as acid rain
damages ecosystems and can erode metal
primary impacts
social
- death
- collapse of infrastructure
environmental
- ecosystems damaged
economic
- businesses destroyed
- agriculture damaged
secondary impacts
fires caused by lava
- destroy ecosystems and buildings
lahars
- bury buildings and ecosystems
flooding from ice melts
food shortages due to damage
short term responses
evacuation
emergency food supplies
long term responses
designed to reduce impacts for future
monitoring
reconstruction - buildings strengthened
barriers to divert flow
preparation
volcanic form on constructive margins
plates moving apart
- basaltic lava
- runny, less viscous, lower in silica
- less violent eruptions
- more frequent
- mainly lava
volcanic form on destructive margins
plates moving towards
- acidic lava
- vicious, higher in silica
- potentially explosive
- less frequent
- tephra and pyroclastic flow
adaptation
buildings strengthened
- reduce risk of collapse under ash
capitalise on opportunities
- farming on fertile soils
- tourism
prevention
not possible
but risk can be reduced
- evacuation, using prediction
- land use zoning, not developing in at risk areas
mitigation
reduce severity
monitoring
- allows prediction and evacuation
emergency shelters and supplies
- save lives
barriers to divert flows away from populated areas
eg Iceland, 4m walls
preparedness
monitoring systems
- allow prediction
- monitor gases and seismic activity
evacuation plans
emergency shelters and supplies
distribution
90% as plate boundaries
other caused by magma plumes
- vertical commons or extra hot magma
- rises and breaks through crust
magnitude
measured on VEI scale
1-8 on destruction
Criticised, Only measures tephra
frequency
depends of type of margin
constructive - more frequent, can be continuous
destructive - less frequent
predictability
monitored
gases and seismic activity measured
can be predicted
- allows of evacuation
eg Iceland, 30 minute warning
regularity
unpredictable
can erupt regularly
or can be dormant or many years
Primary vs secondary impacts
Pyroclastic flow worse primary - hardest to avoid, move fast and far
Secondary worse
Lahars
- Nevada Del Ruiz
Flooding
Tsunamis
Effect climate
- Mount Pinatubo eruption reduced global temperatures by 1c
