Primary and Secondary Hazards

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Primary and Secondary Hazards
Primary = direct e.g. lava flow
Secondary = indirect e.g. underwater volcanic
eruption might cause a tsunami wave
What is a natural hazrd?
• Something caused by nature that is harmful to
people
– Hurting them = injuries or death
– Or damage to property costing money for repairs
or in lost production.
Primary Volcanic hazard –
Lava Flows
Primary Volcanic Hazards
E16 volcano Iceland April 2010
– ash fall – grounded flights
across Europe – airline industry
lost over £1 billion
Primary Volcanic Hazards
Lake Nyos – Cameroun, Africa – 1986 – 1800
deaths. CO2 was released from under the lake –
people and animals suffocated in the dense gas
that hugged the ground.
Heimaey, Iceland 1973 – one rescuer died
searching an evacuated house which was full of
carbon dioxide. Laki, Iceland 1783 – Sulfur
dioxide poison clouds reached Europe.
Primary Volcanic Hazards
Pyroclastic Flows from volcanic
eruptions can burn people
instantly and turn them to
stone – mainly from
Destructive Plate Margin
volcanoes like on Montserrat.
Secondary Volcanic Hazards
Jokulhaups – glacial meltwater
floods from eruptions under
ice in Iceland. E.g. Grimsvotn
volcano
Secondary Volcanic Hazards
Laki – Iceland 1783 – ash smothered
grass and crops – 10,000 died in the
famine that followed.
Secondary Volcanic Hazards
Volcanic lahars or mudflows.
Heavy rain and ash causes
mudflows down valleys. 22,000
died in Armero, Colombia after
Nevada del Ruiz erupted in
1985. Biggest volcanic disaster
death toll of 20th Century
Secondary Volcanic Hazards
Massive landslide occurred with the eruption of Mount St.
Helens, USA in 1980.
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