Primary and Secondary Hazards

Primary and Secondary Hazards

Primary = direct e.g. lava flowSecondary = 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 HazardsLaki – 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.