volcanoes

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Volcanoes

Ocean ridges

Sea floor spreading

Gently sloping volcanoes

Lava – basaltic (low viscosity)

Eruptions – frequent/gentle

Subduction zones

Composite/ steep sided volcanoes

Explosive eruptions

Viscous lava which is andesitic

Ring of Fire – Mt. St. Helens

Rift Valleys

Constructive margin

On continent

Mt. Nyiragongo

Hot spots

Not on plate boundaries

Radioactivity – hot plumes

Oceanic crust – basaltic lava

Hawaii

Shield volcanoes

Plate moves, producing new islands

Hotspot doesn’t move

The magnitude and frequency of volcanic events

Enormous variation between the different types of volcanic eruptions

Measured on the volcanic explosivity index (VEI) – logarithmic scale 0-7

Lower = more frequent and least explosive

Higher = less frequent and more explosive

Impacts of volcanic activity

Primary

Lava flows

Tephra -> solid material = ash/volcanic bombs

Pyroclastic flows

Volcanic gases (co2 co so2 cl2) – poisonous

Secondary

Acid rain

Climate change

Flooding

Lahars

Tsunamis

Management of volcanic events

Prediction

Very difficult

History of previous eruptions – time previous and frequency

Gases released

Ground swell

Ground water levels

Protection

Prior warning

Develop good alert systems

Divert lava flows

Responses

Short term

Provision of emergency services

Food

Shelter

Water supplies

Long term

Rebuilding infrastructure

Developing future methods of protection