Volcanic Hazards

What is the intensity scale for volcanoes

VEI 1-8

Volcanoes can produce…

Different hazardous phenomena at different times and from different places each of which has its own magnitude (size, volume) and intensity (rate)

What gasses are produced by volcanoes

Sulphur gas, fluorine gas, Corbon dioxide

Danger of sulphur gas

Local irritant acid rain

Danger of Fluorine gas

Absorbed onto ash plants, or enters water: bad for stock and people to ingest

Danger of Carbon dioxide

Is denser than air, and will suffocate people who enter or are caught in it

Characteristics of lava fountains and flows

Rarely fast enough to directly threaten people (can be outrun), flows burn things and can physically push structures apart, can cover agricultural land

Dangers of ballistic blocks and crater rims

People can be struck and killed by blocks, can also be burning hot and can be ejected one at a time or in showers that build up a rim around volcanic craters

Dangers of ash plumes and fall deposits

Ash can affect large areas extending 10s or even 1,000s of Km from the volcano, Ash plumes are hazardous to aircrafts, can crush roofs, cover crops, damage electrical and water infrastructure, can trigger famine

Danger of debris avalanche

do not occur often but very disruptive, volcanoes can suffer structural failure causing debris to fall at high velocity destroying infrastructure and populations in their path

Volcanic Tsunami

Can be caused by different typed of volcanic activity, both from submarine and coastal volcanoes

Pyroclastic density currents

Lateral flows of particles and gas generated by volcanic eruptions (driven by excess density, with overpressure-driven blasts. Currents can extend 10s of Km from vent, move very quickly, and cause asphyxiation, thermal damage, and impact form particles

What is the most deadly eruptive process

Pyroclastic density currents

What is a Lahar

Flow of water + debris mixture down the side of a volcanoes

Dangers of Lahars and floods

Both are major cause of damage and casualties but occur after eruption ceases, lahars and floods can extend 10s of Km from vent, move very quickly, and can destroy, bury, and drown infrastructure, people, and stock

What are two prominent NZ volcanic systems

Auckland volcanic field & Taupo volcano

Characteristics of Auckland volcanic field

Many small, scattered volcanoes each formed by one brief eruption. The small volcanoes will nor erupt again, but new volcanoes will form in the filed in the future

Characteristics of Taupo volcano

One large central volcano that has erupted many times (and will erupt again)

How high and fast did that one volcano in the farmer’s field grow

167 meters in 6 days

How deep was the ash fall from the Taupo eruption

up to 200m deep

How much pumice and ash were ejected from the Taupo reuption

800 Km³

Can you tell when the next eruption will occur based on historical gaps

No

What happened in Armero Columbia 1985

Nevado del Ruiz erupted causing lahars and mudflows to travel down river to Armero burying the town and killing 23,000 people. An alert was issued from Ibague at 9:45-10:30 pm and the lahar arrived at Amero at 11:30 pm not giving resident enough time to react