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Forecasting and potential effects of the next super-eruption


An eruption on the scale we consider here must have abundant and obvious precursory activity, such that mankind should not be taken by surprise. Our recent civilization has not suffered from a super-eruption and so large-scale volcanic symptoms have not been experienced. By scaling up from smaller events, the time-scales and types of super-eruption signals around a candidate volcano can be understood. These are expected to be signs such as seismic unrest, ground heating and swelling, changes in groundwater temperature and chemistry, and changes in the composition and fluxes of volcanic gas. Many of these changes are on-going at super-volcanoes such as the Phlegrean Fields, Italy, and Yellowstone and Long Valley, USA, where they are measured routinely these days. However, there are other potentially active super-volcanoes that are not currently monitored.

The list below is a reasoned account of some of the aspects of our lives that would be influenced by a future explosive super-eruption, based on the effects of the various eruptive phenomena and deposits that would be formed. The severity of the effects would depend on the distance from the source volcano, expect for the impact of the atmospheric aerosols. In any region, they will also depend on the location of the volcano.

Ash fall (deposit)

  • Roof collapse in built-up areas – a local effect out to distances where ashfall is a few centimetres thick (10s of kilometres from the volcano). Exacerbated if rain occurs or ashfall is wet.
  • Agriculture – devastation and disruption of for at least a growing season over most of area receiving ash fallout. Longer term changes to soil composition.
  • Drinking water – potential for both chemical and filtration/blockage problems associated with water supply.
  • Aviation – risk to flying aircraft while ash still airborne (days to ?weeks); problems with landing and take-off until airports cleared.
  • Power generation – effects of ash on hydroelectric and nuclear power plants unknown.
  • Power distribution – electric pylons and powerlines might be susceptible to ash loading and associated electrostatic effects. Possibly exacerbated if ashfall is wet.
  • Health (see gas and aerosols)

Secondary mudflows (lahars)

  • These occur in rivers and stream catchments after rainfall on fresh volcanic deposits. Possible damming of rivers, with ensuing break-out floods. [Lahars caused the highest proportions of death and destruction associated with the Pinatubo eruption, but in the years after the activity died down.]

Pyroclastic flows and deposits

  • Burial of all objects on ground and fires on a local scale, up to perhaps 50-80 km from source volcano.
  • Refugees – if pyroclastic flows were predicted, widespread evacuation would be require, which, depending on the area, could lead to a large number of persons requiring re-location.
  • Tsunamis – if the volcano is near the coast, pyroclastic flows entering the sea could cause tsunamis. [Around the island volcano of Krakatoa in 1883, most of the 30,000 casualties were due to tsunamis sweeping ashore.]

Gas and aerosols

  • Climate change – dominantly cooler temperatures for a few years after the eruption might change agricultural yields. Some areas may undergo warming, and there might be short-term, very warm spells that could also affect growing crops. Changes in rainfall patterns may influence liablilty to flooding in certain areas.
  • Dry-fog and acid aerosol air pollution – a Laki-type dry fog in the lower atmosphere (composed of sulphur dioxide gas and sulphuric acid aerosols) could induce respiratory illness, as could fine ash (< 10 microns) and other minerals in the ash. Such clouds can attain complete global coverage within a hemisphere. Chemical etching effects of aerosol particles on aircraft engines and instrumentation is a little understood aspect.
  • Ozone depletion – stratospheric aerosols will serve to catalyse ozone loss, permitting more UV-B flux to the ground in high-mid latitude regions, the effect lasting a few years after the eruption.

General

  • Disruption of national and international relief efforts and cooperation, and of some communications (satellites may not be able to perform normally due to ash and/or aerosols).
  • Possible effects of all the above on world financial markets.

Link to next section, Mitigation