Anonymous asked in Science & MathematicsEarth Sciences & Geology · 6 years ago

What gasses, debris, and dangers occur after a volcanic eruption?

The title pretty much explains it.

1 Answer

  • 6 years ago
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    It is eruptions at convergent plate tectonic margins which generally responsible for poisonous gases & the emissions of ash / volcanic bombs. These volcanoes produce intermediate to felsic lavas & they have steep sides which mean that their craters are often relatively close to population centres.

    What gases? The principal high temperature volcanic gases are water vapour (H2O), carbon dioxide (CO2) and sulphur dioxide (SO2). Low temperature volcanic gases include hydrogen sulphide (H2S), nitrogen, argon, helium, neon, methane, carbon monoxide and hydrogen. Volcanic gases were directly responsible for approximately 3% of all volcano-related deaths of humans between 1900 and 1986. Some volcanic gases kill by acidic corrosion; others kill by asphyxiation.

    Tephra fragments are classified by size:

    Ash – particles smaller than 2 mm (0.08 inches) in diameter,

    Lapilli or volcanic cinders – between 2 and 64 mm (0.08 and 2.5 inches) in diameter,

    Volcanic bombs or volcanic blocks – larger than 64 mm (2.5 inches) in diameter.

    Damage to buildings and structures can range from complete or partial roof collapse to less catastrophic damage of exterior and internal materials. Impacts depend on the thickness of ash, whether it is wet or dry, the roof and building design and how much ash gets inside a building. The specific weight of ash can vary significantly and rain can increase this by 50-100%. Roof collapse can lead to widespread injuries and deaths and property damage. For example, the collapse of roofs from ash during the 15 June 1991 Mount Pinatubo eruption killed about 300 people.

    It is known from the 1783 eruption of Laki in Iceland that fluorine poisoning occurred in humans and livestock as a result of the chemistry of the ash and gas, which contained high levels of hydrogen fluoride. Following the 1995/96 Mount Ruapehu eruptions in New Zealand, two thousand ewes and lambs died after being affected by fluorosis while grazing on land with only 1–3 mm of ash fall. Ash ingestion may also cause gastrointestinal blockages. Sheep that ingested ash from the 1991 Mount Hudson volcanic eruption in Chile, suffered from diarrhoea and weakness. The added weight of ash in the wool led to fatigue and sheep could not stand up.

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