how do a volcanologist predict for an upcoming volcanic eruption?

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  • 1 decade ago
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    A volcanologist predict an eruption by

    Seismicity.

    General principles of volcano seismology.

    Seismic activity (earthquakes and tremors) always occurs as volcanoes awaken and prepare to erupt and are a very important link to eruptions. Some volcanoes normally have continuing low-level seismic activity, but an increase may signal a greater likelihood of an eruption. The types of earthquakes that occur and where they start and end are also key signs. Volcanic seismicity has three major forms: short-period earthquake, long-period earthquake, and harmonic tremor.

    Short-period earthquakes are like normal fault-generated earthquakes. They are caused by the fracturing of brittle rock as magma forces its way upward. These short-period earthquakes signify the growth of a magma body near the surface and are known as 'A' waves. These type of seismic events are often also referred to as Volcano-Tectonic (or VT) events or earthquakes.

    Long-period earthquakes are believed to indicate increased gas pressure in a volcano's plumbing system. They are similar to the clanging sometimes heard in a house's plumbing system. These oscillations are the equivalent of acoustic vibrations in a chamber, in the context of magma chambers within the volcanic dome and are known as 'B' waves. These are also known as resonance waves and long period resonance events.

    Harmonic tremors are often the result of magma pushing against the overlying rock below the surface. They can sometimes be strong enough to be felt as humming or buzzing by people and animals, hence the name.

    Patterns of seismicity are complex and often difficult to interpret; however, increasing seismic activity is a good indicator of increasing eruption risk, especially if long-period events become dominant and episodes of harmonic tremor appear.

    Using a similar method, researchers can detect volcanic eruptions by monitoring infra-sound—sub-audible sound below 20Hz. The IMS Global Infrasound Network, originally set up to verify compliance with nuclear test ban treaties, has 60 stations around the world that work to detect and locate erupting volcanoes.

    Seismic case studies.

    In December 2000, scientists at the National Center for Prevention of Disasters in Mexico City predicted an eruption within two days at Popocatépetl, on the outskirts of Mexico City. Their prediction used research done by Bernard Chouet, a Swiss volcanologist working at the United States Geological Survey, into increasing long-period oscillations as an indicator of an imminent eruption. The government evacuated tens of thousands of people; 48 hours later, the volcano erupted as predicted. It was Popocatépetl's largest eruption for a thousand years, yet no one was hurt.

    Iceberg tremors.

    It has recently been published that the striking similarities between iceberg tremors, which occur when they run aground, and volcanic tremors may help experts develop a better method for predicting volcanic eruptions. Despite the fact that icebergs have much simpler structures than volcanoes, they are physically easier to work with. The similarities between volcanic and iceberg tremors include long durations and amplitudes, as well as common shifts in frequencies.

    Gas emissions.

    As magma nears the surface and its pressure decreases, gases escape. This process is much like what happens when you open a bottle of soda and carbon dioxide escapes. Sulphur dioxide is one of the main components of volcanic gases, and increasing amounts of it herald the arrival of increasing amounts of magma near the surface. For example, on May 13, 1991, an increasing amount of sulphur dioxide was released from Mount Pinatubo in the Philippines. On May 28, just two weeks later, sulphur dioxide emissions had increased to 5,000 tonnes, ten times the earlier amount. Mount Pinatubo later erupted on June 12, 1991. On several occasions, such as before the Mount Pinatubo eruption and the 1993 Galeras, Colombia eruption, sulphur dioxide emissions have dropped to low levels prior to eruptions. Most scientists believe that this drop in gas levels is caused by the sealing of gas passages by hardened magma. Such an event leads to increased pressure in the volcano's plumbing system and an increased chance of an explosive eruption.

    Ground deformation.

    Swelling of the volcano signals that magma has accumulated near the surface. Scientists monitoring an active volcano will often measure the tilt of the slope and track changes in the rate of swelling. An increased rate of swelling, especially if accompanied by an increase in sulfur dioxide emissions and harmonic tremors is a high probability sign of an impending event. The def..................

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  • Anonymous
    1 decade ago

    They monitor the volcano for the volume and type of gas emissions it is producing.

    They also monitor any localised seismic activity to see if they can locate any movements of magma underground.

    Then they monitor the shape of the vocano - it tends to change and grow over time, indicating that magma is growing and swelling beneath the surface and pressure is increasing.

    For example, it has been noticed that Yellowstone National Park is rising up slowly - several inches a year at the moment. This indicates that pressure is mounting underneath the surface and the likelihood of a volcanic explosion is increasing.

  • Prince
    Lv 6
    1 decade ago

    There are many terms like

    *Seismicity

    *Gas emissions

    *Ground deformation

    *Hydrology

    to predict the volcanic eruption......

    Some others also use the "lunar cycle" to predict the eruption.....

    Cheers

  • Anonymous
    1 decade ago

    There are many terms like

    *Seismicity

    *Gas emissions

    *Ground deformation

    *Hydrology

    to predict the volcanic eruption......

    Some others also use the "lunar cycle" to predict the eruption.....

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  • 1 decade ago

    If the plates have been recently active, and / or how much movement / activity the volcano has been showing over time

  • 1 decade ago

    a change in the temperature and the level of lava and ash in the volcano

  • Anonymous
    1 decade ago

    Holy smokes!

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