Monday, February 11, 2013

Colombian Volcano Cerro Machin Showing Unrest

While this has been going on for nearly a year now, a Colombian volcano with no recent records of historical eruption is beginning to show signs that it could be preparing for a bang soon. IGNEOMINAS has raised the volcanic alert level to "Amarillo" (or Yellow) and is beginning to issue warnings. Cerro Machin in Western Colombia is experiencing up to 200+ volcanic quakes a day, and the trend is showing that this is increasing. Cerro Machin, much like Chaiten in Chile, is a small lava dome occupying a small caldera. It's last eruption is thought to be about 800 years BP (however Chaiten's last eruption before its most recent was thought to be about ten times longer ago, 8,000 years at least), and it has not shown signs of unrest since.


Cerro Machin in Colombia. Picture from Smithsonian GVP.


The unrest began about a year ago, and seismicity has steadily risen during that time. The volcanic quakes being recorded are thought to indicate shallow rock fracturing, which is indicative of rising magma within the chamber. An eruption today would most likely be a large initial explosive event, which would be accompanies by pyroclastic flows and heavy ash fall, similar to the Chaiten event. As a lava dome 'plugs' the vent, rising magma would likely destroy it and 'uncork' the system like a bottle of Coca Cola. Simply, if this volcano erupts, it will make life pretty miserable for people in the near vicinity, and undoubtedly cause loss of life for anyone or anything that does not evacuate when told. Warnings from IGNEOMINAS should be quickly heeded by the population.

Colombia is no stranger to volcanic disaster, being one of the big reasons there have been such advances in volcanology and eruption 'prediction' have been made at all. In 1993, Galeras began to show signs of unrest that we now know means that a volcano is inflating with magma. So called 'long period events' and 'low frequency tremor' were detected at the volcano. A scientist with a theory that this meant magma was rising and an eruption was imminent decided to mount an expedition to the summit to see if gases and temperatures had increased with the tremor was tragically killed along with his science team as the volcano erupted when  they were at the summit. Their deaths did, however, result in scientists taking his theory of harmonic tremor and long-period events seriously, and since then volcanologists routinely rely on these types of quakes as good indicators of impending activity.

At this time, it appears that volcanologists are watching this volcano quite closely to see what it will do. As it has no recent eruptive history, it could be quite a large eruption as the pressure it takes for magma to break through to the surface through cooled, solid rock would be immense. It is looking likely, given that quakes are getting much shallower that the magma intrusion is getting closer to the surface, which makes an eruption even more likely. Most magma dike intrusions never result in an eruption, however most intrusions are short lived, and this has been going on for over a year now.

4 comments:

  1. this might be the first VEI 6-7 of the century.

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  2. That would be doubtful, the volcano is about half the size of Chaiten, is not rhyolitic, and has shown no past history of such a scale of eruption. It would more than likely not even be near the size of the eruption of Mt. St. Helens. I would estimate based on its size that it would not be capable of more than a VEI 3 or 4, however the local damage would be significant. VEI 4 is still quite damaging.

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  3. Hi, sorry but I need to point out your mistake regarding the scientist who lost his life. You say he was responsible for the connection between harmonic tremors and eruptions, when in fact it was another guy who was doing the harmonic work at the same volcano several months earlier (they were both there for that eruption). The guy who lost his life was in fact trying to prove a link between gas emissions and eruptions. On that day they went up because the gas emissions where as he saw it, showing the volcano as safe when in fact the harmonics suggested it wasn't, but because the harmonics guy was not there, they didn't know what the tremors meant and tragically misread the situation.

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  4. A Decade Volcano conference in the city of Pasto, in 1993, ended in disaster when several of the scientists present mounted an impromptu expedition on 14 January to the crater of Galeras. An eruption occurred unexpectedly while they were at the summit, which resulted in the deaths of six scientists and three tourists.[6]
    Elements in the media made the event controversial by suggesting the team leader Stanley Williams, who survived, had ignored safety procedures. A prediction had been made three days before the eruption based on B-Type activity seen on a seismograph. Seismic B-types had been used successfully to predict eruptions on other volcanoes. However, the prediction was based simply on the one seismographic printout viewed in the light of previous history of Galeras, without any additional scientific measurements showing any serious activity within the volcano

    the above was taken from here http://en.wikipedia.org/wiki/Galeras

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