Chaitén Going Ultra-Plinian?

I have been watching the eruption of Mt Chaitén in Chile, South America very closely for the last few weeks. It appears as if it may produce a major eruption soon. The last known eruption was in 7420 BC ± 75. The progress of the 2008 eruption has been as follows.

April 30: A significant earthquake preceded the first explosions;
May 2: More earthquakes arrayed radially around the caldera implying a very large magma chamber;
May 15: Near steady-state explosive eruptions (Plinian) releasing about two cubic kilometers of ejecta of 4-5km in altitude.

Eruptions are rated by the Volcanic Explosivity Index (VEI). The following are examples of recent eruptions and their VEI.

VEI=5 Plinian, ejecta > 1 km³, e.g. St. Helens (1980)
VEI=6 Plinian/Ultra-Plinian, ejects > 10 km³, e.g. Mount Pinatubo (1991)
VEI=7 Plinian/Ultra-Plinian, ejecta > 100 km³, e.g. Tambora (1815)
VEI=8 Ultra-Plinian, ejecta > 1,000 km³, e.g. Toba (73,000 BP)

Mt Chaitén eruptions have ejected around 2 km³ of ash, giving it a solid VEI=5 on a par with Mt. St. Helens.
Mt Chaitén eruptions are not yet of sufficient energy to reach the 10km to the stratosphere (Ultra-Plinian), needed to affect weather on the global scale, although emissions reached an altitude of 8 km on the 12th May.

Some of the stunning lighning images being taken of the Mt Chaitén eruption.

The initial fuselage of shallow focus earthquakes (10 km depth), larger than magnitude 4, delineate a potentially very large magma chamber, accompanied the start of the Plinian phase on May 2.

    4.4     April 30, 2008 at 11:52 PM     17km E
    5.3     May 02, 2008 at 01:51 AM     30km NE
    4.9     May 02, 2008 at 07:13 AM     13km NW
    4.1     May 02, 2008 at 06:13 PM     16km SW
    5.0     May 02, 2008 at 10:36 PM     30 km NE

Note the epicenters arrayed radially around the caldera. Their locations imply a very large magma chamber might be released.

Today the Volcanism blog reports changes in seismic activity indicating fragmentation and instability around the volcano’s central conduit and beneath the lava dome. The volcano may go ultra-plinian if the magma conduit breaks up, and the capping lava dome explodes away. The consequences of large-scale injections of ash and gases into the stratosphere are disruptions of global climate, particularly initial cooling for a few years, depending on the amount of material released. A Mt Tambora scale eruption would cause enough disruption of normal climate to cause widespread crop losses.

Below are some resources that I will update over the next few days.

Some Resouces

Volcanism blog.– Latest reports from Chile

Satelite Image – of cloud-top height

Volcano Live – Reports by Jon Seach

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0 thoughts on “Chaitén Going Ultra-Plinian?

  1. That ash ejected 10km into the air could cause global cooling doesn’t sound strange.

    Up to this point, scientists were talking about the need for sulfur dioxide to bring about global cooling. Chaiten unlike Mt Pinatubo(sp?) did not emit much of this.

    So higher ash can bring about global cooling – apart from how much sulfur dioxide is ejected?

  2. That ash ejected 10km into the air could cause global cooling doesn’t sound strange.

    Up to this point, scientists were talking about the need for sulfur dioxide to bring about global cooling. Chaiten unlike Mt Pinatubo(sp?) did not emit much of this.

    So higher ash can bring about global cooling – apart from how much sulfur dioxide is ejected?

  3. Yikes, that would be very bad! Toba nearly wiped out the human race when it blew. Just think, the volcano everyone has been worried about is Yellowstone-but if this could be a Toba style eruption, nobody saw it coming! Or did they?

  4. Yikes, that would be very bad! Toba nearly wiped out the human race when it blew. Just think, the volcano everyone has been worried about is Yellowstone-but if this could be a Toba style eruption, nobody saw it coming! Or did they?

  5. At 42S latitude, in winter, the elevation of the tropopause is quite a bit lower than it is in in the tropics. A plume height of 30,000-35,000′ would suffice for stratosphere penetration.

    On the plus side, however, it takes a longer time for high-latitude haze to mix globally.

  6. At 42S latitude, in winter, the elevation of the tropopause is quite a bit lower than it is in in the tropics. A plume height of 30,000-35,000′ would suffice for stratosphere penetration.

    On the plus side, however, it takes a longer time for high-latitude haze to mix globally.

  7. Alan, as 35,000 feet is 10km the eruption has almost reached the stratosphere already. Thanks to you for alerting us to the potential hazard of this eruption.

    Another blogger has done some back of envelope calculations based on the quake figures, that puts the magma chamber on a par with the Yellowstone Caldera.

    Assuming those large quakes actually mark the outline of the Chaiten magma chamber and assuming it is shaped like the Yellowstone magma chamber and only has a depth of 5km then the chamber could in theory hold over 4,000 cubic km of magma.

    There is no way to know for sure until this is over. But the eruption has been going on for 2 weeks. It is still going strong. The only end in sight might be a catastrophic explosion and a collapse of the volcano itself which will do god only knows what. We do know that the volcanic system already has a caldera that is 3km wide. Who knows how much magma has built up in 9,000 years. But based on what Seach has posted things don’t look good. It has gotten interesting enough that the USGS has just sent a team down to study and observe the event.

    Before anybody starts jumping off bridges, equatorial eruptions seem MUCH more effective at influencing climate.

  8. Alan, as 35,000 feet is 10km the eruption has almost reached the stratosphere already. Thanks to you for alerting us to the potential hazard of this eruption.

    Another blogger has done some back of envelope calculations based on the quake figures, that puts the magma chamber on a par with the Yellowstone Caldera.

    Assuming those large quakes actually mark the outline of the Chaiten magma chamber and assuming it is shaped like the Yellowstone magma chamber and only has a depth of 5km then the chamber could in theory hold over 4,000 cubic km of magma.

    There is no way to know for sure until this is over. But the eruption has been going on for 2 weeks. It is still going strong. The only end in sight might be a catastrophic explosion and a collapse of the volcano itself which will do god only knows what. We do know that the volcanic system already has a caldera that is 3km wide. Who knows how much magma has built up in 9,000 years. But based on what Seach has posted things don’t look good. It has gotten interesting enough that the USGS has just sent a team down to study and observe the event.

    Before anybody starts jumping off bridges, equatorial eruptions seem MUCH more effective at influencing climate.

  9. The magma chamber calculation you saw on abovetopsecret.com was just a wild estimate based on possibilities. I hope nobody reads my figures as fact/reality. It may be but if that were the case it would be complete dumb luck. I went that route because the 5 big quakes that created what looked like an outline happened to be shaped similar to that of the Yellowstone magma chamber. It in reality may be nothing like the Yellowstone chamber in shape or size. Even if I am spot on with my guess it would still be 1/4th the size of the Yellowstone chamber and would be more likely to produce a Tambora sized eruption than a Yellowstone sized one.

    I don’t wish the worst that is for sure. But if it happens I hope it is captured on video. We could very well be looking at the biggest eruption since the invention of recording devices.

  10. The magma chamber calculation you saw on abovetopsecret.com was just a wild estimate based on possibilities. I hope nobody reads my figures as fact/reality. It may be but if that were the case it would be complete dumb luck. I went that route because the 5 big quakes that created what looked like an outline happened to be shaped similar to that of the Yellowstone magma chamber. It in reality may be nothing like the Yellowstone chamber in shape or size. Even if I am spot on with my guess it would still be 1/4th the size of the Yellowstone chamber and would be more likely to produce a Tambora sized eruption than a Yellowstone sized one.

    I don’t wish the worst that is for sure. But if it happens I hope it is captured on video. We could very well be looking at the biggest eruption since the invention of recording devices.

  11. However some sources indicated that the eruption column reached 100 000 feet – or 33 000 meters on one of the first days. In that case it seems that there is an enourmous pressure in the magma-chamber beneath the volcano. Very much eruptive magma could have been trapped within the chamber. This could indicate that Indys calculations could be correct!?

    On the other would probably more vents open if my speculation above are being correct.

  12. However some sources indicated that the eruption column reached 100 000 feet – or 33 000 meters on one of the first days. In that case it seems that there is an enourmous pressure in the magma-chamber beneath the volcano. Very much eruptive magma could have been trapped within the chamber. This could indicate that Indys calculations could be correct!?

    On the other would probably more vents open if my speculation above are being correct.

  13. If you plot the earthquakes accompanying the Chaiten eruption you will find that the earthquakes actually are right ubdr and surrounding the Michimahuida Volcano. This is an important point in the analysis of the chaitren eruption, dormant for over 9000 years, while the michimahuida which has beem active more recently is now covered by a glacier (which would prevent venting) You can look at the Seismicity Map at:
    http://sismoaysen.blogspot.com/
    Regards,

    rafael peraltas last blog post..SE REPORTAN NUEVOS SISMOS CERCANOS AL CHAITEN Y HORNOPIREN

  14. If you plot the earthquakes accompanying the Chaiten eruption you will find that the earthquakes actually are right ubdr and surrounding the Michimahuida Volcano. This is an important point in the analysis of the chaitren eruption, dormant for over 9000 years, while the michimahuida which has beem active more recently is now covered by a glacier (which would prevent venting) You can look at the Seismicity Map at:
    http://sismoaysen.blogspot.com/
    Regards,

    rafael peraltas last blog post..SE REPORTAN NUEVOS SISMOS CERCANOS AL CHAITEN Y HORNOPIREN

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