Archive for the 'Volcano' Category


Chilean volcanic eruption

Vesuvius, Eyjafjallajökull, Grimsvotn, Merapi, Puyehue…………..more will be added  to this list!!

 Volcanic eruptions and earthquakes are part of earth’s dynamic evolutionary processes that started about 4.5 billion years ago and will continue for ever. Such events are not new but because of public awareness and inconvenience caused to public, such activities are coming to forefront. In the olden days population kept away from the regions of volcanic and earthquake zones but now population growth and urbanization rendered civilization to move closer to the foci of such natural hazard zones.  Today greater than 3 million people live around Mt. Vesuvius. When  a volcano ejects lava, there is always methods to mitigate the hazard. The worst hazard is when a volcano ejects ash plume. The extent of disaster that an ash plume can create is what we see now in Pompeii

 One can not forget the Plinian eruption of Vesuvius volcano in 79 AD that buried the towns of Pompeii and Herculaneum, near Naples, Italy. The volcano’s ash plume reached a height of 23 km. Plinian eruptions are characterized by large volume of gases, ash and water vapour.  Because of high gas content and narrow escape conduit at the mouth of the volcano, the ash/gas plume forms a long colum above the conduit, reaching a plume column of 2 to > than 40 km.  The volume of the mass ejected and the hight of the plume defines the Volcanic Explosivity Index of a Plinian eruption. When the volume of the material ejected exceeds 10 km3 and the VEI exceeds 25, the eruption is termed as ultra Plinian eruption.

 The Eyjafjallajökull volcano that erupted in 2010 in Iceland has a VEI of 4 and the  volume of material ejected was of the order of ¼ km3. The ejected ash plume reached a hight of 9 km. The Grimsvotn volcano of Iceland that erupted on 21 May 2011 has VEI of 4 and the ash plume reached a height of 20 km

 Volcanoes with VEI of 4 and above is a cause of concern since the plume spread disrupts normal life across a large area. Eyjafjallajökull volcanic eruption forced closer of airports in Europe and caused extensive damage to life and property.

Invariably the ash travels to severals hundreds of kilometers, depending on the wind velocity and direction and deposits on objects.  The volcanic ash plume has no political or geographic boundaries. All depends on the volume of the ash and the velocity and direction of the wind. Damages to prperty and life is part of this Hazard.

  Puyehue, Chile

            Merapi, Jakarta


After a gap of 51 years, the Chilean volcano, Puyehue, started erupting from 4th June 2011 throwing ash plume to a height of 10 km. It has a VEI of 4.

The ash plume traveled to a distance as far as 9800 km across the Pacific ocean to reach Australia and disrupting air traffic. The air traffic over Argentina is disrupted since 4th June 2011.

The Indonesian islands hosts more than 200 volcanoes and one forth of them are active. The deadliest of them are Mt. Krakatoa, Mt. Toba and Mt. Tambora.  Mt Toba that erupted 74 kilo years ago registered 8 on VEI scale, being the maximum. The ash plume rose to a height > 25 km and the volume of ash ejected was 1000 km3. Sun light was cutoff by the ash plume and the ash traveled as far as Europe.  Toba ash deposits are found at several localities in India.

The VEI of Merapi that erupted on   4th November 2010  is 3. This volcano ejected 100 million cubic meters of ash and disrupted air traffic over Jakarta and caused extensive damage to life and property. 

The lahars generated due to volcanic ash blocks rivers and causes floods. Lahars are very common phenomena around the volcanoes when large volume of ash is ejected. Population around Merapi and Puyehue have witnessed this phenomena in recent times.

The Barren Island volcano (BI)  is the only active volcano in India. This volcano is a part of the Indonesian volcanic chain and represents the northern most limit of this chain. North of BI is the Narcondam volcanic island. Narcondam is an extinct volcano and forms part of the Burmese volcanic chain.  Deep sediment cores from Bay of Bengal revealed the presence of BI ash. Thus, depending on the wind velocity and intensity and magnitude of eruption, the ash plume can travel to larger distances across the Bay of Bengal,

Thus when a volcano erupts it causes concern among all the neighboring countries. Since it is a natural disaster, no country is accountable for such disaster. Each country has to take precautionary measures to safeguard its property and life.  Since rescue operation through air is not possible during such calamities, effective surface evacuation methods are the only solution.  Those that are in immediate risk are the men and material  on the oil platforms that are  located several kilometers from the shore line. Mitigation strategies should be in place for all the countries in an event such hazard happens without any warning.  Having said that,  unlike earthquakes, volcanic eruption can be predicted well in advance. With the current existing communication network, putting mitigation strategies in place well in advance is not a problem for the countries prone to such natural hazards.