Moi, Paul Derand

While investigating about how dangerous each volcano was what types of threat each of them poses, etc, I created a scale to classify them in terms of danger.

The scale is influenced by the Volcanic Activity Index (VAI) and the population that could be affected by at least two different hazards linked to an eruption.

dangerosity = (VAI) * (log (population in thousands of inhabitants))

If of the VAI and/or the logarithm of the population in kilo-inhabitants is/are negative, they should be changed to zero.

In this way it is impossible to have a volcano with a negative dangerosity. However, the top of the scale is open.

Here is a list of some volcanoes, classified by their dangerosity. We can see that half of them roughly have a dangerosity between 3,1 and 0,6, with a median of 1,7:

Class 6 to 6.9 (3 volcanoes):

Etna (6,9), Vesuvius (6,3), Merapi (6,2)

Class 5 to 5.9 (3 volcanoes):

Nyiragongo (5,9), Nevado del Ruiz (5,3), Popocatepetl (5,1)

Class 4 to 4.9 (5 volcanoes):

Santa Maria (4,9), Sakurajima (4,2), Grimsvotn (4,2), Mayon (4,0), Michoacan-Guanajuato (4,0)

Class 3 to 3.9 (7 volcanes):

Villarica (3,9), Bulusan (3,9), Cotopaxi (3,7), Aso (3,6), Tarumae (3,4), Gamalana (3,4), Taal (3,0)

Class 2 to 2.9 (19 volcanoes):

Pico de Orizaba (3,0), Tungurahua (2,9), Piton de la Fournaise (2,8), Guagua Pichincha (2,7), Mt Cameroon (2,7), Asama (2,7), Llaima (2,6), Nyamuragira (2,6), Karangetang (2,6), Hekla (2,5), Agung (2,4), Sinabung (2,4), Karthala (2,4), Lokon-Empung (2,1), Avachinski (2,1), Galunggung (2,1), Acatenango (2,0), Bardarbunga (2,0), Semeru (2,0)

Class 1 to 1.9 (18 volcanoes):

Galeras (1,9), Colima (1,9), Purace (1,9), Telica (1,7), Koriakski (1,7), Fuji (1,7), San Salvador (1,6), Tacana (1,6), Nevado del Huila (1,6), Sundoro (1,5), Caminguin (1,4), Soufrière Guadeloupe (1,3), Santorini (1,3), Teide (1,2), Awu (1,2), Askja (1,1), Banda Api (1,1), Mt Pelée (1,0)

Class 0.1 to 0.9 (25 volcanoes):

Santa Ana (1,0), Vestmannaeyjar (1,0), El Chichon (0,9), Makian (0,9), Manam (0,9), Soufrière St Vincent (0,8), Savo island (0,7), Ubinas (0,6), Almolonga (0,6), Fogo (0,5), Ulawun (0,5), Cumbre Vieja (0,5), Nevado del Tolima (0,5), Guntur (0,5), Papandayan (0,5), Unzen (0,5), Bam island (0,4), Ceboruco (0,3), Cosiguina (0,3), Dona Juana (0,3), Turrialba (0,3), Okataina (0,3), Huaynaputina (0,2), Cumbal (0,1), Ijen (0,0)

Class 0 (17 volcanoes):

Mt Rainier (0), Karymsky (0), Stromboli (0), Campi Flegrei (0), Dukono (0), Ibu (0), Kliuchevskoi (0), Dempo (0), Sangay (0), Kanlaon (0), Lengai (0), Copahue (0), Kikai (0), Suwanosejima (0), Marapi (0), Reventador (0), Ruapehu (0)

However, a more precise scale is this one (I created it in 2016 and it should replace the older one.):

dangerosity = (number of "Erupted Volume Index = 0" eruptions per year) * (number of estimated deaths per "EVI = 0" eruption) + (number of "EVI = 1" eruptions per year) * (number of estimated deaths per "EVI = 1" eruption) + ... + (number of "EVI = 8" eruptions per year) * (number of estimated deaths per "EVI = 8" eruption)

Note that the EVI (Erupted Volume Index) is the same as VEI, but it also includes the volcanic materials that don't come from an explosion.

To estimate the number of deaths per "EVI = x" eruption, we evaluate the different risks that could cause fatalities (lava flows, toxic gases, pyroclastic flows, lahars, ashfall...), the probability that one person would die when he faces those risks and the number of people concerned by each of those risks.

Issued on Thursday 13th August at 05:00 UTC:

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I monitor only very significant tropical cyclones (TCs with wind speed of at least 145 km/h) of the NW Pacific, the S Pacific, the N Indian Ocean and the S Indian Ocean.

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Paul DERAND

As day breaks on the archipelago, the first images start to emerge and media pick up on the spectacular eruption.
From images, it seems that a large effusive-explosive eruption is occurring. Tall lava fountains produce an immense ash plume that rises to up to 14 km altitude. See photo. At the same time, several lava flows descend from the vent(s), likely a fissure on the volcano.

See volcano discovery's website.

I found on volcano discovery website (here) a list of all explosions (see here) from Sakurajima, it is interesting to assess the current intensity/explosivity of the eruption.

Also, there are webcams of the volcano here.

Paul DERAND

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April 24, 2015:

Luckily, activity remains at low levels for the moment in Tungurahua, with small explosions and ash emissions, but this is luckily only VEI=2. This report is short as now I'm getting informed about a more powerful, sub-plinian eruption at another volcano, in Chile: Calbuco.

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April 13, 2015:

"Intermittent mild explosive activity with ash emissions continues at the volcano.
An unusual seismic swarm occurred during the night of 9-10 April, following two volcanic earthquakes at 6 km depth in the evening. More than 1300 quakes were recorded until noon of 10 April. What made it unusual was that the seismic events were of the "drumbeat" type, not seen on Tungurahua during the past 16 years, but thought to correspond to the ascent of viscous magma. 
Gas emissions have continued to show an increase and the presence of black ash also suggests that a new batch of magma is arriving. These observations make the scenario of a sudden violent explosion in the near future a serious possibility.
Authorities have started to take preventive measures in case of a larger eruption. Road conditions and meeting points in case of evacuations were checked and communicated to the local population. Access restrictions were imposed to potentially dangerous areas, in particular valleys draining from the volcano and the road Penipe Los Pajaros - Banos". (Copied from volcano discovery website here.)

Moreover, since april 8, there were new ash emissions, tremor episodes and increased SO2 output.

All of this suggest an increase in activity leading to an intense paroxysm in the next several days or few weeks.

BE CAREFUL: Volcanoes are still unpredictable and there may be errors in these predictions. Moreover these are short term predictions.

Paul DERAND

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