PART 2. Casualties of the eruption






Why should a surge cloud that failed to strip or singe leaves, and only deposited a few cm of ash, kill a cow (or bullock)? The answer is probably not searing of its lungs by inhaling hot gas (although only an autopsy could confirm this), but throttling by relatively cool and slow-moving volcanic dust. This can take place in two ways:

1.      Fine-grained volcanic ash can physically block airways and fill the actual lungs with wet powder. This is asphyxiation.

2.      The ash in the air may dilute its oxygen concentration in air below the value of 18% that is the minimum necessary for a mammal to survive. This process is called hypoxia.

Topic 5 discusses these alternatives, and others, in more detail.


Close-ups of this animal show no signs of external burning; just the thin layer of deadly dust everywhere (doubtless including the victim’s mouth, windpipe and lungs). But note the enigmatic foreground object just visible at bottom left.

An image of the same scene appeared a couple of days later and showed a completely different story. Here you can see that the surge was actually both violent and hot enough to burn the paint off the car and shatter its windows. Nevertheless the car tyres remain. Obviously a breath of such hot air would fell a bullock instantly. Photos can only give a general impression of a scene like this. You must be there in person to spot the crucial details that explain the whole story.


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Both these photos illustrate the relationships between the collapsed cattle and the flying debris, allowing a detailed reconstruction of what happened when the surge struck.

AP Photo/Trisnadi

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The position of this corpse is strikingly similar to that of the asphyxiated/hypoxic goat close to the margin of the11 February 2010 PFs at Trants on Montserrat (see Topic 11). A few windy days would blow all the dry ash off it. Other photos here show victims that clearly encountered wet ash. Of course water vapour further dilutes the oxygen in air and it also causes skin and lung searing at much lower temperatures than dry air.

This horrible photo tells us plenty about the temperature of the surge cloud here (assuming that the injured cattle have not wandered far). Although their skin is severely burned, the wood in the wrecked house roof and on the ground is all completely unscorched. This fixes the surge temperature here at below 250C, when dry wood begins to char, and well above 100C (sensitive to humidity in the ash cloud). Cattle have thick hides and so I suspect that the temperature was around 200C.  Photo  CLARA PRIMA/AFP/Getty Images

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This unfortunate animal has been exposed to a volcanic surge at temperatures high enough to char wood. In such heat it will have died instantly of what is called "fulminant shock" (see below). Doctors consider that such death occurs so fast that the victim feels no pain at all; it is dead long before it realises what is happening.


Photo by Marc Szeglat



Now from cattle to people. DON'T LOOK FURTHER, unless you feel OK about doing so.

Damp volcanic ash is caked around the nose and mouth of this victim but there are no obvious signs of skin burns. Photo  Ulet Ifansasti/Getty Images

The inhaled ash may trigger severe, and potentially fatal, breathing problems in both old people and children.

Here there is damp ash clinging everywhere and ripped clothing, resulting from very violent surge movement. Skin burns are visible and the extent of these decides whether or not such a victim will survive.

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More clingy damp ash; maybe facial burns.

Photo  CLARA PRIMA/AFP/Getty Images

Same clingy ash but a lucky survivor.

Daily Mail, UK

Burned survivors on they way to hospital.

 Photo  SUSANTO/AFP/Getty Images

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Here’s another very lucky survivor, thanks to its built-in thick fur coat. This would be a perfect insulation from surge ash. The owner probably charged into the darkest corner of its cage and curled up into a ball, protecting its face, tail and paws. If a monkey can do all this instinctively, why don’t we follow its example?

This image appeared on the front pages of many newspapers after the first eruption. The man is clearly very severely burned and is holding his hands in rather a strange way, as if trying to fend off some attacking animal. In scientific discussions about how surges affect people, this is known as the “pugilistic pose” because the victim resembles a boxer during a fight. The cause is burning of arms and hands so severe that the scorched muscles all contract violently. 

Photo  AP, Slamet Ryadi

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This shows the scene greeting rescuers after two people have been caught in the open by the "relatively-slow-moving marginal parts" of a pyroclastic surge. The reality is not so pretty as the output graphics of recent sophisticated computer models. This is where science hits reality (note the "pugilistic pose" again). Photo REUTERS/Aditia Surya


If you find this image disgusting and utterly sickening, so be it. The rest of us must continue to see such images at regular intervals, until the people who persist in refusing to leave danger zones around erupting explosive volcanoes finally get the message and do what the authorities tell them to do -- evacuate.


Christians may remember the Book of Exodus and the Angel of Death. It is probable that death came so fast that this couple were unaware of its coming (see next images).


Merapi 2010

Pompeii AD 79

Herculaneum AD 79

A large number of people were sheltering in this seaside cave when a surge at about 500oC invaded it.


Note the crucial difference between the Herculaneum corpses and the others (Pompeii and Merapi). The Merapi and Pompeii victims could have died either from ash inhalation or by internal lung searing; dust seems to be the more likely culprit. The Herculaneum skeletons are amazingly well preserved and seem somehow to be frozen in horror as the surge burst into their shelter (a cave made by fishermen, with  no doors). A short scientific report in the eminent journal Nature in 2001 analyses their deaths, as preserved in the condition and  distortions of their bones. The approximately 500oC temperature of the surge is one of their conclusions. At such a temperature is is clear to pathologists (like Dr Peter Baxter of Cambridge University, the principal author of this report) that the cause of death was what is known technically as "fulminant shock". In such a death, all the major organs of the body (heart, lungs, brain etc) literally boil instantly and therefore cease to exist within a small fraction of a second -- long before the victim can register what is happening. Think of a fly on a road run over by a truck or incinerated in a furnace for an analogy. Those of you who have access to science libraries can find the report thus:  "Herculaneum victims of Vesuviius in AD 79" by Giuseppe Mastrolorenzo, Pier P. Petrone, Mario Pagano, Alberto Incoronato, Peter J. Baxter, Antonio Canzanella and Luciano Fattore. Nature, vol. 410, p. 769. If you lack suitable library access, email me for an electronic copy.


This image is only relevant for medical and rescue purposes; a textbook example of muscle contraction caused by deep burns (see the Nature  paper referenced above). Why was the skin on the lower arm apparently unburned? Maybe there was fabric covering it.  Photo AP / Slamet Riyadi


This extreme burning characterised the bodies of the 43 people killed by a surge in June 1991 during eruption of Mt Unzen (Fugendake) in Japan.

What an awful end. Was staying behind worth it? Why no small shelter installed long ago in the solid house behind (see part 3 below)? After all, Merapi kills people like this every few years. The soldier at the back is clearly using his mobile phone to take a photo. Was this necessary or voyeurism? Photo AP Photo/Trisnadi


This image may horrify many who see it. Nevertheless, it illustrates an important point about the role of photography in disasters. If this sort of tragedy is to be properly recorded and used to improve our chances of preventing this happening again elsewhere, the victim's terrible injuries must be systematically recorded, together with the original location of the body. The same reasoning applies to all recording of the injuries etc of victims of car crashes, fires etc.


In this specific case, with high-definition press cameras everywhere, I can see no reason but voyeurism for a bystander to use a mobile phone to take a snapshot. I guess that this is just one of the sadder by-products of the amazing gadgets that have revolutionised all our lives in recent years.


This photo is a reminder to Montserratians that these wretched people are not aliens from some distant planet. They are exactly like the teenage girl down the road in Salem or wherever. I suspect that this young woman tried to run in bare feet across hot ash. Immersing burned skin at once in cold water will reduce the eventual burn damage.

Photo AP / Irwin Ferdiansyah

No, this is not a scene from "Apocalypse Now" or some second-rate disaster movie. This is real and it happened near Merapi in early November 2010. The burning buildings explain why the rescuers are walking cautiously along the low wall. The ash on the roadway is doubtless still hot enough to burn through their boots. I've emphasised this crucial points elsewhere on the website: do not walk across newly deposited surge ash unless you've tested its temperature.  Photo  SUSANTO/AFP/Getty Images

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The position of this dead cow is quite different from that of the dead cattle in previous photos. It seems possible from the attitude of its front legs that this image shows the bovine equivalent of the pugilistic pose.

BY way of contrast, this person has been killed but without obvious burns. Perhaps this is a case of asphyxiation/hypoxia, rather than the effects of breathing scorching hot air.    Daily Mail UK


During rescue operations on 4 November, the rescuers had to run for their lives from another surge.

Here rescuers are removing a human corpse from a lightly damaged house. Felled branches and pieces from decapitated trees are lying on the ground and were presumably the flying debris that did the structural damage. Note that the concrete water tank is undamaged. This scene closely resembles the one in the Russia Today video of rescuers searching a house for causalities. 




These images are the inevitable end of this sort of incursion by pyroclastic surges into a populated area. Note the ubiquitous digital cameras; even beside the mass grave.

Photos REUTERS/Stringer

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Merapi 2010, Hiroshima in WW2, napalm in Vietnam: is there no end to the horror?

It may seem strange to recall older man-made catastrophes here but the link is obvious. A pyroclastic eruption does much the same to both buildings and living things as these shameful historic events. If we don't like the following images, maybe none of us should condone the events that led to them.





These photos from the Vietnam war are probably the most famous images of what napalm use against civilians does to humans. But they could just as well come from a village near Merapi recently and show the aftermath of a surge hitting a school and evacuation team.

and we dare to call ourselves homo sapiens ........



The obvious next question is; “Why have the Indonesian authorities not provided suitable emergency shelters throughout this densely populated area, so that people have somewhere safe to hide from surges”. The obvious impetus is that similar fatalities occur every few years. The next three photos show that the answer is: yes, of course they’ve tried this approach but it failed catastrophically in 2006.  Who had the bright idea of positioning these shelters in a valley, rather than on higher and/or steeply sloping ground nearby? Apparently, the same team also built them of steel, like ovens when heated by ash. The wall around the unused shelter gives hot ash a perfect place to accumulate.


New shelter (presumably an official "advertising" photo)(AP)

Sabo dams are built to slow down and impede lahars (John Pallister, USGS).

Excavating the buried shelter beside the sabo dam (John Pallister, USGS).

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Indonesia is an extremely rough country, at the best of times. Here's how they deal with someone caught stealing (looting) from wrecked houses and dead people.   ARYA BIMA/AFP/Getty Images


Now it's time to be more positive and see how residents might try to survive such events by seeking shelter. Let's start with a bad example.

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Montserrat places much faith in the abilities of sturdy buildings, like churches, to act as emergency shelters for both hurricanes (tried and tested) and surges (untested to date). Here’s what a surge did to a mosque below Merapi last week


OK, Merapi windows are not fitted with storm shutters, but are the Montserrat churches equipped with the same steel shutters as MVO and do they have concrete roofs?


These photos show that well-built stonework or reinforced concrete are necessary in order to make buildings strong enough to withstand at least moderate surges.



It is easy to see that the surge passed from right to left in this view and that it shattered a thin reinforced concrete wall, leaving the base tilting in the direction of the blast. You do not need to be able to compute dynamic pressures to be impressed by the "pushing power" of this dust-ladened density current.


This image shows that it is not just the use of strong building materials that is crucial in building a safe shelter, it is also the aerodynamic design of the shelter, allowing hurricane-force winds to flow around it.

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