PART 3. Igloos and sugar mills: how to survive pyroclastic surges on Montserrat and elsewhere

 

I never expected to be recommending igloos for Montserrat residents! But this ancient design, easily recreated in reinforced concrete, is perfect for sheltering from hurricane-force winds and surges. You site the entrance facing downwind and fit (on Montserrat) an airtight door insulated with something like felt.

This shows precisely what not to do. The underground cave could be sealed for weeks by hot ashes (or frozen snow).

 

This one is crude but perfectly sited on a slope.

It’s optional as to how you equip your concrete igloo!

 

Do we have to look very far to find igloo-like potential surge refuges on Montserrat? The answer is clearly no, judging from the following images. The island is dotted with the small conical mills that extracted the juice from sugar cane. These sturdy buildings look a bit like igloos and clearly are extremely resistant to both pyroclastic surges and even the actual PFs.

I'm surprised that no oast house owner from Kent, UK, has bought one of these for their Caribbean hideaway!

Bob Thompson

Maybe Bob Dylan will someday buy this one and all the valley for his ultimate secluded place. Of course National Park status is a problem (not that such trivia worry a rich Brazilian friend of mine!).

Greg Scott

Helicopters land in impossible places and make useful scales.

Greg Scott

 

Our ancestors were obsessed with the need to make impregnable dry-stone forts to hide in. As early as at least 3000-4000 years BC they discovered that the conical "sugar mill" design was ideal.

By about 2000 BC, the Nuraghic people of Sardinia had dotted the island with these small forts. I have a local tourist leaflet that calls them the neuralgic people!

The pre-Roman Picts in Scotland built fine examples and called them brochs.

To make a vitrified fort, you fill the structure with wood and ignite it. The raging fire melts a thin layer of the stone, giving you an exceptionally strong fort (or surge shelter on Montserrat?)

 

Modern concrete buildings in Brazil show how easy it would be to use this flexible material to build surge-proof shelters on Montserrat. It is not necessarily a pre-requisite that such shelters should be either artistic or viewed only by moonlight!

 

Now back to Montserrat and pyroclastic surges.

The 25 June 1997 pyroclastic surge that wrecked this sturdily-built house at Streatham, Montserrat, caused no discernable damage to the nearby sugar mill. The mill would have made a perfect shelter, if only people had realised the approaching danger in time.

Paddy Smith

The same mill can be seen to the left of this view over the surge from the 11 February 2010 dome collapse that covered the Farrell's Plain area.

Paddy Smith

If you look very carefully, you can see in the distance left another mill undamaged by the huge surge that accompanied the 8 January 2007 PF down the Belham Valley.

Greg Scott

 

 

What can Montserratians learn from the current agony around Merapi about simple ways to survive a surge in or around their homes?

 

I’ve emphasised elsewhere (e.g. Topic 11) that Montserrat’s residents have become totally acclimatised to their erupting neighbour and complacent about its future activity. Perhaps the current Merapi eruption will help to knock a bit of that complacency out of them. Despite the heroic efforts of the SAC to make predictions about SHV “scientific”, they really have no more insight into what the volcano may do next than any other group of Caribbean shamans reading chicken entrails. The whole thing about both volcanoes and earthquakes is that they are totally unpredictable, despite periods of relative predictability. The entire NDPRAC-equivalent committee on Martinique who met repeatedly in 1902 to decide what to do about the eruption of Mt Pelée nearby were wiped out by the killer surge (PDC) between meetings. Merapi gave no clues at all that it was beginning what has already become its most deadly eruption for a century. I personally live in permanent fear that those who “think they know” what SHV will do next will pay for their hubris with their own or other peoples’ lives. This nightmare must haunt all sensitive Governors and everyone around them.

The inability of hundreds of “at risk” Indonesians to move to safety before a surge wipes out their village is a tragic but “classic” illustration of the “frog in the saucepan” phenomenon (Topic 10). The Indonesian government yesterday did the only thing that might persuade reluctant farmers, caring for their precious cattle, to move away; they bought all the cattle. If only the Montserrat government had bought all the vegetables etc in the Streatham area in 1997. I remember a neighbour in Washington DC in 1971 confessing that she very nearly went back to her house to rescue the beloved family cat, despite the news warnings that a dam above their evacuated neighbourhood was already collapsing and that she might thus join the 150 others drowned during that awful night.

So let’s assume that you live in the Salem-Olveston area and have, by bloody-mindedness, complacency, age, mental state, poverty etc managed to find yourself in the path of a pyroclastic surge. Is there anything you can do to help your survival, even if you lack a prepared sealed room? Here are some untried suggestions, based on the photos from this Merapi eruption, together with other recently published scientific studies on the subject, such as this one about sheltering in buildings. Remember that your objectives are to prevent your skin from scorching and to stop either hot air or excessive dust entering your mouth.

1.      Cover yourself as completely as you can with cotton (or woollen but not artificial fibre) clothing.

2.      Find spare clothes and bury your head inside them.

3.      Curl up beneath your bedroom mattress. These three suggestions are poor substitutes for being a furry monkey, but just might save your life.

4.      If you have a shower, turn it on fully and stand, fully clothed, beneath it.

5.      If either you, or any neighbours, have a swimming pool, dive in and try to stay below the surface for as long as possible. Only do this, if the pool does not have a modesty wall around it or lies on a dip in the ground (both are potential PF/surge traps). The ideal pool is illustrated below; open and on a hillside. Grab a drinking straw, if you have one, before your plunge and use it to take occasional breaths. If no drinking straw, cover your head with your clothing and stay under it when breathing.

Because most Montserrat homes are built on slopes, they each include an obvious place to prepare for emergency shelter use. This is the cavity between the ground and the lower-floor rooms. Make a small entrance to this cavity in the downhill wall and fit it with a tight-fitting door. Even if your entire house was swept away by the surge, as at Harris in February 2010, you would still be cramped but safe in this cavity. Obviously ash could filter between floorboards into your shelter and therefore take some extra clothing in to cover your face and exposed skin (curl up, like that lucky monkey). Also keep some emergency food and water down there, in case your exit is across very hot ash and you must therefore wait to be rescued. When things sound calm again, open the door a crack, wait for the sounds of rescuers and then practice your yelling skills!

Incidentally garages, guest rooms etc in this part of your house are not necessarily any better than a modest bolt hole in the foundations for keeping you safe. How many such places on Montserrat are able to be sealed by steel shutters, like the emergency rooms at MVO? Of course there is a very simple solution to that problem but it will temporarily reduce your alcohol and entertainment budget. Sorry!

 

The felled trees in this view tell you that the surge moved (unsurprisingly) downhill from left to right. The damaged house on the left gives excellent clues as to how to survive a surge, if you are careless enough to be caught out by one on Montserrat (see text). All the rooms above ground have been infiltrated by deadly ash, entering via damaged shutters or through the wrecked roof. So where is the potentially safe refuge?

Here’s another damaged house showing the potential safe zone in its foundations on the downhill side.

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Maybe your (or of course your neighbour’s!) pool will one day save you from an approaching surge. It would be simple during eruptions to keep a full air cylinder and breathing tube at the bottom. Use your imagination to survive or, better still, why not evacuate when the sirens sound?

 

STOP  PRESS in mid-December 2010

There are two further important matters to report:

1. In June this year a multidisciplinary volcanology/museum/medical group published their studies of Pompeii and Herculaneum skeletons, including several dozen found in 2009 at the Roman settlement of Oplontis, a few km NW of Pompeii. Oplontis was slightly nearer Vesuvius than Pompeii but further than Herculaneum. By means of their combined studies, this team has been able to produce an overall map of the dynamic pressures produced by the pyroclastic flows/surges (called PDCs -- pyroclastic density currents -- in modern research literature) throughout the region affected by the AD 79 eruption. At the same time, the AD 79 skeletons have proved to be so well preserved that the group's forensic pathologists could determine the temperatures at which each person died, by comparing the Roman bones with heat-treated modern ones. For readers, the remaining excellent feature of this report is that it is published in PlosONE, an internet journal of peer-reviewed research that is available to everyone and not locked behind a subscription. For the record, the details of the report are:

Lethal Thermal Impact at Periphery of Pyroclastic Surges: Evidences at Pompeii by Giuseppe Mastrolorenzo, Pierpaolo Petrone, Lucia Pappalardo and Fabio M. Guarino.

2. During early December this year, another interdisciplinary team has visited Merapi (funded by the EU programme called MiaVita) and made a comparable study of the disaster-hit region there. Because the residents around Merapi are Muslims, there are strict limits as to what studies may be made of their corpses. But, even with this restriction, the new research should add enormously to our understanding of such tragedies and hence how to reduce the risk of more in the future.

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