Ambae volcano eruption continues

The eruption of Ambae volcano continues, only minor activity has occurred at the summit crater recently and the Volcanic Alert Level remains at Level 3.

Ambae volcano is a large active volcano. In November 2005, the volcano experienced a significant new eruption, followed by unrest until 2017. In early 2017, this volcanic unrest escalated and the volcano started erupting in September 2017. This eruption has occurred over three phases since September 2017: Phase 1 — September to late November 2017; Phase 2 — late December 2017 to early February 2018; and Phase 3 — February to May 2018 (ongoing).

In Phase 3 there has been thick and widespread volcanic ashfalls across the island of Ambae, which have caused significant impacts on food supplies, water, shelter and the health of Ambae Island residents. Significant humanitarian issues have followed this activity.

Drinking water samples have been collected from all sectors of Ambae during April and May. These included both repeat and new water samples – all from after the heavy ashfalls. The results from these show that some rainfall sourced drinking waters are impacted by the eruption. Where the ash is thickest (Ambanga, Lolobinanongue and Red Cliff areas) the heavily ash-impacted waters are not suitable for long-term use currently (or short-term use by babies or younger children). Less impacted water in these areas and elsewhere on Ambae Island are generally safe to drink with suitable treatment (boiling).

If water supplies are affected by volcanic ash, gas or acid rain they need to be treated before use. The DoWR, MoHealth recommend actions like, when you first take water from a tap in the morning, throw away the first cupful of water. If your family only has drinking water with volcanic gas, acid rain or ash in it please ensure babies and younger children drink only bottled water, coconut water or boiled bore water. If water is cloudy: try standing water in a container to allow ash to settle to bottom, or filtering water through a clean cloth. If water tastes sour, adding crushed shells or coral to a container of water (e.g. plastic jerrycan) will help to neutralise the acid and may improve the taste.

Water samples from the evacuation camps have also been tested for bacterial-microbe contamination (not volcano related) and some show signs of contamination. All drinking water should be treated to reduce or eliminate microbes. The DoWR, MoHealth recommend boiling water before use, or filtering through a membrane filter, then adding a chlorine tablet and allowing the water to stand for an hour. Empty bottled water containers can also be reused by filling and then placed in direct sunlight for 6 hours before drinking. If water is cloudy, first filter through a clean cloth then add the chlorine tablet and allow the water to settle for 2 hours. Note also that chlorine may not kill all types of microbes.

The analysis of the volcanic ash from Ambae volcano eruption has found that up to a third of all ash deposits consist of particles that are small enough to be breathed in (less than 0.1 mm). This ash is mostly stable on the ground and only a small proportion is likely to be resuspended by wind and breathed in. Breathing in such small particles as these (between 0.01 and 0.1 mm in size) can cause problems such as sore throats, coughs or throat infections. These problems are usually short term and minor. Correct use of dust masks will minimize how much ash is breathed in. However, if a mask is incorrectly used it will be of little use. To correctly use a mask, use straps and any nose clip to fit mask tightly to face. The top strap should go high on head, and the bottom strap low. A layer of cloth tied on top of the mask can help to hold it to the face. Note that masks will not fit very well to children or people with beards. Some people with underlying breathing conditions such as asthma may find their symptoms getting worse. Anyone who has concerns about their health, or their children’s health, should go to the clinic.

Environmental impacts:

Ashfalls have caused leaves to fall off trees, broken plant stalks and tree branches, buried crops, and collapsed trees. The acid rain from the volcanic steam and gas plume has burnt and damaged plants. Ash coatings released into the water can have a similar impact. The sustainability of local crops for food supply and animal food is greatly reduced.

The ashfalls were thick enough to damage and in some cases, destroy traditional buildings. About half of the traditional buildings that experienced more than about 50 mm of volcanic ash are unusable. More modern buildings appear to be less damaged. No lives have been lost as a result of the eruption.

From observations around the world, following volcanic ashfall events remobilisation of the volcanic ash can occur, months to years later, even after the eruption has stopped. Remobilisation of ash can be due to wind or water (rainfall).

When the deposit dries out, a small proportion of the fine ash can be lifted into the air by wind, so it can cause ongoing breathing problems. Wind remobilisation effectively re-exposes buildings, crops, animals and people to the ash. This means the people may experience the physical impacts again.

If the ash has been washed by rain, there is less of a risk of chemical contamination of water supplies again. Some water supplies will be re-impacted and experience turbidity (milky or cloudy water).

Rainfall induced remobilisation of volcanic ash usually results in streams and rivers carrying significantly larger sediment loads which produce much larger than normal flood impacts. Some floods have occurred in rain. These can occur for several years after an eruption of the current size stops.

Volcanic gas emissions are likely to continue. Gas in village is unlikely to be a health risk for most people but may be a problem for people with breathing conditions such as asthma. If these people are feeling unwell because of gas (headache, difficulty breathing, stinging eyes) take them to clinic.

Further information about Ambae Volcano:

Ambae volcano is a large and geologically active volcano. A large-scale eruption about 400 years ago built a volcanic cone in the summit crater of the volcano. Today the crater is filled by Lake Voui; the recent volcanic activity comes from vents in Lake Voui. Historic activity is poorly understood, but there are records of activity in 1530, 1670, 1870, 1915 and 1966. All recorded activity has been from the summit crater except for the 1670 activity, which included a flank eruption producing lava flows in the Nduindui area.

The 2017-2018 eruption is part of a longer sequence of volcanic activity that started with volcanic unrest in 1991, leading to an eruption in March 1995. From 1995 to 2005 volcanic unrest was often noted at Lake Voui. A significant new eruption started in November 2005. This eruption built a new volcanic cone (island) in Lake Voui and activity continued until early 2006.

Ambae volcano stayed in a variable state of volcanic unrest through to late 2016. Most of the volcanic island built in 2005 was eroded away during this time. Another volcanic eruption occurred around July-August 2016. Volcanic unrest escalated in early 2017 and an eruption was under way by September, building a new volcanic cone (island) in Lake Voui.

The current eruption is characterised by three phases; Sept to late Nov 2017, late Dec 2017 to early Feb 2018 and Feb to May 2018 (ongoing). The eruption has built and destroyed and rebuilt a volcanic cone in Lake Voui. The third phase has produced thick and widespread volcanic ashfalls across the island of Ambae. The Volcanic Alert Level remains at Level 3.

  • Prepared 18 May 2018 by VMGD, DoWR, MoHealth and GNS Science.

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