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Volcanic hazards for the fragile logistic on the islands of Vanuatu!


Research: Volcanic hazards for the fragile logistic on the islands of Vanuatu!

From year to year, erupting volcanoes cause threat and evacuations on some islands of Vanuatu, such as Ambrym, Ambae (Aoba) (in 2004/2005), Yasur, Gaua and Lopevi.

What potential hazard can cause the erupting volcanoes in general?
How does life goes on for the inhabitants?
Would help be needed for villagers and how much?
What logistic challenge has to be faced for aid work?

Vanuatu

ABSTRACT

Since 1980, independent republic of Vanuatu is a group of 80 bigger Y-shaped islands about 1500 miles north of New Zealand and about the same distance east of Australia. Some complex plate tectonics (a kind of island arc mechanism) created this islands by uplift of ocean crust (first emerged from the sea 22 million years ago), but mostly by volcanism. Today we see a vaority of volcanism, such as lava lake activity at Ambrym, strombolian activity at Yasur and explosiv volcanism at the volcanoes Lopevi and Aoba (Ambea island). In 2004 and 2005 the volcano at Ambea and Ambrym caused evacuations to this islands because of very violent and ongoing eruptions.

Garet (Gaua Island) 14.27 S, 167.50 E, Alt. 797 m (Stratovolcano)
The roughly 20-km-diameter Gaua Island, also known as Santa Maria, consists of a basaltic-to-andesitic stratovolcano with an 6 x 9 km wide summit caldera. Small parasitic vents near the caldera rim fed Pleistocene lava flows that reached the coast on several sides of the island; several littoral cones were formed where these lava flows reached the sea. Quiet collapse that formed the roughly 700-m-deep caldera was followed by extensive ash eruptions. Construction of the historically active cone of Mount Garat (Gharat) and other small cinder cones in the SW part of the caldera has left a crescent-shaped caldera lake. The symmetrical, flat-topped Mount Garat cone is topped by three pit craters. The onset of eruptive activity from a vent high on the SE flank of Mount Garat in 1962 ended a long period of dormancy. (GVNŠ)

Aoba (Ambae Island) 15.38 S, 167.83 E, Alt. 1496 m (Shieldvolcano)
Aoba, also known as Ambae, is a massive 2500 cu km basaltic shield volcano that is the most voluminous volcano of the New Hebrides archipelago. A pronounced NE-SW-trending rift zone dotted with scoria cones gives the 16 x 38 km island an elongated form. A broad pyroclastic cone containing three crater lakes is located at the summit of the Hawaiian-style shield volcano within the youngest of at least two nested calderas, the largest of which is 6 km in diameter. Post-caldera explosive eruptions formed the summit craters of Lake Voui (also spelled Vui) and Lake Manaro Ngoru about 360 years ago. A tuff cone was constructed within Lake Voui about 60 years later. The latest known flank eruption, about 300 years ago, destroyed the population of the Nduindui area near the western coast. (GVNŠ)

Ambrym (Ambrym Island), 16.25 S, 168.12 E, Alt. 1334 m (Pyroclastic Shieldvolcano)
Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides arc. A thick, almost exclusively pyroclastic sequence, initially dacitic, then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major plinian eruption with dacitic pyroclastic flows about 1900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the caldera floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations. (GVNŠ)

Lopevi (Lopevi Island) 16.507 S, 168.346 E, Alt. 1413 m (Stratovolcano)
The small 7-km-wide conical island of Lopevi is one of Vanuatu's most active volcanoes. A small summit crater containing a cinder cone is breached to the NW and tops an older cone that is rimmed by the remnant of a larger crater. The basaltic-to-andesitic volcano has been active during historical time at both summit and flank vents, primarily along a NW-SE-trending fissure that cuts across the island, producing moderate explosive eruptions and lava flows that reached the coast. Historical eruptions at the 1413-m-high volcano date back to the mid-19th century. The island was evacuated following eruptions in 1939 and 1960. The latter eruption, from a NW-flank fissure vent, produced a pyroclastic flow that swept to the sea and a lava flow that formed a new peninsula on the western coast. (GVNŠ)

Yasur (Tanna Island), 19,52 S, 169,425 E, Alt. 361 m (Stratovolcano)
Yasur is one of the world's most active volcanoes and has been in continuous Strombolian and mild Vulcanian eruption for at least 800 years. Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous strombolian and vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Yasur, located at the SE tip of Tanna Island, is a mostly unvegetated 361-m-high pyroclastic cone with a nearly circular, 400-m-wide summit crater. Yasur is largely contained within the small Yenkahe caldera and is the youngest of a group of Holocene volcanic centres constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide, horseshoe-shaped caldera associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions of Yasur has raised Port Resolution harbour more than 20 m during the past century.(GVNŠ)

Aid-management because of volcanic disasters!

Volcanic disasters can cause a lot of problems to the inhabitants of some islands of Vanuatu. Beside earthquakes, a hazard by Tsunamis, volcanic acid fall-out is one of the biggest threat by volcanic eruptions. Local habitants have to be evacuated whenever some of this threats or impacts are too severe.
But how can evacuation run efficiantly? Do habitants realy have to leave home and why? How could international aid and help do good for locals? All this is already discussed by organizations and authorities and some things are today solved and well organized. To improve aid-management, different datas and information, as well as diffenrent points of view can help. Thererfore we like to privide our reflection about local logistics on the following islands of Vanuatu:

The main logistic hubs of Vanuatu are the international airports of Efate (Port Vila), and on Espiritu Santo island (Luganville) with Pekoa (or Santo) airport. The so called calm Pasat or traders winds generate mostly southeastern wind directions as predictable circumstances. Dring the Cyclon season from December to March this storms can reach Vanuatu from the Coral See moving south-southeast.


VANUATU GEOHAZARD OBSERVATORY gives many answers and takes care nowadays:


  • Vanuatu Geohazard Observatory: www.geohazard.gov.vu/


  • Garet (Gaua island, 1.500 habitants)
    The entire island of Gaua is dominated by the volcano (caldera) Mt. Garet. To all sides, the flanks of the volcano (caldera) immediately fall down to the sea. The flanks are as well carved by deep drainages and canyons. So what ever leaves the caldera (or the crater lake named Letas) with a volcanic eruption, will reach the costal areas and villages with no doubt and propably with fatal results. This circumstances make Mt. Garet (last notable eruption 1982) one of the most dangerous volcanoes of Vanuatu. High amounts of yearly rainfall are a threat for common erosion as well. It means, that the soils protecting forests should be preserved very well. Somehow a conflict with economic progress on the island in these days (see article below).Because of the geological morphology of the caldera, the most hazardous areas are to the northwest.
    The few settlements on Gaua are all on the coastal lowland or right at the seaside. The only airfield is in the northeast near Aver. A quite well mentained dirt track goes form Masevono (north), via Losalava, Aver, Teuvrat, Lambal to Kweteon. The track continues to Makeone in the south, but we don't know the conditions of the track. On the west coast, a track (unknown conditions) goes from Kwetegaweg to Pwetevut. In the middle, a known safe anchor is off shore the settlement of Ontar. As well Kaska Bay (east coast) is known to be a safe anchor site. Some Pick up trucks and old road mentain vehicles exist on the island.

    Aoba (Ambae island, 10.000 habitants)
    A professional hazard paper exist for Ambae island. So, our information are only additional. As we know from the physical morphology of the island, the central area of Ambae is the most dangerous on, because bigger explosive eruptions can cause lahars (mudflows) in a sudden. The lahars could be a result of rainfalls triggert by eruptions or because of water being blown out of the crater lakes of Aoba volcano by explosive activity. The outburst of lava on the outer flanks of the volcano are possible but usually do give anought time to evacuate dangered areas. Anyway, many villages could be effected by explosive volcanic hazards and this could last for quite a long time.
    Local settlements are all around the volcano. Most of these villages do have 4-wheel-drive roads but during rain this roads may be out of use. The dustroads along the north coast (only) on Ambae is quite ok, but there are not much transport means for habitants and goods. This road might be cut off by eruptions. The evecuation runs usually by ship via Ndui Ndui (northern shore) or from the safer anchor at the notheast part of the island. Beside the Walaha airfield (the safe westend of the island), Laongana airfield is a hop off point for rescue in the east of Ambae.

    Ambrym (Ambrym island, 8.500 habitants)
    A very good volcanic hazard map (paper) by Michel Monzier and Claude Robin (ORSTOM 1996) exsist for Ambrym island. The shield volcano if Ambrym has a dense jungle vegetation around a central caldera. Whenever flank eruptions occure, enough time for evacuation should be no problem. The major threat is certainly acid fall-out (a mixture of ash and acid rain) which can last as long as an eruption goes. This can be up to month. If this acid fall-out poisens the water supply of local habitants, a big logistic problem occures quite in a sudden. If the acid fall-out destroys further on food plants and if it poisons (kills) farm animals such as pigs, chicken and cows, a desaster concering foodsupply for residents can be realy serious. The only way to help locals is with evacuations of the threatened parts of the island.
    Food aid and other supply could be entered by the airfields of Craig Crove (westend of the island) and Ulei (southeast of the island). But for longer lasting help-programs, ships have to bring in supply with the safe harbors of Craig Crove and along the northern shore. A rough dust road winds along the southern shore. This road is good for evacuation, though trucks are short in this area. Locals told us that there are about 5 trucks to serve this road, which aren't enough to do efficient evacuation or help. In the north of the island we have the same situation concerning transport. If a bigger evacuation of the island should be necessary, ships from other part of the country are needed.

    Lopevi (Epi island, 4.500 habitants; Paama island, 2.000 habitants)
    The volcano Lopevi is about 14 km northeast of Epi island and only 5 km east of Paama island. The island is unhabitated since 1960 so we look at hazards only fot the nearby island. In case that a big explosiv eruption occures or that a part oft the steep strato volcano slides into the sea, Tsunamis can hit the islands of Paama, Epi and Ambrym very, very hard. The hole eastcoast of Paama will be effected. Ambrym will be hit at the south east tip of the island. We don't know how this will effect the habitians oft this two islands. But we know, that Epi will be severe effected on its hole eastcoast by any Tsunami. Some villages along the caost are close to the waterfront found on low altitude. The dust raod along the coast would be partly destroyed by a Tsunami so that help would be difficult to be carried out. The one lane road is in a quite good condition. In 2006 we have counted about 8 pick up trucks giving service on that particular raod and the hole island itself. This is not al lot any help can count on.
    But not only Lopevi volcano can cause problems, as well the submarine volcano 2 km offshore of Epi (at Mt. Nitaia) and the submarine volcano Kuwae near Tefala island can especially trigger Tsunamis, but as well any other volcanic threat. The logistic base (gate) for any aid on Epi island would be the airfields of Lamen Bay (at the safer northwestern end of the island) and Valesdir 27 km south of Lamen Bay.

    Yasur (Tanna island, 21.000 habitants)
    The volcano Yasur is monitored by local volcanologists. Implaced are three levels of volcanic hazard to give help how locals and visitiors should react on volcanic activity. The airfield of White Grass has a paved runway and is called "Tanna international airport". This makes it an ideal entry gate for any help. The road toward the east of the island and around the active volcano Yasur is a quite good, but partly a steep track. From the village Yaneumakel, anticlockwise around Yasur volcano as far as Port Resolution, the road goes along the foot of the 400 m high volcano Yasur. With big eruptions - security level 3 - this part of the road is threaten by the volcano. Some villagers towards the mountain of Tokusmera will be cut off by transport. Here we couned on some hundreds of habitants in 8/2006. The Port Resolution area will be cut off too of course.
    In general, transport-logistics on Tanna island are plenty enough, but if bigger eruptions last long, this above mentioned problems and the cut off with supply for villagers will not be solved via the road around the volcano. So evacuation will be essential. A difficult story in terms of local politics and fincanial support.


    GAUA CARVED UP BY INVESTORS

    Open letter to the President and Provincial councillors, Torba
    CLEARANCE WORK ON GAUA RAISES CONCERNE!


    We the undersigned citizens and residents of Gaua would like to express our concern with respect to the work that is taking place on the slopes above Siriti village. The proposed cattle project currently raises three areas of concern: legal, environmental, as well as social.
    To our knowledge there are several steps that must be taken before the government can properly approve of a development initiative within it's borders. At the national level, investors must pass through the Environment Unit and perform an "Environment Impact assessment". At the provincial level the investor must gain the approval from the office of the provincial secretary general and the provincial planner.
    Furthermore the investor in question must have an approval from the Island Council of Chiefs at the local level. And if it's true, that tourism is to be involved within the project scheme, then it is important that the investor passes through the Torba Tourism Association. However, currently, we can find no proof that this development initiative has fulfilled any of the above requirements.
    Environmentally, the project brings several areas into questions. If it is true that the intention of the initiative is to raise cattle, why is it being based on the slopes of a mountain where soil erosion will be greatest?
    (see open letter form Christop Weber below!)
    Soil erosion and the waste run off from the cattle project will undoubtedly reduce the quantity of the island's only river which is the drinking water for two government schools and many homes and communities. Whith the amount of area neeeded to accommodate thousands of head of cattle we believe, that the island of Gaua is far less suited to this type of development than other cattle producing islands of the south. On top of the island is an area being cleared to the lake and is already infringing upon the GEF funded project to preserve the bush around Lake Letas and Lake Letas itself is a national conservation area.
    All this is said without mention of the damage done to the ecosystem and the old growth forest by the current brushing of the bush as well as future brushing. One cannot predict the full effects of this project upon the value of the water system provided by the Siri river.
    With this being the year of the "Custom Economy" which is supported by every department in the national government - and with customary land rights and education such a prominent social issue today, we despite the lack of proper approval and with full knowledge of the negative aspects of this form of developent, the local and national government has been turning a "blind eye" to this situation taking place on our island.
    Siri falls and Lake Letas are considered to be environmental and cultural treasures of the people of Gaua. We gelieve that our government should feel the same, and take the appropriate steps to safeguard these national treasures from exploritation and harm.
    Thank you for your consideration and understanding.



    Signed:
    Chairman Torba Tourism Council - Charles Bice;
    East Gaua Council of Chiefs Chairman - Victor Wotias
    (The Vanuatu Independent, www.independent.vu ; issue # 209, December 2007)
    Open letter to the President and public of Vanuatu
    ABOUT HAZARDS and PROTECTION of the NATURAL ENVIRONMENT of GAUA!


    My name is Christoph Weber. I'm a germany volcanologist and work on active volcanoes since 10 years. I have visited Vanuatu a few times, but Gaua island only the first time in December 2007. I heard and read about the "cattle project" during this visit.
    I fully support the iniciative of the letter of Mr. Charles Bice and Victor Wotias (see letter above) and to my subject of volcanism, I can add some deep concerns too.

    The primary forest around the volcanic caldera of Gaua is not only a natural treasure, it its more like a protecting circle for the inhabitated coastel lowland of Gaua. This Forest on the steep slopes of the volcano holds back partly, whatever is being released by the volcano during eruptions. It could be volcanic ash including the entire lake water. The phenomena which could come with an eruption is called Lahar and is very dangerous. The less protecting vergetation is in an area, the more dramatic a Lahar will be. This is somehow similar to erosion in common.
    The second reason to have this area uninhabitated is the fact, that the circle towards the caldera is just not safe at all during eruptions. Beside the Lahar phenomena, hot clouds of ash can rush down the volcanic cone of Mt. Garet, passing Lake Letas and travelling down the slopes of the cladera. Volcanic blocks will reach upper part of the calera. And again, a protecting forest will reduce the risk for the costal settlements. Last but not least, we know, that erosion of volcanic soil in tropical climat is very quick. That erosion could culminate in a massive land slide. If this happens in the Siri river canyon, the natural barrier holding back the water of lake Letas could be destroyed. This flash flould would effect deadly the western part of the island as fa as down to the coast. Would logging followed by cattle grazing, is known to be one of the quickest release for soil erosion.
    Not to forget the touristic damage for Gaua and hole Vanuatu, by damaging the ecosystem and the old forest of the island. Specially when you know, that not so much is left of this natural treasure of highest value for the next generations of Ni-Vanuatus. All this is said without mention of the damage done to the ecosystem and the old growth forest by the current brushing of the bush as well as future brushing. One cannot predict the full effects of this project upon the value of the water system provided by the Siri river.



    Signed:
    Christoph Weber (c.weber@wtal.de)
    (VHDL, January 2008)

    ACTIVITY-NEWS from Oct. 2009!!!

    GAUA Banks Islands (SW Pacific) 14.27°S, 167.50°E; summit elev. 797 m According to news articles from 2 October, increased seismicity at Gaua was detected during the previous two weeks. Villagers living nearby reported ashfall and sulfur odors. Both villagers and a pilot flying past Gaua heard explosions. The Alert Level was raised to 1 (on a scale of 0-5).

    VHDL - members of the 8/2006 workshop, leaded by Chris Weber:
    Christian Falk
    Franz Neubauer
    Martin Rietze
    Manfred Meyer
    Rainer Albiez
    Gé Beijers
    Sandra Deckert
    Hans-Juergen Knoblauch
    Anita Wassener

    NEWS from 2005 (c)by John Seach:

    Aoba:
    Tuesday 6th December 2005 Ambae volcano has been raised to level 2 alert, indicating regular eruptions are occurring at the summit. Ambae volcano began erupting last week, after being dormant for about 120 years. 5000 people are being evacuated from dangerous areas in the east and west of the island.
    Monday 5th December 2005 The eruption of Ambae Volcano in Vanuatu continues to cause problems for residents. Fears of further eruptions under lake Vui have required evacation of 5000 people from a 10 km danger zone to safer areas on the island. Volcanic activity is increasing, and ash emissions are occurring every 3 to 5 minutes. Emissions can be seen from neighbouring islands of Maewo and Pentecost. Measurements of gas emissions at the volcano indicate large amounts comparable to Yasur volcano in southern of Vanuatu. Acid rain may become a problem. Pentecost and Maewo remain the priority islands to settle the resident in the case of a mass evacuation.
    Tuesday 6th December 2005 Ambae volcano in Vanuatu erupted on 27th November. Up to 5000 people in 15 villages have been affected. A new island was formed in one of the summit crater lakes (Vui). Further eruptions through the crater lake could prove dangerous. Food crops have been covered in ash.
    Friday 25th February 2005 An earthquake on February 16th with an epicenter near Ambae volcano has caused concern among residents of the island. People living in the north to the western side of the island reported smelling sulphuric fumes after the earthquake. The Vanuatu Government is working on contingency plans to evacuate people if there are signs of an eruption. The last activity on Ambae Island was a phreatic eruption at Voui Crater Lake in 1995.
    As of the 6th of December, the Global Volcanism Network (GVN) has reported that Mt. Ambae (a.k.a. Aoba) volcano erupted on 27 November in Ambae Island of Vanuatu. Ambae (Aoba) volcano has been raised to level 2 alert, indicating regular eruptions are occurring at the summit. Ambae volcano began erupting last week, after being dormant for about 120 years. 5000 people are being evacuated from dangerous areas in the east and west of the island. The volcano Ambae (Aoba) is a massive 2500 cu km basaltic shield volcano that is the most voluminous volcano of the New Hebrides archipelago. A pronounced NE-SW-trending rift zone dotted with scoria cones gives the 16 x 38 km island an elongated form. A broad pyroclastic cone containing three crater lakes is located at the summit of the Hawaiian-style shield volcano within the youngest of at least two nested calderas, the largest of which is 6 km in diameter. Post-caldera explosive eruptions formed the summit craters of Lake Voui (also spelled Vui) and Lake Manaro Ngoru about 360 years ago. A tuff cone was constructed within Lake Voui about 60 years later. The latest known flank eruption, about 300 years ago, destroyed the population of the Nduindui area near the western coast.

    Ambrym:
    Sunday 6th March 2005 Volcanic activity continues at Ambrym Volcano. Remote sensing data indicate the proximity of magma to the surface. Ambrym is one of the world's most active volcanoes. It has been in almost continual eruption since Cook's visit in 1774. Destructive eruptions have affected local communities since March 2004, and residents are calling for food aid.
    Wednesday 2nd March 2005 Residents of Ambrym Island in Vanuatu are calling for international assistance to help with the disaster caused by the ongoing volcanic eruptions. Ambrym is one of the world's most active volcanoes and has been in almost continuous eruption for the past 200 years. One year ago there was a change in eruptive activity which caused damage to food crops and created health problems for the residents. One year later, the volcano is still creating problems for the local communities, and the population is still calling for food aid to help prevent a famine on the island. Famine is the great forgotten killer of volcanic eruptions. During a survey of the volcano in November 2004, Volcanologist John Seach surveyed the damage to the island and made observations of the changes in volcanic activity. A new report received from the island 4 days ago by John Seach indicated that the situation is getting desperate for some residents who do not have enough food. So far only $1000 USD has been raised to help with food aid. Ambrym Volcano is closed to the public due to volcanic activity.
    Friday 25th February 2005 West Ambrym has been declared a disaster area following eruptions and acid rain which has caused damage to food gardens. The community needs new crop plants and food aid to assist through the next 4 months of the declared disaster period. There needs to be a continued awareness programme on the volcanic hazard and risk, and measures to reduce the effects of the eruption. The government of Vanuatu is looking at a resettlement programme for the people displaced by the eruption. Reports from the island indicate that food crops have been destroyed by the ongoing eruptions and acid rainfall. Satellite images show continued hotspot activity at the volcano, indicating the proximity of magma to the surface. The volcano has been closed to the public until further notice due to volcanic activity.

    Lopevi:
    Saturday 3rd December 2005 Eruptions continue at Lopevi volcano in Vanuatu. Satellite images show hotspots. There are no reports of ash emissions. Thursday 10th February 2005 Satellite images indicate possible eruptive activity at Lopevi Volcano in Vanuatu beginning at the end of January 2005 and continuing in February. Lopevi volcano is an uninhabited island in central Vanuatu, SW Pacific. Eruptive activity often goes unreported. The hotspot images indicates that magma is close to the surface, or there has been a small lava flow. Reports of eruptive activity in 2004. John Seach visited SE Ambrym volcano in November 2004 and received reports from residents about previously unreported eruptions of Lopevi  in 2004.
    During September 2004, five large booming noises were heard coming from Lopevi volcano by villagers in south Ambrym. Explosions were separated by 2 minutes. The next day there was ashfall on N and W Ambrym. The eruption was confirmed by satellite image on 28th September 2004. Hotspot activity was also noted at Lopevi on 13th May 2004 a satellite image. This correlates with eyewitness accounts of an eruption of Lopevi volcano obtained by John Seach during a field trip to the region.

    Yasur:
    As of the 1st of December, colleague Dr. John Seach, has reported that Yasur volcano in Vanuatu continues it impressive eruptive activity with many eruptions per hour. Yasur is one of the world's most active volcanoes and has been in continuous Strombolian and mild Vulcanian eruption for at least 800 years. Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous strombolian and vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Yasur, located at the SE tip of Tanna Island, is a mostly unvegetated 361-m-high pyroclastic cone with a nearly circular, 400-m-wide summit crater. Yasur is largely contained within the small Yenkahe caldera and is the youngest of a group of Holocene volcanic centres constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. Active tectonism along the Yenkahe horst accompanying eruptions of Yasur has raised Port Resolution harbour more than 20 m during the past century.


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