Vanuatu (beautiful) Manaro Vui volcano remains at alert Level 1

The first listed active volcano in our weekly Active volcanoes list we published earlier today was  Vanuatu's  Manaro Vui volcano (also called Ambae or Aoba). An extremely beautiful island (in fact a 3,900 meter high volcano), with on top a crater lake with an active crater as an island in the lake.

Lake Voui, Vanuatu - Panoramio image courtesy Dockx Thierry - http://www.panoramio.com/photo/37643095

The text below is a recent bulletin published by the Vanuatu Geohazards Observatory

UPDATE July 18, 2011 :
According to the analysis of data collected by the Vanuatu Meteorology and Geohazards
Department (VMGD) in 12 July, the Ambae volcano have had small successive explosions in
July 10th 2011 from 6:45 to 7:15pm. Though the volcano seemed quite in July 12th (see photo)
the data collected shows that volcano earthquakes still exist on this island. This means that
this volcano activity still remains but moderate to weak.
The trend of the activity of this volcano is not clear at this state. It is possible to be quiet but it
is also likely that this volcano continue to go through small explosions from time to time.
Therefore the volcano Alert Level of the Ambae volcano still remains at Level 1
according to the Vanuatu Volcano Alert Levels (VVAL). The risk is still located only
within the 3 km zones from the Crater Lake.

The VMGD has to continue the monitoring of this volcano to better understand the coming
trend of its activity.
The National Disaster management Office (NDMO) advises the communities and visitors to
avoid the risk areas indicated above until the next update is issued.

Information as released on July 11 : It is clear that the earthquakes that occur on the island are triggered by the volcano. The
Ozone Monitoring Instrument (OMI) satellite images are showing that the Ambae volcano is
emitting volcanic gases (So2) to the atmosphere (see photos). Observations made on this
volcano in June 4th 2011 found out that this volcano is sometimes having small explosions in the Crater Lake accompanied by small ash emissions locally in the caldera. This activity has
been witnessed by some villagers in the northern and the western part of the island.

According to this situation, this is a reminder that the Alert level for Ambae volcano is
at Level 1 according to the Vanuatu Volcano Alert Levels (VVAL). This means that the
state of activity of this volcano has been changed compare to its normal activity. The
area of risk to the visitors is centered within 3 km zone from the volcano crater.
VVAL alert 1 description : Increased activity, danger near crater only

Geohazards is monitoring the situation with one officer in the field to analyze the situation
and the volcano data. This Alert Level could quickly evolve with the result of the analysis
of the field officer.

Nasa Aura /OMI So² staellite image from July 12, 2011


General Information

Aoba island (1496 m) corresponds to the Upper part of the most voluminous active volcano of the archipelago (3,900 m-high from the sea bottom, about 2,500 krn3).  Its summit area shows two concentric calderas, the smallest including three lakes. Lake Vui (2.1 km in diameter) is located in the present crater of the volcano.

Recent volcanic activity includes the formation of Lake Vui and Manaro Ngoro explosion craters and cones (some 420 years ago). It also includes N’dui N’dui lava flows, issued from flank fissures, approximately 300 years ago. Possible lahars (devastating mud flows with large blocks and tree trunks rushing down the slopes, which appear when heavy rains occur after an eruption and remove recent ash deposits from the flanks of the volcano) annihilated villages on the SE flanks of the island, about 120 years ago, provoking several casualties. Numerous and thick lahars, probably not older than 100-320 years, may be observed on both toasts in the central part of the island. Possible eruption in 1914 with ash falls and lahars (12 casualties). Formation of a small ash cane in the caldera in 1966.

Activity on December 12, 2005 - image courtesy geohazards.gov.vu

Three anomalous “boiling” areas with large bubbles (10 m in diameter) and burned vegetation were observed at Lake Vui on July, 13, 1991 by a VANAIR pilot. It was the first time he had observed such a phenomenon, and he noted that the vegetation was still green in May. On 24 July 1991, an aerial survey only revealed three areas of discolored water in Lake Vui. Burned vegetation was observed up to the crater rim, 120 m above the water. Thus, an anomalously strong SO2 degassing probably occurred between May and July. This event was unnoticed by island residents.

Aoba probably should be considered at present times as the most dangerous volcano of the archipelago, due to the presence of a large lake in the main crater. Very Young deposits related to strong explosive eruptions as well as thick lahars deposits are frequent in the central part of the island, up to the coastlines. SO, in case of resumption of volcanic activity in the summit area, it Will be wise to evacuate, in a first phase, the population of coastal villages of the central part of the island (in a 10 km radius area surrounding Lake Vui) towards the less hazardous NE and SW extremities of the island. If the eruption occurs near these extremities, or spreads along fractures from central vents towards these extremities (where explosive activity is also possible by magma-water interaction), then it might be necessary to evacuate part of the population to Santo or Maewo- Pentecost.

If the strong SO2 degassing in 1991 has not had consequences for local inhabitants, this is probably due to winds which fortunately quickly moved the toxic plume away from the island. Such an event cannot be forecasted.

Some text and pictures : Vanuatu Geohazards

Copyright Vanuatu Geohazards

Volcano information :
Volcano Type: Stratovolcan basaltique – Basaltic stratovolcano
Current Activity: Vanuatu Volcanic Alert Level 1
Last Known Eruption: 2009
Summit Elevation: 1496 m

James Daniell CatDat activity history
1670 : many people killed
1870 : many people killed
1914 : 12 people killed

Activity video
To give you all an idea how the volcano activity could look like from the air, we show you this (extremely short) YouTube video from Modreneia channel. The video was uploaded on November 2, 2006