Vanuatu

Vanuatu Volcano Alert Bulletin n°7 - Ambae Activity (September 24th 2020)

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AMBAE VOLCANO
15°24’0”S 167°50’0”E Summit 4908ft (1496m)
Current Vanuatu Volcano Alert Level: Level 1

Ambae volcano is continuing in the minor unrest state. The Volcanic Alert Level remains at Level 1.

The Ambae volcano activity is continuing at the low unrest level, consistent with the Volcanic Alert Level 1. New scientific analyses suggest that the Ambae volcano activity is likely to continue at this level of minor unrest. Volcanic hazards remain at the summit area and creeks (e.g. remobilization of remaining ash from 2017 and 2018 eruption).

Some volcanic hazards do remain on Ambae island. These are related to the presence of weak layers of volcanic ash remaining at the summit and elsewhere on the island. The danger zone for life safety at the summit area remains limited in the Danger Zone A (See Ambae caldera safety map below). This danger zone (Danger Zone A) is about 2 km radius from the 2017-2018 active vents. An additional danger zone is within areas of flowing creeks during heavy rain.

Latest observations and daily analysis of the Ambae seismic data from the volcano monitoring system confirm that Ambae volcanic activity conditions remains stable and its activity is continuing in the minor unrest level. There is no obvious emission of volcanic ashes or gases from the eruptive vent(s) of Lake Voui (like it was in 2017-18).

The volcanic ashes that fell on Ambae during the 2017 and 2018 eruption will continue to influence the behaviour of streams and creeks when it rains. The creeks and streams can produce floods and carry debris (sands, gravel and boulders). The flow path of streams and creeks could change due to the flood debris. Landslide may also occur at some areas during heavy rain fall.

The Volcanic Alert Level (VAL) for Ambae has been at Level 1 since 23th September 2019. Observations of the current activity are consistent with the activity of the Volcanic Alert Level 1. Level 1 indicates ‘Minor level of unrest; Danger area remains at 2 km around the volcanic vents and within the area of flowing creeks’. With this current volcanic activity, it is a useful reminder that eruptions can occur at any level of unrest with little or no warning.

Ambae volcano is a very large volcano and is frequently active. A large-scale eruption about 400 years ago built a volcanic cone in the summit crater and that crater is now filled by Lake Voui; however, the modern active vent area is now within the volcanic cone that grew in 2017-2018. Historic activity is poorly known, but there is documented activity in 1530, 1670, 1870, 1915 and 1966. All documented activity has been from the summit crater (Lake Voui) except for the 1670 activity, which included a flank eruption producing lava flows at Ndui Ndui. The 2017-2018 eruption episode started in 1991, with eruptions in 1995, 2005, and 2016 leading to the 2017-2018 activity.

All tourism agencies, local authorities, people of Ambae and the general public are reminded that the danger zone (Danger Zone A) remains at the summit about 2 km radius from the 2017-2018 active vents due to the presence of weak layers of volcanic ash remaining at the summit caldera and elsewhere. These weak layers can collapse at any time into the volcanic crater. In addition, the presence of remaining volcanic ashes elsewhere in the island (deposited during the eruption), can be moved by rainfall. The villages located near flowing creeks (dangerous flow zones) can continually expect changes in stream behavior and larger than normal flow rates during heavy rains. People of Ambae Island need to beware of the dangerous flows while approaching these creeks during heavy rains. More information about the volcanic hazards can be found on the website:
http://www.vmgd.gov.vu/vmgd/index.php/geohazards/volcano/volcano-info/re....

The Vanuatu Meteorology and Geohazards Department will continue to closely monitor this volcano activity. More information will be provided when necessary.

For further information, please contact Geohazards Division at the Vanuatu Meteorology and Geohazards Department at geohazards@meteo.gov.vu or 24686.