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Vanuatu Volcano Alert Bulletin n°2 - Ambrym Activity (14 February 2019)

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Vanuatu
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Govt. Vanuatu
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AMBRYM VOLCANO
16°15’00”S 168°07’00”E Summit Elevation 4377ft (1334m)
Current Vanuatu Volcano Alert Level: Level 2

Ambrym volcano is in the major unrest state. The Volcanic Alert Level is lowered from Level 3 to Level 2.

The current volcanic activity is consistent with the volcanic alert Level 2. This declined activity and the presence of active faults in the South-Eastern part of Ambrym contribute in the change of current danger zones of Ambrym volcano. The danger zones at the caldera is now reduced to 1 km around Benbow and 2 km around Marum craters including Maben-Mbwelesu, Niri-Mbwelesu and Mbwelesu (See Safety Map Fig.1). The Danger Zone for life safety is now limited at the Permanent Exclusion Zone at Benbow and Danger Zone A at Marum. An additional area of risk at the South-East of Ambrym is now identified within 1 km from major cracks(See Safety Map Fig.2).

Latest satellite imagery and observations in the field from 03rd to 09th February 2019 confirm the presence of open cracks and active faults in Paamal village and its vicinity and the uplift at the coastal area of South-East Ambrym. These fractures are oriented in the WSW-ENE direction. Observations of the crack surfaces confirm that there is no steam, no lava flows, not even any smell of volcanic gases in the cracks. A small seashore activity at the edge of one of the major faults ejected small light volcanic stones (pumice) that were washed ashore at Paamal village. Cracks and uplift in South-East Ambrym may be due to the presence of a possible dyke that may form from the drainage of the main craters of Benbow and Marum at the summit and migrating beneath to the eastern part of the island in December 2018. This activity has reshaped the form of the island and may influence the Potential future volcanic hazards impact areas.
These observations also indicate that the volcano activity at the caldera remains with emissions of steam and other gases from the active craters with obvious collapse in areas around the active craters. Lava lakes that used to appear in Benbow and Marum craters have disappeared since 16th December 2018. People from Ambrym and neighbouring islands may no longer see the volcanic glow at night for the next few weeks/months. These observations confirm that the small –scale eruption in the caldera has now ceased.

Though people are not feeling strong earthquakes compare to the past few days in December 2018, current observations and analysis of seismic data recorded from the monitoring network confirm an ongoing seismicity. This is related to the current volcano eruption. This seismicity may continue to affect the existing cracks, especially in the South-East Ambrym area. Latest satellite imagery analysis confirm that there is no continuing land deformation on Ambrym island.

Increase of the volcano seismic activity, followed by the fissure eruption in the caldera and the land deformation of the island started in mid-December 2018, when the Volcanic Alert Level was raised to level 3. Observations of the current activity are consistent with the Alert Level 2 activity. Level 2 indicates "Major unrest ; Danger is now at 1 km around Benbow, 2 km around Marum and 1 km from major cracked areas in the Sout-East part of Ambrym".

The possibility that the Ambrym volcano activity escalate to the level of minor eruption (Level 3) and/or lowered to the lower unrest state (Level 1) is low for now.

Ambrym volcano is a very active volcano in Vanuatu with large caldera of 12 km in diameter and 2 active craters Marum and Benbow. The volcano has been active during historical time at both summit and flank vents, producing moderate explosive eruptions and lava flows that have reached the coast. The larger events include eruptions in 1820, 1894, 1913 or 1929. Over the last seventy years, there are no extra-caldera eruptions. The eruption of 1988 and 2015 are focused in the caldera. The December 2018 eruption was focused in the summit caldera, and affected the Eastern Fracture or Rift Zone with just a ground deformation and uplift, but no eruption occurred there.

All tourism agencies, local autorithies, people of Ambrym and the general public are reminded that due to the curent volcanic activity, changes have been made to the danger zones. Permanent Exclusion Zone at Benbow and the Danger Zone A at Marum are now set about 1 km radius from Benbow and 2 km radius from Marum. Area of these zones are weak due to the seismic activity in December 2018 and volcanic gases may be present. Due to the presence of active faults at the South-East area of Ambrym, communities concerned are advised not to access 1 km from major cracks.

There is a possibility (low) that volcanic activity may start from this area.

See the Ambrym Volcano Advice Key Message at the website

https://www.vmgd.gov.vu/vmgd/index.php/geohazards/volcano/volcano-info/resources

Villages of Ambrym may experience impacts volcanic gases plumes and acid rains when it rains, especially those exposed to prevailing trade winds.

The Vanuatu Meteorology and Geohazards Department continues to closely monitor this volcano activity. More information will be provided as soon as necessary.

Note: « Posted sign » : Signs will be installed later at the locations shown on the above image.

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