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Activity

The volcanoes of Vanuatu are located along a zone of convergence (subduction) of the Australian and Pacific Plates. They are part of the Pacific's "Ring of Fire", which accounts for 70% of the world's volcanic activity. The viscosity of the magma that underlies them gives them explosive characteristics. When a quantity of water is also present, this results in highly spectacular "hydro-magmatic" eruptions. In 1452, the cataclysmic explosion of Kuwae (between the islands of Epi and Tongoa) hurled more than 25 cubic kilometres of pulverized rock into the atmosphere.
Although it is now possible to predict the likelihood of an eruption, it is very difficult to pinpoint the exact timing of the event. Some of Vanuatu's volcanoes are in a state of permanent eruption (islands of Tanna and Ambrym), others, which have been dormant for a few decades, are now showing signs of renewed activity through gas emissions in their crater lakes (islands of Ambae and Gaua). Lopevi, the only Vanuatu volcano lacking a caldera, appears to follow a 15 to 20-year cycle of dormancy and activity. Submarine volcanoes, which will eventually give birth to islands, are evidenced on the surface of the ocean by a discoloration of the water. They may emerge for a time, subside, then reappear to form a new island.

Different volcanological group, including French, New Zealand and Vanuatu, contribute in the studies and monitoring of Vanuatu volcanic edifices. Different approaches (*) were considered including ground base measurements associated with satellite remote sensing. (**). Bulletins (in chronological order below) were released during volcanic crises periods (e.g. Ambae, December 2005 – January 2006) and/or during volcanic high activity phase. (Yasur, 2002; July, 2004).

(*)Yasur is monitored by equipment located on the ash plain, 2 km away from the main crater, which transmits data on the ground movement (volcanic tremors associated with strombolian or vulcanian activity) six times a day to a NOAA-ARGOS satellite. These data have been recorded continuously since 1992, and show the evolution of the activity - and thus the hazard level - of Yasur volcano in real time.

(**) Satellite remote sensing enable the detection of volcanic gas discharge and thermal anomaly (presence of hot corps).