In a few months I plan to visit Vanuatu and would like to climb the active volcanoes there - particularly Yasur on Tanna island and the ones on Ambrym Island. I was wondering what sort of activity I would find, and if it is dangerous. If anyone has been to these volcanoes, I could use any information they might have.

Mike Lyvers

Dear Mike,

You are lucky it's 30 degrees F out today or my brain wouldn't be able to think of places like Vanuatu (the last month or so it has been about -20 F).

Yasur certainly is the place to go to climb an active volcano. It is a stratovolcano, about 1,184 feet (361 m) tall (shouldn't be too bad). It began erupting some time before 1774 (Captain Cook made the first report) and has be going every since. It has had, at times, a lava lake at a central vent. Some phreatic explosive eruptions have occurred. Eruptions tend to be Strombolian, tossing out bombs, or mild Vulcanian explosions. Ash clouds have reached elevations of 6,500 feet (2,000 m). Although it has caused damage and been associated with a tsunami there are no fatalities reported for Yasur. Yasur is 245 miles (390 km) south-southeast of Ambrym. I've listed some references below.

Ambrym Island is a large shield volcano with a caldera. With an elevation of 4,375 feet (1,334 m) it might be more of a challenge to climb. The caldera formed in about 50 A.D. with an eruption of VEI 6. It is also a very active volcano with 48 eruptions since 1774. Most of these eruptions are at cones inside of a caldera (5.5 by 7.5 miles; 9 by 12 km).The eruptions are explosive and usually from a central vent, There have been a few flank eruptions. Fifteen erupts produced lava flows. Ten eruptions involved a lava lake. There were fatalities in 1895 and 1914. Acid rainfall in 1979 burned some of the inhabitants. Local water supplies were contaminated and had a pH of 5.2-5.5. ... there was also a reference on a web page about black magic still being practiced on the island...

Enjoy your trip.

Steve Mattox, University of North Dakota

Sources of Information:

Greene, H.G., and Wong, F.L. (editors), 1988, Geology and offshore resources of Pacific Island Arcs -- Vanuatu Region, Circum-Pacific Council Energy Mineral Resources Earth Science Series, 8, p. 1-442.

McCall, G.J.H., LeMaitre, R.W., Malahoff, A., Robinson, G.P., and Stephenson, P.J., 1970, The geology and geophysics of the Ambrym Caldera, New Hebrides: Bulletin of Volcanology, v. 34, p. 681-696.

McClelland, L., Simkin, T., Summers, M., Nielson, E., Stein, T.C., 1989, Global volcanism 1975-1985: Prentice Hall, Englewood Cliffs, New Jersey, and American Geophysical Union, Washington DC, 655 p.

Robin, C., Eissen, J-P, and Monzier, M., 1993, Giant tuff cone and 12-km-wide associated caldera at Ambrym volcano (Vanuatu, New Hebrides arc): Journal of Volcanology and geothermal Research, v. 55, p. 225-238.

Simkin, T., and Siebert, L., 1994, Volcanoes of the World: Geoscience Press, Tucson, Arizona, 349 p.

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