Report on Yasur (Vanuatu) — 28 August-3 September 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 28 August-3 September 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Yasur (Vanuatu). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 28 August-3 September 2002. Smithsonian Institution and US Geological Survey.
19.532°S, 169.447°E; summit elev. 361 m
All times are local (unless otherwise noted)
An increase in activity at Yasur since October 2001 and the occurrence of a M 6 volcanic earthquake on 29 August at 1500 led scientists to increase the Alarm Level at Yasur to 3. This was the largest earthquake recorded at Yasur since seismic stations were installed in October 1992. Access to the volcano was prohibited and no evacuations were ordered.
Geologic Background. Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous Strombolian and Vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island, this mostly unvegetated pyroclastic cone has a nearly circular, 400-m-wide summit crater. The active cone is largely contained within the small Yenkahe caldera, and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide, horseshoe-shaped caldera associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.