Report on Iliwerung (Indonesia) — May 2015
Bulletin of the Global Volcanism Network, vol. 40, no. 5 (May 2015)
Managing Editor: Edward Venzke. Research and preparation by Jackie Gluck.
Iliwerung (Indonesia) Submarine flank eruption during August 2013 accompanied by crater fumarolic emissions
Please cite this report as:
Global Volcanism Program, 2015. Report on Iliwerung (Indonesia) (Venzke, E., ed.). Bulletin of the Global Volcanism Network, 40:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN201505-264250.
8.53°S, 123.57°E; summit elev. 1018 m
All times are local (unless otherwise noted)
A submarine vent SE of Iliwerung, named Hobal, erupted in December 1973-August 1974, August 1983 (SEAN 08:08), September 1993 (BGVN 28:06), and May-September 1999. No further activity was reported from this volcano until August 2013 when Hobal had another short eruption on the 20th.
The Center of Volcanology and Geological Hazard Mitigation (CVGHM) reported that observers at the observation post 6 km from Iliwerung saw diffuse fumarolic emissions from the crater during the mornings from 1 to 19 August 2013. The various seismic signals fluctuated during the month, but 81 shallow volcanic earthquakes were detected between 1606 and 1741 on 19 August. The Alert Level was raised to 2 (on a scale of 0-4).
At 0714 on 20 August 2013 an eruption from the submarine Hobal vent ejected dense white plumes to 2 km altitude that drifted S. Incandescence at sea level was observed at 0746, and the water around the eruption site turned yellow. Fishermen and tourists were not permitted within a 2-km-radius of the activity.
Although seismicity had decreased on 19 August, the observers reported that the diffuse morning fumarolic crater emissions had continued through 1 September. On 2 September the Alert Level was lowered to 1 (on a scale of 0-4).
Geologic Background. Constructed on the southern rim of the Lerek caldera, Iliwerung forms a prominent south-facing peninsula on Lembata (formerly Lomblen) Island. Craters and lava domes have formed along N-S and NW-SE lines on the complex volcano; during historical time vents from the summit to the submarine SE flank have been active. The summit lava dome was formed during an eruption in 1870. In 1948 the Iligripe lava dome grew on the E flank at 120 m elevation. Beginning in 1973-74, when three ephemeral islands were formed, submarine eruptions began on the lower SE flank at a vent named Hobal; several other eruptions took place from this vent before the end of the century.
Information Contacts: Indonesian Center of Volcanology and Geological Hazard Mitigation, Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).