Indonesia: Sinabung alert level down, Merapi and Karangetang alert levels up

The Volcanological Survey of Indonesia (VSI) has adjusted the alert levels of three Indonesian volcanoes over the past few days: the alert level for Sinabung has been lowered, while the alert levels for Merapi and Karangetang have been raised.

Sinabung, which re-awoke dramatically at the end of August, has seen no further significant explosive activity during the last two weeks but is still producing plumes to altitudes of several kilometres and cyclically inflating and deflating. The government’s evacuation order for the surrounding area remains in force, although many local people have been returning to their homes. Yesterday the VSI reported that ‘the activity of Mount Sinabung showed a decrease according to observations of seismicity, deformation and SO2 concentration’, and accordingly lowered the alert level for Sinabung from the highest level of Red (level 4) to the second-highest level of Orange (level 3). A PDF of the announcement (in Indonesian) can be downloaded from this page on the VSI site.

Merapi, a youthful and highly-active volcano with a deadly history, has been quiet since May 2008. Early this month an increase in seismicity was detected which became more marked over the first two weeks of September. By 19 September the VSI was reporting high levels of seismicity and signs of inflation on the southern flank of the volcano (up to 11 mm per day), and increased gas emissions. After evaluating the observations and data from Merapi, the VSI raised the alert level for the volcano from normal (level 1) to Yellow (level 2) on 20 September 2010.

Karangetang, also known as Api Siau, erupted on 6 August 2010, leaving four people missing and one confirmed dead according to news reports, as a lava dome collapse produced pyroclastic flows that descended the west flank and swept away a number of houses. An ash plume from the eruption rose to 9.1 km altitude. The alert level for Karangetang (contrary to some news reports) was not raised at the time of this eruption but remained at Yellow (level 2).During September Karangetang has continued to display high levels of seismic activity, with an episode of tremor beginning on the evening of 22 September prompting the VSI to increase the alert level from level 2 to Orange (level 3), the second-highest alert level, on 23 September 2010. News reports yesterday spoke of lava being erupted by Karangetang, and ‘thunderous explosions’ being heard by people in surounding communities.

[Thanks to PP for helping with translations from the Indonesian.]

References to volcano alert levels on this blog are not authoritative and are not necessarily up to date. You should always check with official sources for the latest alert levels.

News
Warning status raised as Indonesian volcano heats up – Jakarta Globe, 24 September 2010
Kembali semburkan lava – Indosiar.com, 24 September 2010

Information
Global Volcanism Program: Sinabung – summary information for Sinabung (0601-08=)
Global Volcanism Program: Merapi – summary information for Merapi (0603-25=)
Global Volcanism Program: Karangetang [Api Siau] – summary information for Karangetang (0607-02=)
Volcanological Survey of Indonesia – News and information portal for the Volcanological Survey of Indonesia