Mt. Merapi Threat Level Raised, but Eruption not Imminent

Location of Mt. Merapi. Larger map: maps.google.com

In the wake of a raise in the threat level¹ on Wednesday, April 30, tensions remain high in the shadow of Mount Merapi. In a press release posted on YouTube², Center for Research and Technology Development of Geologic Disaster (Indonesian: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi; BPPTKG)³ head Subiandro cited the increase in seismic activity over the past two days as the reason.

Earthquake activity beneath a volcano tends to increase before an eruption, as magma and volcanic gas is forced through underground passageways and fractures⁴. This causes further breaks and, consequently, vibrations—volcanic tremors or low-frequency earthquakes.

The implication, from both BPPTKG's raising of the threat level from normal to alert and the report of low-frequency earthquakes, is that an eruption is likely to occur. To this effect, Ganjar Pranowo, the Governor of Central Java, is calling⁵ for increased focus on the deprecated state of the region's evacuation routes. Quarries populate Mt. Merapi, its volcanic rock mined and hauled out everyday in large trucks. Over time, these trucks have warped and cracked the roads and bridges, reducing their efficacy. Travel along the volcano's upper regions is already impossible in anything but off-road vehicles.

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Renovation of the roads used by the trucks, as well as regulating the use of—and routes used by—them, will likely end up saving lives in the event of another large eruption. Disconcertingly, however, Ganjar deflected responsibility for the maintenance of the evacuation routes, saying (as quoted by Antara News), "I’m sure that assistance funds from the provincial administration are adequate for the purpose [fixing damaged evacuation routes]. But the evacuation routes are under the authority of the Magelang regency administration, so I hope it will be able to focus on the matter."

Talk of maintaining the evacuation routes therefore at present remains just that: talk. Meanwhile, monitoring continues as life otherwise goes on as normal. Fears of an eruption are also further allayed by observations of the contrast between Mt. Merapi in 2010 and the version of the volcano seen today. Surono, head of the Energy and Mineral Resources Ministry’s geology agency in Jojga, attributes the loud booms heard from Mt. Merapi to the fact that it no longer has a lava dome. According to him, the volcano is still in the process of refilling its magma chamber, which was emptied during the 2010 eruption. This process may account for the low-frequency earthquakes that were recorded.

The BPPTKG nevertheless has a number of recommendations⁶ for residents and visitors:

1. Climbers should avoid Mt. Merapi except for the purposes of investigation and research related to disaster mitigation efforts.
2. Mt. Merapi's status (i.e. threat level) will be reviewed if there is a significant increase in its activity.
3. Residents should be wary of unconfirmed reports regarding an eruption, and follow the direction of local government officials. They can also contact the BPPTKG directly⁷.
4. Local governments should inform the public of Mt. Merapi's current status.

Notes

1. Ari Susanto, "Mount Merapi Alert Level Raised Overnight," The Jakarta Globe, April 30, 2014, http://www.thejakartaglobe.com/news/mt-merapi-alert-level-raised-overnight/.
2. noer cholik, "Peningkatan Status Aktivitas Gunung Merapi 30 April 2014," http://youtu.be/J7KLzgORLRA.
3. http://merapi.bgl.esdm.go.id/; https://twitter.com/BPPTKG.
4. USGS, "Monitoring Volcano Seismicity," http://volcanoes.usgs.gov/activity/methods/seismic/.
5. Suherdjoko, "C. Java, Yogya bracing for more eruptions," The Jakarta Post, May 3, 2014, http://www.thejakartapost.com/news/2014/05/03/c-java-yogya-bracing-more-eruptions.html.
6. http://www.merapi.bgl.esdm.go.id/bpptk.php?page=bpptk&subpage=kegiatan&id=33
7. The BPPTKG can be contacted as follows:
   
   Address: Jalan Cendana 15 Yogyakarta - 55166
   Telephone: (0274) 514192/514180
   Fax: (0274) 563630
   E-mail: office@bpptk.esdm.go.id