Publication Date:
2018-05-07
Description:
The growth of lava domes may cause gradual oversteepening and can lead to gravitational instability and eventual collapse to produce pyroclastic flows that may travel up to several kilometers from a volcano’s summit. At Merapi volcano, Indonesia, pyroclastic flows are a major hazard, frequently involving high numbers of casualties. After the VEI 4 eruption in 2010, a new lava dome developed on Merapi volcano and was structurally destabilized by six steam-driven explosions between 2012 and 2014. Previous studies revealed that the explosions produced elongated open fissures and a structurally delineated sector at the southern part of the dome complex. Here, we investigate the geometry, thermal fingerprint, and hazard potential of the delineated unstable dome sector by integrating drone-based geomorphologic data and forward-looking thermal infrared images. The sector located on the un-buttressed southern flank of the steep dome that is delineated by a horseshoe-shaped structure and we identify intense thermal and fumarolic activity along this structure, hosting the high temperatures of the current dome. From the morphology, structures, and thermal mapping, we conjecture that the horseshoe shaped structure may develop into a failure plane that could lead to gravitational collapse of the unstable dome sector. To further elaborate on this instability hypothesis, we calculate the factor of safety, and run a numerical model of the resulting block and ash flows depositional area using Titan2D. Results of factor of the safety analysis confirm dome instability, especially during typical rainfall events. The titan2D model suggests that a hypothetical gravitational collapse of the delineated unstable dome sector would travel southward for up to 4km distance. This study highlights the relevance of structural development of lava domes, which can affect hazards even years after dome emplacement, and influences the development of thermal and fumarolic activity of cooling lava domes.
Electronic ISSN:
2195-9269
Topics:
Geography
,
Geosciences
Permalink