Figure 6
Oblique view of the 3-D rendered model of the Merapi lava dome, imaged by drone cameras in 2012, 2015 and 2019. The thermal anomaly spot (t1) and the horseshoe-shaped fracture in 2012 has given rise to the site of an explosion crater in 2015. A horseshoe-shaped open fissure formed in 2014 and is visible in the image from 2015. The 2019 data show the new lava dome, mantling and burying the earlier dome structures. This new lava dome erupted in 2018 and began to collapse in 2019 along the fracture system that developed in 2014. The total volume of the 2018/19 dome is assumed to have been twice as large as shown by the 2019 image due to frequent material losses10. Our data imply that the buried 2014 hydrothermally altered fracture system presently exerts a fundamental control on dome stability and associated rock falls and pyroclastic density currents at Merapi. t1 is a local crater that evolved at the high temperature and alteration area seen in 2012 already (cf. Fig. 1). Oblique views were created in Agisoft Metashape (v1.7) (www.agisoft.com).
