Variety in destruction of andesitic lava domes, which were built during the 1998-2017 unrest at Volcán de Colima, México, and the general development of the eruption: Insight from associated seismic signals

The 1998-2017 unrest at Volcán de Colima, México showed a variety in destruction of andesitic lava domes that were formed during seven episodes of the lava-dome eruption. The destructions of the lava domes during six eruptive episodes (1 to 5 and 7) were realized with a sequence of Vulcanian explosions. Another type of destruction of the lava dome, because of a partial collapse of the southern sector of the crater, was recorded during episode 6. This study is based on the seismic signals and video images of destructive events, which were recorded by the networks of Colima University, and demonstrated regularity in the general process of this 20-year eruption. The explosive destruction of the lava domes was studied according to the two-phase conceptual model of explosive process proposed by Zobin et al. (2006a). There were estimated values of durations of the initial phase of the seismic signal, D = t2 – t1, proportional to the length of the way of the magma bubbles from the fragmentation level in the conduit to the surface, where the explosion occurring, and the energy of explosions, E. The temporal variations of these two parameters from episode to episode (in the case of episode 6 with collapse of the lava dome without large destructive Vulcanian explosion, E and D were taken equal to 0) allowed to recognize three destructive periods in development of the eruption. The change in the depth of the feeding magma reservoir was proposed as the decisive element in the change of process of the lava dome destruction. It allows to reconstruct the development of the 1998-2017 eruptive activity as a turbulence of magma deposit with its consumption with every episode of lava dome destruction.