Abstract
Continued post-collapse volcanic activity can cause the rise of a new edifice. However, details of such edifice rebirth have not been documented yet. Here, we present 7-decade-long photogrammetric data for Bezymianny volcano, Kamchatka, showing its evolution after the 1956 sector collapse. Edifice rebirth started with two lava domes originating at distinct vents ~400 m apart. After 2 decades, activity became more effusive with vents migrating within ~200 m distance. After 5 decades, the activity focused on a single vent to develop a stratocone with a summit crater. We determine a long-term average growth rate of 26,400 m3/day, allowing us to estimate the regain of the pre-collapse size within the next 15 years. Numerical modeling explains the gradual vents focusing to be associated with loading changes, affecting magma pathways at depth. This work thus sheds light on the complex regrowth process following a sector collapse, with implications for regrowing volcanoes elsewhere.
Highlights
Continued post-collapse volcanic activity can cause the rise of a new edifice
Within the amphitheater, scattered volcanic activity formed a broad NW–SE elongated edifice that was formed between 1956 and 196735,40–42. This new edifice is separated by a NE–SW linear depression, 200 m wide and 110 m deep, that delineates two consecutive endogenous[43] domes located in the southeast (1st) and northwest (2nd) of the amphitheater, and that coalesced through time[35,41] (Fig. 2a, Fig. 3a, b)
We find that the unloading owing to the 1956 sector collapse favors magma rising towards and beneath the collapse amphitheater ~300–800 m east of the precollapse vent location (0.28 < x < 0.83 km, Fig. 7a), which is in agreement with our photogrammetric observations at Bezymianny and with previous results for the shift of vent location as a consequence of a flank collapse[14] (Supplementary Fig. 7)
Summary
Continued post-collapse volcanic activity can cause the rise of a new edifice. Details of such edifice rebirth have not been documented yet. Worldwide there are only a few cases where cone regrowth after sector collapse had been continuously monitored over decades so that direct observations of geomorphologic and structural changes are limited. The collapse removed over 0.7 km[3] of material from the former edifice[34] and led to a catastrophic eastward directed blast eruption[32] (Fig. 1d) After this climactic episode, construction processes commenced inside the collapse amphitheater[20,35] and continued until today (Fig. 1e, f). Comprehensive petrographic analysis[37] showed that Bezymianny’s eruptive products became continuously more mafic since 1956
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