Exceptionally intense lava fountains at open conduit volcanoes are infrequent, hazardous and little-warned events. Studying their tephra falls may reveal conduit dynamics, eruption source parameters and fragmentation mechanisms. Villarrica Volcano Southern Andes of Chile has sustained persistent open conduit activity, associated with a dynamic lava lake since at least — Increased seismicity and degassing in August were followed by Strombolian activity starting in February and culminated with a 1.
This eruption produced tephra fallout, spatter agglutination, clastogenic lavas and mixed avalanche deposits. Here we characterized for first time Villarrica's 3 March tephra fall deposits produced by lava fountain and its rapid transition to sustained eruption column, providing valuable information on paroxysmal activity in open conduit volcanoes.
Tephra was dispersed southeast of the crater in a narrow, elongated, nearly-elliptic area. At 6—8 km downwind, the tephra fall deposit consisted of a single black scoria layer; fall varied from a lapilli blanket at medial distances 9—19 km to a few individual particles at distal sites 20—43 km.
We estimate that 1. We propose that a rejuvenated, volatile-rich magmatic intrusion probably triggered paroxysmal activity. The Villarrica eruption is classified as a short-lived, large-scale lava fountain, similar to analogous historical events at Mt. As evident by devastating twentieth century Villarrica eruptions which also developed similar lava fountains, this eruption style should be considered as frequent and a potential source of volcanic hazard in the future.
They typically emit lava fragments to heights extending tens to hundreds of meters Bonaccorso et al. Most lava fountains reach — m above the crater e. Their evolution is commonly initiated by Strombolian activity resumption phase followed by lava fountaining, and typically the formation of an eruption column paroxysmal phase , which ends with the waning of the eruption conclusive phase Andronico et al. As fountaining episodes are more frequent at open, passively degassing volcanic systems like that of Villarrica volcano, their onset can be sudden, sometimes with little to no advance warning or signals in monitoring data Ruth et al.
