Tephra fall at Tungurahua Volcano (Ecuador) – 1999-2014: An Example of Tephra Accumulation from a Long-lasting Eruptive Cycle

Abstract

Tungurahua volcano awoke in 1999 after 75 years of quiescence, and its activity continues at the time of writing (2015). After fifteen years of eruptions, roughly 0.13 km³ of tephra have been released and deposited mainly to the west and southwest of the volcano. In order to describe the activity and understand the implications associated to its tephra emissions, we review the: 1) their distribution, 2) quantification of ejecta, 3) their components and 4) eruption dynamics. Most of the eruptions have consisted of short-lived explosions, Strombolian eruptions, hydro-volcanic interactions triggering Vulcanian eruptions, one Subplinian event and transitional style phases, which is supported by analysis of tephra components. Major tephra fallouts occurred in 2001, 2006, and 2014. The rate of tephra discharge increased almost 2.1 times from the pre-2006 period to the post-2006 period. Tungurahua poses a continuing geological hazard across the adjacent regions, but also it is a natural laboratory for studying long-lasting eruptions and their effect.