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(Taken from the article:" Geological History of Volcano Mt. Tungurahua".- Pub. "The VOLCANIC hazards associated with TUNGURAHUA ".- Corp. Edit. Nacional.-Nov. 2005.-2nd Ed.I.S.B.N.:9978-84-402-3 / Pp. 41-48)

...A research study published by M. Hall. et al. (1999) entitled "Tungurahua Volcano, Ecuador: structure, eruptive history and hazards", has demonstrated that, over the millennia and centuries, Mt. Tungurahua has consisted of a series of THREE successive volcanoes:

"...TUNGURAHUA I. On the basis of radioactive dating, it is been estimated that the 'old' volcanic structure, which we will call Tungurahua I, was built by accumulation of the products of successive volcanic eruptions, and on the metamorphous basement of the so-called Royal Range, some 770,000 – 350,000 years ago. During that period, there was a great sloughing accompanied by an explosion that partially destroyed its structure. Then a colossal avalanche of rubble filled what is today the Chambo valley, forming the existing terraces, which are currently town sites: Penipe, San José de Chazo, La Providencia , Guanando, Pillate and Cotaló. This massive avalanche also dammed up, for a long time, the rivers currently called Chambo and Patate, so a number of lakes must have formed and continued for centuries, perhaps millennia, before these rivers got back to their original courses. Findings from recent research suggest that this event must have occurred about 30,000 years ago ...

...TUNGURAHUA II. After a considerable resting and erosion period, the cone of the intermediate structure built itself, i.e., Tungurahua II; which had a period of activity running from 30,000 to 3100 years ago. Another great explosive eruption has been dated, at about 11,200 years. Finally, some 3100 years ago, it was the 'victim' of a great collapse on its western side, probably due to the steep slopes of this volcano, already quite old, and the intrusion of a volume of dacytic magma into the volcanic edifice, resulting in an avalanche caldera which, according to radioactive dating, is inferred (Fig. # 1). When these two first structures were partially destroyed by major sloughing (sectoral collapse) caused by old periods of activity, the vestiges of which correspond to Tungurahua I and II, and we can observe them on the northern, eastern and southern sides of the current volcano (Fig. # 1).-


...TUNGURAHUA III. Tungurahua III is the current structure, developed after the collapse of Tungurahua II, i.e. about 3100 years ago. Considerable progress has been made in the last few years in learning about the past eruptions of Tungurahua III. Thanks to a major program of dating volcanic material contained in old deposits, using the Carbon 14 method, it has been demonstrated that during this period Tungurahua III, has 'blown' at least 16 times, in eruptions with pyroclastic flows, and about 17 lava flows reaching the bottom of the volcanic structure...".

"A HISTORIC SUMMARY of the most outstanding eruptions of the past...
...Tungurahua III. Its eruptions have been regular, with a moderate or heavy eruption about every two centuries. Activity during the last 3100 years has included lava flows, pyroclastic flows and rubble flows, as well as moderate amounts of pyroclastic material tossed into the air by the volcano, and mainly deposited on its own sides and in the western, northwestern and southwestern sides of this colossus...





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