Evidence Of Incremental Growth In The Vulsinian Calderas (Central Italy)

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Journal Article: Evidence Of Incremental Growth In The Vulsinian Calderas (Central Italy)

A comparative work on the Vulsini calderas has been carried out, fundamentally from volcanological field study, drilling and gravity anomalies data. On the basis of a detailed stratigraphy, four volcanic complexes have been recognized in the Vulsini Volcanic District from the oldest to the youngest: Paleo-Bolsena, Bolsena, Montefiascone and Latera, the latter two complexes having a contemporaneous evolution. In their activity, each complex gave rise to several little calderas caused by piecemeal collapses due to moderate-size explosive eruptions or coherent subsidence of a superficial piston-like block. Nevertheless, the extensional volcano-tectonic regime affecting this area could have accounted for as much of the total subsidence as the caldera-forming eruptions. Bolsena and Latera calderas, respectively 16 km and 8 km in average diameter, represent the main depressions of the Vulsini District and their topographic features are still well preserved. Several collapses forming the main poligenetic calderas of Bolsena and Latera are masked at present by the Bolsena Lake, the younger volcanic covering, the lacustrine deposits and erosion in a minor amount. Only the little Montefiascone and Vepe calderas, which represent the youngest collapses of the Vulsini area, have not been masked. Bolsena caldera could be considered a depression caused mostly by a subsidence hinged to the southwest, by down-sagging and by collapses which occurred after the most important explosive eruptions of the Paleo-Bolsena, Bolsena and Montefiascone volcanic complexes. Meanwhile, Latera caldera is mostly due to a piecemeal collapse linked to several moderate-size ignimbrite units which were emplaced throughout the explosive activity of the Latera complex. Therefore, the Vulsinian calderas did not form by catastrophic eruptions, because several and frequent moderate-size eruptions, downsagging and tectonic hinged subsidence concur, indicating an incremental growth.

G. Nappi, A. Renzulli and P. Santi

Published Journal 
Journal of Volcanology and Geothermal Research, 1991

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G. Nappi,A. Renzulli,P. Santi. 1991. Evidence Of Incremental Growth In The Vulsinian Calderas (Central Italy). Journal of Volcanology and Geothermal Research. (!) .