The Phlegraean Fields- Structural Evolution, Volcanic History And Eruptive Mechanisms
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Journal Article: The Phlegraean Fields- Structural Evolution, Volcanic History And Eruptive Mechanisms
AbstractThe main event within the volcanic history of the Phlegraean Fields was the eruption, about 35,000 years ago, of a huge alkali trachytic ignimbrite (80 km3, dre) followed by caldera collapse. The pre-caldera activity (evidence from geothermal wells and surface outcrops) changed from submarine to subaerial shortly before the ignimbrite eruption. The caldera was subsequently invaded by the sea and became progressively filled with tuffites and subordinate submarine flows in its northern half. The last submarine explosive activity dates back to 12000-10500 yr. with the eruption of mostly "hydroplinian" yellow tuffs. Recent, mostly subaerial, activity consists of a series of explosive eruptions whose volume decreases with time, until the last eruption of Mt. Nuovo in 1538 A.D. Two peaks in recent activity occur at 10000-8000 and 4700-3000 years ago. During post-caldera activity, eruptive vents migrated from the caldera rim toward the center where there are two distinct zones of recent vents. Minor collapses occurred within the caldera after the main eruptions; often they are eccentric to the vent and displaced toward the caldera center. Phlegraean explosive activity is characterized by water/magma interaction; eruptive events without a hydromagmatic component are extremely rare. In most cases, the evolved trachytic magmas interacted with surface water (either the sea or intracaldera lakes). However, there is evidence of interaction of magma with deep-seated aquifers for some Plinian events. Explosivity, i.e. the efficiency of the transformation of thermal into kinetic energy during magma/water interaction, is largely controlled by the primary fragmentation of the magmatic melt.
- M. Rosi, A. Sbrana and C. Principe
- Published Journal
- Journal of Volcanology and Geothermal Research, 1983
- Not Provided
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M. Rosi,A. Sbrana,C. Principe. 1983. The Phlegraean Fields- Structural Evolution, Volcanic History And Eruptive Mechanisms. Journal of Volcanology and Geothermal Research. (!) .