Orthophoto of the island of Ischia.
Mount Epomeo seen from the sea, Citara side. In particular, the western slope of the resurgent block of Mount Epomeo is visible, entirely made up of the homonymous Green Tufo (TVME; dated ≈55 thousand years ago). TVME is one of the most widespread Late Quaternary pyroclastic products in the Mediterranean. Based on the proximal and distal deposit thicknesses, some studies (eg Tomlinson et al., 2014) estimate a volume of ≈ 40 km3 for the fallout portion, part of the complete pyroclastic pyroclastic sequence.
Punta Imperatore (West-Southwest side of Ischia): the succession of volcanic deposits exposed along the cliff of the promontory.
Location and maximum height: Southern Tyrrhenian Sea - 40° 43' 00" N, 13° 54' 00" E; Mount Epomeo= 787 m above sea level
Surface area (emerged portion): 46.3 km2
Type of Volcano: Caldera
Main types of eruptions: effusive, phreatomagmatic, Strombolian, Plinian
Prevailing phenomena: hydrothermal activity, soil deformation, seismicity, landslides
Beginning of subaerial eruptive activity: >150.000 years
Last eruption: 1302
Activity state: quiescent
Alert level: Basic
Located in the north-western part of the Gulf of Naples, Ischia is the top of a volcanic system that rises more than 1.000 m from the sea bed and reaches a height of 787 m above sea level, at Mount Epomeo. The island is made up of volcanic rocks, landslide deposits and other sedimentary rocks, which derive from the accumulation and cementation of fragments of pre-existing rocks, dismembered by erosion processes.
The volcanic rocks outcropping on the island are the product of predominantly trachytic magmas that have fueled both effusive and explosive eruptions. From the former, lava flows and domes were formed, from the latter extensive layers of ash and lapilli. The eruptive history of Ischia began more than 150.000 years ago and continued, alternating with long periods of quiescence, until the last eruption, which formed the Arso lava flow in 1302 AD. About 55.000 years ago, the violent explosive eruption of the green tuff of Mount Epomeo, fueled by an alkali-trachytic magma, was responsible for the formation of a caldera in the current central part of the island. Since at least 30.000 years ago, a process of uplift of the bottom of the caldera has been established. This phenomenon, known as resurgence, began following the intrusion of new magma (trachi-basaltic) into the volcanic system, and caused the central block of the island to rise by at least 900 m. The phenomenon of resurgence has strongly conditioned volcanic activity, determining the conditions for the ascent of magma only in the eastern sector of the island and along pre-existing regional fault systems. Over the last 30000 years, the rate of uplift due to resurgence has been about 3.3 cm/year. Volcanism in historical times has been particularly intense, with over 46 effusive and explosive eruptions concentrated mainly in the last 3.000 years, and the formation of many monogenic volcanoes around the uplifting block. Most of the recent eruptive centers are located in the depression located east of Mt Epomeo (e.g. Vateliero, Cava Nocelle, Molara, Arso, etc.) while only a few (e.g. those that produced the lava flow of Zaro or the pyroclastic unit of Chiarito), are located outside this area.
Since the last eruption, the volcanic system of the island has continued to show its activity through recurring seismicity, culminating in the disastrous Casamicciola earthquake of 1883 and in that of 2017, and a widespread activity of the hydrothermal system (high temperatures ≈250–300 °C, boiling springs, fumaroles and high fluxes of CO2 from the ground).
link: