Ischia is an island consisting of several volcanoes, which rises for about 900m from the sea floor, in the north-western part of the Gulf of Naples. Eruptions have occurred until 1302, the year of the last event: the accumulation of volcanic products has thus built an island about 46km2 wide that reaches a maximum height of 787m above sea level, at Mount Epomeo.
Most of the island is constituted by deposits of both effusive and explosive eruptions, which have built volcanic buildings, some of which are still clearly visible in the south-eastern sector of the island, others completely dismantled or buried. Landslide deposits are also widespread, resulting from the accumulation of pre-existing volcanic material.
Every month the Civil Protection Department organizes videoconferences with the Centre of competence in charge of monitoring the volcanic activity on Vesuvius: the Vesuvius Observatory of the National Institute of Geophysics and Volcanology (Ingv) and the Institute for the electromagnetic survey of the environment (Irea) of the CNR-National Research Council. The Directorate General for the government of the territory, public works and civil protection of the Campania Region also participates in the videoconferences.
On the basis of the phenomena and risk assessments provided by the Centers of Competence, the Department of Civil Protection declares the levels of alert and operational phases in close collaboration with the structure of civil protection of the Campania Region, after hearing the opinion of the Major Risks Commission - Volcanic Risk Sector.
At the outcome of the videoconferences, the Department issues a document reporting the results of the videoconferences.
Currently the level of alert for Ischia is green.
The strong hydrothermal activity - hot waters, gas emissions - and the eruptive history of Ischia, indicate that the island is a volcanic area still active. Currently the volcano is in a state of quiescence; it is however important to keep constantly monitored its state of activity, since 50,000 people live permanently on the island.
On the island there are fumaroles with maximum temperatures close to 100 ° C on the slopes of Monte Nuovo and Monte Cito and along the coast of Maronti. In other localities the present fumaroles instead don't exceed the 46°C.
Every year the seismic stations detect few events of low energy, even if in the past on the island there have been strong earthquakes that have caused extensive damage. In particular, the event of March 4, 1881 caused serious damages to Casamicciola and Lacco Ameno and was felt also in other localities. The earthquake of July 28, 1883 was instead the most catastrophic event occurred on the island in recent centuries: it destroyed most of the town of Casamicciola and was distinctly felt throughout the island with particular intensity in Lacco Ameno and Forio.
The structure in charge of monitoring volcanic activity on the island of Ischia is the Vesuvian Observatory - Naples Section of the National Institute of Geophysics and Volcanology (INGV).
The network consists of systems for monitoring seismicity and soil deformation. Periodic measurements and sampling of water and gas are also carried out
Ischia is a volcanic complex that has had different periods of activity and also gave rise to large explosive eruptions.
The event that has marked the geological history of the island is the eruption of the Green Tuff of Epomeo. The eruption, highly explosive, occurred about 55,000 years ago, and is responsible for the formation of a caldera, which occupied the area where the central part of the island is today. The formation of pyroclastic flows has partially filled the caldera depression, which in the meantime had been invaded by the sea, and has partly covered the areas then emerged.
After the Green Tuff eruption, volcanic activity continued with a series of explosive eruptions until about 33,000 years ago. Approximately 10,000 years ago, after a relatively long period of stasis, the activity continued even in historical times with a series of eruptions. The last one, which occurred in 1302 AD, determined the formation of the Arso lava flow.