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1301 eruption, which originated the trachytic flow from the Arso,
was the last one to ever happen on the Island. However, the differential
bradyseisms, the earthquakes and the exhalent -hydrothermal manifestations
in particular, show that the magmatic field on Ischia is still active.
There are 29 thermal spring groups distributed on the island territory,
from which 103 springs and 69 fumarolic groups spout. The latter forms
a manifestation that is strictly linked to the previous one since
it is produced by the evaporation from the thermal table. It can be
stated that wherever exhalant phenomena are present there are thermal
waters in the subsoil. The link between the two types of manifestations
is obvious since they both originate from the same thermal table.
Areas with fumarolic fields and hydrothermal springs are distributed
more or less along the whole area behind the coastline, particularly
in Maronti and near the town centres of Ischia, Casamicciola, Lacco
Ameno and Forio. Further concentrations can be found in the internal
area along the western border of Epomeo and the hinterland of Barano
and Panza. It is noted that all the fumarolic and hydrothermal groups
can be found along the volcanic-tectonic lines or in correspondence
of ancient crateral vents. If it is considered that the table temperature,
the level of permeability (to vapour and water) of the complex of
terranes where the table is placed, and the ones overlooking the same,
influence the vaporous manifestations originating from a water table
and their characteristics, , it can be seen how, basically,
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