The volcano originated as a
stratovolcano in the
Garigliano rift valley, with a group of eruptive mouths spread in a area; later an
effusive activity concentrated in the central area, forming a volcanic cone some 1,800 m-high, mostly formed of
tephra and accompanied by minor cones such as the Monte Ofelio at south-west. Some 400,000 years ago, the collapse of the volcano's eastern sector formed a
caldera which, for some time, was occupied by a
volcanic lake. A second period of volcanic activity began some 385,000 years ago with an
explosive eruption, including eruptions from the former caldera. This phase continued until some 285,000 years ago. The formation of the volcano also modified the course of the
Garigliano and
Volturno rivers. The Volturno moved southwest in what is its current course; the Garigliano no longer reached the sea, and formed a lake (Lake Lirino) until (around 200,000 years ago) it eroded rocks near
Suio and assumed the current course. Although there are current records of no eruptions however geological process varies and pleistocene volcanoes oncd thought extinct rejuvenates. However based on current scientific study, it exhibits there are no current magmatic ongoing activity or seismic unrest hence the eruption index is quite low. However being extinct is relatively vague term as it is too young in terms of geological epoch ==References==