The Volcanic Origins of Casamicciola

An island made of volcanoes

Ischia is a volcanic island of about 46 km² that rises some 900 metres from the floor of the Gulf of Naples; its highest point is Monte Epomeo, 787 metres above sea level. According to the Vesuvius Observatory of Italy's National Institute of Geophysics and Volcanology (INGV), the oldest dated rocks are about 150,000 years old, and the island's history unfolds in several eruptive phases separated by long periods of calm. Casamicciola, on the northern slopes of Epomeo, is an excellent place to read this history in the landscape.

The Green Tuff and the caldera

The event that defined the island's geology was the eruption of the Monte Epomeo Green Tuff, dated by INGV to about 56,500 years ago. The eruptions of that period caused the central part of the island to collapse, forming a caldera that was partly filled by volcanic deposits and then flooded by the sea. Marine sediments built up on the floor of that basin.

Epomeo on the rise: resurgence

From more than 33,000 years ago, new magma intruding at depth pushed the central block upwards. Monte Epomeo rose by about a thousand metres in successive phases: one of the most pronounced and most studied cases of caldera “resurgence” in the world. That is why the green tuff, laid down in the caldera later flooded by the sea, is now found at the island's summit. The resurgence is bounded by fault systems, which have shaped the slopes of Epomeo facing Casamicciola and Lacco Ameno.

The last 10,000 years: the Rotaro and its craters

Over the last 10,000 years activity has been concentrated mainly in the eastern part of the island, with at least 34 eruptions in roughly the last 2,900 years. The most recent eruption, that of the Arso, dates from 1302.

Looking east from the Casamicciola coast you can clearly make out Monte Rotaro, one of the few volcanic centres on the island that was active several times during this period. INGV identifies at least nine eruptions there, with the eruptive centre shifting northwards over time:

• an early pumice cone, whose deposits are exposed in the Puzzillo quarry, dated to between about 8,500 and 6,200 years ago;
• a lava dome, partly dismantled by later explosions that opened the Fondo d'Oglio crater;
• the pyroclastic deposits of the Bosco della Maddalena (Maddalena Wood) and a small lava dome;
• finally, two lava flows that reached the sea to the north, near Punta La Scrofa.

Next to the Rotaro is the Montagnone, while west of the town Monte Cito is home to a fumarole field.

Walking through geological history

Many of these places can be explored on foot: the Maddalena Trail crosses woods that have grown on the Rotaro's volcanic products, while the trail from the Maio towards Monte Epomeo climbs onto the block uplifted by the resurgence. Along the way you will also come across signs of the island's inner heat, such as the Monte Rotaro fumaroles: we describe them in The heat of the earth.

An active, closely monitored volcano

Ischia's volcano is currently dormant. Seismic activity, ground deformation, water and gases are monitored by INGV's Vesuvius Observatory, and Italy's Civil Protection Department sets the island's alert level at green.