The Heat of the Earth: Fumaroles and Thermal Waters

A volcano that heats the water

Italy's Civil Protection Department describes Ischia as a still-active volcanic area, as shown by intense hydrothermal activity in the form of hot water and gas emissions. Heat from the deep magmatic system warms the water circulating through the island's rocks; where fractures and faults provide a way out, the water rises to the surface as a thermal spring and the steam as a fumarole. To understand how this landscape formed, read The volcanic origins of Casamicciola.

The fumaroles

Fumaroles are jets of steam, often mixed with other gases, that escape from cracks in the ground. According to the Civil Protection Department, on Ischia they reach temperatures close to 100 °C on the slopes of Monte Nuovo and Monte Cito and along the Maronti shore, while elsewhere they do not exceed 46 °C.

Monte Cito and the alum route

The fumarole field of Monte Cito, at around 220 metres above sea level, is recognisable by the ground, which takes on colours ranging from white to purple to deep yellow. It is crossed by the Sentiero dell'Allume (Alum Trail), which follows the old Via dei Carri (cart road): along this route alunite, the mineral from which alum was obtained, was carried to the Caulare area, where the processing tanks still survive, and then down to the port of Casamicciola.

The fumaroles of the Rotaro and the coast

Fumarolic activity can also be found on Monte Rotaro, along the Maddalena Trail, and on the eastern coast between Bagnitiello and Castiglione, where it seems to form a single system with the hot springs. In the past some fumaroles were harnessed in the “stufe”, the natural sweat rooms of the spa establishments.

Casamicciola's four hydrothermal basins

• Gurgitello basin, on the eastern side of Piazza Bagni, at the foot of the Ombrasco hill: seven springs with saline-bicarbonate-alkaline waters between 60 and 65 °C. In the 16th century the physician Giulio Iasolino called it the “queen” of the island's waters.
• Cotto and Sinigallia basin, on the western side of the same square, with springs between 50 and 60 °C.
• La Rita basin, at the bottom of a ravine that forms part of an ancient crater, with waters between 60 and 72 °C.
• Castiglione basin, on the eastern coast, with springs emerging near the sea at around 70 °C.

These waters gave rise to the town's spa vocation, as shown by historic establishments such as the Antiche Terme Belliazzi and the Antiche Terme Manzi.

Hiking tips

Fumarole areas have hot and at times unstable ground: always stay on marked trails, keep away from the steam vents and wear hiking boots. The Alum Trail is about 8.4 km long and takes around three hours, starting from Fango and ending in Piazza Maio.