The island belongs to the southern Aegean volcanic arc and is designated as an active volcano together with Methana, Milos (and nearby Kimolos) and Nisyros.
The first elements (minerals in the area, older volcanic cones) on volcanic activity in the region indicate that it existed 2000 years ago. Until the first and largest historically recorded eruption in around 1500 BC, volcanic cones were created in the area and eventually also the Strogyli (Rounded) Island, named cause of its shape.
The first eruption in recent years was in 16th century BC and was also called Minoan. The amount of hurling volcanic material reached a height of 40 km and the whole eastern Mediterranean was covered by ash. The chamber with the volcanic material was emptied, the mountain collapsed, forming the caldera, the amount of land now was lower to that of the sea and thus filled with water.
The archaeologist Spyros Marinatos claimed that the tidal wave that was created was responsible for the destruction of the Minoan civilization.
In the early 2nd century BC a small island, named Iera (Holy), was created. In 46 AD a new island was united with the island Iera, thus created the current Palea (Old) Kameni. In 726 AD a small explosion created a piece of land at the port of Agios Nikolaos. The area still has warm water. This explosion in accordance with myth lovers was a warning for the believes, since the Emperor Leo III's Byzantium was an iconoclast.
In 1459 AD another small island was shaped next to the Palea Kameni, which in the next century will be formed into the Mikri (Small) Kameni.
In 1650 AD an explosion of the underwater volcano Columbo creates a big tidal wave and also gases that cause human deaths.
In 1711 AD eruptions cause the sinking some of Thira’s coast and part of Mikri Kameni. Nea Kameni and the small island Aspronisi are formed.
The 1860’s have a great volcanic activity; Mikri Kameni is joined with Nea Kameni and new volcanic craters are created.
The 20th century is also marked with volcanic activity and pouring lava, like visible through the recent major eruption of 1950.
On the island of Nea Kameni there are currently seven craters, one lies on Palea Kameni and there is also the underwater crater Columbo near Oia. According to scientists, the craters are vital for the stability of the region since they relax the gas chamber of the volcano.
Visitors nowadays have the opportunity to visit the craters of Nea and Old Kameni as well as swim in the hot and sulfur waters, which have many beneficial properties.