Overview

The island of Nissyros is a volcano, located at the eastern end of the Hellenic island arc in the Dodecanese. This arc of volcanoes is related to the northward section of the African plate beneath the Aegean micro plate. Santorini, a better-known volcano, is west of Nisyros the base of the island is made of hyaloclastite, lava flows, and breccias, mostly of andesine composition. Pyroclastic deposits and volcanic domes of dacite composition cap these rocks. The pyroclastic deposits are related to two explosive erruptions of the volcano.

The volume of magma erupted was great enough to cause the summit of the volcano to collapse, making a crater (caldera). The two explosive erruptions were probably several thousand years apart and occurred roughly 25,000 years ago. After the crater formed, eruptions produced the lava domes. It is suspected that the volcano erupted in 1422. In 1871, earthquakes, detonations, and red and yellow flames accompanied an eruption. Ash and lava erupted and covered the floor of Rammos, destroying the fruit gardens there.

During a three-day-long eruption in 1873, a 20-25 foot (6-7 m) diameter crater formed and ash and blackish mud was ejected. The bottom of Lakki and Ramos was transformed into a lake by hot saline water that overflowed the crater. The most recent eruption was in 1888. This strong eruption threw out a cylindrical pipe of volcanic material at least 80 feet (25 m) in diameter. Mud, lava, and steam were also ejected. In 1956, fumes were observed along the west and south sides of Rammos.