Nisyros

Geography & Climate

Nisyros is located in Greece, within the Hellenic Volcanic Arc of the broader European Volcanic Regions. Situated at 36.59° N, 27.16° E in the Northern Hemisphere, the volcano lies within a temperate climate zone. With a summit elevation of 698 meters above sea level, Nisyros is a moderately sized peak that remains accessible to hikers and researchers for much of the year. The volcanic landform is characterized as a composite, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Nisyros sits in a subduction zone, where one tectonic plate dives beneath another, creating intense heat and pressure that generates magma. Subduction zones are responsible for many of the world's most explosive volcanoes and deadliest eruptions. For communities in Greece near Nisyros, this tectonic setting means the volcano is capable of producing powerful explosive eruptions, pyroclastic flows, and lahars that can threaten populated areas within tens of kilometers of the summit. The dominant rock type is dacite, an intermediate to silica-rich volcanic rock. This composition typically produces more viscous magma, leading to more explosive eruptions with ash columns and pyroclastic flows. Andesitic and dacitic magmas build pressure before erupting, which is why volcanoes with this rock chemistry are often associated with Plinian-style eruptions that can send ash tens of kilometers into the atmosphere and disrupt aviation across entire regions.

Eruption History Summary

Nisyros has 4 recorded eruptions in the geological database, spanning from 1422 CE to 1888 CE. The most powerful recorded event was an explosive event producing ash plumes up to several kilometers in 1888 CE, reaching VEI 2 on the Volcanic Explosivity Index. These eruptions span roughly 466 years of volcanic history.

GVP Reference Summary

The easternmost volcano of the Aegean arc forms the 9-km-wide island of Nisyros, which is truncated by a 3-4 km wide caldera. The island was constructed during the past 150,000 years, with three cone-building stages including explosive and effusive andesitic eruptions and effusive and extrusive dacitic and rhyolitic activity. The age of the caldera is variously considered to be less than 24,000 years before present (BP) (Keller et al., 1990) and older than 44,000 years BP (Limburg and Varekamp, 1991). Five large post-caldera lava domes completely fill the western part of the caldera. The NE-most (Boriatiko) and SW-most (Karaviotis) lava domes and flows are significantly younger than the other domes. A sixth post-caldera dome, outside the SW caldera rim, produced lava flows that reached the coast. Historical phreatic eruptions occurred from craters within the caldera between 1422 and 1888. Intense hydrothermal activity continues in the form of many fumaroles on the caldera floor and hot springs along the coast.

— Smithsonian Institution, Global Volcanism Program