According to a news article, the crater of Nisyros was declared off limits to visitors, due to increasing temperatures and growing surface cracks. Evangelos Layios, the director of Athens University's geophysics laboratory, stated, ". . . earthquakes in 1995-96 triggered changes in the general condition of the volcano. For example, the hydrothermal system has increased in [temperature] from 210 to 315 degrees Celsius, there is continuous microseismic activity as well as changes on the surface of the ground." The ban on visitors was prompted by a crack on the volcano that almost tripled in length over the past year to 139 m.

Geological 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 <24,000 years before present (BP) (Keller et al., 1990) and >44,000 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.

Source: Kathimerini News