Introducing the Volcanic Island Nisyros

[BrickFielder]

Introduction
My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles.

Introducing Volcano Nisyros

Reason for Interest
An secret Greek island with rising fumarole temperatures and tectonic activity raises my curiosity.It is not a highly populated Island or much of a tourist destination yet is steeped in human history along with a history of earthquakes and past minor eruptions. I guess being off the beaten track makes it worthy in mind of being more widely talked about.

The setting
Nisyros is one of the most beautiful Aegean islands, still untouched by the tourism growth. It is part of the Dodecanese group of islands, situated between Kos and Tilos. The island extends over a surface of 41 km and its coastline is 28 km long. Its coasts are generally rocky or pebbled, but there are also a few sandy beaches (mainly in the northeastern part). Some sea temperatures around me can reach 60 degrees Celsius due to hot spring waters.  Nisyros can experience the Meltemi Etesian wind through June to August. This is most obvious on the eastern and western flanks of the volcano (known locally as Polyvotis), where trees are bent towards the south from the force of the winds. The wind may be especially strong on the island due to jet effects as it passes over Kos. In many parts of Nisyros you can find hot springs but the only ones that have been subject to economic exploitation are those of Paloi and Mandraki. The use of the waters of Mandraki began in 1870 by Nicholas Apostolidis. After he was cured, he built two rooms and three baths, which he donated to the community of Mandraki. The island is criss-crossed by a dense network of kalderimia, the traditional stone-paved mule-paths that used to link the settlements.

Mandraki is the capital and main harbour where the houses are made of volcanic rock and insulated with pumice stone. The Monastery of Panagia Spiliani is the religious centre of the island. Located above the wild black beach at Mandraki, the largest part of the monastery is set within a cave. The main church is dedicated to the Assumption of the Virgin Mary, while the adjacent chapel celebrates Agios Charalambos.

 

Picturesque Nikia clings to the rim of the caldera, and is said to be the island’s most beautiful village. With its elegant elliptical shape and cobblestone mosaic floor, Porta Square is the heart of Nikia and home to the stunning church, Agios Ioannis Theologos, which has panoramic views into the volcanic craters from its bell tower. Nikia is also home to the only volcanology museum in Greece, with fascinating displays about Nisyros and other Greek volcanoes. The Prophet Elias in Nikia is probably the most beautiful chapel in the Aegean and is located on a hill a bit outside the village of Nikia.

A mountainous village Emporios on the northeast of Nisyros was destroyed in the 1933 earthquake, but is today regarded as the heart of the island. At the heyday of Emporios there were more than 3000 people living there and this was the commercial hub of the island, which is kind of hard to believe as it lies on top of a hill and quite a distance from the port were all the goods are coming from. Built on layers of lava, ash and pumice, this traditional village is home to the medieval castle of Pantoniki and the Taxiarhis Church with its rich frescoes. There's even a cave that's used as a natural sauna. Houses have been built in and around the castle, on top of each other, and in a jumble along the hill, but only 25 or so are still lived in. 

Paloi the youngest village is the other coastal town with a sailing marina and was the destination for refugees from Emporios.The sandy beach of Paloi is shaded by tamarisk trees and popular with local children. 

On Nisyros you will get to taste traditional dishes like pitia (chickpea nuggets),kapamas (stuffed goat) and of course fresh fish. To accompany your meal  you can have a refreshing soumada (almond-based soft drink), kanelada (cinnamon-based soft drink) or koukouzina (high alcoholic drink). 

The Tectonic environment
The island belongs to the Hellenic Orogenic Arc, which is formed along the convergent plate boundary of the northwards subducting African plate underneath the active margin of the European plate. As a result of subduction and extension, significant magmatic activity occurred in the past. The subducting African plate’s rocks are dehydrating and as a result of the high temperatures that the plate encounters as it descends deeper the African plate remnants are melting. The melt that is produced has a lower density than the surrounding rocks, and as a result, ascends toward the surface, penetrating the overlaying Eurasian plate rocks. Nisyros developed within a graben (rift) formed by the localized twisting and stretching of the plate causing the seabed to sink and the melt from below to percolate through.

The Volcano
The small round island of Nisyros is one of the more active but less known volcanoes in Greece. It is located south of the popular beach holiday island of Kos. The last eruption of Nisyros were phreatic explosions in 1881-87. They left a moonscape with colorful craters and very active fumaroles. A Magma chamber below Nisyros is only 3-4 km deep and still rising up. Since 2000 when the Nisyros research program of the GEOWARN-Team started, the temperatures of the fumaroles have been changing from 98 C to 103 C in 2004. There was also a high tectonic (earthquakes) activity in the last years and so a program to prevent volcanic hazards is still ongoing. The biggest and most impressive crater on the island of Nisyros is called Stefanos, and is the center of attention for most tourists as it is one of the biggest and best preserved hydrothermal volcanoes in the world. The crater is ellipsoidal in shape its longest axe being 330 meters in length while its shortest is 260 meters. Its walls culminate at 30 meters while it is estimated to be 3.000 to 4.000 years old. The island has a 3-to-4 kilometre wide caldera, and was formed within the past 150,000 years, with three separate eruptive stages. This caldera is divided into two parts: the NE one (Lakki), featuring lush vegetation, and the SW one (Ramos) which hosts intense steam emissions. 

Past Eruptions

It is believed that the volcano erupted in 1442. In 1872 an eruption ocured accompanied by several earthquakes,  the volcano emitted red and yellow flames and ashes covered the ground of Rammos. During the eruption of 1873, a 6 to 7 meters crater was formed and ash and mud spewed out. The ground of Lakkoi and Rammos were covered with hot salty water that came out of the crater. The most recent eruption was in 1888 which formed a cylindrical aqueduct of volcanic elements with a minimum diameter of 25 meters. They left a moonscape with colorful craters and very active fumaroles.

Recent Activity
ter a repose time of several years, intense, shallow seismic activity started at the end of 1995 in the volcanic region of Nisyros island. By the end of October 1997, hundreds of shocks had been recorded, the largest one being that of 27 August 1997. A  focal  migration  was  found  from  a  region  situated  off  of  the  NW  coast  of  Nisyros  towards  the  central  caldera.  This  was  interpreted  as  the  brittle  response  of  the  volcanic  edifice  to  an  inflation  of  a  magma chamber located to the NW of the island. In January 2003, the crater of Nisyros was declared off-limits to visitors. Temperatures in the hydrothermal system had increased from 210°C to 315°C, there was continuous microseismic activity as well as changes on the surface. The ban on visitors was prompted by a crack on the volcano that almost tripled in length over one year (but was apparently not of volcanic origin).

Discussion

The historical hydrothermal eruptions, the present chemical changes of the fumaroles and the physical phenomena affecting Nisyros could represent long-term precursors of a new period of volcanic unrest, which might culminate in a magmatic eruptive phase. However the type of earthquake swarms so far are thought to be typical of calderas that do not culminate in a volcanic eruption.