It is more accurate to describe Nisyros as a volcano than as ‘volcanic’.
Lots of bits of countries are ‘volcanic in that they are have areas of either lava (cooled magma) or igneous rock (rock modified by super-heating) … like Edinburgh Castle which sits on a volcanic plug and much of Cornwall which is granite, though there is nothing active going on at the moment apart from the occasional minor croinking of a fault line..
But Nisyros is still huffing and puffing. The organisation GEOWARN is monitoring things on the island partly because it is still active, partly because of the numbers of tourists who flock here each day from Kos for a quick ogle, and partly because access is easy and monitoring relatively cheap. Since I was last here in 2013 a series of red-pained rocks have been placed linearly in a strict grid across the floor of the Stephanos crater and signs warn that because they are part of the monitoring programme moving them incurs a €20 fine. Not the worst scenario.
Most Greek islands attract visitors to their beaches. Not Nisyros. People flock by small boat for day trips and are whisked up to the rim of the caldera on a coach and then down inside. It’s a bit strange seeing the place treated like a theme park especially as people seem to have no sense that while measures are taken to regulate theme parks in the interests of safety there can be no control over an active volcano. They teeter down the rough path and prance across the crater floor in flip-flops, boiling water, steam and sulphur gas hissing up around them. The only nod to health and safety is a notice at the top of the path saying that you go down at your own risk and this year there is an area of especially large fumaroles with a string fence around it in the centre of the crater floor.
Brief history. Nisyros, at the eastern end of the ‘Aegean Volcanic Arc’ blew its top a long time ago (estimated at 160,000 years). Before then it was estimated to be double the height. Longer ago still it was part of an even larger volcano which encompassed Kos. Between the two is now open sea with smaller islands including Yiali comprised largely of pumice (being quarried away by Lafarge to meet the industrial needs of the world) and Strongyli which is smaller but rising. Slowly.
Nisyros is almost circular with a hole in the middle. The caldera floor, about 4 kilometres across, is some 100 metres ASL at its lowest but within that the Stephanos crater drops vertically another 25-30 metres.
(An apology here. I referred in the last post on the blog to the major crater on Nisyros being Alexandros. Well, of course it isn’t, it’s Stephanos!!!! Mental aberration, confusion between Alexander being Great – Megas Alexandros in Greek – and the size of the crater.)
Most of the tourist interest focuses on Stephanos because it’s the biggest and the coaches park right alongside but it’s by no means the only location of volcanic activity within the caldera.
Nisyros is classed as an ‘active’ volcano and an assessment published in 2010 concludes that in comparison to US volcanoes Nisyros is in the ‘Very High Threat’ category (see). The last major eruption was in 1888 but “more recently, in 1996–1998, Nisyros experienced a volcano-seismic crisis, accompanied by ground uplift of more than 10 cm, indicating a period of unrest”. That seismic activity, recording 5.5 on the Richter scale, damaged 30 houses in Mandraki a few kilometres away on the coast. In 2001 or 2003 (accounts seem to differ) a tremor opened a fissure up to 6 metres deep in the floor of the caldera. The magma chamber under the island is only 3-4 kms deep and still rising.
Indications of seismic activity are confined to the main caldera at the centre of the island but there are other smaller caldera which appear dormant. Within the main caldera activity isn’t limited to the main Stephanos crater but is also found in a number of smaller craters including Megalo Polyvotis and Micro Polyvotis and at various other points around the western end.
That volcanic activity continues is clear from the many fumaroles which emit sulphur gases, crystallising out in weird and wonderful bright yellow encrustations. The temperature of the fumaroles has been increasing, apparently from 98oC to 103oC in 2004. Many years ago I put my hand above one and it was …. uncomfortably hot. Foolishly I did the same again recently. I can confirm it was hotter but couldn’t put a precise figure on the difference!!! Just “ **** OWE! Stupid fool!” There seem to be more sulphur-emitting fumaroles this year than the last time I was here in 2013 though that may be memory playing tricks.
There is also boiling mud and water, though these are less in evidence this year than previously. However water flows hissing out of the ground below an almost microscopically thin crust at well above boiling point and you need to be careful not to linger too long in some areas. Feet can become painfully hot while dallying with a camera.
Not as evident but still a sign that activity continues, are the thermal springs which emerge at various points around the perimeter of the island. Most famous historically is the one at Palloi to which Hippocrates (he of the Oath) who practiced and taught medicine on nearby Kos used to send patients for a cure. Now patients are sent to the establishment at Loutra. You can’t pay to go in as a tourist attraction, you have to be referred by your doctor. At Hochlakos beach there is a rope for non-swimmers to pull themselves out over an underwater spring. At Avlaki there are springs within the tiny protected harbour left by failed industrial activity.
What is it that draws people in their hundreds to spend time and money to walk on the floor of an active volcanic crater? There is no doubt that there is a buzz from knowing that the ground is grumbling, boiling away inches below the sole of your sandals … and may decide to belch at any moment.
Now and again I walk up to one of the non-active calderas at the millennia old deserted settlement at Nifios and sit on a rock looking straight down into the Polyvotis craters steaming away far below and think “wouldn’t it be great if it blew while I’m here”. I may not survive the experience but what a great last memory ….. and what great photos.
The photos below are examples of the continuing volcanic activity of the island. More to follow on the rocks and the settlement history