NISYROS – (re-)Visited

Nisyros: Caldera view from above Nikia village.

So far, when I wrote about volcanoes around the world, I could only dream of ever visiting them. Researching for my first Nisyros post, though, it occurred to me that the idea of a short holiday there was not entirely out-of-bounds. It didn’t take long and I had convinced daughter & granddaughter to come with me. We travelled to Nisyros in October, and, what can I say – it was a wonderful, if too short a holiday! Here are some impressions, thoughts and photos from our visit.

Mandraki, the capital  town, in front of caldera wall and lava domes.

Nisyros is no less than an open-air geological museum. Each stone on the island owes its existence to volcanic action, each of the hundreds of layers of rocks forming the island was placed there by some eruption. Layers are cut vertically by sea erosion all around the shores, there for everybody to admire or study the history of the volcano. Every building, wall or stone paved road on the island is made of its volcanic products.

Volcanological Museum Nikia, Nisyros. (© Tobias Schorr)

In 2010 an excellent volcanological museum opened its doors in the village of Nikia, overlooking the caldera craters several hundred meters below. This is said to be one of the best geological museums in Greece, which I can believe easily. The introductory video leaves a long-lasting impression even on the non-enthusiast (and even non-English-speaking) visitor. All explanations on the exhibits are also given in English. We only regretted that we had not seen the museum first before exploring the volcano.

Schematic of the Nisyros volcano’s innards, shown in the volcano museum

However, if you have not prepared your holiday via internet and planned to visit the museum, you might miss the fact that there is one altogether. It is not mentioned in the outdated (but otherwise very good) visitor guide sold in the shops, and I seem to remember just a placard for it near the main harbour. –

Alighting from the local bus in the town square of Nikia, looking for the museum, it is not obvious for a foreigner that you actually stand in front of it: there’s just a banner hanging down the building’s front, saying something in faded letters. If there hadn’t been an invitingly open door we might have walked away from it. – After two hours of appreciating everything in this great museum I would have liked to ask someone some volcano questions… alas, the lady at the desk didn’t understand me.

Piece of a rhyolite lava flow in the volcano museum.

 

Nisyros Map

Map of Nisyros (original in very large resolution HERE)

 

A Day in and Around the Caldera

3D-IKONOS Satellite image of real monitored data of Co2 emission (hight of the peaks) and temperature (color) from the hydrothermal craters on the Nisyros caldera floor. (Volcanological Museum Nikia, Nisyros)

One day we took a tourist bus up (and down) into the caldera. Our visit was – at least for me – a somewhat taxing undertaking: I had planned on seeing everything and taking lots of photos, yet, a while after leaving the bus I began to feel weak and slightly nauseous. It must have been from the hot sun and the dazzling white reflection all around. Yes, the smell of H2S was overpowering at times, but there was a steady light wind blowing the fumes in the other direction. Anyway, it was an amazing experience; sadly I couldn’t muster the strength to go to all the places I wanted to.

The volcano of Nisyros consists of at least twenty craters, ten of which can be made out more or less clearly and have even been named. These are all hydrothermal explosion craters, located on the remaining flat (SE) part of the caldera floor, called Lakki plain:
We can see, from the youngest,
1 Mikros Polyvotis (1887) – 2 Alexandros or Flegethron (1873) – 3 Polyvotis (1873) – 4 Ahileas – 5 Megalos Polyvotis – 6 Logothetis
7 Mikros Stefanos – 8 Stefanos – 9 & 10 Kaminakia.

Overview of the craters in the caldera of Nisyros volcano.

In spite of the stand I took in my first post, of course, I couldn’t refrain from climbing down into Stefanos crater. It is huge with its depth of 27 m and diameter of 330 m, and, phew, what a smell! The Crater surface is made up of clay-like deposits from the hydrothermal activity. It’s mainly alunite, anhydrite opal(-CT) and quartz, and significant amounts of kaolinite-group minerals. What made me cringe at times was the distinctly hollow sound underfoot when walking on the more gray-stained areas: one could just imagine breaking in and landing directly at the devil’s furnace…

Here are some photos of the day; click on the first one to enter.

Nisyros: Caldera view from above Nikia village.

Sulfur deposits on the outer slopes of Polyvotis crater.

Erosion gully into Stefanos crater.

Overlooking Stefanos crater. (No. 8 in the overview photo)

Pieces of Sulfur along the path. And no, I didn’t take any away, as I have seen some other visitors doing.

The last significant hydrothermal eruptions in the caldera occurred in the years 1871-1888. Present-day activity consists of smelly fumarolic degassing of mainly H2S, CO2, H2O, H2 and CH4.

Walking up to the Polyvots crater group. The rhapsody of colours is a welcome set-off from the blinding white of the pumice and other hydrothermally altered rocks. Yellow is sulfur, orange derives from iron compounds and pink/purple from manganese.

View into the Megalos Polyvotis and Polyvotis (1873) craters. (No. 5 and 3 in the overview photo)

Polyvotis (left) and Mikros Polyvotis (1887) craters. (No. 3 and 1 in the overview photo). Mikros P. is the youngest of them all.

Cracks here in Polyvotis crater, and elsewhere along the main faults in the caldera, could have been caused by deformation through magma intrusion below the island. In modern times, Nisyros showed significant ground deformation between 1996 and 1998. Uplift of 14 cm was recorded, which was partly interpreted as the elastic response of the shallow volcanic edifice to the inflation of a magma chamber. A ground rupture 600 m in length formed in the caldera floor between 2001 and 2002 and another in 2011. Those ruptures have been attributed to stress release along existing faults, sub-surface erosion or magma intrusion; they could be a result of a combination of any or all of them.

Several feeder necks (or plugs) from vents of past volcanic activity are exposed through erosion on the inner and outer slopes of the caldera. None of the others I have seen is corroded such as this one. It stands above the Stefanos crater directly in the flow of the emanating volcanic gases which have eaten big holes in the rock on its affected side.

The village of Nikia perches several hundred meters high above the caldera. It enjoys not only a rare view over the landscape and sea, but also the stench of the fumes that rise from below.

View over the SW part of the caldera, where the domes of the latest magmatic activity can be seen outside the caldera on the far left.

The village of Nikia is built on ancient lavas and incorporates rock boulders and volcanic necks into its structures.

The rocky slopes just above the last houses of Nikia.

View into the caldera from the village of Emporios. On the right are three of the five huge lava domes rising from the NW part of the caldera. The area left of the road (center) is where in 2001-2002 a 600m ground rupture opened in the caldera floor. Behind, barely visible under the fumes, is the large Stefanos crater.

 

 

“Upper Pumice” on Plomos beach. It begun with the pumice deposits of a Plinian eruption and wavy surges, then followed by a pyroclastic block flow of 6-20 m thickness.

A Day by the mighty Pumice Cliffs

Another day took us to a beach near Katsouni Cape, on the northeastern side of Nisyros. Here are the mighty pumice cliffs, offering some impressive views.

The first catastrophic subaerial eruption shaped the island around 25,000 years ago. Within a few days, 8 billion tons of molten rock were hurled into the atmosphere producing over 20 billion cubic meters of pumice and ash. This layer is called the “Lower Pumice” on geological maps and reaches several tens of meters of thickness. After a period of lava flows and dome growth a second devastating explosion of Nisyros, approximately 15,000 years ago, added new layers, the “Upper Pumice”, on the island.

Click on the first image to enter:

Pumice is formed when molten lava (here rhyolithic lava) cools quickly. It is porous, containing tiny bubbles of air, and floats in water. It is very light in weight, usually a dusty white or pale gray. The Latin word “pumex,” from which the name pumice is derived, means “foam”.

“Upper Pumice” on Plomos beach. It begun with the pumice deposits of a Plinian eruption and wavy surges, then followed by a pyroclastic block flow of 6-20 m thickness.

Pumice – close up

A lava flow stretches out from below the pumice layers on Plomos beach. (Note how the girl holds a sizeable boulder of pumice on the fingertips of her right hand… hmm, is it really a rock?)

Near Katsouni Cape: Each pumice formation is divided by a paleosoil horizon (reddish) indicating waning stages in the volcanic activity. These are enormous banks of pumice surge deposits and one can hardly imagine their catastrophic effect when they were laid down on the island.

Near Katsouni Cape

Caves in the cliffs caused by sea erosion.

Layers…

Shrunken and wrinkled lava boulder at the beach.

I am not sure what this material is, on top of a cliff, is it also pumice? Could it be perlite?, a chemically and physically altered obsidian. I have heard perlite has been mined on Nisyros for export. Perhaps one of our readers can identify the material?

Amazing shapes…

 

Exploring the volcanologically oldest part of Nisyros: the Northwest. Click on the first image to enter.

Before landing on Kos we flew over Yali (Giali) island, NNW of Nisyros. This is an Upper Quaternary rhyolitic volcanic edifice. The very young age (probably Neolithic) of the last explosive eruption of Yali, leads scientists to consider it a potentially active volcano. Here two volcanic cycles deposited masses of rhyolitic pumice, followed by an extrusion of obsidian-perlitic lava domes and flows. Pumice and perlite are mined in a big style, there won’t be much left of the island in few decades…

Mandraki town, in front of caldera wall and lava domes.

One huge eye-catching erosion cave in the uplifted cliff above Mandraki town. There must have been a layer of softer material within the cliff which then has been eroded out by the elements.

Black pebble beach (Chochlaki) at the NW corner of Nisyros. An ancient castle and a monastery sit on top of the oldest rocks of the island. They are a mixture of altered and brecciated seafloor sediments and volcanic products. Chunks of pillow lava make the dark roundish inclusions in the cliff face. The whole rock has been uplifted from sea bottom by tectonics, i.e. the rotation of a fault plane.

The oldest lavas of Nisyros (basaltic andesite pillows, tubes and pillow breccias in “potato sack” morphology) can be seen from Chochlaki beach near Mandraki town. Lavas with pillow structures were emplaced in submarine conditions but they are now exposed.

The oldest lavas of Nisyros (basaltic andesite pillows, tubes and pillow breccias in “potato sack” morphology) can be seen from Chochlaki beach near Mandraki town. Lavas with pillow structures were emplaced in submarine conditions but they are now exposed.

The oldest lavas of Nisyros

The Paleokastro (ancient castle), built from the 6th to the 4th century BC on the hill overlooking Mandraki town with heavy basaltic andesite lava blocks.

Paleokastro: The huge volcanic slabs interlock tightly; they are up to 3.5 meters long and weigh some 3-4 tons (note red pen for scale).

 

Elsewhere on Nisyros there be dragons… Click on the first image to enter.

Yes, I have seen a “Nisyros dragon” – minus its tail. Even so it was 25-30 cm long. Stellagama stellio is also called hardun, painted dragon, sling-tailed agama, or kourkoutavlos in Greek. It is very shy and you might only get a glimpse of it when you manage to sit still and keep quiet for a quarter of an hour or so.

Hidden inside a small cave in the village of Emporios is one of the island’s “apyries”: natural saunas, fuelled by steam (36-40°C) escaping through vents in the ground. Some of the residents have included such a sauna within their houses, where it also provides natural heating in winter.

Natural saunas in Emporios: as you go to the “door” and look inside you already feel the hot humid air billowing out.

Everywhere in towns and villages of Nisyros you find these lovely pebble mosaics. They adorn paths and steps, make patterns or pictures, and you feel almost ashamed stepping careless on such beautiful artistic work.

All of Nisyros’ roads are prone to unexpected rock falls from its loosely consolidated slopes – I have seen many during my short stay on the island. Here a rolling boulder has been caught between two trees, probably after crossing the road a few meters above.

Big lava boulders are as common on the slopes as massive pumice is elsewhere. This one again lies just beside a road. Most lava looks very vesicular with big bubbles.

At Afionas: an andesitic and dacitic tuff cone sits on top of a dacite lava flow.

Several hot springs and fumaroles can be found at the shores around Nisyros. From pre-Christian and Roman times to the early 20th century Nisyros had been a favored spa locality with ten times as many inhabitants as today. The ruins of historic saunas and baths can be found throughout. Here on the southern shore in the former village of Avlaki. (Author not found)

An andesitic volcanic neck outside the caldera rim (cut open on the roadside, probably a former quarry) marks another eruptive center. Lavas erupted from here once covered the entire island.

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So, you can see, we had a really great “field trip”. We, that were one volcanoholic, one less geologically inclined person and a 10-year-old who had quite different ideas of fun. Yet, we all enjoyed Nisyros – including its volcano. We had a lovely host (thanks, Renata!) and, even though it was already late October, it was still warm enough for a good swim. Nisyros has so many different things to offer, there must be some fun in store for every visitor.

On the path to the pre-Christian Palaeokastel, S of Mandraki

In spite of its rich geology, the residents of Nisyros don’t make much of it in terms of attracting interested visitors. Yes, in summer there is the constant flow of day tourists that ferry over from Kos Island. They get carted into the caldera by busses, have two hours time to see “everything” and have a meal, and off they go, back to the ferry. Even though the word “volcano” is omnipresent with every tourist related business on the island, there is literally no information, nothing pointing out (or even explaining) the geological treasures along the way. So I wonder – what had become of a proposal, made in 2007, to assign the status of National Park and Spa to Nisyros island? If this would get through, it could greatly help develop ecotourism (instead of pouring masses into the crater) and create informative nature trails on the island.

In this image one can see the five large rhyolithic-dacitic lava domes crowded into the caldera of Nisyros volcano. (© anaema.gr/nisyros/) Good bye Nisyros, nice to meet you, hope to see you again!

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Correction/Update:

Nisyros Island, booklet

I have to take back my claim that there is “literally no information, nothing pointing out (or even explaining) the geological treasures along the way”. I don’t know whether there is info “along the way” (I didn’t see any myself) but, back home now, I stumbled over this little booklet on the internet (published by the Greek Geological Institute in 2009) describing 10 Geotrails on Nisyros:

“Nisyros Island”

Following on from there I found a website “under construction” http://www.nisyrosvolcano.com/, which looks promising so far. Perhaps this will become a site to keep an eye on.

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Disclaimer: I am not a scientist, all information in this (and any of my other posts) is gleaned from the www and/or from books I have read, so hopefully from people who do get things right! 🙂 If you find something not quite right, or if you can add some more interesting stuff, please leave a comment.

Note: All photos in this post are copyright of the author – except where stated otherwise. Please contact Granyia if you want to use one or several of them.

 

Enjoy! – GRANYIA

 

SOURCES & FURTHER READING
– Geology of Nisyros Volcano (Book, 2017, Active Volcanoes of the World series)
– Visit Nisyros
– Nature Discovery/Nisyros
– Ground deformation of Nisyros 1995–2002 (2005)
– Ground deformation of Nisyros-Yali 2002-2012 (2015)
– Management of the Natural Environment of Nisyros […] (2007)
– Water-rock interaction in the magmatic-hydrothermal system of Nisyros (2010)
– Very detailed Map of Nisyros
Added:
– “Nisyros Island” (Geo-trails)
– Nisyros volcano website