Sun, Sea, and Sarakiniko

The volcanic island of Milos is a horseshoeshaped gem rising out of the azure waters of the Aegean Sea, where the geological tourist will never be bored.
This article appeared in Vol. 11, No. 5 - 2014


White Neogene submarine layered ash flows have been intruded into by darker Quaternary lava flows. At the base of the cliff the intruded andesite has formed hexagonal columns. (Source: Jane Whaley)

What do you want on a holiday?

Beautiful quiet beaches? Milos has more beaches than any other Greek island, ranging from small coves with volcanic sand to long white stretches backed by mulitcoloured cliffs. Plenty of sunshine? With a Mediterranean climate, you are sure to be happy. Stunning scenery? Steep rocky cliffs and inlets, beautiful white hilltop villages and a central mountain rising to 750m with wonderful views in all directions will definitely satisfy. Peace and quiet? With the western half of the island virtually inaccessible except by boat, and no large hotels or package tours, even the most unsociable tourist will be able to get away from it all. Some antiquities to excite the imagination? As the place where the famous Venus de Milo was discovered, and with evidence of habitation dating back over 3,000 years, you are not going to be disappointed.

And for the geotourist? Something to wonder at round every corner. Let me take you on a short geological tour of this beautiful island.

Plugs and Craters

Location map showing Milos in the Cyclades group of islands of the Aegean Sea. (Source: B. WInslade). The best way to arrive at Milos is by boat – about three hours by fast ferry from Athens – as this allows you to slowly appreciate the scene as you sail through the large bay in the centre of the island into the small main town of Adamas. At a first glance, this bay resembles a classic flooded caldera, the centre of an extinct volcano, as in the similarly shaped volcanic island of Santorini 100 km to the east, but the bay was created through faulting and erosion.

Rising above Adamas, the whitewashed houses of the village of Plaka can be seen winding up to a castle perched at the top of a steep-sided 200m high hill. This is a Lower Pleistocene volcanic plug, the result of magma rising through the Earth but cooling in situ rather than erupting, and exposed when the softer surrounding ash and other sediments eroded away.

Volcanism was initially centred in the western half of the island, when undersea volcanic explosions resulted in large domed structures, the oldest being the rhyolitic Profitis Elias complex (3.08 Ma), followed by the deposition of a series of predominantly submarine volcanics including ignimbrites and tuffs with ashy layers. These are overlain by sub-aerial Quaternary andesitic to dacitic (depending on silica content) lavas, tuffs and pyroclastic flows.

The eastern half of the island is slightly younger, with primarily Late Pliocene–Quaternary volcanics overlying probably Mesozoic crystalline basement. There were a number of main centres of activity, including Filakopi in the north-east, which formed about 2.66 Ma. in a submarine environment, unlike the northern Trachilas and southern Fyriplaka complexes, which date from between 0.5 and 0.1 Ma., by which time much of the present day island of Milos was above sea level. Both of these exhibit visible crater rims composed of successive layers of ash, sand and lava flows, with evidence of occasional marine inundations.

  • Milos from the air, looking south, showing the white cliffs of Sarakiniko in the forground, the central, faultbounded bay and Profitis Elias as the peak in the background. (Source; Jane Whaley)

  • Small coves and isolated beaches, with volcanic sand and multi-coloured cliffs. (Source; Jane Whaley)

  • Abandoned sulphur mines at Paliorema. (Source: Richard Roscoe)

  • Kleftico. Layered tuffs with evidence of synsedimentary deformation. (Source; Jane Whaley)

  • Complex Mesozoic greenschist outcrops at Paleochori, highly altered by fumarolic activity, resulting in multicoloured cliffs. (Source; Jane Whaley)

  • Abandoned manganese mine at Vani. (Source; Jane Whaley)

  • Layered submarine and subaerial ash flows, Paleochori. (Source; Jane Whaley)

Multicoloured Cliffs

The headland to the south-east of the Fyriplaka crater is an exciting stop for the visiting geotourist. Composed of Lower Pleistocene brecciated lava flows overlain by ‘green lahar’, a volcanic mud and debris flow, the rocks have been highly altered by hydrogen sulphide-rich gases escaping to the surface via vents known as fumeroles. These are easily spotted; apart from the unmistakable ‘bad egg’ smell and the steam rising from them, the vents are surrounded by bright pink, yellow and light green crystals and are hot to touch. You can still see the old kaolin mining galleries here. Fumeroles are present in a number of other locations in Milos.

Brightly coloured rocks, the result of geothermal and hydrothermal alteration, can be seen at a number of coastal locations, one of the most spectacular being Paleochori in the south-east. As well as the hydrogen sulphide which is responsible for these colours, the gases causing this phenomenon can be rich in arsenic, carbon dioxide and methane. They reach the surface via fractures and vents, which are also present offshore.

Pirates and Pumice

One of the most visually stunning places to visit on Milos is Sarakiniko on the north coast, where the stark, dazzlingly white rock formations contrast vividly with the gaudy colours of Paleochori. These are formed from thick beds (up to 100m) of white diatomite and pumice tuffs, alternating with thinner layers of greyer pumice tuffs and pale yellow, shallow marine Pliocene limestone. Differential wind and water erosion has sculpted these soft layers into pillars, mushrooms and other shapes, in which almost horizontal layering and bedding is clearly seen, together with minor faulting and slumping evidence of earth movements.

The people of Milos have taken advantage of the soft nature of the rocks underlying much of their island by digging into it to make stores and boat houses, known as syrmata, sealed by brightly coloured wooden doors.

There are no paved roads in the western half of the island, but many boats offer tours around the coast to the ‘pirate cove’ of Kleftiko on the south-west tip of Milos – a recommended trip, as the western coast offers much for the geologist to wonder at. Kleftiko itself is very picturesque, with caves and arches carved out of Neogene tuffs, large and sheltered enough for pirates to hide their boats in, and best explored by swimming in the clear turquoise water.

Important World Source

Unlike the rest of Greece, the Miloan economy is booming, and did not suffer in the recent recession. This is not due to a massive influx of geotourists, although geology is indeed responsible, as volcanic processes have produced a range of rare metals and minerals. These resources have been exploited since 9,000 BC, when Neolithic man used the obsidian found near Adamas and in the east of the island for tools and weapons. Commonly called ‘volcanic glass’, obsidian is formed when viscous high temperature lava cools very rapidly.

Milos is the world’s most important source of perlite, which forms when volcanic ash cools rapidly, trapping water. Perlite expands 20 times in volume when heated to about 950°C, becoming light and porous and making an excellent sound and heat insulator. It has been extracted through open cast mining in Milos since the 1950s. Disused mines are found on the island, but careful environmental reinstatement means that they blend in well with their surroundings. Bentonite, a plastic clay generated from the alteration in situ of volcanic ash, has similar insulation properties, as it swells when coming into contact with water. It is used in oil drilling and civil engineering projects.

As hot volcanic fluids rich in molten metals made their way to the surface, they cooled and metals such as manganese formed, along with smaller amounts of silver and lead. From 1890 to 1928 manganese was extracted at Vani, on the north-west point of Milos, and exported directly onto ships at the mine. It is an interesting spot to visit, with plenty of evidence of the mine workings remaining, but is a remote spot, so a pair of hiking boots is recommended.

As already noted, alteration of the volcanic deposits by hydrothermal activity produces sulphur, which has been exploited in Milos since the time of the ancient Greeks, only stopping in 1958 when it became easily obtained as a byproduct of petroleum refining. At Paliorema on the east coast one can explore the deserted mines, where the old galleries used in sulphur extraction can be seen climbing up the walls of a steep ravine, with the rocks showing the typical bright colouration of hydrogen sulphide alteration.

  • Bentonite, a plastic clay generated from the alteration of volcanic ash is used in oil drilling. (Source: Jane Whaley)

  • Paliorema Sulphur mine. (Source: Richard Roscoe)

  • Hydrothermal activity produced sulphur, which has been exploited in Milos since the time of the ancient Greeks. (Source: Jane Whaley)

  • Layered submarine and subaerial ash flows. (Source: Jane Whaley)

  • Shining blindingly white in the Greek sun, the ravine, cliffs and pillars of Sarakiniko show clear evidence of recent tectonic movement. (Source: Jane Whaley)

  • Thick beds of white diatomite and pumice tuffs. (Source: Jane Whaley)

  • Light coloured volcanic ashes deposited in a submarine environment were overlain by a darker, subaerial mudflow, and eroded to form these interesting rock formations on the north-easternmost point of Milos, near the village of Pollonia. (Source: Jane Whaley)

  • The 'pirate bay' of Kleftico. (Source: Jane Whaley)

  • Spectacular scenery and geological wonders, Kleftico. (Source: Jane Whaley)

Proud Heritage

The people of Milos are rightly proud of their geological heritage, and also grateful for the employment and wealth it has brought them. There is an excellent mining and geology museum just outside Adamas, well worth a visit, as well as an interesting archaeological museum in the town, where you can learn about the long history and the many interesting archaeological sites of the island. A number of geological routes have been identified and described on annotated maps, obtainable from the museum or online (, a commendable and really useful initiative.

There are also, of course, beautiful beaches, colourful villages, excellent Greek food and many a taverna in which to rest after all that hiking and geology. 

As I said, what more could you ask for in a holiday?

Further reading:


Many thanks to Bernard Cooper, Horus Petroleum, and Richard Roscoe, Photovolcanica, for assistance with this article.

A Quaternary volcanic plug is at the centre of the highest point on Milos, Profitis Elias, surrounded by Pliocene to Quaternary pyroclastic lava flows with a number of cones and extrusive centres. In the foreground are the Neogene tuffs that form the cliffs and caves of Kleftiko, a safe haven for pirates in the past. (Source: Jane Whaley)


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