In August we posted a report on explorations of the cave complex at Pemonia in Apokoronas and the major caves of Gourgouthas and Liontari. At the same time preparations were being made for another international expedition, to the cave complex of Sternes near Anopolis in the municipality of Sfakia. The two sites are on opposite sides of the Lefka Ori mountain range, which is known locally as the Madares or Madara, from the Cretan word madaros meaning bald or bare of vegetation. The Sternes expedition, the latest in a series carried out since 2017, was organised by the Speleological Association of Crete (SPOK), and a preliminary report from the Association was published on the Haniotika Nea website on 20th November. It is reproduced here, with some of the more technical details omitted for the sake of brevity.

Announcement of initial results of Sternes Speleological Expedition 2025

Greece has now acquired its third cave with a length exceeding 10 km. Alongside Diros, with its unmatched beauty and archaeological importance, and Maara – the cave at the source of the Aggitis with its unique underground river – Sternes now occupies an outstanding position on the map of Greek speleology.

The cave’s impressive depth, its uncounted unexplored galleries and high scientific value demonstrate the wealth and variety of the country’s underground heritage, while at the same time they illustrate the devotion and persistence of the speleologists who continue to widen the bounds of exploration.

The field phase of this year’s expedition to Sternes, which was organised by the Speleological Association of Crete (SPOK), was successfully completed a few weeks ago. We are still at the beginning of preparing the full report, and although we expect the process to last several more weeks, as there is much data to be recorded and interpreted, we understand that the rate of information dissemination in the age of social networks necessitates the publication of some results earlier.

The speleologists of SPOK have been organising annual expeditions to Sternes since 2017, continuing the work of the Hellenic Speleological Association (SELAS) which mounted expeditions in 2005 and in the period 2009-2012. These expeditions in their turn were the first visits to the cave since the original exploration of the area by the Groupe Spéléo d’Orsay in 1988, which discovered the cave and made the first recorded exploration of Sternes in the period 1990-1992.

There follows a summary of the activities and the results of the 2025 expedition, while a fuller account will follow in due course.

Preparatory work
At the beginning of the year, the length of the investigated sections of the Sternes cave complex had reached almost 8 km. The extent of the network was such as to require the establishment of bivouacs at selected points, so that the cavers could spend the night and start the next day as near as possible to the areas being explored. This year the expedition set up three active bivouacs, each comfortably equipped to accommodate four speleologists (and more in case of need). It was the first time in cave explorations in Greece that three bivouacs have been set up.

Bivouac 1 was 570 metres down (about 3 to 4 hours from the surface), Bivouac 2 was 565 metres down in ConCrete Canyon (around 5 to 6 hours from the surface) and Bivouac 3 around 560 metres down in Pandora (around 8 hours from the surface). Bivouac 1 was connected with the base camp through a telephone line which also reached to within 45 minutes of the other two bivouacs.

The first bivouac was set up and equipped during the preliminary expedition at the beginning of August, while the other two were established during the main expedition which began on 23rd of August. The large distances between the points of investigation, and the often labyrinthine nature of the cave, led us to establish signage of the routes with indications of direction and distance to facilitate movement.

This non-exploratory but necessary work was carried out during the first days of the expedition, as was the installation and support of the bivouacs, and the placing of the telephone line to a point near Bivouacs 2 and 3. The work was carried out by members of the expedition who had fewer opportunities for research for the benefit of the whole team, making the expedition a truly collective effort.

Areas of research
This year’s research focused on the following areas of the cave:
1) In ConCrete Canyon: the active meander which brings water from the east and flows down from the Lagonia valley. The exploration proceeded to the east and included many different branches….
2) In the Labyrinth: a particularly complex area which starts from Gaia, the last hall of last year’s investigation to the west of the cave. …
3) Dormant galleries which branch out from the Ichor River: the two main galleries which were explored and mapped from the north of the river Ichor were subsequently named Lara and Markos after the base camp’s dogs. …
4) First Light: the northern branch of the cave, a dormant gallery oriented from east to west and rich in aragonitic crystalline forms….

In total this year more than 2,700 metres of cave were investigated in hitherto unknown areas. In addition 600 metres were remapped, either to improve the definition or to replace old mappings with digital data. The whole length of the cave as investigated and as explored and mapped is now more than 10 kilometres (10,741 metres). These significant results are due to the persistence and conscientiousness of the speleologists who undertook the exploration and mapping this year.

The three bivouacs supported the total of more than 110 overnight stays within the cave and contributed decisively to the extensive investigation, while the very large number of artificial climbs established was also critical for the success of the expedition.

Surface research
Those who were not in the Sternes Cave were not left idle. The members of the expedition worked methodically and systematically in surface research, contributing significantly to understanding of the karstic [limestone] landscape which extends between the peaks of Sternes, Pachnes, Trocharis and Kakovoli. The surface research this year concentrated on three objectives: (re-)investigation and study of particular caves, targeted surface research and general surface mapping .

As regards the targeted surface research, the teams investigated and recorded known and new entrances to caves in selected areas which members of the expedition had identified as interesting on the basis of pre-mapping studies of geological characteristics. This led to the discovery and investigation of a cave from which extremely cold air was was emitted (3.8 degrees), suggesting a possible connection with the underground system 300 to 400 metres lower down.

Another cave was investigated and easily mapped down to 60 metres below the surface, from where it continues, while new entrances and other interesting points were located above ConCrete Canyon. More general surface research was organised around known entrances referred to in older expeditions. This work led to the collection and assessment of data for more than 20 entrances which apart from their location did not in any way constitute accessible features.

During the course of a year’s work the members of the expedition have recorded data for more than 10% of the known entrances of the area of interest. The work of surface research will be recorded and presented as a case study to the Greek speleological community, with the aim of contributing to compilation of a modern and user-friendly “cadastre” of Greek caves, something which would be exceptionally useful both for the speleological community and for the responsible authorities.

Other caves explored
Finally the two big caves of the expedition apart from Sternes, Triplotafki and Vomvospilia, were intensively explored this year.

Vomvospilia (LB OH/LA 13) was known to terminate in a snowbank, according to the only available mapping. In 2009 and 2010, the expedition by the Hellenic Speleological Association (SELAS) had confirmed that the situation remained unchanged. This year however, as the snow bank had gone, the team managed to continue deeper, reaching a depth of 139 metres (while an earlier mapping had reached a depth of 125 metres). Continuing further requires widening of the narrow terminal meander. While it may not be an immediate aim of the next expedition, the cave is nevertheless of considerable interest, since its vertical development is over a geological cleft visible even in satellite pictures.

The exploration of Triplotafki (LXO4/11003) was continued beyond last year’s termination of -140 metres. The cave is now mapped to -200 metres and continues, the exploration having been cut off because of lack of time and equipment. Triplotafki is especially interesting, because it is expected to constitute an “easier” entrance to the Sternes cave complex provided that exploration at a greater depth confirms that there is a connection.

Science
Cave exploration brings together scientists and chiefly citizen-scientists with interests in a variety of disciplines. This year’s expedition once again assembled cave explorers with an interest in different branches of the natural wealth of Lefka Ori, resulting in the collection of useful data for other researchers, namely:

— Measurements of the geological characteristics of fissures which are found in the three caves being studied were carried out with the expedition’s geological compasses. These measurements were taken at many points in Sternes, in the final series of shafts in Triplotafki and in the Vosbilias fissure, as well as at different points on the surface.

— Air temperature measurements were carried out with scientific thermometers accurate to two tenths of a degree both at Sternes and elsewhere. The air temperature inside caves can amplify other information collected by different methods, contributing to the drawing of conclusions on their morphology and especially on the possible existence of unexplored sections.
Apart from the portable thermometers, the expedition members collected data from Tinytag data loggers which have been installed in the caves since 2023. These recordings are part of the Palaeolus research project, which the expedition is collaborating with. The data from 2024 have already given interesting results, while it is expected that this year’s data will further reinforce the understanding of the cave. We hope to extend the network of sensors with the installation of additional units in the future.

– Cooperation with the LIFE Grecabat project of the Institute for Speleological Research (INSPEE) and the Museum of Natural History of Crete at the University of Crete (MFIK) led to the placing of three further sensors/recorders in the cave. A TrogloAir wind sensor was installed in the Beautiful Rosa branch, in order to record the speed and direction of air throughout the course of the year. This point was of special interest, because it appears that a significant body of air is concentrated here from the whole of the cave. In addition the Life Grecabat project provided two TrogloWater appliances to record the conductivity and temperature of water in the Ichor and in ConCrete Canyon.

— The team also carried portable PH and conductivity sensors which were used for measurements in ConCrete Canyon, with interesting results: the water appears more alkaline than expected.
At the same time water samples were collected which will be delivered to the IGCP 715 project “A new approach to karst modelling along different tectonic contacts”, so as to contribute to the study of the Pachnes Thrust. This is a geological phenomenon which has been proposed by the research teams of IGCP 715, to interpret particular discoveries both on the surface and in the interior of the cave. Data from previous missions have already been utilised in support of this hypothesis.

— Radon detectors have been installed at Bivouacs 1 and 3, with the aim of estimating the concentration of radon in the interior of the cave. Additional measurements were carried out at other points inside and outside the cave for purposes of comparison. The data collected to date show that it would be of particular interest to carry out long-term measurements.

– Finally, in the context of the effort to understand the ecosystems which develop in the caves of the “high desert” of Lefka Ori, which are particularly poor in organic carbon, the mission placed traps for invertebrates in Sternes and collected additional samples by hand both there and in Vomvospilia. The samples will be transferred to Heraklion for study.
The traps in Sternes used as bait various foul smelling substances, but it seems that in the end they were found to be almost empty. Despite this, further examination is needed in case microscopic samples were collected which were not visible on the spot. Conversely, collection by hand had considerable success, with quite a few examples of spiders, beetles and isopods both in Sternes and in Vomvospilia. In addition some crane flies (Tipula) and caddis flies (Trichoptera) were collected which seemed to have deviated significantly from their customary environment, since they were found at -500 and -135 metres respectively in Sternes.

The team
All the above was made possible thanks to the continuous and persistent work of the team of volunteers of the Speleological Association of Crete and other speleological organisations in Crete. Many of those who offer their time and their efforts do so without even setting foot on Lefka Ori with us. The support of all the Cretan associations was, for yet another year, of critical importance. Also most valuable was the advice of the speleological team of the Mountaineering Association of Chania (EOS) in the west, the local branch of the Hellenic Speleological Society in Rethymnon and the Mountaineering Association of Sitia in the east of the island. These groups helped with both with volunteer work and equipment.

From the first year that the SPOK took on the organisation of the expedition, more than 160 people have taken part, each of whom made their own small contribution to the progress of the exploration. This year, like last year, we were accompanied by Jeff Gaucher, head of the 1990-1992 expeditions and the first person to map the cave. The expedition was also visited by Kostas Adamopoulos, who had coordinated the SELAS expeditions of 2005 and the period 2009-2012.

The expedition had been supported by successive municipal authorities of Sfakia from 2017 onwards. This year for the first time, the Mayor of Sfakia Ioannis Zervos visited the base camp and the entrance to the cave complex. His appearance underlined the Municipality’s ongoing support and its interest in the success of the expedition. Together with the deputy mayor and two municipal councillors, Mr Zervos expressed the unwavering interest of the Municipal Council and the citizens in the continuation and successful outcome of future efforts.

Until today, the Municipality has supported the expedition by providing transport from Anopolis to the base camp, a task which has been carried out for years by the Glymenaki brothers. Their sister Georgia has also supported the expedition with bakery products; indeed this year she visited the base camp for the first time to offer us (amongst other things) an excellent orange pie. The Sfakian bakery of Giorgos Orfanoudakis has from the first expedition continued to provide us with an uninterrupted supply of bakery products.

Sponsors
Apart from the Municipality of Sfakia, this years’ expedition managed to secure the support of a series of important sponsors and supporters, each of which contributed in their way to our efforts. These include: CDC (caving equipment), Creta Farms (everyday food products), the Giannakaki Brothers (tools), the Zouboulaki Brothers (gas), Cretan Bites (cereal bars and snacks), El Sabor (tortillas), Fresh Snack (croissants and other snacks), Montainclub (caving equipment) and Halkiadakis AE (food). And of course, Avax Computer Applications in Chania, who provided us with access to the outer world through a satellite internet connection.

The team members from the US also secured sponsorship from their National Speleological Society, which was used for the purchase of sleeping bags and mattresses for Bivouac 3. In addition, members of the expedition donated two solar panels with battery and inverter, enabling the expedition to enjoy clean electrical power for charging batteries, the operation of the satellite connection and also for showing transparencies and a film on the last evening at base camp with the use of a projector.

We are also grateful to the 2025 Gourgouthakas-Liontari expedition, which lent us their line telephone sets and offered food. Finally, we express our thanks to the local businesses which supported the expedition with donations: Fragioudakis Yachting NEPA, Fibremax, K.K. Sifakis AE, Aiolos Cruises and M. Kanakakis & Co.

The Speleological Society of Crete (SPOK)
The SPOK was founded by speleologists in 1999 with the aim of exploring and protecting the caves and the karstic landscapes of Crete, as well as the wider natural environment. In addition to a regular cycle of events, expeditions and educational seminars for beginners, the society has been conducting regular international expeditions to the Sternes cave complex since 2017. For more information about the expedition and SPOK, contact info@spok.gr or sternes-expe@spok.gr.

(Haniotika Nea, 20/11/25)
About IGCP 715: www.unesco.org
About the Pachnes Thrust: https://www.episodes.org/journal/view.html?uid=2424&vmd=Full