The Lengarices 2023 expedition has come to a close with the return of the final four participants to Ancona.

This expedition, which began on April 19, aimed to continue explorations in areas between Greece and Albania. Back in December and January, we conducted a survey in these same regions to confirm the presence of hypogenic sulfuric acid caves (SAS) and initiated the exploration of three new and intriguing hypogenic caves, two in the Sarandoporos River Valley in Greece and one in the Lengarices Valley in Albania. (These explorations were presented in February at the Scintilena meeting in Narni.)

In the Greek area, three days of exploration led to the discovery of new passages in both caves, adding up to about one kilometer of new branches. The two caves, "Grotta della Rondinella" and "Sistema di Pixaria," now have respective lengths of approximately one kilometer each. Both are active sulfuric systems where we reached the sulfuric water table, in the form of active feeders and deep siphons.

The involved springs exhibit temperatures of approximately 30.2°C, and the caves reflect the significant thermal anomaly, creating strong air currents with temperatures reaching 28°C. These complex airflows can lead to areas of intense condensation.

On April 24, the expedition moved to Albania, specifically to the Lengarices Gorge. Three months prior, we had identified a significant draught with intriguing air temperatures and flow rates (26°C > 5 cubic meters per second). We had explored approximately 500 meters (The Dragon's Breath), focusing on large chambers and shafts at a depth of around -80 meters from the entrance.

The SAS nature of the phenomenon was evident from both internal morphologies and the presence of ten sulfuric pools in the gorge. Just below the previous exploration limit, an additional 20-meter shaft led to the current river level, revealing an incredible network of large and massive galleries.

This active level encounters the sulfuric aquifer in several places, through large feeders and lakes, and in one area, it accesses a true sulfuric river with a flow of about 50 liters per second, flowing through an enormous gallery to create an extensive lake. This active level is characterized by strong air circulation, which has its main "inlet" in "The Dragon's Breath," the first discovered entrance.

The underground atmospheric complexity results in visible condensation effects, including fog and clouds at the thermocline, where the two air masses meet. The wall morphologies clearly show the significance of this phenomenon, with upper sections visibly colonized by bacterial matrices and lower areas characterized by concretions.

In this context, the large lakes act as thermal engines for the system. Corrosion processes due to H2S degassing and condensation are evident throughout the explored area, resulting in substantial deposits of gypsum and sulfur.

Above this active level, the system presents at least three additional gallery levels leading to two other entrances that act as "sucking mouths," introducing "cold" external air into the system. The emerging structure after two weeks of intense exploration resembles a four-level matrix that covers just under half a square kilometer, extending well below the impermeable flysch layers covering the limestone anticline.

The feeding and genesis of the system appear to be almost entirely hypogenic, with internal waters seemingly unaffected by external precipitation, maintaining consistent parameters over time (TDS 1910, pH 6.85).

The currently explored system has a recorded total length of approximately 6.3 kilometers (we are in the process of finalizing measurements), with several hundred meters uncharted. Structurally, about half a kilometer has been explored and mapped in the "Grotta dei Colombi," which effectively serves as a "low" fourth entrance to the system. According to our surveys, it appears to be separated from the main system by only a few meters of rubble, and we aim to connect the two sides during our next expedition, potentially extending the explored length to around 7 kilometers, with numerous leads left open!

For now, the entire system appears to feed primarily from one of the ten pools in the gorge. Temperature, flow, and other data confirm this hypothesis. However, the proximity of two other large, similar pools, with equally significant flow rates, gives us hope that we can further explore within the gorge.

On the other side of the gorge, we've also identified extensive gallery levels, explored for over 1.5 kilometers so far, in non-active areas. Many wall-entry points remain uncharted due to time constraints.

In total, the expedition has explored and mapped over 9.5 kilometers of caves in less than twenty days, with an intense pace that called for "overtime" work even on May 1st!

To begin building a meteo-climatic map of the systems, we continuously measured temperature and flow, and we documented our progress with video and photos. We even experimented with a nerve-wracking drone flight in the large active gallery!

At this point, based on the literature, it appears that the Lengarices system currently ranks among the world's most extensive active hypogenic sulfuric systems, second only to the Frasassi-Fiume Vento system. Given its exploratory and research potential, a new expedition is already on the horizon.

We can say that we had some good luck in discovering this truly amazing place on our first try, but we also can say that we've really earned these kilometers!

Of course, the mantra now is, "Never again without sulfuric!"

The expedition included cavers from all over Italy and beyond: Alessando and Furio from Piedmont; Alessandro, Giulio, Andrea, Giulia, Lorenzo, and Andrea, Nicola, and Iacopino from Tuscany; Hena and Daniele from the Marche; Roberto from Umbria, Andrea from Emilia-Romagna, Pino from Puglia; Christophe and Éric from France.

Andrea Benassi

The water temperature is 30.4°C, while the air temperature varies greatly in different areas, ranging from 20.1°C to 29°C, depending on the proximity of incoming external "cold" airflows.

The large chambers are distinctly stratified, with significant pockets of hot air often overlying pockets of cold air, resulting in continuous temperature fluctuations of over 10°C in just a few meters.

In this surreal environment, you can go from feeling like you're boiling in a steam bath to feeling cold within moments. So far, the only suitable attire to prevent heatstroke after twelve hours in these conditions is typical of warm tropical caves: a short-sleeved shirt and lightweight pants.

Fortunately, the multi-gas monitors we carried with us did not indicate any issues with toxic gas buildup or oxygen levels, as the strong air circulation makes most explored areas reasonably safe, and we didn't need our ABEK masks this time.

The only exception was an unusual level of carbon monoxide, up to 20 ppm, in a specific area characterized by heavy moisture and guano deposits. These conditions may vary depending on the season and airflows.