Grotta di S. Angelo Muxaro

The “Cave of Sant’Angelo Muxaro” Nature Reserve  is located in the inland of the Free Municipal Consortium of Agrigento, at the foot of the hill of Sant’Angelo Muxaro, a gypsum tabular elevation about 350 meters above sea level, where the homonymous town stands.

The area of the Reserve extends over about 21 hectares and is divided in two zones depending on the environmental features and the different use purposes:

• Zone A, the surface area, with the main entrance of the cave, and the sinkhole located immediately to the west (the former known locally as “Grotta Ciavuli” or “Grutta Ciavuli”, and the latter as “Infantino sinkhole”); both are located along the southern slope of the hill of Sant’Angelo Muxaro. Included in zone A are also the underground paths that start from the two cavities, for a total length of about 1.7 Km;
• Zone B includes a pre-reserve area that protects part of the water catchment basins that feed the two karst cavities: these are two blind valleys hollowed out from the clays below the evaporitic deposits.

Since 2015 the karst system, only partially protected by the reserve, has been included, as a multiple geosite named “Karst System of Sant’Angelo Muxaro”, among the Geosites established by the Sicilian Regional Government. Besides the above mentioned two cavities, also the resurgence of the karst system has been put under protection. This is a cavity located at the foot of the north-west side of the hill, from which underground water, flows into the Vallone del Ponte (Bridge Valley), a tributary of the Platani River.

The landscape of Sant’Angelo Muxaro is characterized by rises consisting of sequences of evaporitic rocks (formed by evaporation of sea water and the following precipitation of salts dissolved in it) deposited in the Messinian age, about six million years ago, in coincidence with the isolation of the Mediterranean basin. These sediments are part of the gypsum-sulphur series, widely spread in the South-West of Sicily. The evaporitic deposits are essentially made up of limestone, gypsum and various kinds of salts.

The general morphological structure of the region shows a great variability due to the presence of isolated ridges and reliefs, made predominantly of gypsum, with altitudes ranging from 200 m to 500 m above sea level, rising from the clayey-marl substrate, with steep escarpments affected by various land-falls.

The evaporitic deposits of the area consist mainly of gypsum crystals of different shapes and sizes: selenite, gypsum-alabaster, gypsum-“balatino”, gypsum sericolite, gypsum-arenite. Salt outcrops are instead present to the north of the town, along the Platani River, whose waters are in fact brackish.

Gypsum rocks are soluble in water.  Over time this has caused the formation of a typical karst landscape with medium and large forms, such as sinkholes, blind valleys, etc., and of smaller extensions such as different types of karren.

The main river is the Platani, which flows north of Sant’Angelo Muxaro in an east-west direction. Tributaries of the Platani River are the Gracella Valley (also known as Grovello Stream, which includes Margi Paolino Valley and Ponte Valley) and the Porcospino Valley, located respectively to the west and to the east of the town. The tributary watercourse of the Gracella valley, which feeds the Sant’Angelo Muxaro Cave, flows underground at the foot of the gypsum hill on which the town stands. Water is absorbed by sinkholes present on the side of the gypsum slope, and surfaces from the resurgence of the Ciavuli Cave. After a short distance the watercourse flows into the Ponte Valley (the name derives from the natural bridge – a typical karst construction – present along the riverbed, evidence of ancient sinkholes).

The Ciavuli cavThe major protected cave is locally called “Ciavuli”.

It derives from the Sicilian name for the jackdaw, a bird in the craw family that is constantly present in the cavity.

The cave is part of a karst system, about 1,700 m long, formed by surface waters that flow from the blind valleys into the two sinkholes, and then, after flowing underground, emerge from the resurgence.

Waters disappear underground at an altitude of approximately 173 meters, and spring up at an altitude of about 126 meters.

The cave is divided in two branches: one is active and can be reached by descending vertically, for a stretch of about 10 m, through an area characterized by large blocks of gypsum rock that have detached from the vault. The second branch is inactive – both at the beginning and final sections – and is the best known part of the protected site. The access is via a rolling-plain path through the large entrance hall, lit up by a large opening formed by the collapsing of the vault.

Proceeding along the active branch, about 170 m. long where currently water from the outside is channeled, one enters into an environment where the stream forms suggestive little waterfalls, and then flows into a small siphoning pool, a few tens of square meters wide, with progressively reduced lenticular cross-sections. Along the tunnel, often characterized by mud deposits, splendid crystal formations are visible, as well as a series of karstification features in evaporitic rocks. Such features  include an interesting and rare gypsum column; a spindle-shaped surface concreted with stalactites and a hemispherical dome a few meters in diameter and about 40 cm deep.

The inactive branch is accessible through two overlapping passages, located at the end of the large cave. The first section, which leads into a large collapse hall, is characterized by a meandering passage with an eight-shaped cross- section, probably caused by the fusion of overlying galleries. As for largeness, the collapse room is second only to the cave entrance. From this chamber, through three alternative routes, it is possible to reach again the actual water stream (the two active segments of the cavity are separated by a siphon ). In this part the tunnel has a circular section and an average height of 2 m. The following section develops through a gorge tunnel, where various collapses occurred and there are evident alluvial clay deposits. This branch goes on for about 80 m, overlapping the lower active tunnel, to which it connects, among fallen blocks, in four sectors. Moving on further, the trail passes by areas characterized by large mud accumulations, then it reaches two not very tall lamination layers, after which the tunnel returns to be high enough to stand upright. Along the way, besides viewing splendid gypsum crystals and suggestive sinuous shapes, there are interesting supply chimneys and small collapse-halls. The water that flows down the river, after passing through a narrow, tall and meandering tunnel, merges into a siphoning pool, located in a small chamber on the western side of the main gallery, characterized by interesting layers of selenite.

The final section, beyond the chamber  where the siphoning pool is located, is the non-active portion of the cave, which lies at a higher level than the above mentioned  chamber, and which develops towards the northern side of the gypsum hill. This last branch , at the beginning consists of fairly wide rooms where large deposits made mostly of clay, that have created paragenetic formations, are present. The final section gradually shrinks until it becomes inaccessible, stretching up to a few meters from the surface, just north of the actual the karst system resurgence.

Although caves may seem to be inhospitable habitats, they host a rich and diverse fauna which, in some cases has developed an extraordinary capability to adapt to the underground environment. Regular cave dwellers are the bats, which, although not relegated there, have found in the underground environments ideal microclimatic conditions for wintering, with low and constant temperatures and high air humidity. Many species of these useful insect-eating mammals are now endangered and therefore strictly protected by Community directives.

Research carried out in the reserve has highlighted a considerable faunal interest in the Gracella Valley, in particular in the area called Ponte Valley. The importance of the site is linked to the high number and high conservation value of the species present, which nowadays are considered faunal emergencies or critical issues.

Among the species or populations that require special protection, along the Grovello Stream, is the Sicilian pond turtle, endemic to Sicily and particularly sensitive due to the delicate balance of the freshwater habitat. Other threatened species are the river crab, widely spread along the Ponte Valley and in the resurgence of the Sant’Angelo Muxaro Cave, is now rare in Sicilian rivers; the Sicilian rock partridge, a species whose population decrease is unfortunately very evident, and which requires proper hunting regulations in Sicily; the lanner falcon, that breeds on small rocky walls above the meadows, its nesting sites need to be carefully monitored in order to avoid illegal removals and disturbance actions.

Finally, the Ciavuli Cave and the various natural cavities present are the roosting and nursing sites for different species of bats; therefore this area deserves to be particularly protected, considering the high sensitivity of this species of mammals.