Grotta di Masaniello - Atrani

The Masaniello cave and new discoveries
The territory of Atrani is enclosed to the east and west by two ∆-shaped slopes open towards the sea, overhanging and deeply engraved by the Dragone valley in a natural setting of incomparable attraction. Human settlement has shown a clear tendency to concentrate in the lower area but has not completely escaped the adverse morphological conditions. While the eastern side is sheer, the western one has preserved a morphology with jutting and isolated spurs where small shelves have formed. On one of these at approximately 130 m above sea level. the Sanctuary of Santa Maria del Bando rises, almost suspended, and is, practically at the same altitude, a short distance away as the crow flies the Masaniello cave, an integral part of the church's heritage. In this area, following the reclamation works, new caves and forms of karst erosion and sedimentation have surprisingly come to light.

Karst morphologies

1) The Masaniello cave.

This historic cave consists of a single cavity similar to an ellipsoid whose major axis is slightly inclined to the left (photo n 1), where a calcareous-dolomite bank emerges which, more resistant to the action of chemical dissolution, has limited growth of the cavity downwards. The internal rock surface has an angular and chipped appearance, not rounded due to the resistance of the dolomite. The rock is crossed by fractures of modest length (leptoclasis) which intersect, dividing it into protruding and angular elements, with pre-established separation, which have played a role in the formation of accessory carbonate structures. The karst phenomenology manifested itself with the formation of stalactites, more or less tapered (photo n° 1), rich in concretions and nodules which give it an asymmetry and an apparent twist. The development of these forms was affected by factors not of a chemical nature (crystallization force), but by air currents and vibrations, so that the external supply of calcium carbonate was greater on one of the sides of the concretion which did not grew along a vertical axis symmetrically to form concentric layers of ring-shaped calcite crystals.
The irregularities on the surface of the vault have favored irregularly shaped nodular calcitic deposits and concretions, elongated downwards due to the force of gravity (fig 1) constituting pseudo-stalactites. On the right side of the entrance there is a stratiform formation which, with a wider base, rises a few meters up to the floor with a sloping side facing outwards rich in limestone encrustations which mask its original morphology. This element ends with two columnar shapes of different sizes, more or less squat, similar to stalagmites. Stalagmitic deposits can form without the corresponding stalactite: this happens when the water circulation in the ceiling fractures is rapid and the drops do not have time to deposit the carbonate at the edges of the ducts. Continuing inland, two large stalactite forms stand out which are a residue of chemical erosion along vertical fracture planes.
It may happen that the stalactites may fall due to excessive weight or vibrations amplified by the cavity which acted as a sound box; no pieces of stalactites have been found that fell from the vault, also due to the limited and uneven basal morphology.

The lower cave system

Below the limestone-dolomite bank, a system of caves and cavities has developed which, although belonging to the same rock formation, was shaped at different times and in different ways (photo no. 1). The structure is made up of two rooms, the right branch is larger than the left one located just below (fig. 2). Near the first room, before the entrance, a rocky wall extends covered by deposits of wall scrolling, enclosed and shaped like a round arch, perhaps an embryonic attempt, in the writer's opinion, by the Cenobites to complete a more extensive project . The layer of encrustations with a brownish color could be examined for a possible verification of the presence of colors from the time of the settlement. Under a smaller cavity you can see thin stalactites like acicular druses, grown in a similar way to organ pipes (photo n° 2). The genesis of these delicate shapes depends on a slow dripping of rivulets and fillets aligned on a single lesion
The first compartment has a roughly triangular shape (photo no. 3) with a height of 3.20 m, a width of 4.10 m and a depth of more than 8 m. The action of chemical dissolution manifested itself with various forms of cavities even of the size of the mc, with knotty stalactites and protuberances determined not by the force of crystallization, but by the co

conditions of the non-quiet precipitation environment, including the circulation of air currents. The walls are covered with layers of calcite which have erased the pre-existing angularities of the rocky surface, the concretions have the shape of drapery, marked by rounded ridges and vertical corrosion grooves.
On the right side, stalagmitic deposits rise from the floor (photo n° 4) with a variety of geometric styles with a conical profile with growths of large rounded nodules. The initial growth phase occurred on a calcite disk formed in a pool of water, subsequently the deposits merged, creating a crust that covers the entire formation. In adjacent cavities, conical stalagmites of a few cm were found fed with a pseudo meatus by a porous areal source covered by moss.
Particular attention deserves a massive pillar located at the beginning of the cavity (photo n°3), fusion of a piece of stalactite clearly distinct from the underlying stalagmite. The base of the latter structure is connected to the parent rock by crystalline limestone flows deposited by rivulets of water still rich in crystallized calcium carbonate and clearly visible along the sides. The stalagmitic body has the appearance of a conical trunk ending in a mushroom-shaped head whose circumference reaches approximately 2 m, the height from the floor measures 1.30 m. The stalactite, 92 cm long, has a notable section, then the growth stopped, the same phenomenon happened to two others hanging laterally.
Separated by a dome-shaped rise in the bottom (right side photo n° 3) the left cavity, flattened in the innermost part, gains volume towards the outermost area with a width of approximately 4.10 m and a height of 2 m. The floor has a slope that becomes an inclined plane beyond the entrance (photo n°5). This morphology was favored by the stratification in banks of considerable power whose position is oriented in a south-east direction. At the junctions of the layers, excavations and linear erosions occurred (photo n° 5 left below) modeled by the water flowing on the surface of the layers. The left wall has cavities with a circular shape index because the corrosion proceeded in a symmetrical way, higher up concretions of cemented debris are highlighted, a thin panel of calcite is well developed which masks the irregular underlying morphology. On opposite sides of the floor, two deposits of rags and limestone blocks were found: the purpose is unknown, other than to arrange the flooring, already partially modified, which connects the two rooms.
Continuing to the left, beyond the impervious plane, a vertically elongated cavity was found, protected at the entrance by a columnar shape similar to a stalagmite, with a circumference of 1.40 m, full of welded encrustations which give it a detrital appearance.
Cave formation

The territory of Atrani from the Pliocene to the Early Pleistocene can be imagined as consisting of a block not yet incised (fig. 7 a). With the lowering of the temperature, a cycle of erosion began which leveled the surface, the intense rains brought an influx into the upper rocky levels, saturating them first. The cracks in the limestone, similar to a pipe under hydraulic pressure, were thus enriched with carbonic acid which dissolved (fig. 7b) the rock starting from an embryonic cavity up to the formation of the single elliptical cave. The underlying interlayers of dolomite composition received less influx and offered more resistance to corrosion. In this phase the Dragon, the Paleo-Dragon, began a notable erosion with a U-shaped bed of which the AB section (fig. 4) of the valley profile remains evidence.
In the Lower Pleistocene, the block broke up with a system of faults that delimited the slopes, severing the Masaniello cave (fig, 8). The erosion of the Paleo Dragone began on the fault lines, whose transverse profile had the typical U shape in the A-B section (fig. 3 and 4)
In the Middle Pleistocene there was a rapid rise of the right (M. Aureo) and left (M. Civita) orographic massifs with the definitive identification of the slopes and on them cataclastic zones (thicknesses of deeply fractured rock). The collapse of the intervening crustal plate gave rise to the aforementioned ∆ morphology, on the left side of Mount Civita the tectonic depression of the Castiglione beach was formed, the trace of this relative movement is the sliding surface indicated in the arrow in fig. 3 The Dragone valley underwent over-excavation due to erosion on the river bed, resulting in a gorge whose profile is shown in section B-C (fig. 3 and 4). In this period the karst cycle continued with the formation of stalactites.
The forces that caused these new geo-morphologies have dgave rise to a new cycle of erosion: the less intense and longer-lasting rains had a greater penetration into the depths of the rocky masses favored by the rising motion already mentioned. Dissolution reactions were triggered in the interlayer joints, as can be seen in (photo n° 5) of the left compartment, as the water had greater freedom to flow.
The right compartment reached its current shape (photo n° 6) with this mechanism: the dissolution started from the bottom where the waters were more saturated and more reactive and continued upwards following a reverse erosion: the original fracture of the source rock evolved by antigravity erosion in phases 1,2,3 of (fig. 9). Once the floor was reached, the erosion continued laterally, phase 4 (fig. 9), with wall encrustations. At times a sort of canal remained. Further internally you can see a series of small suspended arches, it is the residue of a double fusiform erosion (fig.10) which ended in a similar way on the floor.
Looking at the right orographic slope in the lower band towards the north, a larger fusiform cave can be seen.
The formation of stalactites, which began with the second karst cycle, lasted longer. Their detrital texture and contorted shape indicate that the flowing waters carried small particles and impurities subsequently bonded by calcitic cement, the gray color indicating not pure calcite. The stalactite growth process was interrupted, the supply channels became blocked but the water continued to flow, also welding stalactites and stalagmites of which a magnificent example is the pillar of the first compartment. The left part of the entire karst complex (photo n° 1) was shaped by landslides (effect of the formation of the cataclastic zone) whose detachment niches were preserved on the rock walls and on the lower surfaces of the layers perpendicular to them. The limestone rocks allow the landslide surface to be maintained over time; this geometry at the interlayers is given by the fracture planes (lithoclasis) and they intersect perpendicularly. On the lower surface of the layers, stalactites were formed whose characteristics recall those already examined.
Starting from the town centre, the site can be reached by crossing an initial easy stretch of stairs, then continuing with a second stretch with ramps halfway up the hill from which you can admire the houses shrinking in a fusion of colours. Similar to a joint, the entire town is connected to the Collegiate Church of S.M. Magdalene leaning towards the sea The fruitful reclamation work, desired by the Sanctuary Manager Giovanni Proto, affected the valley area limited by the cultivated terraces. In the Masaniello cave, remains of structures were found, in plan rooms, which testify to a rustic settlement, dating back in all probability to the M.E. The sacred place and the natural history phenomena observable in the karst complex are immersed in the past, when the rugged morphological conditions and the difficult accessibility of this area ensured tranquility and a religiously inspired existence, in history there has always been a close relationship between man and the nature that surrounds him.
Geologist Vittorio Di Benedetto