The “Macalube di Aragona” nature reserve, located 15 km from Agrigento, in the municipality of Aragona, was established to protect the extremely rare evidence of the so-called “cold mud volcanoes,” whose geomorphological and genetic interest is also compounded by that relating to the mechanisms of methane formation. Scientific research activities promoted by the managing body have also revealed interesting naturalistic peculiarities of the faunal and botanical type.

The territory of the Reserve has been divided into two different areas according to environmental characteristics and different management objectives:

Zone A, covering about 93 hectares, is the area of greatest naturalistic importance related to the presence of mud volcanoes and wetlands as well as the presence of numerous endemic species of flora;
zones B and B1, covering a total of 163.45 hectares, serve as buffer areas to protect the maximum protection zone.
Zone A is interdicted for tourist use and is reserved for conservation and scientific research activities

The territory of the reserve has the typical landscape characteristics of the Sicilian hinterland, with a prevalence of hilly forms with a rounded profile related to the presence of clay-marly deposits, incised by a dense network of shallow valley furrows, traversed in the autumn and winter months by waters of meteoric origin.
In this general context, a circular heath stands out, covered with ashy clays and cracks from which rise, as if resembling a moonscape, small cones from which rivulets of clayey mud flow out: this is the so-called Vulcanelli Hill.

This is a rare geologic phenomenon that, by morphological analogy with volcanic phenomena, is referred to as sedimentary volcanism and is one of the gaseous surface oil manifestations. The gas, due to the pressure to which it is subjected, escapes from the subsurface by crossing such discontinuities, dragging clay sediments and water with it. The material is then deposited on the surface where it gives rise to a more or less regular cone of mud from the top of which gas escapes through a crater. The gas mixture exhaled from the Aragon Macalubes consists mainly of methane, with low concentrations of carbon dioxide, helium and other trace constituents. Their origin is biogenic in nature, which excludes any connection with phenomena of volcanic origin.

The Macalube hillock is also locally called the “Occhiu di Macalubi” because of its circular shape and the whitish color of the crystal dust that is deposited on it by evaporation of the water, rich in salts, that escapes from the volcanos. Periodically, when the normal gas vents become obstructed and the pressure of gas accumulations below the surface exceeds the lithostatic pressure, the hill is affected by explosive eruptions that disrupt the normal flow of gas. During such events, large masses of clayey material mixed with mud, water, and gas are hurled to considerable heights (the term “macalube,” by which the phenomenon is referred to in geology, is probably derived from the Arabic “maqlùb”: overturning, toppling over). The particular rarity and extent of the geological phenomenon give the reserve characteristics of absolute uniqueness.