The Thermal Hypogenic Caves of Acquasanta Terme (Central Italy)

  • Sandro GaldenziEmail author
Part of the Cave and Karst Systems of the World book series (CAKASYWO)


The karst area of Acquasanta Terme is located in the eastern side of central Apennine. The thermal sulfidic springs reach the surface in the core of the anticline where the river valley reaches the top of a Meso-Cenozoic limestone succession, capped by less permeable rocks. An important terraced travertine deposit was produced by the thermal water throughout the Pleistocene. The most interesting caves are in the valley of the Rio Garrafo, a tributary of the Tronto River. These caves developed mainly below the valley bottom, and a part of the stream water sinks through preexisting karst passages mixing with the thermal groundwater ~50 m below. Water temperature in the caves reaches 42 °C, and the water has high salinity (up to > 6 g L−1) with elevated levels of chloride, sulfates and carbonates. Sinking water from the caves and the travertine plate is responsible for the significant dilution of thermal water at the main spring, located 2 km downstream, in the Tronto Valley. The speleogenetic process is mainly related to H2S oxidation, which is enhanced by the recharge of oxygenated fresh water from the surface. Cave development occurred in different phases. Early passages formed mainly in the phreatic zone, due to the rising thermal water. Deepening of the main surface stream (Tronto River) caused lowering of the water table. As a result, the Rio Garrafo caves were partly dried and invaded by sinking water, while rising gases activated condensation corrosion and the growth of replacement gypsum crusts.


Acquasanta Terme Hypogene caves Thermal caves Apennine Italy 


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© Springer International Publishing AG 2017

Authors and Affiliations

  1. 1.JesiItaly

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