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The fascinating story of the gypsum outcrops

The Messinian gypsum outcrops are the park’s most significant geological feature and the basis on which the protected area was instituted. They are part of the geological formation known as the Gessoso Solfifera Formation. The gypsum of the Bolognese outcrops is also referred to as selenite, due to its moon-like glow, and it occurs as clusters of large crystals having characteristic swallowtail or spearhead shapes. Chemically, it is a salt, calcium sulfate dihydrate (CaSO4.2H2O), and, together with other salts, it constitutes the standard solution of seawater, from which it precipitates during prolonged periods of evaporation. During the Messinian age (roughly between 6 and 5 million years ago), the Mediterranean underwent several periods of isolation from the Atlantic Ocean, probably due to the lowering of ocean levels, and during these periods the high rate of evaporation caused the Mediterranean to desiccate, transforming it into a vast, white salt bed.