Paleorooms, so called because they represent a static position of the Caves of Frasassi through the times, represent the primordial stage of sulphureous water reaction over solid limestone. In the point where sulphureous water and river cold water met, took place the reaction ,with a mix carbonate waters that made limestone walls melt and causing chalk deposit after solution saturation. These paleorooms have always a bell shaped transversal section which should refer to a complete erosion cycle of river Sentino and to the whole hydrography. Paleorooms, if not interested by water filtering or dripping, don't present any limestone concretions but they are rich of white chalk deposits (Manhattan room).
Developed or collapsed rooms represent a further stage of the formation of the combination. After repeated erosion cycles of the river, reflected inside the Cave forming several stages represented by paleorooms, came a period of stasis of the position of Sentino's river-bed. Then the reaction zone could work always at the same altitude enlarging the paleorooms horizontally. Because of this phenomenon the limestone vault lost its support and it collapsed. Its collapsing took to the union of a great room.