About 290-270 million years ago, as a consequence of the magmatic processes, the porphyries of the so-called "Piattaforma Vulcanica Atesina" (Atesina Volcanic Platform) deposited. Afterwards, the eruptions came to an end. The erosion of the volcanos gave origin to sediments which formed the Sandstones of Val Gardena. Then the sea advanced and the deposit of the Bellerophon Formation began where there was a strong evaporation and settlement of calcium sulphate (gypsum).
Continuously varying its own entrances towards the land, the sea caused the settlement of various members of the Werfen Formation.
Atolls even formed, like in the Maldives, whose existence is witnessed by the dolomia forming Pale di San Martino. With the compression that gave life to the formation of the Alps, the folding of the whole block of the Dolomites began, until they totally emerged about 20 million years ago.