From Tropical Sea to Alpine Peaks
Around 250 million years ago, during the Triassic Period, the region now occupied by the Dolomites was a shallow, warm tropical sea called the Tethys Ocean. In this sunlit water, vast carbonate platforms began to grow, forming structures similar to modern atolls in the Bahamas. These were not built by modern corals. Instead, the primary architects were calcareous algae, sponges, microbial mats, and early species of scleractinian corals. Over millions of years, the accumulation of their calcium carbonate skeletons and other marine sediments built up massive platforms, some rising up to 1,500 meters from the surrounding sea floor.
The rock that forms these mountains is primarily dolomite, a calcium magnesium carbonate mineral, CaMg(CO3)2. This mineral gives the peaks their characteristic pale, ghostly color. The process of dolomitization, where magnesium-rich water alters the original limestone, likely occurred soon after deposition in the hypersaline, evaporative conditions of the Triassic sea. The dramatic vertical walls and towers seen today, such as in the Sella Group and the Sciliar/Schlern formation, are the direct remnants of these ancient platform margins and reef fronts. Volcanic eruptions periodically interrupted this process, depositing darker layers of rock that contrast with the pale carbonate, a feature still visible today.