Lammassaari is a delta belonging to the First Salpausselkä’s ice-marginal formation and it began to accumulate around 12,300 years ago. Lammassaari reveals the landscape’s history in three time domains: the 1.9 billion-year-old shore cliffs and 12,000 years old sandy slopes of Lammassaari. The ancient shorelines on the slopes form the third time domain.