Approximately 8,900 to 7,600 years ago, water covered the entire coastline, which is now 3 to 7 km wide. The dominant southwesterly and westerly winds, as well as ocean currents and waves, began to form sand and gravel dunes. This created a plain more than 40 km long and 200 to 300 m wide. Gradually, the sand dunes amalgamated, rising above sea level. The dry sand flowing to the coast formed a long island parallel to the coastline, with a lagoon between the sea and the island. The Strait of Roja connected the narrow Littorine marine lagoon and its numerous small estuaries to the open sea. The humid Atlantic climate fostered the development of a rich and diverse flora in the lagoon, which was particularly noticeable between 6500 and 5000. Grassy marshes and wet meadows began to form along the lagoon's shores. Later, the sea level dropped by 1 to 1.5 meters, dividing the lagoon into shallow freshwater lakes, each 2 to 6 kilometers long. The three largest were Lakes Vidale, Melnsils, and Purciems. Approximately 4,400 years ago, a permanent Neolithic settlement with several seasonal cultic settlements was built on the shores of Lake Purciems. One of these was located next to the White Dune. The sand outcrops of the White Dune are the result of human activity. The present-day Pilsupe River serves as a watercourse to the sea, constructed approximately 150 years ago to drain the shallow Lake Purciems for agricultural purposes.
Clay figurine from Pur
Clay figurine f