During a milder period from about 14 2000- 12 800 years ago, Bjørna Fjord and Fusa Fjord were ice-free. The clay, with shells, was deposited on what then was sea bottom, but which today is dry land at Vinnes. In the area from the lumber storage locality at Skåte and southward toward the school on Vinnes, one often finds crushed shell in the hard-packed clay. The shell was crushed when the glacier advanced about 1 500 years later and stopped a bit south of Vinnesholmen. There, it laid down an end moraine that today appears as a tongue out into the fjord (Skagen)made of big stone blocks. The moraine extends from the fishing grounds west of Hatlemnesholmen and right across the fjord all the way to Os. On the land side, it extends from the earthen hill behind the school and up toward the mountain. Silt and clay were carried by the current and deposited on the bottom in the area that now is Vinnesleira and the big lowland plain along the road to Strandvik. Drillings on this lowland plain reveal an over 27 metre-thick layer, mostly deposited when the glacier lay nearby; only the uppermost 6-7 metres are from the years following. The area here (4 metres over sea level) was dry land about 2600 years ago. Later, about 1 metre of peat has accumulated up over the clay.
During the period from 1878 -1923, there was a brick factory in operation at Vinnes. The sea was dammed up so that clay could be removed from the sea bottom. The dams, just inside of the bay where the brick factory was located, are still visible today.
