Hadde ikkje Hardangerfjordbreen mot slutten av istida rykt fram over fjordbotnen, ville Halsnøy ikkje eksistert som éi øy, men som mange småøyar. Breen skuva framfor seg så mykje leire frå havbotnen at Brattåsen, Toftåsen, Landåsen og Svartaberg vart samla i eitt landområde.
Ølve has a special soil type. Here one finds an extra hard clay soil. This is especially noticed by those who work with excavating for building foundations and the like. Often it is necessary to use especially big digging machines and sometimes even dynamite in order to break up the compact masses. The reason for this is the growth of the glaciers toward the end of the Ice Age: The clay, that was first deposited in front of the glacier, came under great pressure when the glacier later grew and slid out over the clay.
Below a south facing, steep rock at Årsand, there is one of the strangest ancient relics in the whole of Hordaland. The jutting rock wall forms a shallow flagstone – Geithilderen. Parts of the rock wall are covered by a light lime crust and on the crust figures have been painted in golden and rusty red colours.