Muddy volcanoes in the Prut River Basin valleys. Muddy volcanoes were formed in different periods in some valleys of the left part of the Prut River Basin in the territory of the Republic of Moldova. Their appearance was conditioned by artesian alkaline waters which appear on the surface. Such formations have been established in the valley of the Prut River (com. Barboeni, dist. Nisporeni), in the valley of the Delia River (com. Pirlita, dist. Ungheni), on the divergence of the Camenca River Basin (com. Malaesti, dist. Riscani). The muddy volcanoes are active recurrently; nowadays, most of them are at the rest state.