Mountain and basaltic crater of La Coupe, in the Vivarais, France, from Louis Figuier's The World Before the Deluge, 1867 American edition. This plate illustrates a old flow of basaltic lava, coming down the flank of the mountain. Solidified basalt at the mountain's base is exposed by the river Volant. Formations such as these were held up as proof, in the early days of geologic science, of the idea that basaltic rocks had come to the Earth's surface from its interior.