Geology: It's What the Cool Kids Do

"Leonardo had an instinctive sense of the vast geological forces that threw up the mountains, raised seabeds to great heights, and changed the form of continents. . .While in the mountains he observed marine fossils (including 'the bones and teeth of fish, which some call arrows and others serpents' tongues') lying in the strata, and wrote at length about the conflict between the presence of these shells and the biblical account of the the Flood. Leonardo's interest in geology must have been well known, for he recalled that 'when I was making the great horse for Milan, a large sackful [of fossil shells] was brought to me in my workshop by certain peasants.'"

From Amazing Rare Things: The Art of Natural History in the Age of Discovery