Nicolas Steno · Strata
Which layer of rock is older?
That time, that place
A Dane serving as physician to the Grand Duke of Tuscany. One day he was given the head of a huge shark the fishermen had landed, and when he saw the teeth he stopped.
He had seen that shape before. They were identical to the objects people called tongue stones, said to fall from the sky or to grow inside rock of their own accord.
Why this question
Then those stones are shark's teeth. And that raises a hard question.
How does a tooth get inside solid rock? If the rock was there first, nothing could push its way in.
What was found
Steno reversed the order. The tooth came first, and mud settled over it and hardened later.
Several principles follow. In a stack of layers, the lower was laid down earlier. Layers are laid horizontally to begin with. So a layer that is tilted or broken tells you something happened after it was laid.
A way of reading rock as a sequence in time. Using it, he drew six diagrams showing the stages by which the Tuscan landscape reached its present shape. He had said, in effect, that the ground has a history.
Fossils were shapes that grew inside rock on their own
Tongue stones identical to shark's teeth, and tilted strata
He later became a Catholic priest, set science aside, and was in time beatified