Geology
Fossils, Stone, and the Deep History of the Earth
In every concavity at the summit of the mountains we shall always find the divisions of the strata in the rocks.
— Leonardo da Vinci
Overview
Leonardo's geological observations are scattered through several manuscripts but concentrated in the Codex Leicester. He examined how stone forms from sediment, how river deposits create stratified layers, how fossils of sea creatures come to rest on mountaintops, and how erosion sculpts the landscape over vast periods of time.
His conclusions were revolutionary. He rejected the idea that Noah's flood deposited marine fossils on mountains, arguing instead that the land had once been under the sea and had been raised over immense spans of time — an insight that anticipated modern geology by three centuries. (See also Physical Geography.)
On the Formation of Stone
Sediment, time, and pressure
That stone isite which is produced by the consolidation of sand by the drying up of moisture. By the lapse of time this sand is consolidated and returned to the state of the stone from which it was formed; and every colour that the stone had is found again in the grain of the sand.
Codex Leicester
River Sediment and Mountain Erosion
How water reshapes the land
The rivers have sawn through and divided the members of the great Alps one from the other; and this is manifest in the order of the stratified rocks in which from the summit of the mountain down to the river the correspondence of the strata on one side is visible on the other.
C.A.
Every river carries its sediment towards the sea; and the stones are not carried far unless they be reduced to powder by continual attrition, and the large stones rest on the lower part of the bed of the stream in the places where it flows most swiftly.
This is where Leonardo most clearly breaks with his own era. Every educated person in 1500 believed the Earth was roughly 6,000 years old and that fossils were deposited by the Biblical flood. Leonardo looked at the evidence — stratified rock, marine shells on mountaintops, river sediments — and concluded that the Earth must be immensely old and that the land and sea had changed places over geological time. He was right. He was also 300 years ahead of anyone who would agree with him. -D