Sedimentary rocks that contain fragments of another rock are younger than the rocks that the fragments came from.Look at the two nearly identical diagrams, Figures 7 and 8.Leonardo seems to have been among the first of the Renaissance scholars to “rediscover” the uniformitarian dogma through his observations of fossil marine organisms and sediments exposed in the hills of northern Italy.
The most recent change of all is the modern bridge support.
We know it is the most recent because it has cut through all of the others.
He also recognized that the rivers of northern Italy, flowing south from the Alps and emptying into the sea, had done so for a very long time.
In spite of this deductive approach to interpreting natural events and the possibility that they might be preserved and later observed as part of a rock outcropping, little or no attention was given to the history—namely, the sequence of events in their natural progression—that might be preserved in these same rocks.
As such, they were considered unlikely to recur on what was thought to be an unchanging world.
With the exception of a few prescient individuals such as Roger Bacon (Leonardo da Vinci (1452–1519), no one stepped forward to champion an enlightened view of the natural history of the Earth until the mid-17th century.This biblical history of the Earth left little room for interpreting the Earth as a dynamic, changing system.Past catastrophes, particularly those that may have been responsible for altering the Earth’s surface such as the great flood of Noah, were considered an artifact of the earliest formative history of the Earth.Earth’s surface is a complex mosaic of exposures of different rock types that are assembled in an astonishing array of geometries and sequences.Individual rocks in the myriad of rock outcroppings (or in some instances shallow subsurface occurrences) contain certain materials or mineralogic information that can provide insight as to their “age.”For years investigators determined the relative ages of sedimentary rock strata on the basis of their positions in an outcrop and their fossil content.If they are folded into a syncline (a U-shaped fold) the youngest rocks are in the core of the fold.