Relati ve dating of geological strata
A chance encounter between determined fishermen and a great white shark off the Tuscan coast in 1666 sparked a chain of events that would help change humans views of fossils and Earth’s geologic past (Cutler 2003, pp. Nicolas Steno (1638-1686) dissected the head of this shark and realized fossil tongue stones believed to be petrified snake or dragon tongues were actually fossil shark teeth (Prothero 1998, p. One problem still existed, how do fossils become embedded in solid rock?Steno recognized that fossils represent organisms that became buried in sediment, which later turned into rock.Simply stated, each bed in a sequence of sedimentary rocks (or layered volcanic rocks) is younger than the bed below it and older than the bed above it.This law follows two basic assumptions: (1) the beds were originally deposited near horizontal, and (2) the beds were not overturned after their deposition.Relative time places events or formations in order based on their position within the rock record relative to one another using six principles of relative dating.
Although there might be some mineral differences due to the difference in source rock, most sedimentary rock deposited year after year look very similar to one another.However, relative methods are , which is that if there are layers of deposits, those laid down first will be on the bottom and those laid down last will be on the top. However, geological strata are not always found to be in a neat chronological order.Wind and water erode strata and some areas are uplifted or even tilted.For instance, if we find a fossil bone below the strata 3 rock level shown above, we assume that the animal most likely lived at a time before that layer was formed.However, we must be careful to note whether or not the fossil comes from the mixed strata zone of the filled in hole..