Suppose an archaeologist uses dendrochronology to determine that a city was built in 2500 B.C. Several years later, another archaeologist is digging deeper under the site of the city and, in a lower layer of rock, he finds the remains of another city. Unfortunately, there is nothing that he can use for any dating technique. He can still conclude something about the age of the city. Assuming that the Principal of Superposition is true in this situation, what can he conclude?
He can conclude that the city he found was built before 2500 B.C. Assuming the Principle of Superposition is true, the lower layers of rock are older than the upper layers. Since he found this city in a lower layer of rock, it must be older than the city that was discovered in the upper layer of rock.