Relative Dating

QUESTION: What is relative dating?

ANSWER:

Relative dating is used to determine the relative ages of geologic strata, artifacts, historical events, etc. This technique does not give specific ages to items. It only sequences the age of things or determines if something is older or younger than other things. Some types of relative dating techniques include climate chronology, dendrochronology, ice core sampling, stratigraphy, and seriation.

Seriation uses the assumption that once a tool was developed, its use would become more widespread. Stratigraphy uses the assumption that higher layers or strata were laid down after lower layers. Ice core sampling normally uses the assumption that the ring bands observed represents years. One known example where this assumption was used is very misleading. Ice cores showed the age of a military plane buried in the artic as thousands of years old. Similarly, dendrochronology measures the tree rings in trees and assumes they represent years. Climate chronology uses evidence of a climatic change, such as an ice age, as a benchmark for dating.

Encyclopedia.com states, “Before the 20th century, archaeologists and geologists were largely limited to the use of relative dating techniques. Estimates of the absolute age of prehistoric and geological events and remains amounted to little more than inspired guesswork, as there was no scientific basis for testing such proposals.”

With this background, it is strange that the “standard geologic column” that identifies the rock strata on the earth and assigns very old ages to those strata was developed by Sir Charles Lyell in 1830. This was done 100 years before absolute dating methods were available. The ten strata systems that compose the “standard geologic column” are the familiar Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, and Tertiary periods.

Although no absolute methods were available to establish actual dates, Lyell needed to assign very old dates to the strata to make them consistent with the long eons of time that would be necessary to meet the new uniformitarianism theory developed by James Hutton and himself. This theory held that the past was the key to the future and that processes that formed the layers were the very slow processes that we see forming layers at the bottom of the ocean today. All catastrophic depositions were rejected.

Until Lyell successfully convinced scientists that uniformitarianism was the correct theory, it was believed that the worldwide flood and other catastrophic events were primarily responsible for the formation of the geologic layers and that they didn’t represent long ages.

Later, when radiometric absolute dating methods were developed, they still were not applicable to sedimentary layers. Consequently, today the dates assigned to the “standard geologic column” are still based upon Lyell’s assignment where index fossils are used to date the rocks and the rocks are used to date the fossils. This is a classic case of circular reasoning.

Today, it is not surprising that many geologists are rejecting uniformitarianism and embracing catastrophism again. There is much evidence that refutes uniformitarianism. Mount St. Helens demonstrated that rapid deposition and rapid canyon erosion are a fact. It doesn’t take eons of time. Also, when life forms die they only become fossils when they are buried rapidly. Otherwise they decompose. Polystrate tree fossils that extend through multiple layers are common. That could only happen with rapid deposition.

Consequently, the uniformitarianism model, along with the age assignments of the geologic column, is in doubt.

The relative dating methods themselves are generally sound when used with good assumptions. However, when scientists apply relative dating to a preconceived uniformitarianism model, the dating methods are only as good as the model.

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