Stanford University Press, Relative dating of fossils, CA. Possibly the single most comprehensive book on this subject. Artisian Sales, Thousand Oaks, CA. Dating is a technique used in archeology to ascertain the age of artifacts, fossils and other items considered to be valuable by archeologists.
There are many methods employed by these scientists, interested in the old, to get to know the age of items. It is possible to tell the number of years ago a particular rock or archeological site had been formed. Two broad categories of classification methods are relative dating and absolute dating. Though using similar methods, these two techniques differ in certain ways that will be discussed in this article.
As the name implies, relative dating can tell which of the two artifacts is older. This is a method that does not find the age in years but is an effective technique to compare the ages of two or more artifacts, rocks or even sites. It implies that relative dating cannot say conclusively about the true age of an artifact. Absolute dating, on the other hand is capable of telling the exact age of an item using carbon dating and many other techniques that were not there in earlier times. Relative dating makes use of the common sense principle that in a deposition of layers.
A layer that is higher is of later age than a layer that is lower in order. This means that the oldest are the strata that are lying at the bottom. However, age of deposition does not mean the age of artifacts found in that layer. Artifacts found in a layer can be compared with other items found in layers of similar age and placed in order. However, archeologists still require further information to find out the items that are oldest and those that are youngest in the order.
It is left for absolute dating to come up with the precise age of an artifact. This type of dating employs many dating techniques like atomic clocks, carbon dating, annual cycle methods, and trapped electron method. Dendrochronology is another of the popular method of finding the exact age through growth and patterns of thick and thin ring formation in fossil trees. It is clear then that absolute dating is based upon physical and chemical properties of artifacts that provide a clue regarding the true age. This is possible because properties of rock formations are closely associated with the age of the artifacts found trapped within them. C-14 has a half life of 5730 years which means that only half of the original amount is left in the fossil after 5730 years while half of the remaining amount is left after another 5730 years. This gives away the true age of the fossil that contains C-14 that starts decaying after the death of the human being or animal.
Relative dating comes to a conclusion based upon the study of layer formation of rocks. Upper most layers are considered the youngest while the lowermost deposition is considered as oldest. Relative dating does not tell the exact age, it can only compare items as younger and older. Absolute dating techniques can tell the exact age of an artifact by employing various techniques, the most popular being C-14 dating.
Help us to improve our writing. Difference Between Relative and Absolute Dating. Protected by Copyscape Plagiarism Checker – Do not copy content from this page. This clock representation shows some of the major units of geological time and definitive events of Earth history. The following four timelines show the geologic time scale.
The first shows the entire time from the formation of the Earth to the present, but this gives little space for the most recent eon. Therefore, the second timeline shows an expanded view of the most recent eon. In a similar way, the most recent era is expanded in the third timeline, and the most recent period is expanded in the fourth timeline. Geologists qualify these units as “early”, “mid”, and “late” when referring to time, and “lower”, “middle”, and “upper” when referring to the corresponding rocks.
Earth’s past has been organized into various units according to events which took place. Geologic units from the same time but different parts of the world often look different and contain different fossils, so the same time-span was historically given different names in different locales. Earth, and events on Earth had correspondingly little effect on those planets. Construction of a time scale that links the planets is, therefore, of only limited relevance to the Earth’s time scale, except in a Solar System context. The existence, timing, and terrestrial effects of the Late Heavy Bombardment is still debated. You can edit this timeline. Please use the preview button before saving.