Earth Science Guide to Fossil Dating
If you have ever stumbled across an old arrowhead or a piece of pottery, you may be wondering how old the fossils are. Finding and understanding fossils has fascinated man for many centuries. The technology for dating and identifying fossils has improved over time. There are archeological crews that spend years digging up one site and carefully cataloguing and dating the different fossils that they find. The fossils can tell us a lot about the conditions of the humans and animals that lived in various time periods. The ages of the fossils can help to explain certain periods of history or to place the fossils in a specific time period. There are two main methods of dating fossils: relative dating, and absolute dating. Most people use a combination of the two to accurately date the age of the fossil.
a. - Relative dating
Relative fossil dating is done by looking at the layers of earth around the fossil. The scientists will look at how deep the fossil was in the earth's strata and look at the other artifacts with the fossil to give it an approximate date. This works for a general date because it shows where the fossils are in relation to other fossils and time periods. One of the assumptions of relative dating is superposition. This means that scientists assume that the older fossils will be found in the lower layers of earth while the newer fossils will be found closer to the surface. They will also compare fossils to each other, and if they are similar in composition and style, they will be considered to be about the same age as the fossils around them. Relative fossil dating can save time and money because using it means that it is not necessary to find the absolute date of every item in a dig.
b. - Absolute dating
Absolute dating is a more accurate method of determining the date of a fossil. This is often done with radiometric testing. You may have learned a little bit about carbon dating in your science class in school. It is the method where they measure how quickly the carbon molecules are breaking down. Unfortunately, this method only works on plant and animal fossils and only up to 50,000 years ago. However, scientists can also use rubidium-strontium or potassium-argon to date the items. While carbon dating measures the half-life of carbon, these methods also look at the half-life of different isotopes within the material. It allows scientists to test materials that come from the prehistoric and paleontological ages. The process to complete absolute dating can take time, and it can be quite expensive. The method of absolute dating that scientists use will depend on the estimated age of the item, as well as the composition of the item.
Dating a fossil allows the archeologists to begin to build a picture of what the world was like centuries ago. It can help fill in gaps in the history of a specific area or reveal new discoveries about the evolution of man. If you find something in your backyard or when you are out camping, you may be able to use relative dating to determine the approximate date of an item. You can also visit your local museum to learn more about similar items found in your area. If the study of fossils truly fascinates you, you may be able to spend some time volunteering an archeological dig. They may require you take some training, but it is a fascinating way to learn more about finding fossils, and the processes used to date them. When you can date the fossil, you can really begin to learn more about it and the people or animals that created it.
Content written and provided by Vanessa Lebeau
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