After a quick definitional search on Wikipedia, paleomagnetism is defined as the study of the orientation of archaeological materials which is used to determine the orientation of the Earth’s magnetic field over a geological time frame. The goal of paleomagnetism is to use archaeological material as a means to gain more insight on the Earth’s process in the past. For this paper I will discuss how paleomagnetism works, the equipment used, the materials analyzed, and costs of this method. I will also introduce two studies that utilize the paleomagnetic method to further exemplify how this technique can is used.
HOW IT WORKS
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Materials like rocks, sediments, core from a bedrock, lake, ocean, or lava flow are all eligible samples. Obtaining material is not usually an issue for many paleomagnetists; it is raising the funds to properly observe the samples. There are grants provided by organizations, such as the National Science Foundation, that accommodate the monetary necessities required for the completion of a scientific study. The smallest grant offered from the National Science Foundation is about $200,000. Assuming this grant was all the money a paleomagnetist and his or her team received, if they were to take about five samples from 100 sample sites, samples would cost about $400 dollars each.
Lisa Tauxe, author of Essentials of Paleomagnetism, discusses the different procedures used when collecting samples. She specifies two methods: samples cut out using a drill and block samples. The first method requires paleomagnetists to use an electric or gasoline powered drill to remove a piece of core from a bedrock, lava flow, etc. Once the sample has been removed, it must be marked to indicate its location at the the time of its collection. After this step, the sample is taken back to the lab where a magnetometer will be used to detect the sample’s orientation of the magnetic north pole when the sample was heated. Block sampling differs from the drill method in how the sample is retrieved. Paleomagnetists use this method when they are working with material that cannot be drilled. With the hand rasp, the samples are shaved from the ground to create a flat surface. Once these samples are collected, they are delivered to a laboratory and inspected with a magnetometer.
Tauxe emphasizes two main goals of paleomagnetic sampling: “assessing the reliability of the recording medium,” and “averaging out the errors involved in the sampling process itself.” However, Tauxe reveals the limitations of the paleomagnetic method that compromises the effectivity of this technique. Paleomagnetism is useful when studying early hominids because it can only date material that is hundreds of thousands to millions years old. The disadvantages is that today’s humans and natural processes cannot be studied using this technique. Another error is the lack of eligible samples. Sediment can be disturbed which can change the orientation of the iron particles and even remove sediment parts. This forces paleomagnetism to focus on the long term changes in Earth’s magnetic field in order to produce an accurate observation and prediction of the record. Changes in iron particles is an early indicator that an error has occured. There are instances where it is not the paleomagnetic method that is the problem, but the paleomagnetist. The archaeologist must know how to properly gather samples. If an paleomagnetist does not collect a correct number of samples or collect them in a proper way, then the precision of the determined date is negatively impacted.
PALEOMAGNETIC LABORATORY STUDIES