Investigation of a Dating Technique
Uranium-Lead Radiometric Dating
Uranium-lead dating works just like any other radiometric dating method. Uranium is present in specific rocks around the Earth's surface, over long periods of time that radioactive uranium decays to another element which is lead. (238U, 206Pb are the isotopes that are involved mainly in this process) 238U has the longest half life out of an isotope of any element. The half-life is approximately 4.5 billion years. Therefore, if you find a rock that has undergone this decay and it has a-lot of lead (206Pb) then you know that the rock you are looking at is very old. For how old these rocks are that contain this material, this process is so precise it can be accurate to within 200,000, which is kind of accurate when considering the age of our Earth (4.5 billion years old)
This dating method is expressly linked with geomorphology specifically when understanding history over a vast time scale. Since Uranium-lead dating offers a massive period of time to date from, geomorphologist can use it to date events from billion of years ago. Such events include large scale volcanism, continent collision and divisions, as well as much more that effects the landscape over time.
Karabinos, P., & Olson, E. (2019, January 02). Dating - Importance of Zircon in Uranium-Lead Dating. Retrieved October 02, 2020, from https://www.britannica.com/science/dating-geochronology
After reading this article, I became familiar with the use of Zircon in the radiometric dating method of uranium-lead. Zircon offers three major elements to this type of dating. Firstly, zircon is highly resistant to change, this is need since the U-Pb decay is the longest in the earth. Secondly, it's crystal structure allows for uranium to substitute for zirconium and thus excludes the incorporation with lead (206Pb) (Karabinos & Olson, 2019) Putting these three components together, one can measure the time of crystallization and the time of melting in different parts of the same grain. (Karabinos & Olson, 2019)
Miller, Brent V. “Introduction to Radiometric Dating.” The Paleontological Society Papers, vol. 12, 2006, pp. 1–23., doi:10.1017/S1089332600001327
In this article, I read about how radiometric dating especially Uranium-lead dating is not distributed throughout geologic history evenly. However, it is spread out with more dates from certain time and certain time periods with no ages at all. For example, they're not many radiometric dates from the late Cenozoic. Nevertheless, the rock record such as the Permian-Triassic and Cretaceous-Paleocene have significantly helped geomorphologist understand the past. (Miller, 2016) Lastly, many geologic dates and timelines are constrained to just a few ages/dates or none at all.