Uranium-238 is primarily used for dating what type of geological materials?

Uranium-238 is primarily utilized for dating old rocks due to its long half-life of about 4.5 billion years, which makes it suitable for determining the ages of geological materials that are millions to billions of years old. This isotope decays into lead-206, and the process allows scientists to measure the time that has passed since the rock solidified, providing insights into the history of the Earth's crust and the geological events that have occurred over vast scales of time.

In contrast, more recent fossils, which are typically dated using carbon-14 or other methods, are not well-suited for uranium dating. Marine sediments and organic materials, while also having their own dating techniques, do not align with the long time frames that uranium-238 is equipped to handle. Therefore, its application is most effective for dating ancient rocks, enabling geologists to reconstruct the Earth's history accurately.