Which method detects the presence of specific radioactive elements in rock layers to determine their age?

Radiometric dating is the technique that allows scientists to measure the presence of specific radioactive elements in rock layers to determine their age. This method relies on the principle of radioactive decay, where unstable isotopes turn into stable ones at a predictable rate known as their half-life. For example, the decay of uranium to lead or carbon-14 to nitrogen can be measured in various materials, allowing researchers to ascertain how long it has been since the rock was formed or since the last significant alteration occurred to it.

By measuring the concentration of radioactive isotopes and knowing their decay rates, scientists can accurately calculate the age of the rock layer. This provides vital information for understanding geological history, the timing of events on Earth, and evolution.

Other methods listed do not focus on radioactive elements. Oxygen isotope analysis deals with variations in oxygen isotopes and climate reconstruction. Biostratigraphy utilizes fossil content to date and correlate strata, and geochemical dating typically refers to broader methods, not specifically focusing on the radioactive decay process. Thus, radiometric dating stands out as the most precise and direct method for determining the age of rocks based on the presence of radioactive elements.