How can the absolute age of earth layers be determined?

Question

Luke Allen · Accepted Answer

Almost entirely by radiometric age dating of certain minerals.

Scientists discovered that certain elements decay into other elements at a very constant and predictable rate - called, the "half-life". For example, Uranium decays to lead, rubidium decays to strontium, potassium to argon and so on.

So, in the pic included if you start with a mineral that has say 25 of the yellow uranium atoms in it, after 1 billion years, 1/2 have decayed to thorium, after another billion years, another 1/2 have decayed to thorium, and so on. By knowing this decay half-life, the age of the sample, and hence the rocks the sample came from, can be determined.

Hailey Alvarez · Answer

undefined The absolute age of Earth layers can be determined through various methods, including radiometric dating, such as uranium-lead dating, potassium-argon dating, and carbon-14 dating. These techniques rely on measuring the decay of radioactive isotopes within the rocks or fossils found within the layers. Additionally, stratigraphic principles, such as superposition and cross-cutting relationships, are used to correlate layers and establish relative ages, which can then be further refined using radiometric dating.