Combining numerical and relative age dating
Therefore, due to the very long half-life of uranium 238, we can use that element and its decay to lead to date the age of the Earth.
Other elements have different half-lives and may be more suitable for dating younger rocks.
But how do we talk about time, and how do we know how old our rock formations are?
The geologic timescale is the most common way geologists organize and communicate major periods of the Earth’s past.
Dating refers to several methods we use to measure how old a rock is.
There are two main ways to determine the age of rocks: relative and absolute dating.
Over very long periods of time, uranium decays to lead.Absolute age dating usually involves measuring the radioactive decay of isotopes of minerals contained within a rock.For example, some of the oldest rocks on Earth are located in the Pilbara Craton of western Australia.In addition, not all rocks contain suitable minerals for absolute age dating, especially sedimentary rocks.However, we do have ages for some sedimentary rocks due to the presence of bentonites, or ancient volcanic ash horizons, that do contain minerals that can be used for absolute age dating.
Thus, by measuring the ratio of lead to uranium within a zircon mineral, we can determine the age of the zircon mineral with very low error (or high precision).