Question

What is used to date rocks older than 10 million years and has half-life of isotope of 4.5 billion years?

Answer 1

Radiometric dating can be used.

Explanation:

I have explained how it works in this answer:

https://socratic.org/questions/a-rock-is-found-contains-uranium-238-and-also-lead-206-scientist-analyze-the-roc#382407