Current scientific evidence shows that the Earth is: c) more than 4 billion years old 2.
Look at the diagram below representing layers of rocks and the fossils buried in them. (The bottom layer is circled)b) Explain how you know which layer is the oldest.
Relative dating involves things like higher layers are most recent than rocks lower in the sequence.
This can be extended to the known sequence of fossils.
Compare and contrast relative dating and absolute (radiometric) dating.
For example, the decay of potassium-40 to argon-40 is used to date rocks older than 20,000 years, and the decay of uranium-238 to lead-206 is used for rocks older than 1 million years.
These break down over time in a process scientists call radioactive decay.
Each original isotope, called the parent, gradually decays to form a new isotope, called the daughter.
Each isotope is identified with what is called a ‘mass number’.
When ‘parent’ uranium-238 decays, for example, it produces subatomic particles, energy and ‘daughter’ lead-206.