Relative dating and numerical dating
Studying the layers of rock or strata can also be useful. If a layer of rock containing the fossil is higher up in the sequence that another layer, you know that layer must be younger in age. This can often be complicated by the fact that geological forces can cause faulting and tilting of rocks.
Absolute dating is used to determine a precise age of a rock or fossil through radiometric dating methods.
Then after another 5,000 years half of the remaining parent isotope will have decayed.
While people are most familiar with carbon dating, carbon dating is rarely applicable to fossils.
This uses radioactive minerals that occur in rocks and fossils almost like a geological clock.
Unlike relative dating, absolute dating can be used to assign a specific numerical age to events or structures.So, often layers of volcanic rocks above and below the layers containing fossils can be dated to provide a date range for the fossil containing rocks.The atoms in some chemical elements have different forms, called isotopes.The great abyss of geologic time was discovered in the late 1700s by scientists like William Smith, who used observations of rocks and fossils to piece together an understanding of how Earth has changed over time and to ascertain that it is ancient.Prior to this understanding, it was largely accepted that Earth was only a few thousand years old.