Ways of dating fossils
Most scientists and many Christians believe that the radiometric dating methods prove that the earth is 4.5 billion years old.
Uranium is present in many different rocks and minerals, usually in the form of uranium-238.These skeptics do not provide scientific evidence for their views.Current understanding of the history of life is probably close to the truth because it is based on repeated and careful testing and consideration of data.This problem is now reduced by the careful collection of samples, rigorous crosschecking and the use of newer techniques that can date minute samples.Volcanic rocks – such as tuff and basalt – can be used in dating because they are formed at a particular moment in time, during an eruption.The rejection of the validity of fossils and of dating by religious fundamentalists creates a problem for them: Fossil sequences were recognized and established in their broad outlines long before Charles Darwin had even thought of evolution.
Early geologists, in the 1700s and 1800s, noticed how fossils seemed to occur in sequences: certain assemblages of fossils were always found below other assemblages. Since 1859, paleontologists, or fossil experts, have searched the world for fossils.
So, when looking at the history of a cliff face, it is important to read the story it tells from the bottom layer up.
Our understanding of the shape and pattern of the history of life depends on the accuracy of fossils and dating methods.
Scientists use two kinds of dating techniques to work out the age of rocks and fossils. This considers the positions of the different rocks in sequence (in relation to each other) and the different types of fossil that are found in them.
The second method is called absolute dating and is done by analysing the amount of radioactive decay in the minerals of the rocks.
Some critics, particularly religious fundamentalists, argue that neither fossils nor dating can be trusted, and that their interpretations are better.