Radiometric Methods of Dating Fossils

by: Kimberly Wylie

Table of Contents

Abstract 2

Introduction 3

Carbon-14 Dating  3

Uranium-238 5

Conclusion  6

References 7

Abstract

Today, most of the methods utilized for chronometric dating of fossils are radiometric. Radiometric dating, in general, refers to the dating of material by using the known rate at which certain radioactive isotopes decay, or at what rate there are collective changes due to radioactivity. Even though isotopes of an element can be different when it comes to atomic mass, the atomic number of the isotope is always the same. Radioactive elements decay at unique rates, dependant on the isotope. This rate of decay is known as half-lives, it is the time necessary for ½ of the atoms to decay in a particular element. The decay follows a geometric scale, in that in the first half-life of an element, ½ of the atoms decay, yet in the second half-life, ½ of those remaining decay, meaning a ¼ of the original atoms decay, and so forth. By measuring this decay, and knowing the half life of an element, scientists can date a sample.

Introduction:

Today, most of the methods utilized for chronometric dating of fossils are radiometric. Radiometric dating, in general, refers to the dating of material by using the known rate at which certain radioactive isotopes decay, or at what rate there are collective changes due to radioactivity. Even though isotopes of an element can be different when it comes to atomic mass, the atomic number of the isotope is always the same. Radioactive elements decay at unique rates, dependant on the isotope. This rate of decay is known as half-lives, it is the time necessary for ½ of the atoms to decay in a particular element. The decay follows a geometric scale, in that in the first half-life of an element, ½ of the atoms decay, yet in the second half-life, ½ of those remaining decay, meaning a ¼ of the original atoms decay, and so forth. By measuring this decay, and knowing the half life of an element, scientists can date a sample.

Carbon-14 Dating:

One of the most common forms of radiometric dating applied today is radiocarbon, or Carbon-14 dating. This method is used in the dating of organic materials. Cosmic radiation is constantly assailing the Earth’s atmosphere, and when it hits an atom of nitrogen, it alters the nucleus, changing the atom into hydrogen and Carbon-14. These two atoms then bond with oxygen and form carbon dioxide, which is utilized by plants in photosynthesis. Animals then eat these plants, then other animals eat these animals, and the spread of Carbon-14 through all living things is completed.

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