It is the interpretation of these chemical analyses that raises potential problems.
To understand how geologists “read” the age of a rock from these chemical analyses, let’s use the analogy of an hourglass “clock” (Figure 2).
Some isotopes are radioactive; that is, they are unstable because their nuclei are too large.
To achieve stability, the atom must make adjustments, particularly in its nucleus.
This process of changing one element (designated as the parent isotope) into another element (referred to as the daughter isotope) is called radioactive decay.
The parent isotopes that decay are called radioisotopes.
In some cases, the isotopes eject particles, primarily neutrons and protons.