Each dark band represents a winter; by counting rings it is possible to find the age of the tree (Figure 11.22).The width of a series of growth rings can give clues to past climates and various disruptions such as forest fires.The thin, dark part of each ring represents slow autumn and winter growth.Several other processes result in the accumulation of distinct yearly layers that can be used for dating.
Because these rates do not change and because the radiation that rocks give off can be measured, it became possible to calculate the time the rock was formed or, in other words, the rock's birth date - give or take a few thousand years or so.
The methods work because radioactive elements are unstable, and they are always trying to move to a more stable state. This process by which an unstable atomic nucleus loses energy by releasing radiation is called radioactive decay.
The thing that makes this decay process so valuable for determining the age of an object is that each radioactive isotope decays at its own fixed rate, which is expressed in terms of its half-life.
Radiometric dating is a method used to determine the age of rocks and other materials based on the rate of radioactive decay. Radiometric dating is a method used to date rocks based on the known decay rate of radioactive isotopes. Now, they do not give off enough radiation that you have to be afraid to pick them up, but they do contain naturally occurring radioactive elements like uranium, for example.
Learn about three common types of radioactive decay: alpha decay, beta decay and gamma decay. You simply subtract your birth date from the current date. It was also discovered that these elements decayed into other elements at fixed rates.