It is an amazing accomplishment that allowed geologists everywhere to put local rocks into a global sequence. Armed with the time scale, it became possible to examine the various processes operating on the Earth's surface and crust during specific intervals of time. Its construction was a major first step toward the development of the plate tectonic theory. Unfortunately for us, the names of the various subdivisions within the scale are a bizarre mix of Greek roots and geographic terms that few of us will recognize. This makes memorization difficult, but memorize it we must.
Eons are the longest time intervals represented.
Eras within the Phanerozoic are themselves broken down into periods . The names are derived from geographic locales where the period was first identified or from Latin roots for characteristic deposits formed within the period. I want you to know the Eons, Eras, Periods and Epochs. Yes they are hard to memorize, but they are the lingua franca of geologic time and you need to know them. You should also know the age boundaries between the eras.