Evolving timescale

The names of geologic periods on the geologic timescale we use today represent an international melting pot of terms derived from earlier efforts to divide up the history of the Earth. The period names Triassic and Quaternary are holdovers from earlier version of the timescale that divided Earth history into three (tri-) and four (quater-) slices. The names for the Periods of the most geologically recent Cenozoic Era continue to evolve. The Tertiary Period has been divided into two periods, the Paleogene and Neogene (meaning, old recent and neo recent, respectively). This fine-tuning permits more precise correlation of rock units around the world allowing for greater detail in our reconstructing the history of the Earth. The chart shown here is the work of an international committee.