What is the Geological Time Scale and what does it consist of?
Scientists who have done extensive testing, over many years, using various means (many of which overlap and therefore double check each other) and have determined that the Earth is approximately 4,600,000,000 years old. For additional information on telling the age of things, see “Showing Your Age” (an award-winning article by your Curator). Since 4.6 billion years is a very long period of time, earth scientists have broken this 4.6 billion years down into units, called geological ages. These geological ages are determined by a number of factors, not just arbitrary numbers of years. Geological time is divided into various units of time. EONs: There are two (2) Eons. The Precambrian Eon, which commenced at the formation of the Earth and ended when fossils became abundant in rocks about 570,000,000 years ago (570 MYBP). The other eon is the Phanerozoic Eon, which commenced at the close of the Precambrian Eon and has lasted to the present. ERAs: There are five (5) major categories called
