Geological clock

The Earth was formed almost 4.54 billion years ago. This figure is to be placed in comparison with other figures such as:

• 13.6 billion years: estimated age of the universe.
• 4.57 billion years: Sun's age (which is half of his entire life).

The history of the Earth is divided as follows:

• 4 "aeons" or "eons" that last between 540 Myr (Myr = million years) and 2 Byr (Byr = billion years).
• Each aeon is subdivided into three or four "eras" of a few hundred million years (> 100 Myr).
• An era divides three or four "periods" of a few tens of millions of years (> 10 Myr)
• The periods are divided into "epochs" whose unit of time is the million years (> 1 Myr).

The animation does not illustrate the epochs and only the periods of the last aeon (Phanerozoic) are represented.

The main educational objective of this animation is to represent the history of the Earth in the form of a geological clock to reveal the order of magnitude of the durations and the proportions. Indeed, our usual perception of time does not allow us to correctly grasp the gigantic geological durations at work here. Thus, a mass extinction that appears punctually in the illustration spreads in reality over thousands or even millions of years. Such an event remains however very brutal on a geological time scale.

If the age of the Earth is reduced to a 12 hour clock, then the first three aeons (called Precambrian) occupy more than 10 hours, the Phanerozoic is only the last 90 minutes and the appearance of hominids the last 30 seconds. Homo sapiens only appears in the last two seconds, at 11:59:58!

The International Commission on Stratigraphy (ICS) has in its missions the establishment of a geological time scale. This scale is available at http://www.stratigraphy.org/. It is updated according to the discoveries of paleontologists.