How Long is an Eon

Geologists have meticulously classified and given names to every phase of Earth’s roughly 4.54-billion-year existence. These intervals of time are referred to as eons, eras, periods, and ages, going from longest to shortest.

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Eon is the longest unit of geologic time according to official definitions and the era is the second-longest. As old as time is a quote, we’re familiar with it.  But how long is an Eon? And is there anything older than an Eon? How it is important for our civilization. Come find out!

1. What Eon are You Currently in?

We are currently in the Phanerozoic eon. It belongs to Cenozoic era, Quaternary period, Holocene epoch, and the Meghalayan age. This age refers to the current human civilization period along with the past 4,200 years. The Cenozoic, the age we are currently living in, divides into three sections.

  • The most contemporary epoch.
  • The Quaternary, which includes the Holocene.
  • The Pleistocene, that ended 11,700 years ago, is the one in which we currently live.

But, some geologists strive to redefine the naming trend to the Anthropocene, or human era. It will replace the term Holocene. (See What is Caribbean Time Zone from GMT?)

2. How Long is a Eon Time? How Long is an Eon?

In geological time units, an eon is of billion years or an extremely long period of time. These geological eons are not defined by set lengths of time. Instead, geologists divide them into significant eras in Earth’s geologic history.

The Phanerozoic, Proterozoic, and Archean eons are the three recognized eons. The Phanerozoic eon spans from the present to the beginning of the Cambrian Period. Eon is a more informal term for a period of one billion years.

3. Is an Eon 1000 years?

Eon is derived from the Greek word aion meaning age. Both an age and an eon are difficult to quantify. A thousand years make up a Millenium which is a fragment of what an eon stands for. But an eon is around one billion years in science, and you can use Eon to describe anything that takes a long time.

But. Precambrian Time refers to the oldest three eons, which account for almost 90% of geologic time. So, when we ask how long an eon is, you know it is definitely not 1000 years. (See What Year was 2000 Years Ago?)

4. What does Eon Mean in Years?

The longest period of time on the geologic timescale is a geologic eon. The chronostratigraphic term for geologic eons is an eonothem, often known as an eon.
But exactly how long is an eon? Eons have a duration of several hundreds or thousands of years comprising 4.5 billion years. This billion-year period is broken down into smaller chunks or units. They are eons, eras, periods, epochs, and ages. For instance, the Hadean, Archean, Proterozoic, and Phanerozoic eons categorize the entire age of the earth.

5. How many Years are 4 Eons?

After learning about how long is an eon i wonder how many years are in 4 eons. Well, 4 eons will be 4 billion years. The Proterozoic, Archean, and Hadean eons make up the division of the vast Precambrian period of time according to age. 88% of geological time make up the Precambrian eons (Hadean, Archean, and Proterozoic). With htis now you know how many years make up 4 eons. (Must read What is Grandfather Clock History?)

6. What are the 4 Eons?

JAN23 How Long is an Eon 1
By Levi Meir Clancy from Unsplash+

The earliest three eons of Earth’s history, the Precambrian, lasted from roughly 4.6 billion to 635 million years ago. The Proterozoic, Archean, and Hadean eons make up the Precambrian period. The Proterozoic is the most recent eon. 88% of Earth’s history occurs during the Precambrian. Only 12% of Earth’s history since its birth 4.6 billion years ago accounts for the Phanerozoic eon. The 4 eons are:

  1. The Hadean lasted from the time the Earth formed, 4.6 billion years ago, to around 4 billion years ago. There is scant evidence of this time frame in the geologic record. According to geologists, the surface of the planet would have been in a molten state. It was then that the Earth’s layers began differentiating. This includes defining characteristics like the number of minerals in the various layers and the geothermal gradient.
  2. The Archean eon lasted for 4 billion years and ended 2.5 billion years ago. The Earth’s crust started to chill during the Archean eon. Young tectonic plates and oceans emerged. Microfossils of bacteria represented the earliest life on Earth, during this eon. (Read What is the Study of Fossils Called?)
  3. The Proterozoic eon began 2.5 billion years ago, and ended 541.0 million years ago. The Proterozoic eon saw the birth of the preponderance of Earth’s supercontinents. Along with the first stable continental plates when the planet was cooling. The Precambrian eon succeeded it that marked the beginning of the Phanerozoic.
  4. The Phanerozoic eon is the current geological eon. It started about 541.0 million years ago. The Phanerozoic eon consists of three eras.
  • The Cenozoic (or the Age of Recent Life)
  • The Mesozoic (or Age of Middle Life)
  • The Paleozoic (or Age of Ancient Life)

7. Is an Age or Eon Longer?

Age is usually used to refer to a defined period characterized by a notable figure or feature. In the geological timescale, it serves as a tool to showcase a narrower window of time in an epoch. As the smallest units of geologic time, they are also known as stages and are often only a few million years long.

Eon is the longest unit of time, also termed as eonothem. So, how long is an eon? It is thousands of millions of years long. These persist for at least one billion years. It means that an eon is considerably longer than an age. (See How does World Age affect Civ 5?

8. What is the Longest Eon of All Time?

The 4 eons aside, here is the most contemporary division of the Precambrian or Proterozoic Eon. With a start date of 2.5 billion years ago, it ended 541 million years ago. It is also considered the longest eon. But, it covered less than 4/9ths of geologic time.
This longest eon saw the emergence of contemporary plate tectonics. It caused the primordial cores of the continents to wander across vast regions of the planet. Smaller pieces of crust occasionally crashing into other massive land masses. It was interesting to know about longest eon after learning about how long is an eon.

9. How Old is the Oldest Eon?

The oldest eon is the Hadean Eon. It is after the Greek god and lord of the underground world Hades, spans between 4.5 and 4.0 billion years ago. The terminology was first used in 1972 by Preston Cloud, a geologist. Older texts alluded to it as the Pre-Archean age or eon.

But W. Brian Harland subsequently labeled it as the Priscoan period. Intense volcanism, which occurred as Earth proceeded to cool, is associated with the Hadean Eon. Hadean Eon was too unstable for life to develop and establish. Even if it had started, it was impossible for it to survive. (Also read What is the Instrument used to Measure Time?)

10. What is Older than an Eon?

Super Eons span for incredibly long eons of time and contain many eons. Being older than an Eon in the geological record of our planet, there has only ever existed one Super Eon. This honor goes to the Precambrian Super Eon. The Precambrian Super Eon began about 4.56 billion years ago and concluded about 541 million years ago. It separated into three distinct eons.

11. How Long is a Supereon?

Now that you are aware of how long is an eon get to know how long is a supereon. About 85 to 89% of the earth’s geological time frame, ranging from 5 billion to 600 million years, accounts for the Precambrian supereon. It is older than an Eon. The Earth’s solid crust fractured during this eon, and tectonic plates were created. There are no known fossils from this time period.

Since, life first evolved on Earth some 700 million years ago. The earliest life that emerged from the water was a unicellular creature. Around 800 million years ago, there was the first rainfall. With this the atmosphere was forming at the same time. So, a supereon is many eons which would be several billion years in total. Wow, that is an incredibly long expanse of time in comparison to how long is an eon. (Also read What is Mesopotamia Social Structure?)

About the author
Jack Williams is a multifaceted lifestyle writer who has a passion for bringing interesting and enlightening content to his readers. With a strong background in researching and writing, he has made a name for himself in the world of lifestyle journalism, covering a wide range of topics including Wikipedia, facts, and trivia.

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