Almost a century ago, a multitude of highly venerated academicians put a lot of effort into determining the Earth’s age. The figure they could come up with was 100 million years, only to be refuted by a more advanced study that came half a century later.

The then new study put the earth to an estimated age of around 3 billion years. But sadly, this claim was also invalidated. The work must have been debilitating considering the lack of technology and sparseness of scientifically sound individuals during the time.

Now, scientists have determined the Earth’s age to be 4.54 billion years old, give or take 0.1 billion years. So how did they figure out the number? And how do we put this into graspable way?

How Scientist Figured Out the Age of Earth

Estimating the age of Earth centers around finding an oldest piece of rock, and working out how old that piece is through a scientific technique called radiometric dating. Of all methods, radiocarbon dating is the most popular. The process zeroes in on the ratio between the number of radioactive isotopes of carbon – carbon-14 and carbon-12 – in any being that once used to live, and that ratio determines how old that being is.

The element that can be dated is not limited to just carbon, because plenty of other elements are in existence. For example, to determine the age of earth we resort to uranium-lead dating – the radioactive decay of uranium into lead. It is the oldest and most reliable of all the isotopic dating methods.

So using this dating method on the very old lead-filled zircon rock found in Western Australia, we know that the Earth is at least 4.4 billion years old. Other evidence from meteorites suggests that the earth is even older, and hence we tend to agree that the earth was formed 4.54 billion years ago, with an error of 0.1 billion years. The age of the Earth now seems very tenable.

Through radiometric dating, scientists have calculated that the Earth is 4.54 billion years old, with an error of 0.1 billion years.

Putting the Age of Earth into Clearer Perspective

If you’re familiar with the concept of Deep Time – time scale that the earth was formed roughly 4.5 billion years – we know we suck at trying to wrap our head around this hugeness of time. And, I can say with certainty that even if we, the lay people, try to make sense of such amount of stretch, our effort would be just unavailing.

Geological Time Spiral. [via Wikimedia Commons]
Geological Time Spiral. [via Wikimedia Commons]

The hitch here is that this type of thing falls prey to esoteric interpretation and it would be content to leave to the experts. However, many scientists, geology and archaeology connoisseurs stepped in, and without much reluctance, came up with different analogies in a hope to help us trounce this stumbling-block.

D. J. Mahony was one of the iconic archaeologists of the 16th century. The analogy he came up with takes you to the avenue of time into the past, and each step you make covers a thousand years. The first step would send you all the way to the battle of Hastings, the second step would take you to the genesis of the Christian era, and the third to Homeric Troy. So if you managed to cover a journey of more than 250 miles, you would be greeted by the most ancient fossil organisms. The man was a genius, but you wouldn’t find him anywhere except in some books.

Then in the 18th century, came James Hutton whom many considered the father of modern geology. From studying the soils and rocks, he suggested that the formation of earth took much longer than what Archbishop Ussher stipulated in the 17th century: the earth was created on the evening of October 22, 4004 BCE.

I know this sounds utterly absurd, but if Ussher had not made such preposterous claim, we would not have been able to build the body of knowledge we currently have.

In the 19th century, geologist Charles Lyell concocted different ways to study the earth’s current geological processes to understand the changes happened in the past. And, this subsequently gave birth to the idea of continental drift, which later came to be known as plate tectonics.

However, the concepts proposed by the trio: Hutton, Lyell, and Wegener were confronted with repudiation, and were not readily established.

But from Pangea – a supercontinent about 200 million years ago which later began to split forming the present continents on the earth – scientists have extrapolated that the concepts of continental drift, and every proposition they made were authentic, and that these processes have been recurring again and again.

Although speculations concerning Earth’s origin and its formation seem to arbitrate with radiometric dating, scientists are still working to accumulate evidences necessary to reveal the exact age of earth and its formation with new technologies.

Studying the Earth’s Interior

The core of the earth, which has a radius of almost 3,500 km (2,200 miles), consists of hot, molten material. On the top of it, is a mantle of semi-fluid material, which helps heated material to rise up and push down cooler material.

It is through this process called convection, the earth gradually loses its heat with each layers. The process also weakens the crust, the region just above the mantle consisting of a layer of magnesium-silicate and alumina-silicate layer, which makes up the present landmasses. It also moves the crust sideways, and sometimes the process spews out molten material, as in seafloor spreading.

Landmasses that came forth following volcanism, faulting, and countless of upheavals attributed to continental collisions got exposed to atmosphere. They made up sediments that were carried by water, wind, ice which then got deposited to lower elevations or the bottom of a body of water.

This process of deformation of crust has continued through time, and in times, gets consolidated into a complex surface.

Geologic Time Scale

Here we have the geologic time scale break down to help you put the age of earth in better perspective.

Geological Time Scale:  A Time Line for the Geological Sciences  [via]
Geological Time Scale: A Time Line for the Geological Sciences [via]

An Overview on the Aforementioned

The Precambrian period covered more than 80 percent of the geologic record. Because of its huge length of time, it was divided into eon: the Archeozoic, and the Proterozoic. Numerous deformation, major orogenies (mountain formation), erosion and deposition, including the ice ages were recorded during the period.

Well, if you happen to pass by every continent on the Earth, you would notice that each of them accompanies Precambrian shields. These shields are rich in minerals, as well as elements such as iron, cobalt, copper, nickel, silver, and gold.

The Paleozoic era had six major divisions: Cambrian, Ordovician, Silurian , Devonian, Carboniferous , and Permian.

The trilobites, fusulinids, blastoids and other marine fossils appeared during the Cambrian period, but majority of these invertebrates experienced climatic warming and were wiped out at the end of the Proterozoic ice age, or the Permian extinction.

The Ordovician period was the most significant of all submergences. Reef systems and marine fossils of this period – extending from the tropics to the arctic regions – can still be seen today.

Prior to Pangea, which incorporated almost all the landmasses on Earth, the world looked different. But it is from the rocks of this period that we get gas and oil, and sculpture and building material such as marble, slate, limestone, as well as hematite, zinc and lead.

The Silurian had a serene setting. During this time, terrestrial life started to flourish along with scorpions and millipedes. Diversification of marine life also still continued in this period.

The Devonian was relatively calm as well, but it had some upheavals. Flora as well as marine fauna started to flourish during this stage. It also marked the ascent of fish, as well the amphibians.

The Mississippian and Pennsylvanian periods, also known as the Carboniferous period, was famous for its swamp vegetation. But the Permian marked the end of it all with major orogenies occurring during the time. Deserts were prevalent during this time, as well as huge terrains in the southern hemisphere which were enshrouded with ice.

The Mesozoic era encompassed the divisions: Triassic, Jurassic, and Cretaceous. This period is best known as the dawn of dinosaurs. Many other smaller reptiles, birds, and mammals emerged in great quantities as well. Many of the major plants and animals you see today can trace their origins back to Mesozoic. The end of this period came with orogenesis and cold climatic conditions.

The Cenozoic era still extends to the present day. It began 65 million years ago. It must be remembered that the landmasses had different shapes prior to Cenozoic, but the continents’ present-day configurations and geographic positions were acquired during the period.

Gauging the magnitude and durations of major events that transpired during this stage such as – the formation of vast mountain ranges, birth of volcanoes, episodes of earthquakes that resulted in faults, plateaus, hills and plains, makes it much easier for us to grasp the scale of time where humankind emerges.