Have you ever wondered how scientists and other experts determine the age of something that existed millions upon millions of years ago, long before people roamed the earth? It’s through radiocarbon dating! Is this method of age identification viable for dinosaur specimens as well?
Radiocarbon dating like carbon-14 does not work on dinosaur fossils, and that’s due to the half-life of carbon-14. If a fossil sample is older than 50,000 years old, which almost all are, carbon-14 dating is not an option. Instead, scientists can use potassium-40 dating.
If you’re still confused, don’t worry. We’ll clear it all up in this article. First, we’ll explain how scientists can estimate how old dinosaurs are based on fossil records. Then we’ll explain radiocarbon dating, how it works, and why it’s not always usable for determining the age of dinosaur remains.
Let’s get started!
How Are the Ages of Dinosaurs Determined?
Okay, so you know from the intro that carbon-14 dating is not an option for verifying the age of a fossil. Still, you have these dinosaur bones you want to have dated. We’ll tell you more about why that is in the next section, but for now, we want to focus on which methods scientists use to confirm how old dinosaur fossils are.
There are two methods: geologic time and absolute geologic time. Let’s take a closer look now!
Geologic time, better known as the geologic time scale or GTS, determines stratigraphy over time. Stratigraphy refers to the age of geological strata. Scientists, paleontologists, and geologists alike use the GTS.
The GTS scale currently has four designated eons, with an eon being defined as approximately one billion years. Then the scale includes eras within that eon, with an era being several hundred million years.
Within every era are periods, which geologic time defines as tens of millions of years in duration.
For example, in the Phanerozoic Eon was the Mesozoic Era. It included the Cretaceous Period between 66 and 145 million years ago, the Jurassic Period between 145 and 201.3 million years ago, and the Triassic Period between 201.3 and 252.17 million years ago.
Also in the Phanerozoic Eon was the Cenozoic Era. The era included the Quaternary Period (Holocene/Pleistocene) up to 2.588 million years ago, the Neogene Period (Pliocene/Miocene) between 2.588 and 23.03 million years ago, and the Paleogene Period (Oligocene/Eocene/Paleocene) between 23.03 and 66 million years ago.
How did the scientists that created the GTS scale curate this data? They observed rock layers, in which fossils are usually buried several layers deep. It’s not only fossils that scientists look for, but also strata changes. These changes alone can indicate whether a paleontological or geological event occurred, especially massive ones such as the extinction of the dinosaurs.
The GTS scale goes very deep, as scientists have created a table that highlights all geological time. They’ve been able to determine when the moon might have formed when the first plate tectonics appeared on the planet that became the earth and when the first living cells appeared.
Rather than use radiocarbon dating, as we’ll explain momentarily, the GTS scale is more like chronological dating. It’s very detailed and often complex stuff. Still, it’s so fascinating to see how our world unfolded over the eons, including when dinosaurs eventually entered the picture and were then removed. (Source)
Absolute Geologic Time
If geologic time tells us the eon, era, and period in which a dinosaur fossil was found, absolute geologic time takes it one step further.
Absolute geologic time is a form of radiometric dating that’s better known as absolute dating. Used primarily in geology and archaeology, absolute geometric time also goes by names such as calendar dating and chronometric dating.
The concept behind radiometric dating is that radioactive isotopes are consistently decaying. A radioactive isotope, aka a radionuclide, is an unstable nuclide due to all its nuclear energy.
A radioactive isotope can release beta or alpha particles from its nucleus to make a fresh particle. The isotope can also produce a conversion electron or make gamma radiation.
Since isotopes can contain varying atom types, some are useful in determining age.
Another form of radiometric dating known as potassium-argon dating uses the radioactive isotope potassium-40, which will later become argon-40.
Why Can’t We Use Carbon-14 on Dinosaur Remains?
We noted in the intro that one form of radiocarbon dating is not effective in aging dinosaur remains. That’s carbon-14 dating, also known as radioactive dating.
To explain why that is, we must delve into carbon-14 dating and how it works.
Carbon-14 dating uses a radioactive carbon isotope known as a radiocarbon. Radiocarbons, nicknamed carbon-14s, has eight neutrons and six protons in their atomic nucleus.
In the 1940s, Willard Libby, a chemist at the University of Chicago, created the process of carbon-14 dating.
We won’t dive into the complexities of carbon-14 dating too much (because it truly is very complicated), but here’s the gist of it.
The planet’s atmosphere consistently produces radiocarbons when atmospheric nitrogen and cosmic rays meet.
The carbon interacts with atmospheric oxygen and becomes radioactive carbon dioxide. Plants photosynthesize this carbon dioxide. When animals consume plants, they ingest the radioactive carbon dioxide as well. (Source)
When an animal dies, it stops making carbon-14. Radioactive decay causes the levels of carbon-14 to decrease incrementally. Taking a sample of the dead animal or plant (organic material) then makes it possible to determine how old it was when it died.
Notice, though, how we’re saving animals and not dinosaurs. That’s a shortcoming of carbon-14 dating.
Carbon-14 has a half-life of 5,730 years. A half-life is how long it takes for a quantity of something to deplete to half of its original value. (Source)
In radiocarbon dating, the half-life refers to how long it takes for half the radioactive isotype atom to begin decaying and form into another isotope.
Due to the half-life of carbon-14, its use as a radiocarbon dating option only extends to 50,000 years ago. Some experts argue that carbon-14 dating can be effective on specimens as old as 60,000 years, but at that point, the results are likelier to be inaccurate.
That’s not to say that you can’t learn incredible things about our planet through carbon-14 dating, as you absolutely can. However, the extent of that knowledge only goes so far. No dinosaur lived 50,000 years ago.
We can use carbon-14 dating to understand better the creatures that evolved from dinosaurs, as 50,000 years back, the planet was very different to how it is today, as were its inhabitants.
Scientists who want to use radiocarbon dating to understand dinosaur fossil age are much better off with potassium-40 dating instead. As you’ll recall from the last section, potassium-40 dating has a much longer half-life of 1.3 billion years.
Even that is not enough time to tell us about all the dinosaurs that existed but learning about some is better than none!
How Accurate Is Carbon Dating?
Given the downsides we’ve addressed, you may be wondering just how accurate carbon dating is, to begin with. The answer is incredibly accurate.
As technology and science progress, new ways are being found to test the age of old fossils and artifacts. Fossil fuels might also have the potential to reduce the efficiency of carbon dating, says this 2016 article from Smithsonian Magazine.
Even still, scientists, paleontologists, geologists, and other experts vouch for the accuracy of carbon dating.
Now, we must note, of course, that carbon dating isn’t 100 percent perfect 100 percent of the time.
Scientists don’t assume that if they find a discrepancy in their carbon dating results, their new timeline is automatically the correct one.
Instead, they’ll use chronological dating to determine where the discrepancy may lie and then go from there. The scientist will share their findings to make sense of the discovery.
In a body of research, contradicting evidence might be included only as a footnote. The evidence could even be discarded altogether, depending on the extent of the discrepancy.
Carbon-14 dating has too brief of a half-life to tell us viable information about the age of dinosaurs. However, other forms of radiocarbon dating can be useful tools for determining when these creatures may have lived and died.
No method for calculating a fossil’s age is completely accurate, and that’s true of radiocarbon dating as well. However, the long track record of this method’s accuracy proves it’s a viable option for understanding a timeline of events for how our world transpired long before we were in it.