Q&A: Eon vs era vs epoch

Each week here at the Australian Writers’ Centre, we dissect and discuss, contort and retort, ask and gasp at the English language and all its rules, regulations and ridiculousness. It’s a celebration of language, masquerading as a passive-aggressive whinge about words and weirdness. This week you'll be surprised to learn that in an eon there are eras, within which there are epochs.

Q: How do you even hear that?

A: It’s definitely “Laurel”

Q: No way, it’s “Yanny”…

A: Oh, hang on I think we’re starting.

Q: Really? Ahem, okay. Um… Hey AWC – I had a question this week inspired by my favourite Billy Joel song, “Fungalungus time”

A: Um, don’t you mean “The Longest Time”?

Q: Oh really? Next you’ll be telling me that he doesn’t sing “Bondo, Buddha pest, Alabama cruise chest…” in We Didn’t Start the Fire”

A: He doesn’t. It’s “Bardot, Budapest, Alabama, Krushchev.”

Q: Oh. Well, anyway, speaking of ‘the longest time’ – I wanted to know which is longer – an eon, epoch or era?

A: How long have you got?

Q: About 600 words. I’m guessing they’re all fairly interchangeable, yeah?

A: No, not really. In geological terms, an eon is the longest – roughly a billion years. Within this, you’ll find eras, and within an era, you find periods, epochs and ages.

Q: So if I’m talking about Jurassic or Cretaceous – what are they?

A: They’re periods of approximately 56 million and 79 million years respectively. Together with the Triassic Period, they formed the Mesozoic Era.

Q: So what are we living in right now?

A: Good question. While we’re still in the same eon as the dinosaurs – called the Phanerozoic Eon – we moved into the Cenozoic Era 66 million years ago, and within that, the Quaternary Period – which began with the most recent ice age.

Q: But the most recent Ice Age only came out in 2016.

A: No, not the movie. The ice age wasn’t actually an age at all – it was the Pleistocene epoch, lasting from 2.5 million years ago until 11,000 years ago. At that point, the current Holocene epoch kicked in.

Q: All these holograms, plasticine and Jurassic Parks are making me dizzy. Surely we don’t need to be so specific when writing?

A: No, you’re right – we attribute the terms a lot more freely in historical writing. However, away from geology, the order often switches.

Q: Seriously?

A: Sorry, we don’t make the rules. Let’s deal with the easy one first – an eon (sometimes written as “aeon”) is still the longest one – an “indefinitely long period of time”. That said, it is often used in hyperbole, i.e. “they hadn’t seen each other in an eon”.

Q: Okay. What about era and epoch?

A: Macquarie Dictionary simply defines an “era” as a period of time marked by distinctive character or events. But that period of time can range in length from a few years (“American Civil War era” or “the Reagan era”) to decades (“Cold War era”, “Bradman era”) or longer (“the Modern Era” or “the Roman Era”). These are very date specific.

Q: So “the Facebook era” or “the smartphone era”?

A: Yes. Or the “television era” and so on. It’s flexible.

Q: More flexible than a Russian gymnast.

A: Actually, “Soviet-era” is another good one – ones like these are often used as adjectives to describe things like clothing or politics or architecture.

Q: And is an epoch longer than an era this time?

A: When you’re not talking geology, an epoch is generally considered a longer time period than an era, although it can also be interchangeable (eg “an epoch of social revolution” could also be “an era of social revolution”).

Q: How very unhelpful.

A: But wait, there’s more. Epoch also has another meaning – describing a specific “turning point” event that begins a new time or development.

Q: Example?

A: As a writer, you might say “the invention of nuclear weapons marked an epoch in the history of warfare”. Or you might refer to “epoch-making” events.

Q: Any other epoch-making surprises to share?

A: Yes actually. Modern computing’s epoch began on 1 January 1970. And in America they pronounce it similar to the word “epic”, while elsewhere it’s more commonly “ee-pock”.

Q: Okay, so to recap?

A: Geologically, eons are longer than eras, while eras are longer than epochs. More generally however, eons are still the longest yet epochs usually last longer than eras. BUT epochs can also be relate to “turning point” moments in time – and an era might contain many epochs.

Q: Clear as primordial mud.

A: That mud’s probably from the Hadean Eon.

Q: I think we’ve reached an epoch in understanding. It’s the end of an era for today’s column.

A: This is no time to be resting on our laurels…

Q: Don't you mean our yannys?

A:Haha, well either way, it's time to go. After all, we have been discussing it… oooh oh oh oh, for the longest time…

If you have a grammar gripe or punctuation puzzle that you’d like our Q&A to explore, email it to us today!

Browse posts by category
Browse posts by category

Courses starting soon


Nice one! You've added this to your cart