Posted by: Kash Farooq | February 21, 2011

The Geologic Eras, Mnemonics and Open University course S193 “Fossils and the History of Life”

The first ever Open University course that I did was the excellent “Fossils and the History of Life” course (course code S193).

Open University Course S193: Fossils and the History of Life

Open University Course S193: Fossils and the History of Life

It was a “short science course” and I enrolled on it to see if I wanted to study again. I picked this course as I wanted to study something I’d never studied before.

It was a great course with great materials: two fantastic books, a DVD/CD-ROM and a “fossil kit”. It wasn’t a chore to read the books, it was a pleasure.

One of the books, The Atlas of the Prehistoric World, is full of fantastic illustrations. I think it would even pass as a coffee table book:

The Atlas of the Prehistoric World

The Atlas of the Prehistoric World. Still available to buy second hand.

Sadly the course is now discontinued.

The course got me completely and utterly addicted to studying again. I wanted to do a Geology degree. Now I am about a third of the way through a Physics Degree (specialising in Astronomy). It turns out that I’m rubbish at Geology!

Whilst studying the Fossils course, it was useful to learn and memorise the geologic eras:

Era Time period
Pre-Cambrian 4,500 – 543 mya
Cambrian 543 – 490 mya
Ordovician 490 – 443 mya
Silurian 443 – 417 mya
Devonian 417 – 354 mya
Carboniferous 354 – 290 mya
Permian 290 – 248 mya
Triassic 248 – 206 mya
Jurassic 206 – 144 mya
Cretaceous 144 – 65 mya
Palaeogene 65 – 23 mya
Neogene 23 – 2.5 mya
Quarternary 2.5 mya – present

(mya = millions of years ago)
An easy way to remember the order of these eras is to use the old trusty method of mnemonics:

For Cambrian to Cretaceous:
Camels Often Sit Down CARefully, PERhaps Their Joints CREak

For the full lot:
Professors Contend Older Strata Definitely Confirm Previous Times, Judging Current Period Non-Quiescent



  1. I love the mnemonics! I learned them the hard way. The full “professors contend” mnemonics is fantastic.

  2. Crack

  3. I learned a slight variation on the Camel one that includes the Precambrian and Periods of the Caenozoic:

    Pack CAmels ORDinarily SIt Down CARefully, PERhaps Their Joints CREak, Perhaps Not. Questions?

  4. I wish I had known these mnemonics 35 years ago, when I was studying “O” and “A” level Geology. We too had to learn them the hard way, ..only I didn’t! I’m no good with bare facts, but one reading of these and there they are, memorised and stuck in my foggy brain. Many thanks, and also to Barry on “Eggheads” last night, who rattled them off too fast for me to catch them, so I found this page instead.


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