Time Periods Made Simple(ish)

Okay, this one will be rather simple, there’s just a lot of it. Now we all know of human years and dog years, some of us even know of horse years and parrot years; human years are the same as earth years but the earth has it’s own timescale: the geological timescale.

To us, a year is three hundred and sixty five and a quarter days, but to the earth, that’s not even a plank unit (the smallest measurable amount of time). Looking back on human history, one would say we’ve been around for quite some time, but as members of the genus Homo we’ve barely been around for 2.5 million years, as Homo sapiens we haven’t even been around for half a million years. Our history as humans is nothing to the earth in terms of time. Dinosaurs, on the other hand, they really stuck around, having ruled the planet for almost 183 million years, the only clade of animals to have gone through almost an entire era of the earth’s history.


Speaking of eras, this is where I take the earth’s history and show that it has been segmented into (relatively) bite-sized chunks.

The earth’s history can be separated into Eons, Eras, Periods, Epochs and Ages.


Precambrian Eon: by far the longest of the two eons of the earth, the Precambrian stretches from about 4500mya (millions of years ago/million years ago) to roughly 542mya. Under some systems the Precambrian is split into two eons, the Archean and the Proterozoic.

Archean Eras – Eoarchean, Palaeoarchean, Mesoarchean and Neoarchean.

Proterozoic Eras – Paleoproterzoic (which is split into the Siderian, Rhyacian, Orosirian and Statherian Periods), the Mesoproterzoic (containing the Calymmian, Ectasian and Stenian Periods) and the Neoproterzoic (which is split into the Tonian, Cryogenian and Ediacaran Periods).


Then comes the Phanerozoic Eon, stretching from the end of the Precambrian all the way up to present day.

Eras = Paleozoic, Mesozioc and Cenozoic.

Paleozoic Periods – Cambrian, Ordovician, Silurian, Devonian ,Carboniferous and Permian.

Cambrian Epochs – split into the Lower Series (Fortunian and Stage 2 Ages), Series 2 (Stage 3 and Stage 4 Ages), Series 3 (Stage 5, Drumian and Guzhangian Ages) and Furongian (Paibian, Stage 9 and Stage 10 Ages).

Ordovician Epochs – Lower (Tremadocian and Floian Ages), Middle (Dapingian and Darriwilian Ages) and Upper (Sandbian, Katian and Hirnantian Ages).

Silurian Epochs – Llandovery (Rhuddanian, Aeronian and Telychian Ages), Wenlock (Shienwoodian and Momerian Ages), Ludlow (Gorstian and Ludfordian Ages) and the Pridoli (so short that it shares it’s name with it’s only Age).

Devonian Epochs – Lower (Lochkovian, Pragian and Emsian Ages), Middle (Eifelian and Givetian Ages) and Upper (Frasnian and Famennian Ages).

Carboniferous Epochs – Mississippian (split into the Tournaisian, Visean and Serpukhovian Ages; which are also called the Lower, Middle and Upper Ages of the Mississippian Epoch) and the Pennsylvanian Epoch (which is split into the Bashkirian/Lower, Moscovian/Middle, Kasimovian and Gzhelian (both Upper) Ages.

Permian Epochs – Cisuralian (containing the Asselian, Sakmarian, Artinskian and Kungurian Ages), Guadalupian (Roadian, Wordian and Capitanian Ages) and Lopingian (Wuchiapingian and Changhsingian Ages).

Now for everyone’s favorite Era, the Mesozoic.

Mesozoic Periods – Triassic, Jurassic and Cretaceous.

Triassic Epochs – Lower (Induan and Olenikian Ages), Middle (Anisian and Ladinian Ages) and Upper (Carnian, Norian and Rhaetian Ages).

Jurassic Epochs – Lower (Hettangian, Sinemurian, Pliensbachian and Toarcian Ages), Middle (Aalenian, Bajocian, Bathonian and Callovian) and Upper (Oxfordian, Kimmeridgian and Tithonian Ages).

Cretaceous Epochs – Lower (Berrisian, Valanginian, Hauterivian, Barremian, Aptian and Albian Ages) and Upper (Cenomanian, Turonian, Coniacian, Santonian, Campanian and Maastrichtian Ages).

The Cenozoic Era.

Cenozoic Periods – Paleogene and Neogene.

Paleogene Epochs – Paleocene (Danian, Selandian and Thanetian Ages), Eocene (Ypresian, Lutetian, Bartonian and Priabonian Ages) and the Oligocene (Rupelian and Chattian Ages).

Neogene Epochs – Miocene (Aquitanian, Burdigalian, Langhian, Serravallian, Tortonian and Messinian Ages), Pliocene (Zanclean, Piacenzian and Gelasian Ages), Pliestocene (Calabrian, Ionian and Upper Ages) and the Holocene (the period we are currently living in, also so short that it technically counts as it’s own Age).


Now, you may be thinking; “cannibalpredator, that’s a lot to take in, you said this would be simple and easy to understand”. Well, it is simple, there’s just a lot of it.

This will probably be my last post for the day, but I’ve now explained the absolute basics of prehistory and palaeontology, now that we’ve been through classifications and the geological timescale. Up next, The Formation of a Fossil.


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