May 23, 2011
|Geologic Timescale Spiral. Image courtesy of USGS. Taken from Wikipedia here. Click to enlarge.|
A geologic Age spanning from ~5.33 million years ago to ~3.60 million years ago in the Pliocene Epoch.
Never heard of the Zanclean? Don’t worry. I had never heard of it either before I did a little research for this blog post. I have only memorized the geologic timescale through the Epochs, and then only for the Cenozoic (65 million years ago to present).
The Zanclean is defined as the geologic Age which spans from ~5.33 million years ago to ~3.60 million years ago. You might be thinking to yourself that this is a strange bracket for geologic time. Why not just make the Age an even 5 to 3 million years ago? If you look closely at the geologic timescale you’ll notice that the geologic Ages (as well as the Eons, Eras, Periods, and Epochs… but we’ll get to that in a minute) are all different lengths of time that seem random.
The geologic Ages do span inconsistent lengths of absolute time. This is because Ages such as the Zanclean (which was introduced in 1868, according to Wikipedia) were defined long before absolute dating of rocks became possible after the discovery of radioactivity in the late 1800s and the development of radioactive dating of rocks and minerals in the early to mid 1900s. Scientists have only been able to confidently determine absolute ages for rocks since the 1960s or so, and every year techniques for dating rocks become better with smaller error bars.
Remarkably, geologists defined the entire geologic timescale (although standardizing this timescale internationally is still an ongoing process) prior to the development of absolute dating of rocks and minerals. Although the absolute ages were unknown, geologists were able to work out the time periods based on the evolution of the fossil record. The main divisions of time are based on time periods when certain types of ancient organisms lived.
Boundaries between different periods of geologic time often mark periods of mass extinctions where there was a sudden, dramatic change in the fossil record. The most famous example of this is the boundary between the Tertiary and the Cretaceous, also known as the K-T boundary. This boundary ~65 million years ago is marked by a mass extinction event famously known to have wiped out all non-avian dinosaurs. The boundary is known at the K-T boundary because “K” is used for Cretaceous and “T” is used for Tertiary on geologic maps and other places where shorthand is appropriate. Geologists have known for generations about boundaries such as K-T and about ages such as the Zanclean, but it has only been in the second half of the 1900s that they were able to start assigning absolute ages to these geologic times.
I mentioned above that I had never really heard of the Zanclean before. That’s true– I have never bothered to memorize the geologic Ages, one of the smallest divisions of geologic time, and the smallest one recognized by the International Commission on Stratigraphy or ICS. I don’t think I will ever bother to memorize them as I can easily look them up and, honestly, I think it’s a bit silly to subdivide geologic time into such small sections. Whenever I read papers that bother with naming various Ages, I just keep a copy of the geologic timescale nearby. I have taken the time to memorize the larger divisions of geologic time, which are (from largest to smallest): Eons, Eras, Periods, and Epochs. And, as I mentioned previously, I’ve only memorized the Cenozoic Epochs because they’re the only Epochs with names. Otherwise, it’s just “early,” “middle,” and “late,” and I find these very difficult to memorize.
The way that I originally memorized the Periods and so on was through use of mnemonics. My favorite mnemonic for the geologic Periods is Cold Oysters Seldom Develop Many Precious Pearls, Their Juices Congeal Too Quickly which helps me remember: Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, Permian, Triassic, Jurassic, Cretaceous, Tertiary, Quaternary. For the Cenozoic Epochs, I like the mnemonic Pigeon Egg Omelets Make People Puke Hourly which helps me remember Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, Holocene.
So perhaps what I need to remember the Ages is an appropriate (and very long!) mnemonic. I propose a challenge to my blog readers: come up with a mnemonic for the geologic Ages.
The Ages are: CALABRIAN, GELASIAN, PIACENZIAN, ZANCLEAN, MESSINIAN, TORTONIAN, SERRAVALLIAN, LANGHIAN, BURDIGALIAN, AQUITANIAN, CHATTIAN, RUPELIAN, PRIABONIAN, BARTONIAN, LUTETIAN, YPRESIAN, THANETIAN, SELANDIAN, DANIAN, MAASTRICHTIAN, CAMPANIAN, SANTONIAN, CONIACIAN, TURONIAN, CENOMANIAN, ALBIAN, APTIAN, BARREMIAN, HAUTERIVIAN, VALANGINIAN, BERRIASIAN, TITHONIAN, KIMMERIDGIAN, OXFORDIAN, CALLOVIAN, BATHONIAN, BAJOCIAN, AALENIAN, TOARCIAN, PLIENSBACHIAN, SINEMURIAN, HETTANGIAN, RHAETIAN, NORIAN, CARNIAN, LADINIAN, ANISIAN, OLENEKIAN, INDUAN, CHANGHSINGIAN, WUCHIAPINGIAN, CAPITANIAN, WORDIAN, ROADIAN, KUNGURIAN, ARTINSKIAN, SAKMARIAN, ASSELIAN, GZELIAN, KASIMOVIAN, MOSCOVIAN, BASHKIRIAN, SERPUKHOVIAN, VISEAN, TOURNAISIAN, FAMENNIAN, FRASNIAN, GIVETIAN, EIFELIAN, EMSIAN, PRAGHIAN, LOCKHOVIAN, PRIDOLIAN, LUDFORDIAN, GORSTIAN, HOMERIAN, SHEINWOODIAN, TELYCHIAN, AERONIAN, RHUDDANIAN, HIRNANTIAN, KATIAN, SANDBIAN, DARRIWILIAN, DAPINGIAN, FLOIAN, TREMADOCIAN, STAGE 10, STAGE 9, PAIBIAN, GUZHANGIAN, DRUMIAN, STAGE 5, STAGE 4, STAGE 3, STAGE 2, FORTUNIAN.
Phew! I hope I didn’t miss any of the ages. I apologize that they are all written in capital letters. I’m not yelling at you. I just copied and pasted the names from a geologic timescale, and I’m too lazy to change them out of all capital letters.
So, see if you can come up with a long-winded mneumonic. You know, something like:
Campbell gave pretty, zany, messy, terribly sexy, lovable, bright, amazing, cheerful Rachel praises by letters youthfully, tentatively sent. Did Mister Campbell say convincing truths carefully ascertained about beautiful, hauntingly vividly beautiful, tantalizing, kiss-invoking, outstanding, creative, breathtaking, blushing, all-knowing, terrific, pleasing, scintillating, hot Rachel? No. Courage leaves an overwhelmed, inconsolable Campbell. Why?! Campbell wondered. Rachel knows a summer affair grows kinda muted because summer visions tear, famously fragmenting ephemeral, end-bound, primitive love. Perhaps lust graces hot summer times, announces Rachel. However, keep summer dreams dampered, flowing temporally, staying 10, staying 9, painfully gone days, staying 5, staying 4, staying 3, staying 2, forgotten.
Please improve upon my rather “film noir”, adjective-filled, and, admittedly, very terrible mneumonic. Though, on second thought, I don’t think this (or any) epic mnemonic is going to be that helpful in memorizing geologic Ages. On third thought, memorizing the geologic Ages is stupid. The only reason I can fathom for memorizing the Ages is to impress geology friends at a bar. Maybe I’ll work on it sometime, but honestly I think it’s only marginally more useful than memorizing digits of pi.