GEOLOGICAL PERIODS
http://www.real-memory-improvement.com/geological-periods.html
The geological periods are those long, long time frames, spanning millions of years, that
geologists have split Earth's history into, in order to make some sense of it all. Each of these is
called a geological period, and it, in turn, is split into epochs. The history of the Earth is
fascinating and dramatic, and if you want to read a wonderful introduction to the studies and
explore geology for yourself, visit this BBC site which contains many links to the various
geological periods and further links to pages on the various life forms around at the time.
or take a look at this page, which presents the subject of geology for kids, but does it so well
that we can all appreciate it.
For the rest of us, content, for the time being, to settle for memorizing the names and the order
of the geological periods, let's just focus on that. The main geological periods (working from
the distant past) are classified as:
Pre-Cambrian
Cambrian
Ordovician
Silurian
Devonian
Carboniferous
Permian
Triassic
Jurassic
Cretaceous
Eocene
Oligocene
Miocene
Pliocene
Pleistocene
Recent
A widely used mnemonic to help remember this list is as follows:
**note – The two top phrases refer to the Periods, while the phrase in
parentheses refers to the last 7 Epoch’s. (The 8th Epoch is suggested as
Anthropogene. (in some text it is still part of the Holocene Epoch)
Pregnant Camels Often Sit Down Carefully.
Perhaps Their Joints Can’t Tolerate Quickness?
(Perhaps Effective Oiling Might Prolong Perfect Health)
Now that's what I call a mnemonic! It's not hard to remember, it brings up vivid images, and it
makes sense, in a sort of weird, humorous way. Spend a few minutes memorizing that
mnemonic and you'll have made a good start in remembering the different periods of geological
time, in order. And once you have that boxed off, you can go further if you choose to. You can
learn more about what characterizes each geological period, what life forms were about at the
time, and what geological or paleontological event brought about the change to the next period
(since the geological periods are defined by the events, sometimes events of cataclysmic
geology, that either started or ended them).
This is just one example of how using a mnemonic can be a valuable stepping stone on the way
to really learning a subject.
The table below gives you some brief details of each of the geological periods. It indicates when
certain life forms appeared and gives a very broad overview of the way life itself developed, in
all its amazing diversity. This isn't a magic bullet to make learning an automatic process, but it
certainly is a shortcut to getting a good grounding in a subject. It's also a perfect way to
present geology for kids.
Bear in mind that the geological periods from the Cambrian onwards cover only a fraction of
Earth's history. The planet has been around for probably 4.5 billion years. The first life probably
didn't evolve until 3.8 billion years ago, and consisted of single celled prokaryotic cells (the
cells lacking both a nucleus and a membrane) such as bacteria. The kind of life forms that we
are familiar with didn't begin to appear until about 570 million years ago.
Human life, in comparison, has only existed for perhaps a couple of million years, a mere blip
in the Earth's long and varied history - much, much less than one percent!
An overview of the periods of geological time
If you take a look at the table you can learn a lot in just few minutes. For
example,

Most of the Earth's history lies in the Pre-Cambrian Period (about 90%),
stretching way back into the Earth's mostly lifeless era, when the only life
consisted of tiny multi-celled organisms

Life on Earth after the Pre-Cambrian Period (complex organisms at least) was
mainly marine life and plants for about 130m years or so

For another 150m years life abounded and developed in all imaginable forms,
then most species became extinct

For another 100-200m years dinosaurs were dominant, with mammals eventually
starting to make an appearance

Then, about 65m years ago, the dinosaurs and most other species were wiped
out, possibly by an asteroid strike, and then, after the cataclysm, smaller
animals, including mammals, slowly came into their own

Over the last 50m years or so, monkeys, apes and hominids developed to the
point where various species of humans eventually gained a foothold

Homo sapiens (modern man) developed over the last 2m years or so

Over the last 50-100,000 years or so homo sapiens developed the skills and
techniques that allowed him to spread into every part of the world and make use
of tools, farming and eventually living in a society rather than just as scattered
individuals and families
Obviously this is just my brief take on things, and I don't claim any great
accuracy. But the thing is, it shows the kind of thinking that can start to make
sense out of a brief list of details. And that list is of very limited use to you if
you can't even remember it! That's where mnemonics come in, or any
memorization method that works for you.
An example of memory techniques in use
So this is just an example of how you can really use your improved memory. Instead of grinding
to a halt because the subject just seems too complex and too difficult to remember, you can at
least make a start by using simple memory techniques. From there, who knows? Perhaps you'll
go on to study geology, or paleontology, and be better prepared to handle it.
You can, for instance (as shown above) use a simple mnemonic to get a handle
on something as huge as the geological time scale, and from there you can
move on, memorizing some basic facts about each of the respective geological
periods. Working this way, and treating it as a bit of a memory game, you might
find it a lot more fun and a lot easier and more useful than more traditional
learning methods.
Geological Periods
Period
Recent =
Cenozoic
Approx.
Duration
Characteristics, Events
10,000 years
ago to the
Larger mammals - humans
present time
Pleistocene
2 million years
Pliocene
3 million years
Mammals developing further, many of
them (such as lemurs) very small to
better cope with the harsh temperatures
of the ice ages - apes, primates,
Miocene
17 million
hominids appear - cataclysm, possibly
years
caused by an asteroid strike in the
Yucatan Peninsula, about 65m years
Oligocene
13 million
ago, wipes out most of the larger
years
dominant species of the time (inc.
Eocene
Cretaceous
Jurassic
Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
22 million
dinosaurs)
years
80 million
Dinosaurs and other reptiles dominant
years
- seed-bearing plants appear
54 million
Flying reptiles (pterosaurs), larger
years
dinosaurs, earliest birds
51 million
Crocodiles, turtles, early dinosaurs, first
years
mammals appear
48 million
Large reptiles and amphibians - most
years
species become extinct
60 million
Swampy forests - insects, amphibians,
years
reptiles, crustaceans, fishes
57 million
Diversity in marine life and plants - first
years
trees - wingless insects
28 million
First jawed fish - giant scorpions -
years
corals
45 million
More diversity in marine life, Including
years
vertebrates - vascular plants
54 million
years
Invertebrate sea life
Ended about
Pre-Cambrian
542 million
Formation of oceans, atmosphere and
years ago.
continents - bacteria - oxygen builds
Covers about
up - multi-celled organisms begin to
90% of the
appear
Earth's history
Note: This is not an exhaustive list of characteristics of the geological periods, just a cut-down
version suitable for grasping an overview of the subject, and for providing an exercise in
memorization. It can be helpful though if you want to start to explore geology, or if you are
presenting geology for kids to learn.