Geologic Time Scale

GEOLOGIC TIME SCALE
Scientists have put together the geologic

time scale to describe the order and
duration of major events on Earth for the
last 4.5 billion years. Some examples of
events listed on the geologic time scale
include the first appearance of plant life on
Earth, the first appearance of animals on
Earth, the formation of Earth's mountains,
and the extinction of the dinosaurs. The
geological history of the Earth is divided into
several Eras. These eras are further divided
into Periods, which are sub-divided into
Epochs. Durations of each Period have been
demarcated and the evolution of vegetation
and animals have explained accordingly.
After this lesson, you are expected to describe how Earth’s history can be
interpreted from the geologic time scale. (S1/12ES-I-e-29)
Specifically, you will be able to:

a. explain the geologic time scale;
b. interpret the history of the Earth based from the geologic time scale;
c. differentiate eons, eras, periods, and epochs; and
d. value the importance of geologic time scale.
Geologic time scale
The geologic time scale (GTS) is a system of chronological

dating that relates geological strata (stratigraphy) to time. It is
used by geologists, paleontologists, and other Earth scientists to
describe the timing and relationships of events that have
occurred during Earth's history.
4 MAJOR
DIVISIONS OF
THE GEOLOGIC
TIME SCALE
EON
The largest time span of the
geologic time scale
GEOLOGIC TIME IS DIVIDED
INTO TWO EONS
A.Precambrian Eon
refers to the earliest part of the earth’s history.
B. Phanerozoic Eon
the current geologic eon in the geologic time

scale.
PRECAMBRIAN EON
divided into three eons, the Hadean, Archean, and Proterozoic eon.
HADEAN EON
occured 4.6 billion to 4 billion years ago. During this time the solar system
is forming within a cloud of dust and gas known as the solar nebula which
eventually spawned planets and ect.
ARCHEAN EON
between 4 billion and 2.5 billion years ago, the first form of life on our
planet was created in the oceans.
exactly when or how it happened is unknown, but micro fossils of this
time indicate that life began in the oceans about 3.5 billion years ago
By the end of the Archean the ocean floor was covered in a living mat
of bacterial life.
PROTEROZOIC EON
also called the age of the hidden life, started 2.5 billion years ago. In this
time, enough shield rock had formed to start recognizable geologic
processes such as plate tectonics.
PROTEROZOIC EON
contain many definite traces of primitive life forms – the fossil remains of
bacteria and blue-green algae as well as of the first oxygen dependent
animals.
PHANEROZOIC EON
The time in which abundant animal and plant life has existed. It covers 541
million years to the present.
The Phanerozoic eon is subdivided into three
ERA
Paleozoic Era Mesozoic Era Cenozoic Era

PALEOZOIC ERA
The era ran from about 542 million years ago
to 251 million years ago.
The era began with the breakup of one supercontinent and
the formation of another. plants became widespread.
The Paleozoic era was divided
into:
1.Cambrian
2.Ordovician
3.Silurian
4.Devonian
5.Carboniferous
6.Permian
The Divisions of Percent Millions of years
Geologic Time
The age of the
100% 4,600 my
Earth
Cenozoic Era 1.5 69 my
Mesozoic Era 4 184 my
Paleozoic Era 6.5 299 my
Precambrian
88 4,048 my
Time
Cambrian Period
(53 million years ago)
Known for ushering in an explosion of life on earth.

This Cambrian explosion included the evolution of
arthropods(ancestors of today’s insects and
crustaceans) and chordates (animals with rudimentary
spinal chords).
Ordovician Period
(45 million years ago)
Marked in the fossil record by an abundance of

marine invertebrates. Perhaps the most famous of
these invertebrates was the trilobite, an armored
arthropod that scuttled around the seafloor about
270 million years before going extinct.
Silurian Period
(443 million to 416 million years ago)
The spread of jawless fish throughout the seas,

mollusks and corals thrived in the oceans and land
the first undisputed evidence of terrestrial life.
This was the time the plants evolved though they
most likely did not yet have leaves or the vascular
tissue siphon up water and nutrients.
Carboniferous Period
Long before the birds evolve the tetrapods began

laying eggs on land for the first time during this
period. Allowing them to break from an amphibious
lifestyle.
Tetrapods were
bocoming more
specialized and
two new groups
of animals
evolved. The first
were marine
reptiles including
lizards and
snakes.
The second were
archosaurs which
would give rise to
crocodiles,
dinosaurs and
birds.
Permian Period
This period would end wit the largest mass extinction

ever. The Permian extinction.
Before the mass extinction the
coral reefs flourished providing
shelter for fish and shelled
creatures such as nautiloids
and ammonoids.
Modern conifers and ginkgo
trees evolved on land.
Terrestrial vertebrates evolved
to become herbivores taking
advantage of the new plant life
that had colonized the land.
MESOZOIC ERA
This period spans
from about 252
million years ago
to 66 million years
ago, was known
as the age of
reptiles or the
age of dinosaurs
because of its
famous
inhabitants.
Triasic Period
252 million – 200

million years
ago.
Jurassic Period
200 million – 145

million years ago
Cretaceous Era
145 million – 66
million years ago
CENOZOIC ERA
began 65
million years
ago
The current locations of the
continents and their modern-day
inhabitants including humans can
be traced to this period
The Cenozoic era also
known as the age of
mammals because
the extinction of many
groups of giant
mammals allowing
smaller species to
thrive and diversify
because their
predators no longer
existed.
Paleogene Period
(65 million – 23 million years ago
consist of the Paleocene, Eocene,

and Oligocene epoch.
The beginning of the Paleogene period was a time for
mammals that survived from the Cretaceous period.
Later in this period, rodents and small horses, such as

Hyracotherium are common and rhinoceroses and
elephants appear. As the period ends, dogs, cats, and pigs
become commonplace.
Neogene Period
(23 million – 2.6 million years ago)
consist of the Miocene and

Pliocene epochs
Neogene Period
Gives rise to the early primates, including the early
humans. Bovids including cattle, sheep, goats,
antelope, and gazelle flourish during this period.
Quaternary Period
(2.6 million years ago to the present year)
consist of the Pleistocene and

Holocene epochs
cave-lions, sabre-toothed cats, cave bears, giant deer, wolly
mammoths and wolly rhinoceroses, were prevailing species of the
quaternary period.
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GEOLOGIC TIME SCALE

Scientists have put together the geologic

Specifically, you will be able to:

The geologic time scale (GTS) is a system of chronological

the current geologic eon in the geologic time

Paleozoic Era Mesozoic Era Cenozoic Era

Known for ushering in an explosion of life on earth.

Marked in the fossil record by an abundance of

The spread of jawless fish throughout the seas,

Long before the birds evolve the tetrapods began

This period would end wit the largest mass extinction

252 million – 200

200 million – 145

consist of the Paleocene, Eocene,

Later in this period, rodents and small horses, such as

consist of the Miocene and

consist of the Pleistocene and

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