Earth and Life Science

1. GEOLOGIC TIME SCALE
for Earth and Life Science/Grade11
Quarter1/ Week 7
NegOr_Q1_Earth and LifeSci11_SLKWeek7_v2

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FOREWORD
This Self-Learning Kit introduces the concept of
geologic time scale being divided into time segments that
will explain the major events in Earth's history.
Moreover, dating methods will be discuss in this learning
kit, to reconstruct clues from the history of rocks, minerals,
and other materials on earth in order to understand the
subdivisions of geologic time scale.
Hence, this learning kit will be very helpful in enriching
your knowledge and ideas on the science concepts.

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LEARNING COMPTENCIES:
➢ Explain how relative and absolute dating were
used to determine the subdivisions of geologic
time(S11/12ES -Ie-27)
➢ Describe how the Earth's history can be
interpreted from the geologic time
scale(S11/12ES -Ie-29)
OBJECTIVES:
At the end of this module, you will be able to:
K: Describe each division of time in the history of life on
Earth;
S: Determine the subdivisions of geologic time using the
dating methods; and
A: Appreciate the use relative and absolute dating to
determine the subdivisions of geologic time.
1.

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I. WHAT HAPPENED
Activity 1: IT’S show TIME!
Calculate the length of time of each of the Eras and Precambrian Time
and write it in your science notebook.
Hint: Focus on the time divisions between the eras and subtract to find out how long
each era lasted)
PERIOD MILLIONSOF
YEARS AGO
CENOZOIC ERA QUATERNARY
__________________1.6_____
NEOGENE
__________________23_____
PALEOGENE
__________________66_____
MESOZOIC ERA
CREATACIOUS
__________________146_____
JURASSIC
__________________200_____
TRIASSIC
__________________251_____
PALEOZOIC ERA
PERMIAN
__________________299_____
CARBONIFEROUS
__________________359_____
DEVONIAN
__________________416_____
SILURIAN
__________________444_____
ORDOVICIAN
__________________488_____
CAMBRIAN
__________________542_____
PRECAMBRIAN
TIME
4,600

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I. Complete the information below with your correct answer and
write it in your science notebook.
Find out how long each Era lasted million years ago?
Cnezoic = ___ Mesozoic = ___
Paleozoic = ____ Precambrian=
____
II. WHAT I NEED TO KNOW
Scientists created the
geologic time scale based
on fossil evidence. It divides
Earth’s history into blocks of
time with each block
separated by important
events, such as the
disappearance of a species
of fossil from the rock record.
In the geologic time scale,
the youngest ages are on
the top and the oldest on
the bottom. The time scale is
based upon relative times,
therefore there aren’t any
specific times listed with
each era. The timescale is
divided into eons, each eon
into eras, each era into
periods, and each period
into epochs.
Geologic Time

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Living things play critical roles in the development of geologic time
scales, because they have undergone evolutionary changes over
geologic time. Moreover, particular kinds of organisms are
characteristic of particular parts of the geologic record. By
correlating the strata in which certain types of fossils are found, the
geologic history of various regions—and of Earth as a whole—can be
reconstructed. The relative geologic time scale developed from the
fossil record has been numerically quantified by means of
absolute dates obtained with radiometric dating methods.
https://www.britannica.com/science/geologic-time
The extensive interval of time occupied by the
geologic history of Earth. Formal geologic time began at the start of
the Archean Eon (4.0 billion to 2.5 billion years ago) and continues
to the present day. Modern geologic time scales additionally often
include the Hadean Eon, which is an informal interval that extends
from about 4.6 billion years ago (corresponding to Earth’s initial
formation to 4.0 billion years ago. Geologic time is, in effect, that
segment of Earth history that is represented by and recorded in
the planet’s rock strata.The geologic time scale is the “calendar”
for events in Earth history. It subdivides all time into named units of
abstract time called—in descending order of duration—
eons, eras, periods, epochs, and ages. The enumeration of those
geologic time units is based on stratigraphy, which is the and
classification of rock strata. The fossil forms that occur in the rocks,
however, provide the chief means of establishing a geologic time
scale, with the timing of the emergence and disappearance of
widespread species from the fossil record being used
to delineate the beginnings and endings of ages, epochs, periods,
and other intervals. One of the most widely used standard charts
showing the relationships between the various intervals of geologic
time is the International Chronostratigraphic Chart.

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Dating Methods: Establishing the Evolution of Earth
To reconstruct the history of rocks, minerals, and other materials on
earth geologists use two kinds of dating methods.
1. Relative dating
Relative dating is a method that determines the order of
geologic event is used to arrange geological events, and the
rocks they leave behind, in a sequence. The method of
reading the order is called stratigraphy (layers of rock are
called strata). Relative dating does not provide actual
numerical dates for the rocks.
Timeline of Earth's history Significant
moments in Earth's history.Encyclopædia
Britannica, Inc./Christine McCabe
Grand Canyon rock layering The steep walls
of the Grand Canyon contain a number of
layers of sedimentary rock laid over millions
of years. The lower formations belong to the
early Precambrian age, while the upper
layers are of the Paleozoic age.
The line between the two sets of formations
is called the Great
Unconformity.Encyclopædia Britannica, Inc.
Rock layers and relative dating
The image on the left shows cliffs near Whanganui. The diagram on the right
shows how the original, horizontal rock layers have changed due to tectonic
activity. Relative dating puts the sequences of rocks layers into chronological
order. Although the layers are no longer horizontal, geologists able to
determine their order.

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Fossils and relative dating
Fossils are organisms that have existed, disappeared and become
extinct whose remains are left in sedimentary rocks. They are
important in showing the relative ages of sedimentary rocks.
Geologists have studied the order in which fossils appeared and
disappeared through time and rocks as biostratigraphy.
Fossils are helpful guide to match rocks of the same age, even
when they a long way apart. This process is called correlation, an
important matching process in constructing geological timescales.
Using index fossils
Trilobites lived at a different time to ammonites and belemnites.
Finding a trilobite fossil in a rock tells you the rock was formed in the
Palaeozoic era.
A particular useful in correlating rocks is an index fossil. A good
index fossil needs to have lived during one specific time period, be
easy to identify and have been abundant and found in many
places.
The ammonites for instance have lived in the Mesozoic era. If you
find ammonites in a rock in the South Island and also in the North
Island, you can say that both rocks are Mesozoic. Various species of
ammonites lived at different times within the Mesozoic, therefore
identifying a fossil species can help tell when a rock was formed.

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2. Absolute dating
Geologists use the absolute method also known as numerical rating
in giving the rocks actual date or date range in number of years. This
is in contrast to relative dating which only gives the order of time to
geological events.
Absolute dating is helpful in determining which sediments settled first
and in providing their approximate age. This method uses
radioactive materials that calculate the age of rocks. There are
isotopes in these radioactive materials that breaks or decay at a
constant rate. When the rates of decay of the parent and daughter
isotopes is measured, then when the rocks were formed can be
calculated. Each element has a unique rate of decay that will tell a
particular age range. For instance, rocks older than 1 million years is
determined based on the decay of isotope Ur-238 to Pb-206.

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III. WHAT I HAVE LEARNED
Activity 2.1
Activity 2.2 : Wazz Up in the Chart?
Directions:
Identify in which characteristic corresponds to the type of dating method.
Place a check mark (√) in the correct column to indicate your answer. Use
the discussion above or other reference materials if necessary for your
answer.
GEOLOGIC TIME SCALE AND THE DATING
METHOD
Evidence Relative Dating
Method
Absolute Dating
Method
1. layers in the rocks
2. radioactive
isotopes determine
rocks older than 1
myo
3. actual date of
parent and
daughter formation
in rocks
4. ammonites lived in
the Mesozoic era

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REFERENCES
“Absolute dating”.
https://www.sciencelearn.org.nz/resources/1486-absolute-
datingPublished 20 May 2011. Retrieve from Science
Learning Hub July 10,
2020.
“Back to the Past with the Geologic Time Scale”. Florida State
University.
https://www.cpalms.org/Public/PreviewResourceLesson/Previe
w/43470.
Retrieved from Science Learning HubJuly 10, 2020.
“Dating the Past”.
https://www.sciencelearn.org.nz/resources/1478- dating-the
- past-introduction. Published 11 May 2011. Retrieve from
Science Learning
Hub July 10, 2020.
“Relative dating”. Curious Minds by New Zealand Government.
https://www.sciencelearn.org.nz/resources/1485-relative-
dating. Retrieve
from Science Learning Hub July 10, 2020.

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DEPARTMENT OF EDUCATION
SCHOOLS DIVISION OF NEGROS ORIENTAL
SENEN PRISCILLO P. PAULIN, CESO V
Schools Division Superintendent
FAY C. LUAREZ, TM, Ed.D., Ph.D.
OIC - Assistant Schools Division Superintendent
Acting CID Chief
ADOLF P. AGUILAR
OIC - Assistant Schools Division Superintendent
NILITA L. RAGAY, Ed.D.
OIC - Assistant Schools Division Superintendent
ROSELA R. ABIERA
Education Program Supervisor – (LRMS)
ARNOLD R. JUNGCO
Education Program Supervisor – (SCIENCE & MATH)
MARICEL S. RASID
Librarian II (LRMDS)
ELMAR L. CABRERA
PDO II (LRMDS)
WINDA D. OBEDENCIO
Writer/ILLUSTRATOR
WINDA D. OBEDENCIO
RAFAEL REX B. FELISILDA
LAY-OUT ARTISTS
BETA QA TEAM
ZENAIDA A. ACADEMIA
DORIN FAYE D. CADAYDAY
MERCY G. DAGOY
RANJEL D. ESTIMAR
MARIA SALOME B. GOMEZ
JUSTIN PAUL ARSENIO C. KINAMOT
ARJIE T. PALUMPA
ALPHA QA TEAM
LIEZEL A. AGOR
EUFRATES G. ANSOK JR.
JOAN Y. BUBULI
MA.OFELIA BUSCATO
DEXTER D. PAIRA
LIELIN A. DE LA ZERNA

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This engaging module discusses the
significant events of the earth’s
history through the Geologic time
scale. The timescale is divided into
eons, each eon into eras, each era
into periods, and each period into
epochs.
The dating methods namely the
relative dating and absolute dating
validates the certainty of each
subdivisions in the geologic time
scale.
SYNOPSIS
ABOUT THE AUTHOR
WINDA D. OBEDENCIO is a senior high school
teacher at Sibulan National High School and
the Teacher-in-Charge of the same school. She
graduated at Silliman University with the
Bachelors Degree in Secondary Education
major in General Science. She finished her
graduate studies at Southwestern University in
Cebu City with Master of Arts in Teaching
Science.