WEEKLY LEARNING ACTIVITY SHEETS

Earth Science, Quarter 2, Week 7

HISTORY OF THE EARTH AND GEOLOGIC TIME

Learning Competency:
Describe the history of the Earth through geologic time (MELC-S11ES-IIj-39)

Specific Objectives:
1. Describe the history of the Earth through geologic time;
2. Determine what happened in each era or period of the geologic time; and
3. Discuss the impacts of human beings despite their brief existence according to the
geologic time scale.

Key Concepts

History of the Earth

• The Earth’s history is recorded in the rocks of the crust. Scientists used assumption
called uniformitarianism in order to relate what we know about present-day processes
to past events – the present-day is the key to the past.
• Uniformitarianism states that the natural laws we know today have been constant
over the geologic past.

Earth’s Early Evolution

• As materials continued to accumulate, the high velocity impact of interplanetary debris
and the decay of radioactive elements caused the temperature of our planet to steadily
increase.
• During the period of intense heating Earth became hot enough that iron and nickel
began to melt. This process occurred rapidly on the scale of geologic and produced
Earth’s dense iron-rich core.
• The early period of heating also resulted in a magma ocean, about hundred kilometers
deep. Within the magma ocean buoyant masses of molten rock rose toward the surface
and eventually solidified to produce a thin, primitive crust – thus, the three major
divisions of the Earth’s interior – a) the iron – rich core, b) the thin primitive crust,
and c) its thickest layer, the mantle.
• The light materials – including water vapor, carbon dioxide and other gasses
escaped to form primitive atmosphere and shortly thereafter the oceans.

Geologic Time Scale

• The history and evolution of Earth are described using the geologic timescale. 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.
• The Geologic Time Scale is divided into big portions of time known as Eons. Eons are
further divided into Eras. Eras are divided into Periods.
• The Precambrian Time (the time of hidden life) is the point of time in which our planet
started to form. This is subdivided into Hadean, Archean, and Proterozoic Eon.
Meanwhile, Phanerozoic Eon, living organisms like plants and animals existed. It

Author: Laugo, Angie Flor A. / Monter, Lovely Fe G.

School/Station: Socorro National High School
Division: SIARGAO
email address: angieflor.arcular@deped.gov.ph/lovelyfe.monter@deped.gov.ph
 constitutes the time of multicellular life on Earth and the evolutionary process
happened.
• Phanerozoic Eon is further divided into the Paleozoic Era (time of ancient life),
Mesozoic Era (time of middle life), Cenozoic Era (time of recent life).

The Precambrian time

• Ranges from about 4.6 billion years ago, when the earth formed, to about 544 million
years ago, when abundant microscopic life appeared.
• Most of the rocks in this early part of Earth’s history have been extensively eroded
away, metamorphosed, obscured by overlying strata or recycled into Earth’s interior.
• The Earth’s earliest gasses were hypothesized to be swept into space by solar wind. As
the planet slowly cooled, a more sustaining atmosphere was formed.
• Gasses brought to the surface by volcanic processes created both primitive atmosphere
and an ocean. The first simple organisms were plants.
• During mid-Precambrian, organisms such as blue green algae developed a simple
version of photosynthesis.
• Photosynthetic organisms require carbon dioxide to utilize the sun’s energy. They keep
the carbon dioxide and expel oxygen. With the release of free oxygen, a primitive
ozone layer began to develop which reduced the amount of harmful ultraviolet radiation
reaching the Earth.
• The most common Precambrian fossils are stromatolites. These are not remains of
actual organisms, rather indirect pieces of evidence of algae. Many of Precambrian
fossils were preserved in hard, dense chemical sedimentary rock known as chert.
• Fossils of plants date from the middle Precambrian, but fossils of animals date in the
Precambrian. Towards the end of this period, fossil records revealed that diverse and
complete multi-celled organisms existed.

HADEAN EON
• Greek for “beneath the Earth”. It is the earliest time in Earth history and ranges from
the planet’s origin 4.6 billion years ago to 3.8 billion years ago.
• Solar System and Planet formed. Only a few Earth rocks are known that formed during
the Hadean Eon and no fossils of Hadean age are known, making it difficult to subdivide
the Hadean Eon based on fossils.

ARCHEAN EON
• Greek for “ancient”. There are few fossils among the rocks and they are not preserved
well enough to allow for finely tuned subdivision of this eon that spanned from 3.8 to
2.5 billion years ago.
• It was a time when the planet was inhospitable to life. However, it was during this time
that life on earth started to appear since the oldest dated bacterial microfossil were 3.5
billion years old.
• The fossil record does indicate that life began on Earth 3.2 to 3.5 billion years ago,
although the exact date is uncertain.

PROTEROZOIC EON
• Greek for “earlier life”. Diverse groups of fossils have been found in sedimentary rocks,
2.5 billion to 543 million years ago.
• It was a time of many important geologic events: appearance of stable continents,
bacterial, and archaean fossils, and eukaryotic cells.

Author: Laugo, Angie Flor A. / Monter, Lovely Fe G.

School/Station: Socorro National High School
Division: SIARGAO
email address: angieflor.arcular@deped.gov.ph/lovelyfe.monter@deped.gov.ph
 • The most complex are multicellular and have different kinds of cells arranged into
tissues and organs.
• Few types of shell-bearing organisms have been identified, but shelled organisms did
not become abundant until the Paleozoic Era.

PHANEROZOIC EON
• Phaneros is Greek for “evident”. Sedimentary rocks cover the most recent 543 million
years of geologic time and contained abundant fossils.
• Four changes occurred at the beginning of Phanerozoic time that greatly improved the
fossil record:
1. The number of species with shells and skeletons dramatically increased.
2. The total number of individual organisms preserved as fossils increased
greatly.
3. The total number of species preserved as fossils increased greatly.
4. The average sizes of individual organisms increased.

Paleozoic Era
• Began about 544 million years ago and lasted about 300 million years, during
which time sea levels rose and fell worldwide, allowing shallow seas to cover the
continents and marine life to flourish – from marine invertebrates to fishes, amphibians
and reptiles.
• The Paleozoic Era is divided into six (6) major periods: Cambrian, Ordovician,
Silurian, Devonian, Carboniferous, and Permian.

a. Cambrian Period
Almost all marine organisms came into existence as evidence by abundant
fossils. A most important event is the development of organisms having the ability to
secrete calcium carbonate and calcium phosphate for the formation of shells.
b. Ordovician Period
All major group of animals that could be preserved as fossils had appeared. This
period marks the earliest appearance of vertebrates – the jawless fish known as
agnatha. c. Silurian Period
The Silurian brought about the emergence of terrestrial life, the earliest being
the terrestrial plants with well-developed circulatory system (vascular plants). As
plants move ashore so did other terrestrial organisms. Air-breathing scorpions and
millipedes were common during the period.
d. Devonian Period
This period is known as the “age of fishes”. Lowland forests of seed ferns, scale
trees and true ferns flourished. Sharks, insects, and bony fishes developed. Today
the lung fishes and coelacanth, a “living fossil” have such internal nostrils and
breathe in a similar way. The first amphibians made their appearance, although able
to live on land, they need to return to water to lay their eggs.
e. Carboniferous period
Warm, moist climate conditions contributed to lash vegetation and dense
swampy forests. Insects under rapid evolution led to such diverse forms of giant
cockroaches and dragonflies. The evolution of the first reptiles took place with the
development of the amniotic egg, a porous shell containing a membrane that
provided an environment for an embryo.
• Ice covers large areas of the earth; swamps cover low lands; first mosses; great
coalforming forests form; seed ferns grow; winged insects appear

Author: Laugo, Angie Flor A. / Monter, Lovely Fe G.

School/Station: Socorro National High School
Division: SIARGAO
email address: angieflor.arcular@deped.gov.ph/lovelyfe.monter@deped.gov.ph
 f. Permian Period
The reptiles were well-suited to their environment that they ruled the Earth for
200 million years. The two major groups of reptiles – diapsids and synapsids
dominated this period. Diapsids gave rise to the dinosaurs. Synapsis gave rise to
mammals.

Mesozoic Era
• Known as the age of reptiles, it is made up of three periods: Triassic, Jurassic, and
Cretaceous. The most significant event was the rise of the dinosaurs.
• A famous Jurassic deposit is the Morrison Formation, within which the world’s richest
storehouse of dinosaurs was preserved. True pines and redwoods appeared and rapidly
spread. Flowering plants arose and their emergence accelerated the evolution of
insects. A major event of this era was the breakup of Pangea.
• By the end of this period, the dinosaurs and reptiles were completely wiped out.
a. Triassic Period- “Age of reptiles” begins; first mammals; corals, insects, and fishes
resemble modern types.
b. Jurassic Period- the Rocky Mountains rise; first birds; palms and cone bearing tress
dominant; large dinosaurs thrive; primitive mammals developed.
c. Cretaceous Period- First flowering plant; placental mammals developed; dinosaurs
die out, as do many marine animals at the end of the period.

Cenozoic Era
• This era is known as the “age of mammals” because mammals replaced reptiles
as the dominant land animal. It is also sometimes called “age of flowering plants”
because angiosperms replaced gymnosperms as the dominant land plants.
• Cenozoic era is made up of two periods: Tertiary and Quaternary. From oldest to
youngest the periods are broken up into the Paleocene, Eocene, Oligocene,
Miocene, and Pliocene for the Tertiary period, and the Pleistocene and
Holocene for the Quaternary period. Climates cooled during this era, hence the
widespread glaciation.
• This era also brought about the advent of humans. The lowered sea level resulted in
the “land bridges” connections between land masses. One of these land bridges
provided the route for the human migration from Asia to North America, also
throughout the world. a. Paleogene Period
• Paleocene Epoch- beginning of “age of mammals”; flowering plants and small
mammals abundant; many different climates existed.
• Eocene Epoch- fossils of “dawn horse”; grasslands and forest present; many small
mammals; larger mammals such as whales, rhinoceros, and monkeys begin to
develop.
• Oligocene Epoch- fossils of primitive apes; elephants, camels, and horses
developed; climate generally mild.
b. Neogene Period
• Miocene Epoch- many grazing animals; flowering plants and tress resemble
modern types.
• Pliocene Epoch- fossils of ancient humans near end of epoch; many birds,
mammals and sea life similar to modern types; climate cools.
c. Quaternary Period
• Pleistocene Epoch- “The Ice Age”; modern humans present; mammoths and
other animals become extinct.
• Holocene Epoch- Humans are the dominant forms of life and civilization begins
and spread.

Author: Laugo, Angie Flor A. / Monter, Lovely Fe G.

School/Station: Socorro National High School
Division: SIARGAO
email address: angieflor.arcular@deped.gov.ph/lovelyfe.monter@deped.gov.ph
Activity 1. Fill me In!

What you need: Long bond paper and ballpen.

What to do:
1. Copy the table below on a long bond paper.
2. Complete the table by filling in the missing periods, significant event of the era, and
the organisms that first appeared in each period. Select your answers for the last
column from the box below.

Author: Laugo, Angie Flor A. / Monter, Lovely Fe G.

School/Station: Socorro National High School
Division: SIARGAO
email address: angieflor.arcular@deped.gov.ph/lovelyfe.monter@deped.gov.ph
Activity 2. Discover that Human In You!

What you need: Ballpen and paper

What to do:
1. Read and Bird Air-breathing animals
Fish
understand Amphibian Dinosaurs Land plants the
article inside the box
and answer Mammals Reptiles Modern the guide
question Humans below.
Mosses Flowering plants Eukaryotic
Anthropocene cells Epoch
Earth’s Bacteria multicellular
Archaean fossil history is
divided into a Organisms
hierarchical Dawn horse Grazing animals series of
smaller chunks Marine Organisms bacterial of time,
referred to as microfossils the
geologic time Organisms scale.
These Eo Significant Events of the divisions,
Era Period present in
in descending n Era
each Period length of
time, are called
P Cenozo
eons, eras, periods,
ic
epochs, and ages.
These
H units are
classified based on
Earth’s rock A layers, or
strata, and the fossils
Mesoz
found within N them.
oic
From
examining E these
fossils, scientists
know that R certain
organisms are
characteristic O Paleoz of
certain parts of oic the
geologic Z record.
The study of this
correlation is O called
stratigraphy.
I Officially,
the current epoch is
called the C
Holocene, which
began 11,700 years
ago after the last
major ice age.
However, theP
Anthropocene R Proterozoic Eon Epoch is
an unofficialE unit of
geologic time,C used to
describe theA most
recent periodM Archean Eon in
Earth’s historyB when
R
I A. / Monter, Lovely Fe G.
Author: Laugo, Angie Flor
A National
School/Station: Socorro Hadean Eon
High School
Division: SIARGAO N
email address: angieflor.arcular@deped.gov.ph/lovelyfe.monter@deped.gov.ph
 human activity started to have a significant impact on the planet’s climate and ecosystems. The
word Anthropocene is derived from the Greek words anthropo, for “man,” and cene for “new,”
coined and made popular by biologist Eugene Stormer and chemist Paul Crutzen in 2000.
Scientists still debate whether the Anthropocene is different from the Holocene, and the
term has not been formally adopted by the International Union of Geological Sciences (IUGS), the
international organization that names and defines epochs. The primary question that the IUGS
needs to answer before declaring the Anthropocene an epoch is if humans have changed the
Earth system to the point that it is reflected in the rock strata.
To those scientists who do think the Anthropocene describes a new geological time period,
the next question is, when did it begin, which also has been widely debated. A popular theory is
that it began at the start of the Industrial Revolution of the 1800s, when human activity had a
great impact on carbon and methane in Earth’s atmosphere. Others think that the beginning of
the Anthropocene should be 1945. This is when humans tested the first atomic bomb, and then
dropped atomic bombs on Hiroshima and Nagasaki, Japan. The resulting radioactive particles were
detected in soil samples globally.
In 2016, the Anthropocene Working Group agreed that the Anthropocene is different from
the Holocene, and began in the year 1950 when the Great Acceleration, a dramatic increase in
human activity affecting the planet, took off.

Guide Question
1. What is the impact of human beings despite their brief existence on Earth? Discuss your
answer in three to five sentences.

Scoring Rubric for Guide Question

3 points Practical application is scientifically explained consistent to the
concepts, and has no misconception.
2 points Practical application is scientifically explained consistent to the
concepts, but with minimal misconception.
1 point Practical application is explained consistent to the concepts, but with
misconceptions.
0 point No discussion.

Reflection

As a grade 11 student, how did your community evolve for the last 5 years? How do
you think it will be 10 years from now? Discuss your answer in three to five sentences.

Scoring Rubric for Reflection

3 points Practical application is scientifically explained consistent to the concepts, and
has no misconception.
2 points Practical application is scientifically explained consistent to the concepts, but with
minimal misconception.
1 point Practical application is explained consistent to the concepts, but with
misconceptions.
0 point No discussion.

References for learners:

Author: Laugo, Angie Flor A. / Monter, Lovely Fe G.

School/Station: Socorro National High School
Division: SIARGAO
email address: angieflor.arcular@deped.gov.ph/lovelyfe.monter@deped.gov.ph
Dela Pena, Renato Jr. H., 2016. Earth Science. Pasay City: JFS Publishing Services.

Laylay, Marilou H. et.al., 2007. Evolution and Natural Selection. Mandaluyong City: Merryland
Publishing Corporation.

Macarayo, Carrie M., 2020. Earth and Life Science. Cagayan de Oro City: Department of
Education, Division of Cagayan de Oro

National Geographic, 2020. Anthropocene Epoch. https :/ /www. Nationalgeographic .org/

encyclopedia/anthropocene/

Salandanan, Gloria G. et.al., 2016. Earth and Life Science. Quezon City: Lorimar Publishing
INC.

Author: Laugo, Angie Flor A. / Monter, Lovely Fe G.

School/Station: Socorro National High School
Division: SIARGAO
email address: angieflor.arcular@deped.gov.ph/lovelyfe.monter@deped.gov.ph