The document summarizes geological time scale and Precambrian life. It discusses that the geological time scale is used by scientists to describe timing of Earth's history. It then explains that the Precambrian period lasted over 4 billion years and encompasses the earliest evolution of life on Earth, including during the Hadean, Archean and Proterozoic eons, when life evolved from simple bacteria and algae to more complex organisms. The document also notes several major environmental changes on the early Earth during this period, such as the formation of oceans and atmosphere.

2. Assignment of
paleontology

3. Topic
Geological time scale and
Precambrian life

4. Contents
 Geological Time Scale
 What is Pre Cambrian life?
 Big Bang Theory
 Conditions on early earth
 Eons of pre Cambrian era
 Hadean eon
 Archean eon
 Proterozoic eon

5.  Major events occur during pre Cambrian
era
 Fossils

7.  The geological time scale (GST) 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.

11.  The term Precambrian is informal.
 But widely used , referring to both time
and rocks.
 The pre Cambrian lasted for more than 4
billion years .
 This large time span is difficult for humans
to comprehend.

12.  Suppose that a 24 hour clock
represented,
 All 4.6 billion years of geologic time
 Then pre Cambrian would be slightly
more than 21 hours long
 Constituting about 88% of all geologic
time

15.  Pre Cambrian encompasses,
 All rocks older than Cambrian age rocks.
 No rocks are known for the first 640
million years of geologic time.
 The oldest known rocks on earth are 3.96
billion years old.

17.  Formation of sun and light
 Creation of earth
 Creation of atmosphere through volcanic
out-gassing
 Creation of oceans and glaciers

18. Creation of life
 Simple life such as bacteria and simple algae.
 Simple organisms such as jellyfish and sea
worms.

25. Big Bang Theory

27. Conditions Of Early Earth

29.  Hadean eon
 Archean eon
 Proterozoic eon

31.  The Hadean Eon took place 4500-4000 million
years ago.
 Our planet formed, gravity pulled gas
and dust from the solar system into what
we know now as earth.
 Friction then heated the material that
would eventually become earth into a
sphere of hot molten lava.

32.  At that time the earth was a very harsh
environment .
 There was no solid crust just molten lava
covering the surface.
 It is theorized that a mars-sized object
crashed into earth early in the hadean
eon.

33.  The theory states that the impact caused
a large amount debris to be ejected from
the earth , which later combined to form
the moon.

35.  The Archean eon took place 4000-2500 million
years ago.
 Over the time , the earth cooled the outer
edge of the planet solidified from molten
lava to a solid crust.
 It was not perfectly solid large volcanoes
were erupting all over earth and forming
new land

36.  With the crust shifting and cracking
below , collisions formed the beginnings of
early continents.

37. As the earth cooled even more, the water
in the atmosphere began to rain out.
 As the water evaporated in the
atmosphere pour down onto the newly
formed solid ground.
 Most of the water rained down from the
atmosphere and covered earth with a global
ocean.

38. Global oceans

39.  First signs of life formed during Archean
eon in these oceans.
 Cyanobacteria, commonly known as blue
green algae was present in ocean 3000
million years ago.

41.  The Proterozoic eon took place 2500-541 million
years ago.
 In this eon , the continental rock has not
deformed.
 The earth has cooled more and the
number of volcanoes has decreased from
that seen in the Archean eon.

42.  Plate tectonics were still very active, and
by this eon , there were two
supercontinents on either side of the
planet.
 Not only they were shaped differently, but
were completely void of life.

44. Micro fossils
 Carbonaceous aggregates
 Carbonaceous filamentous Threads
stomatolites

48. “Thank you all for being with
us”