The document summarizes the evolution of the Earth and solar system. It describes how the universe began with the Big Bang around 14 billion years ago. Over time, gas and dust coalesced to form stars and planets, including our sun and solar system approximately 4.5 billion years ago. As the early Earth formed and cooled, differentiation occurred with iron sinking to form the core and lighter elements floating upward. The atmosphere gradually evolved from a primitive mix including hydrogen and helium to today's nitrogen and oxygen-rich atmosphere through volcanic outgassing and the rise of oxygen-producing life.

1. The Evolution of the Earth
I F F A T A R A
Lecturer, Geomatics
LMA,PSTU

2. Solar System
The universe began
about 14.4 billion years
ago
The Big Bang Theory
states that, in the
beginning, the universe
was all in one place
All of its matter and
energy were squished
into an infinitely small
point, a singularity
Then it exploded

3. Origin of the Universe
The tremendous
amount of material
blown out by the
explosion eventually
formed the stars and
galaxies
After about 10 billion
years, our solar system
began to form

4. We know how the Earth and Solar System are today
and this allows us to work backwards and determine
how the Earth and Solar System were formed
Plus we can out into the universe for clues on how
stars and planets are currently being formed
Birth of the Solar System

5. In cosmogony, the Nebular Hypothesis is the
currently accepted argument about how a Solar
System can form
The Nebular Hypothesis

6. We have now discovered over two hundred planets
orbiting other stars
The processes that created our solar system have
also created an uncountable number of other solar
systems
Other Solar Systems

7. A large gas cloud (nebula) begins to condense
Most of the mass is in the center, there is
turbulence in the outer parts
The Nebular Hypothesis

8. The turbulent
eddies collect
matter measuring
meters across
Small chunks
grow and collide,
eventually
becoming large
aggregates of gas
and solid chunks
The Nebular Hypothesis

9. Pictures from the Hubble Space Telescope show
newborn stars emerging from dense, compact pockets
of interstellar gas called evaporating gaseous globules
The Nebular Hypothesis

10. Gravitational attraction causes the mass of gas
and dust to slowly contract and it begins to rotate
The dust and matter slowly falls towards the
center
The Nebular Hypothesis

11. Protostar

12. After sufficient mass and density was achieved in
the Sun, the temperature rose to one million °C,
resulting in thermonuclear fusion.
H atom + H atom = He atom + energy
The Sun

13. Birth of the Solar System

14. Birth of the Solar System

15. Size of the Planets

16. A billion Year Old Earth
By 3.5 billion years ago, when the Earth was a
billion years old, it had a thick atmosphere
composed of CO2, methane, water vapor and
other volcanic gases
By human standards
this early atmosphere
was very poisonous
It contained almost no
oxygen
Remember, today our
atmosphere is 21%
oxygen

17. Earth is ~ 4,570,000,000 years old
The Age of the Earth
Meteorites give us access to debris left over
from the formation of the solar system
We can date meteorites using radioactive
isotopes and their decay products

18. Bombardment From Space
For the first half billion years of its existence, the
surface of the Earth was repeatedly hit by asteroids
and comets of all sizes
One of these collisions formed the Moon

19. The Early Earth Heats Up
1. Collisions (Transfer of
kinetic energy into
heat)
2. Compression
3. Radioactivity of
elements (e.g. uranium,
potassium, or thorium)
Three major factors that caused heating and melting
in the early Earth’s interior:

20. The Core
About 100 million years after initial accretion,
temperatures at depths of 400 to 800 km below the
Earth’s surface reach the melting point of iron
In a process called global
chemical differential, the
heavier elements, including
the melted iron, began to
sink down into the core of
the Earth, while the lighter
elements such as oxygen
and silica floated up towards
the surface

21. Global Chemical Differentiation
This global chemical differential was completed by
about 4.3 billion years ago, and the Earth had
developed a inner and outer core, a mantle and crust

22. Lithosphere: strong, rocky outer shell of the solid
Earth including all the crust and the upper part of
the mantle to a depth of ~100 km (forms the
plates)
Asthenosphere: weak,ductile layer of the mantle
beneath the lithosphere; deforms to
accommodate the motions of the overlying plates
Deep Mantle: mantle beneath the asthenosphere
(~400 to 2900 km in depth)
Outer core: liquid shell composed of mostly iron
Inner core: innermost sphere composed primarily
of solid iron
Chemical Composition of Earth

23. The Evolving Atmosphere
Right after its creation, the Earth is thought to have
had a thin atmosphere composed primarily of
helium (He) and hydrogen (H) gases
The Earths gravity
could not hold these
light gases and they
easily escaped into
outer space
Today, H and He are
very rare in our
atmosphere

24. The Evolving Atmosphere
For the next several hundred million years,
volcanic out-gassing began to create a thicker
atmosphere composed of a wide variety of gases
The gases that were released were probably similar
to those created by modern volcanic eruptions

25. These would include:
Water vapor (H2O)
Sulfur dioxide (SO2)
Hydrogen sulfide (H2S)
Carbon dioxide (CO2)
Carbon Monoxide (CO)
Ammonia (NH3)
Methane (CH4)
The Evolving Atmosphere

26. The Earth’s
Atmosphere
Overview of the Earth’s atmosphere
Other planetary atmospheres
Vertical structure of the atmosphere
Weather and climate

27. Overview of the
Earth’s Atmosphere
• The atmosphere, when scaled to the size of an
apple, is no thicker than the skin on an apple.
• The atmosphere is a gas.
• The atmosphere is a fluid.
• There is a surface but no “top” – the atmosphere
gradually thins out with increasing altitude

28. Composition of the Atmosphere
permanent gases
variable gases
trace gases
aerosols
• .

29. Composition of the Atmosphere
The “dry atmosphere”: 78% N2, 21% O2, 1% Ar
• N2 is primordial – it’s been part of the atmosphere as long
as there’s been an atmosphere
• O2 has been rising from none at all about 2.2 Gya – comes
from photosynthesis
• Ar40/Ar36 tells us that the atmosphere has been outgassed
from volcanoes

30. Composition of the Atmosphere
Water Vapor: H2O 0-4%
• H20 can exist in all three phases at the surface of the Earth – solid,
liquid and gas
• Liquid or solid H2O can be suspended by atmospheric winds (clouds)
or fall to the surface (precipitation)
• VERY powerful greenhouse gas (both in vapor form and as clouds)

31. The Hydrological Cycle
.

33. Composition of the Atmosphere
The Global Carbon Cycle

34. Composition of the Atmosphere
Aerosols
• Dust
• Sea-spray
• Microbes
Suspended particles in the atmosphere are responsible for cloud
formation: water drops nucleate on them
Cloud Condensation Nuclei (CCN)

35. The Early Atmosphere
 Reduced primitive atmosphere(H, He, CH4, NH3)
 Outgassing and the second atmosphere (N2, Ar – still no
oxygen!)
 The evolution of life and the atmosphere are closely linked –
life produced the oxygen (photosynthesis) and cycles the
carbon (e.g. limestone)
 Oxidized modern atmosphere (N2, O2, CO2, etc.)

36. Other Atmospheres
YES NO
Earth The Moon
Mars all the other satellites
Venus Mercury
Jupiter asteroids
Saturn
Uranus
Neptune
Pluto
Triton (Neptune’s moon)
Titan (Saturn’s moon)
The Sun

37. Other Atmospheres
Planet Composition Temperature Pressure
Venus CO2 96.5%, N2
3.5%
750 K 90000 mb
Earth N2 78%, O2 21%,
Ar 1%
290K 1000 mb
Mars CO2 95%, N2
2.7%, Ar 1.6%
220K 10 mb

38. Vertical Structure of the
Earth’s Atmosphere

41. Layers of the Atmosphere
vertical temperature (T) profile
troposphere
stratosphere
mesosphere
thermosphere

42. Q & A