Lebanese University

Lebanese University Faculty of Sciences

Faculty of Sciences

B1103
Geology
Department of Life and Earth Sciences

Spring Semester
2020 - 2021

©opyright Reserved
 Summary
This module is divided into 4 chapters:
Ø Chapter I - The Universe & the Solar System
Ø The evolution of the Universe, galaxies, stars (their characteristics and their evolution), the solar
system (composition and origin), the sun, the planets, the moon the asteroids and the comets
Ø Suggested reading: The Physical Universe, 14th edition (2011) by Konrad Krauskopf and Arthur
Beiser
Ø Chapter II - The lithosphere
Ø Differentiation of the Earth, internal structure, theories of continental drift and plate tectonics, plate
boundaries, natural hazards (earthquakes, volcanoes), the rock cycle, rock deformations and formation
of fossil fuel
Ø Suggested reading: Geodynamics, 3rd edition (2014) by Donald L. Turcotte and Gerald Schubert
Ø Chapter III - The Atmosphere and its dynamics
Ø Role of the atmosphere, its origin, the atmospheric layers, its chemical composition, the energy
balance, the global atmospheric circulation and the greenhouse effect
Ø Suggested reading: The Physical Universe, 14th edition (2011) by Konrad Krauskopf and Arthur
Beiser
Ø Chapter IV – The hydrosphere and its dynamics
Ø Water reservoirs, water cycle, oceans (composition and characteristics), ocean circulation
Ø Suggested reading: The Physical Universe, 14th edition (2011) by Konrad Krauskopf and Arthur
Beiser
1

The Universe & the Solar System

Evolution of the Universe, galaxies, stars: their

characteristics and their evolution, the solar system:
composition and origin, the sun, the moon, planets,
asteroids and comets
What is the Universe?
} The Universe or Cosmos is what contains everything around us: galaxies,
stars, planets, nebulae, supernovas, pulsars, black holes, quasars, interstellar
dust ...
} Among these objects, stars represent almost all visible matter.

} Composition of the Universe:

} Just 4% visible matter
} 23% dark matter
} 73% dark energy
} 0.005% of electromagnetic radiation Source:
http://chandra.harvard.edu/learn_galaxyCluster.html

Units used in astronomy

} The Astronomical Unit (AU) is a unit used to measure distances in our solar
system.
The value of the AU is the Earth-Sun distance.
=> 1UA = approximately 150 x 106 km

} A light-year is the distance traveled by light in vacuum during one year.

Calculation:
D= v x t
v= 300 000 km/s and t= 1 year = 31 557 600 s
D = 300 000 x 31 557 400 = 9.47 x 1012 km
=> 1 LY = 9.47 x 1012 km

4
 Evolution of the Universe
} A remarkable property of the galaxies that make up the Universe is that
most of them grow apart from each other, so that the Universe as a whole is
expanding.
} If we project this expansion backward, we find that it began 13.7 billion
years ago.
} Everything we know about the Universe points to the Big Bang event that
occurred back then in which space and time, matter and energy were
created.

The Big Bang and the expansion

Very hot mixture (matter + energy), destruction between particles and
Age 0
antiparticles

Frac. of sec Number of particles> antiparticles, quarks and leptons appear

1 sec Formation of neutrons and protons but also of electrons => Neutral universe

formation of light elements nuclei

3 min
Ratio of H: He was 3: 1 = same ratio found in Universe today

390,000 y The Universe is cold enough for electrons and nuclei to combine into atoms

Condensed dust and gas clouds form stars and galaxies

1 billion y The process continues today ...
6
Galaxies
} All the matter of Cosmos is grouped into galaxies.
} Galaxies are regions of the Universe where there are billions of celestial
bodies (planets, asteroids, comets), gases, interstellar dust, stars, and so on.
} A large part of galaxies is invisible (dark matter)
} Galaxies are grouped into small groups called galactic clusters:
} For example, our Milky Way is part of the « Local Group » that contains
around 30 other galaxies.
} And clusters are not scattered randomly, they are clumped into bigger
structures called superclusters.

The 3 classes of galaxies

1. Elliptical galaxies (2/3 of galaxies)
They contain few young stars, little gas and dust but
many old red stars. https://www.cfa.harvard.edu/n
ews/su201047
These systems have little rotation and no longer form
stars.
2. Spiral galaxies (1/4 of the galaxies)
They contain a lot of bright young stars, are rich in gas
and interstellar dust, but few old red stars.
http://boojum.as.arizona.edu/
These are huge rotating, flattened systems of stars, gas ~jill/EPO/Stars/galaxy.html
and dust.
3. Irregular galaxies (<1/10 of galaxies)
These galaxies are located near large galaxies, which
disturb them and change their appearance

http://server7.wikisky.org/starview?ob
8
ject_type=2&object_id=1
The Milky Way: Our Galaxy
} With a diameter of 130,000 LY and a
maximum thickness of 10,000 LY, it is a
large galaxy with at least 200 billion stars.
} The stars are mainly on the arms of this
spiral galaxy and revolve around its center
} Ex: the solar system => on Orion arm
nearly 26 000 AL of the center and it
moves to almost 200km / s
} Scientists think that there is a black hole in
its center
(M black hole = 3.7 million x M sun)
Source: https://www.nasa.gov/jpl/charting-the-milky-way-from-the-inside-out

Stars
} Stars are the most famous astronomical objects

} They are giant balls of gas that represent the building blocks of galaxies.

} Stars are responsible for the production and distribution of elements such as
carbon, nitrogen and oxygen ... That surround us.

Source: https://www.australiangeographic.com.au/topics/science-environment/2016/06/amazing-hubble-photo-of-sagittarius/

10
Stellar properties - temperature
} The surface temperature of a star is determined by finding the part of its
spectrum having the most intense radiation.
} Surface temperatures are mainly 3000 to 12 000 K (but up to 40 000 K)
} The hottest stars are blue-white
} Those with an intermediate temperature are yellow orange
} The coldest are red
} There are currently 7 primary classes of stars: O, B, A, F, G, K, M.
} L & T are the coldest stars (T <2500 K)
Sun: 5800 K
yelow

11 Blue Red

Stellar properties - distance

} An indirect method for finding distances from distant stars is based
on the knowledge of:
} The luminosity which expresses the total amount of energy that it radiates
in space per unit time (power).
} The absolute magnitude of a star which is how bright a star would appear
if it were placed at a standard and conventional distance of 32.6 LY from
Earth. It gives an idea of the true brightness and is calculated from the
luminosity.
} The apparent magnitude of a star which is its brightness as we see it from
Earth. It depends on the absolute magnitude and the distance.

} If we know both the apparent magnitude and the absolute magnitude

of a star, we can calculate its distance by calculating how far it must
be in order to send us the apparent brightness that we observe.
12
Stellar properties - diameter
} If we know the surface temperature of a star and its luminosity, we can find
its size.
} The temperature given by its color indicates how much radiation is emitted
by each m2 of the surface of the star
} The luminosity-> measures the total radiation of the entire surface of the
star.
} It is enough to divide the total radiation by the radiation per m2 => to find
the surface of the star => to calculate the diameter and the volume
} The diameters of stars vary in a wide range. The smallest stars only measure
10 to 15 km. The largest, like the giant Antares in the constellation Scorpio,
have diameters of more than 500 times that of the Sun.
n
Sun W
White dwarf

Antares
13
Source: Krauskopf, Konrad B., and Arthur Beiser. "The physical universe." (2011).

The HR diagram

} The relationship (temperature-

absolute magnitude) is shown in the
Hertzsprung-Russell (H-R) diagram.
} The position of a star on the H-R
diagram is related to its physical
properties.
} Most stars (90%) belong to the main
sequence.

14 Source: Krauskopf, Konrad B., and Arthur Beiser. "The physical

universe." (2011).
The HR diagram
} The stars at the upper end of the main sequence are large hot bodies.
} The stars at the lower end of the main sequence are small, dense and
reddish, and colder.
} In the middle are medium stars like our Sun, with moderate temperatures,
densities, masses and rather average diameters.
} The position of the white dwarfs reflects an intensely warm surface and low
radiation that suggests that such stars should be small. However, they are
very dense!
} Giants have opposite properties, ie low density, high volume and high
absolute magnitude in addition to low surface T.

Stars are stable on the main sequence but can evolve slowly:
Our Sun for example had 30% less brightness 4.6 billion years ago

15

Stellar population
} Stars are classified into 2 categories that express their location and age.
} Population I
} located in the central disk of the galaxy
} of all ages with many young stars
} richer in heavy elements compared to population II stars (same
composition as their nebulae).
} Population II
} located in the halo of the central zone of the galaxy
} mainly old stars
} poorer in heavy elements than the population I stars (same composition
as their nebulae).

16
Formation and evolution of the stars
} Stars are born in clouds composed mostly
of Hydrogen and Helium with small
amounts of heavier atoms (C, N, O):
nebulae
} These clouds are of very low density and
are in rotation
} Some regions of the nebula begin to
contract under the effect of gravity,
following a disturbance
} The speed of rotation increases then a
collapse occurs forming a central nucleus
and a disk of matter: it is a Protostar https://www.forbes.com/sites/briankoberlein/2017/07/27/th
e-orion-nebula-has-created-new-stars-at-least-three-
} A few million years later, the temperature times/#32f556328b34
rises so as to allow the nuclear fusion of H
in He: it is now a star

17

Formation and evolution of the stars

} During most of its lifetime (the main sequence), a star
gets its energy from hydrogen fusion reactions into
helium. Nuclear
pressure
} This energy helps to maintain in its heart a sufficient
pressure to allow it to resist the collapse under the
gravitational pressure of the upper layers’ weight.

Gravity
} When the star is in hydrostatic equilibrium, its size remains stable, it reaches
a phase called Main Sequence.
} This phase can be very short, hundreds of thousands of years if the star is
massive because it uses its fuel quickly
} This phase can be longer, several billion years for the stars with a mass
similar to the sun’s.

18
Death of stars
} When hydrogen reserves are depleted in the core, the gravitational pressure
becomes higher than the nuclear pressure.
} For stars of all masses, this causes a contraction, a rise in temperature and
the fusion of helium ... While further reactions with even heavier nuclei
continues only for massive stars.
} The heated star undergoes expansion (100 times its size) into a red giant or
red supergiant according to its initial mass (its is now of the MS)
} The surface temperature of the giant decreases because of its expansion
} Subsequently, depending on its mass, the star will undergo different fates.

19

Death of stars

Source: https://asdfscience.wordpress.com/2013/03/06/life-and-death-of-stars/

20
Death of stars
} Sun-like star
} after passing through the red giant phase and after the new energy producing
reactions are also running out of fuel, the star shrinks to the white dwarf
state.
} A shell of gas from the outer part of the star comes out into space to form a
planetary nebula. As a dwarf, the star can shine for billions of years and
eventually, the star will stop shining, it will be a black dwarf.

} Massive star
} after passing through the supergiant phase it undergoes a violent explosion
in Supernova causing the formation of heavy elements and sending these
elements into space.
} The end of a massive star is in the form of a very dense body, the neutron
star, or, when it is even more massive, the remain will be a black hole.

21

Composition of the solar system

Source: https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA17046

22
 Composition of the solar system
} The eight planets revolve around the Sun in the same direction.
} Their orbits are approximately in the same plane, so that the whole solar
system looks like a slowly rotating disk.
} The planets rotate in the same direction. (Venus does not seem to do so
because it has flipped and Uranus is very inclined).
} The telluric planets are rocky, while the Jovian planets are gaseous
} Some planets have one or more satellites called moons revolving around
them.
} Numerous frozen comets, rocky asteroids populate the solar system in 3
zones: the Asteroid Belt, the Kuiper Belt and the Oort Cloud.
} All parts of the solar system seem to have been set in motion at the same
time.

23

Origin of the solar system

1. Gravitational collapse
2. Protoplanetary disk (accretion
disk)
3. Aggregation of material: formation
of planetesimals
4. Formation of protoplanets
5. Planetary differentiation

Source: https://taylorsciencegeeks.weebly.com/blog/solar-system-review
24
Origin of the solar system
} The solar system was initially a large mass of gases of chemical
composition close to that of the Sun: hydrogen and helium, then smaller
proportion of C, N, O, Si, Fe, Mg and other elements.
} This mass of gas (primitive nebula) is the remnant of a supernova explosion.
} Under the effect of its own gravity, the primitive nebula condensed and then
collapsed on itself forming the proto-sun nearly 4.56 billion years ago.
} Around this proto-sun, is formed what is called the accretion disk, several
hundred AU, composed of grains of matter rotating around the center.
} These grains aggregate and form the planetesimals, which will later form
the planets
} Moving away from the center of the disc, the temperature decreases and the
composition of planetesimals changes in function of this temperature.

25

Origin of the solar system

} There is a radial temperature profile

in the solar nebula
} Near the center only silicate dust
and metals exist in the solid state.

Source: http://lasp.colorado.edu/~bagenal/1010/SESSIONS/11.Formation.html

} From a 175 K limit, also called the frostline, water vapor methane and
ammonia condense to ice. Silicates and iron are also present, but are
covered with an icy frost.

26
Origin of the solar system
} Near the proto Sun, it is too hot which explains why the inner planets are
bodies formed by the accretion of rocky and metallic planetesimals.
} In the outer region, the ice-dominated planetesimals grow and soon become
the icy and dense nuclei we see today surrounded by enormous clouds of
accumulated gas (Jovian planets). Just like a protostar, these gas balls can
grow enough to cause a gravitational collapse without becoming stars
because their mass is not high enough to induce nuclear fusion.
} The smaller particles in the surrounding disc become the moons that now
orbit the jovian planets.
} At the same time, the protosun became a young star with hydrogen fusion.
} Following all these events, the young Sun went through a stage of intense
activity characterized by the emission of an intense solar wind that swept all
the gases and dust of the solar system.

27

Origin of the solar system

Nebula

Gravitational collapse

Protoplanetary disk
Proto Sun
Condensation (gas =>
Warm-up => solid)
fusion

Sun Metal, rocks Gas, ice

Earth-like planets Jovian planets Excess material:

Excess material:
Asteroids Comets
2288
Properties of the Sun
} Average star of 1.5 million Km in diameter.

} On the surface of the Sun called photosphere, the

temperature is about 5800 K.

} The sun consists of 70% Hydrogen, 23% Helium

and 2%, other heavier elements.

} It contains 98.8% of the material of the solar system.

} The sun is currently mid-life. The sun will probably

go out in 5 billion years to end as a white dwarf.

Source:
29 https://www.jpl.nasa.gov/spaceimages/search_grid
.php?sort=views&category=sun

Impact of solar radiation on Earth

} Solar energy is the ultimate force behind many geological processes that
continually change the surface of the Earth. For example,
} Sunlight contributes to the evaporation of surface water, which forms
clouds and rain, providing water for rock erosion.
} the sun's radiation creates winds and ocean currents.
} the energy variations of the Sun can trigger glaciations.

} Although the Sun is at the origin of light and the energy required for the
geological and biological processes supporting life on Earth, the Sun aslo
constantly ejects a stream of charged particles and energy called the solar
wind that is harmful to living beings. Our planet is protected from this solar
wind by its magnetic field.

30
 Characteristics of planets
Approx
Diameter Mass Density Rotation
Planet gravity distance to
(Earth=1) (Earth=1) (g/cm3) period (d)
the sun (AU)
Mercury 0.4 0.06 5.4 58.6 0.38 0.4
Venus 0.9 0.82 5.2 -243.0 0.91 0.7
Earth 1.0 1.00 5.5 0.99 1.00 1.0
Mars 0.5 0.11 3.9 1.02 0.38 1.5

Jupiter 11.2 317.8 1.3 0.41 2.53 5.2

Saturn 9.4 94.3 0.7 0.43 1.07 9.5
Uranus 4.0 14.6 1.2 -0.72 0.92 19.2
Neptune 3.9 17.2 1.6 0.67 1.18 30.1

31

Characteristics of planets

Inner planets (telluric) Mercury, Venus, Outer planets (Jovian): Jupiter, Saturn,
Earth, Mars Uranus, Neptune

Small Large

High density Low density

Rocks and metal Gas and ice

Slow rotation Fast rotation

Few satellites (3) More than 130 satellites

No rings Several rings

High surface T Low surface T

32
Characteristics of planets
} The gases present in a planetary atmosphere are related to
size, mass, temperature, how the planet was formed and the
presence of life.

} Mercury: no atmosphere.

} Venus: a dense atmosphere (mainly CO2) => trapping heat

and raising surface temperatures. Clouds form from sulfuric
acid.

} Earth: mainly nitrogen, oxygen, argon, water vapor and

traces of other gases.

} Mars: thin atmosphere (mainly CO2), with nitrogen, argon

and traces of oxygen and water vapor (clouds).

33

Characteristics of planets
} Atmospheres of jovian planets:
mainly (hydrogen + helium) +
compounds containing hydrogen,
such as water, ammonia and
methane.

} The differences in the amounts of

these trace gases and the
temperature variations of these
planets are the cause of the
different colors of these giant
planets.

34
 The Earth’s Moon
} The Moon is ¼ the size of the Earth.
} Earth-Moon distance = 380,000 km.
} It revolves around the Earth (revolution), and
around itself (rotation) during the same period
of 271/3 days.
} It means that the same side of our moon is Source: https://www.skyandtelescope.com/astronomy-
news/the-moons-uncertain-age/
always visible and the other always hidden from
the Earth
} The widely accepted theory of the origin of the
moon assumes that at the beginning of the solar
system's history another planet has developed
near Earth, and that it has collided with our
planet. The moon would be the debris of that
collision
35
Source: https://apod.nasa.gov/apod/ap070225.html

The asteroid belt

} Beyond the orbit of Mars -> a ring of thousands
of asteroids surrounds the Sun.
} These large interplanetary bodies are composed
of rocks and metals such as iron and nickel.
} The largest asteroid is about 1/10th the size of the
Earth, but the majority is only a few Km in Source:
https://sites.google.com/site/fd0
diameter. 06444/the-asteroid-belt

}
}
Asteroids gravitate
Most are objects thataround the Sun
have never in the same
accumulated enough debris to become a planet.
direction as the planets.
Others are fragments produced by collisions between asteroids.
} Most meteoroids are thought to be smaller debris from asteroid collisions.
} Meteoroids that burn in the atmosphere are called meteors while those that reach
the ground are called meteorites.

36
The Kuiper Belt and the Oort Cloud
} These are the two reservoirs of
comets in the solar system.
} The Kuiper Belt, discovered in
1992, is shaped like a donut around
the sun.
} It is 30 to 50 AU of the sun.
} The Oort Cloud is a thick bubble of
icy debris that surrounds our solar
system.
} This distant cloud ranges between
5,000 and 100,000 AU.
Source: https://solarsystem.nasa.gov/resources/491/oort-cloud/
} Most comets in the solar system
come from the Oort cloud.
37

Comets
} Comets are debris from the formation of the solar system
formed of rocky materials, dust and ice.

} They have very elliptical orbits that bring them very close to
the Sun and sway them deeply in space. Unlike planets, the
orbits of comets are randomly oriented.

} Two comet reservoirs are the Oort cloud (long-period

comets) and the Kuiper belt (short-lived comets, less than
200 years old).
Source: Krauskopf, Konrad B., and
Arthur Beiser. "The physical
universe." (2011).
} Comets are visible as they approach the Sun and develop a tail that points in
the opposite direction to the sun. The tail is an ambient cloud of diffuse
matter, resulting from the sublimation of volatile materials.

38
 The lithosphere

Differentiation of the Earth, internal structure, theories of

continental drift and plate tectonics, boundaries between
plates, natural hazards (earthquakes, volcanoes) rock cycle,
rock deformations and fossil resources

Differentiation of the Earth

} Earth was formed (4.56 billion years ago) as one of the heaviest inner planets.

} In the beginning, Earth was nothing more than a giant ball of hot melted and
mixed rocks that were unsorted and unorganized.

} This primitive Earth had no breathable air, no life, no oceans, and no familiar
landscapes as seen today. But with time, Earth has changed.

} Around the planet, the atmosphere formed and cooled water condensed in the
oceans.

} Inside the planet, rocks began to cool down and settle into more organized
layers.

40
Differentiation of the Earth
} Some of the melted rocks began to solidify.

} The densest and heaviest of these rocks sank to the center of the planet while
the less dense, and lighter, molten rock floated to the surface.

} Over hundreds of millions of years, the planet harden and took shape,
differentiating itself into three main layers: the core (17% by volume), the
mantle (81%) and the crust (2% ).

41

Internal structure of the Earth

} Analysis of the behavior of seismic waves made it possible to deduce the
internal structure of the Earth, as well as the state and density of the matter
inside.

} Boundaries between the different envelopes of Earth where the seismic

waves undergo a sudden change of speed or direction are called
discontinuities.

} Thus, three important discontinuities separate crust, mantle and core:

} The Mohorovicic discontinuity or MOHO: between the Earth's crust and
the mantle
} The Gutenberg discontinuity : between the mantle and the core
} The Lehmann discontinuity: between the inner core and the outer core

42
 Internal structure of the Earth
Upper mantle
Mohorovicic
discontinuity

Lower mantle

Oceanic crust
External core
Gutenberg
discontinuity

Continental crust Lehmann Internal core

discontinuity

https://mern.gouv.qc.ca/publications/territoire/outils/guide_sur_les_referentiels.pdf

43

Internal structure of the Earth

Main Density Physical
Thickness (km) Age (year) T (°C)
composition g/cm3 state
Basalt and
100 million
Crust granites Up to 70 km 2.2 solid 15
- 4 billion

600 km Semi-liquid
Upper Around 4
(Transition except the
mantle billion
Rich in Fe + zone included) top
Mg Around 4
Lower
2200 billion solid
mantle

Around 4 Molten
Outer core 2200
billion metal
Iron alloy
Around 4
Inner core 1200 13.1 Solid metal 5000
billion

44
 The crust: a non uniforme layer
} There are 2 types of crust
The oceanic crust: The continental crust:

• Thin layer (5-12 km) • Thicker layer (20-70 km)

• Consists of upper sediments (less 1 km of clay • Formed by granitic rocks
grains and plankton shells), then basalt and with a density of 2.7 to 3
gabbro of density 3.2 • is called SIAL: SI- Silicon,
• Also known as SIMA: SI- Silicon, MA - Al-Aluminum
Magnesium • Much older layer
• Young layer because it is constantly renewed

Basaltic Rocks and

gabbro (3.2 g/cm3)
Continental
oceanic crust
crust
Source: The Earth through time,
10th edition (2013) by Harold L. Levin
45

The lithosphere
} The lithosphere is about 100
km thick and floats above the
asthenosphere. It consists of
the crust and the superficial
and solid part of the upper
mantle.

} The asthenosphere is hot

(1500 ° C) and is the most
plastic section of the upper
mantle. It behaves like a very Source: https://www.aquaportail.com/definition-2667-lithosphere.html
thick liquid.

46
The lithosphere
} The lithosphere is composed of rigid plates in motion that slide on the
asthenosphere.
} The origin of the movements of these plates is the convection movement
that occur in the Earth's mantle.
} This mechanism is explained by the theory of plate tectonics which
describes geological phenomena such as earthquakes, volcanic eruptions,
deformation of the Earth's crust and formation of mountain ranges.
} But before the establishment of this theory, another theory had been
proposed, that of continental drift.

47

Continental Drift
} Continental drift is a theory proposed at the beginning of the
20th century by Alfred Wegener (physicist-meteorologist).
} For Wegener, based on his observations, all land masses were
once united in a single megacontinent, Pangea around 245
million ago, and continental drift followed.
} Wegener, however, failed to properly explain the mechanism https://opentextbc.ca/ge
ology/prof-dr-alfred-
behind his observations. wegener-ca-1924-1930/

} The observations on which he based his theory are:

} The parallelism of coastlines
} The distribution of some fossils
} The traces of ancient glaciations
} The correspondence of geological structures

48
The Earth through time, 10th edition (2013) by Harold L. Levin
 Continental Drift
The parallelism of coastlines
} By observing a map of the world, one can observe a clear parallelism of the
coastal lines between the Americas and Europe-Africa.
} According to Wegner, these two continents were, in the past, two parts of
the same block.

Current position of the continents Wegener's pangea

Source: http://www2.ggl.ulaval.ca/personnel/bourque/s1/derive.html

49

Continental Drift
The distribution of some fossils
} Nowadays, we can find on both sides of the Atlantic Ocean, common plant
and terrestrial animals fossils that are 240 to 260 M.Y old.
} To explain their presence on territories separated by oceans, it is suggested
that formerly all these continents formed only one, Pangea, where the
distribution areas of organisms would be more coherent.

Source: Wegener's solution

http://www2.ggl.ulaval.ca/personn
el/bourque/s1/derive.html

50
Continental Drift
The traces of ancient glaciations
} In southern Africa and India there are glacial markings dating 250 MY ago,
which is abnormal for these tropical areas. Moreover, the flow of ice is
towards the interior of a continent, which is unlikely.
} The theory of continental drift suggests that the south of Pangea was
covered by an ice cap and that the flow of melted ice occurred on the
periphery of the ice cap, as it should be.

direction of ice flow Wegener's solution

51 Source: http://www2.ggl.ulaval.ca/personnel/bourque/s1/derive.html

Continental Drift
The correspondence of geological
structures
} Apart from the concordance between
coastlines, there is another
concordance between the geological
structures inside the continents.
West African
} The correspondence of geological shield

structures between Africa and South Guyane

America for example is in favor of shield
Angolan
Wegener's argument (the existence of shield
Tanzanian
Pangea). shield
Brasilian Atlantic
shield Ocean Rhodesian
shield

http://www2.ggl.ulaval.ca/personnel/bourque/s1/derive.html

52
Continental Drift
} Illustrations showing the
different stages of
dislocation of the
megacontinent (Pangea) that
was surrounded by an ocean
(Panthalassa) through the
geological age (from -225
million years until today).
} First in two large continents:
Laurasia and Gondwana
separated by the sea Thetys,
then into smaller continents.

http://svt4vr.e-
monsite.com/pages/premiere/la-
tectonique-des-plaques/
53

A Planetary Theory: Plate Tectonics

} Plate tectonics is a theory that states that deformations of the lithosphere
are related to convection cells in the plastic mantle (asthenosphere).

} These convective cells are

generated by a heat flux due
to the radioactive decay of
chemical elements.
} These deformations are
expressed by the movements
of the lithosphere.

http://sciences-et-cetera.fr/la-tectonique-des-plaques/

54
A Planetary Theory: Plate Tectonics
} Geologists distinguish twelve large plates and many microplates (eight to
twenty, depending on the criteria used to define the limits).
} These plates move slowly (1-10 cm / year)
} The crust is formed and destroyed at the boundaries of the plates
} When these plates move, they often cause changes to the surface at their
boundaries that affect the lives of people who live nearby.

55

A Planetary Theory: Plate Tectonics

North American
plate
North Eurasian plate
American
plate

Arabian
plate
Caribbean
Philippine plate
plate Pacific Plate Coconut
plate
African Plate

South Nazca
plate
American Australo-Indian plate
plate

Antarctic Plate

https://clercsvt.jimdo.com/ancien-progamme-college/quatrieme/3-les-plaques-lithosph%C3%A9riques/

56
The boundaries of tectonic plates
} These movements define three types of
boundaries between plates:
1- Divergent boundaries (the two plates
move apart),
2- Convergent boundaries (the two plates
come closer)
3- Transforming boundaries(the two plates
move laterally against each other).

http://data.allenai.org/tqa/theory_of_plate_tectonics_L_0078/

57

Divergent boundaries
} A divergent boundary is where two plates are moving away from each other,
with new crust rising up to fill the gap.
} Heat concentration leads to a partial melting of the mantle which produces
magma.
} Convection produces tension in the lithosphere, which result in collapse and
open fractures (a rift) and cause the two plates to be dragged away from
each other across the divergent border.
Mid-ocean ridge
} A divergent boundary can be formation of océanique c
rusCristallization and formation Oceanic crust
observed at the bottom of the oceans of oceanic crust

at mid-ocean ridges
} Between these two diverging plates,
Heat accumulation
the arrival of the magma creates the = partial melting
new oceanic lithosphere. Asthenosphere
} As the spreading and filling
continue, wrinkling in the new crust
often creates a ridge of underwater http://www.simplegeo.ca/2015/02/zone-de-fracture-charlie-gibbs-
mountains. dorsale.html
58
Divergent boundaries
Upwarping
} A divergent border can also be
observed on the continent, in the
rift zones.
} Rifting, a process by which a Rift valley

continent splits into a new

divergent boundary, causes the
continent to crack and break.
Linear sea
} A new mid-ocean ridge is formed,
and the expansion of the seabed
begins.
Mid-oceanic ridge

https://wps.prenhall.com/wps/media/objects/374/382993/Fg02_20.gif

59

Examples of divergent boundaries

In the ocean: Mid-Atlantic On the Continent:
Ridge African Rift Zone

http://www.crystalinks.com/mid-atlanticridge.html http://www.simplegeo.ca/2012/01/le-gand-rift-africain.html
Convergent boundaries
} Increase of the surface of oceans is compensated by the destruction of the
lithosphere on convergent borders (by subduction) in order to maintain
constant the terrestrial surface.
} A convergent boundary is where two plates are moving towards each other.
} Depending on the density of the plates involved, one plate may slide below
the other, or they may just smash together.
} Destruction of plates is done in the asthenosphere by depression of one plate
under another, and by destruction of the portion of the plate pressed into the
asthenosphere.

} The results (earthquakes, volcanoes, mountain ranges, deformations) differ

according to the nature of the plates (oceanic or continental) that converge.

} Thus, convergent boundaries can be of 3 types.

61

Convergent boundaries (O-O)

Convergence between two oceanic plates
} The oldest and densest oceanic plate sinks under the other to form a
subduction zone.
} The pressed plate undergoes a partial melting and the resulting magma
moves towards the surface.

} Part of this magma is expelled to the

surface, producing a series of volcanic
islands (island arc).

} This type of boundary is characterized

by an oceanic trench (topographic
indicator of the phenomenon of
subduction). Subduction
n zone and slab
pull
https://www.elcamino.edu/faculty/tnoyes/Units/11A_Unit2-Plate_Tectonics.pdf
62
 Example of Convergent boundaries (O-O)
} The Mariana’s Trench in the Pacific Ocean is created by the convergence of
the fast moving Pacific plate against the slower moving Philippine plate.
} The Mariana’s Trench is the deepest part of the Earth’s oceans (11,034 m).

https://fr.wikipedia.org/wiki/Fosse_des_Mariannes
http://data.allenai.org/tqa/the_ocean_floor_L_0019/

63

Convergent boundaries (C-O)

Convergence between an oceanic plate

and a continental plate
} In this type of convergence, the denser
oceanic (basaltic) plate sinks under the
continental plate :subduction
} The result is a chain of volcanoes on the
continent :volcanic arc.
} This type of boundary also causes the
oceanic-continental convergence
onverg
formation of ocean trenches.
Subduction zone and
a slab
pull

https://www.usgs.gov/media/images/subduction-fault-zone-diagram

64
 Example of Convergent boundaries (C-O)
Tectonic plate - cascade range
The snowy peaks of the Cascade range are
Cascade range part of a 1,300-kilometer volcano chain
stretching from northern California to
Juan de Fuca
southern British Columbia. It results from
ridge the convergence between the oceanic plate
Juan de Fuca and the North American plate.
North
American
Pacific Plate
Plate Spreading
zone Subduction
zone
Juan de Fuca
ridge

North
Pacific Juan De Fuca American
Plate plate Plate https://www.tuxboard.com/les-chaines-de-montagnes-les-plus-
https://commons.wikimedia.org/wiki/File:Cascade_Range_related_plate impressionnantes-a-travers-le-monde/
_tectonics-fr.svg
65

Convergent boundaries (C-C)

Convergence of two continental plates

} Because of the low density of the continental lithosphere compared to that of

the asthenosphere, none of the plates sink.

} There is no subduction zone.

} All the sedimentary material wedged between the plates compresses and rises
to participate in the formation of a mountain range.
} The ancient oceanic plate breaks off and
flows into the mantle. Flaps of the oceanic
crust may be stuck at the weld of these two
plates.

httphttps://pubs.usgs.gov/gip/dynamic/graphics/?C=M;O=D
66
Example of Convergent boundaries (C-C)
A famous example is the convergence between
the Indian continental plate and the Eurasian
continental plate to form the Himalayan
mountains, home to some of the world's largest
mountains, including Mount Everest (8,850 m) .

https://www.reddit.com/r/EarthPorn/comments/1rze28/3008x2000_k2 https://en.wikipedia.org/wiki/Indian_Plate#/me
_the_worlds_next_highest_mountain/ dia/File:Himalaya-formation.gif

67

Transform boundaries
} Transform boundaries or transform faults are large fractures that affect
the entire thickness of the lithosphere;
} They are most often, but not exclusively found in the oceanic
lithosphere.
} The two plates on either side of the transforming fault slide pass by each
other and can have different speeds of movement.
} In this type of border, the crust is neither created nor destroyed.
} These borders frequently cause earthquakes.

68
 Example of Transform boundaries
} The Fault in California, for example, is a transform boundary where the Pacific Plate
slides past the North American Plate.
} The San Andreas Fault Zone, located on the western coast of the US is about 1,300
km long and in some places tens of kilometers wide.

Continental
plate

Oceanic
plate

Vue aérienne de la faille de San Andreas (Californie). https://le-grand-talisman.vraiforum.com/t9242-Seisme-en-Californie-

https://fr.wikipedia.org/wiki/Faille retour.htm?start=25

69

Natural hazards
} It has taken scientists centuries to
understand the basic process of plate
tectonics.

} The more details of the upper mantle

are understood, the more scientists can
http://www.smartdrones.fr/video-un-drone-filme- help develop tools to make it safer to
leruption-volcanique-du-piton-de-la-fournaise/0016894
live in tectonically active places,
subject to earthquakes and volcanism.

http://fracladin.over-blog.com/article-risque-sismique-en-guadeloupe-
42962090.html
70
Earthquakes
} An earthquake is a sudden movement of large blocks of the Earth’s crust
} During the movement of the tectonic plates, there is an accumulation of
energy in the lithosphere.
} As the limit of elasticity is reached, fractures occur which result in faults
that suddenly release energy that causing earthquakes.

} When an earthquake occurs, the rocks vibrate

propagating seismic waves in the Earth's crust.
} The place of rupture where the earthquake
actually occurs is called focus point, while the Epicenter
point on the Earth's surface vertically above it is
called epicenter. Focus point

http://www2.ggl.ulaval.ca/personnel/bourque/s1/seismes.html

71

Seismic waves
} Seismic waves cross both the interior of the Earth - ”body waves" - and
along its surface - "surface waves".
} Two types of body waves:
} P waves (primary waves) are compression waves; the soil particles move
in a forward-backward motion in the direction of wave motion. They are
the fastest (6-8 km / sec). They propagate in solid, liquid and gaseous
materials.
} S waves (secondary waves) are called shear waves; the particles oscillate
in a vertical plane with respect to the propagation of the wave. They are
slower (3.5 to 5 km / s) and come next. They can only move through
solid materials.
} It should be noted that the propagation speed of seismic waves is a function
of the density of the material they pass through.
72
Seismic waves
} Surface waves appear last. They can produce the strongest vibrations,
especially in zones at a distance that does not exceed a few thousand
kilometers from epicenter. They cause the greatest destruction in densely
populated areas.
} Two types of surface waves:
} Love's surface waves involve horizontal oscillation movements and are
responsible for most of the damage caused by earthquakes to buildings
and other structures.
} Rayleigh waves are like water waves (elliptical rolling) and are the
slowest.

73

Seismic waves

Body waves Surface waves

P waves
L waves (Love)
Particle movement wave movement

Expansion Compression
Rayleigh waves
S Waves

http://www2.ggl.ulaval.ca/personnel/bourque/s1/seismes.html
74
 Recording of seismic waves
} Seismographs are devices that record seismic waves in many parts of the
globe.
} The vibrations of the seismic waves are transmitted to a needle which
records them on a cylinder rotating at a constant speed. We obtain a so-
called seismogram recording, like this one.

cylinder
pen spring
Rayleigh waves
mass noise Arrival of P waves Arrival of S waves

Vertical movement
of ground

http://tpeseismes.joueb.com/news/partie-
ismael
http://www2.ggl.ulaval.ca/personnel/bourque/s1/seismes.html

75

Example of localization of the epicenter of an

earthquake

} An earthquake is recorded at three points; Halifax, Vancouver and Miami

indicating that the earthquake is within 560 km, 3900 km and 2500 km,
respectively.

} Accordingly, the epicenter of the

earthquake is located in La Malbaie,
the intersection of the three circles
from the three recording points,
Halifax, Vancouver and Miami.
} In practice, it is necessary to use more
than three records.

http://www2.ggl.ulaval.ca/personnel/bourque/s1/seismes.
html
 Magnitude of an earthquake
} The Richter scale was developed Energy
in 1935.
} It expresses the magnitude of the
earthquake, ie the quantity of
energy released.
} It is measured on an open
logarithmic scale.
} Nowadays, we use a modified
calculation of the basic Richter
calculation, including the
dimension of the fault involved.

http://www2.ggl.ulaval.c
a/personnel/bourque/s1
/seismes.html

77
Magnitude at the Richter scale

Intensity of an earthquake
} Two scales are used to evaluate
earthquakes: the Mercalli scale and the
Richter scale, which is the only one
currently used.
} The Mercalli scale was introduced in 1902
and later modified. It indicates the
intensity of an earthquake on a scale from
I to XII.
} This intensity is determined by:
} the extent of the damage caused by an
earthquake (related to the magnitude, the
duration, the geology of the area, the distance
to the epicenter, the degree of urbanization ...)
} the perception that the population had of the
earthquake.
http://godof.yoo
78 7.com/t8075-
topic
Earthquake distribution
Earthquakes are not distributed randomly on the surface of our planet. They
are located mainly, but not solely, on the borders of lithospheric plates because
they are linked to the existence of tectonic movements in perpetual action.
Earthquake

Map of the earthquakes distribution on the surface of the Earth

http://sciences-et-nature.e-monsite.com/medias/images/2014-svt-dig-repartition-volcan-seisme.jpg

Types of earthquakes
} Earthquakes can be:
} superficial (0 - 70 km) located within convergent and divergent
boundaries
} Intermediate (70 - 300 km) located mainly within convergent boundaries
} deep (300-700 km) located exclusively within convergent boundaries
(subduction zones)
} Some earthquakes occur far
away from the boundaries inside
the plates and are associated
with hotspot volcanoes.
} Most earthquakes are superficial
to intermediate.

80 http://www.physicalgeography.net/fundamentals/10m.html
 Tsunamis
} Tsunami is a destructive phenomenon Swelling of the ocean surface

caused by an underwater movement

related to an earthquake, a volcanic
eruption or a landslide. Movement the ocean floor

Withdrawal
} (A) The rising of the seabed causes the Tsunami wave
water mass to swell.
} (B) A retreat from the sea occurs as the
first wave of tsunami approaches.
flood
} (C) This wave becomes dangerous when
approaching the shore; the frictional
interaction of the waves with the ocean
floor causes the waves to slow down and
collide into each other, creating a great
Withdrawal
wave… It sweeps everything on its path.
} (D) This can be followed by a second
withdrawal, then another wave.
81 http://www2.ggl.ulaval.ca/personnel/bourque/s1/seismes.html

Volcanoes

Volcanoes are systems that

relate the surface of the globe
to internal areas where the
materials are at a temperature
that allows them to fuse. A
volcanic eruption is an
intermittent phenomenon.

Source: http://planet-terre.ens-lyon.fr/planetterre/objets/Images/google-earth-
volcans1/volcan1-galapagos600.jpg

82
Distribution of volcanoes
Like earthquakes, volcanoes are not randomly distributed over the surface of
the earth.

Pacific Ocean

Indian
Ocean
Atlantic Ocean

explosive volcano
calm volcano with casting
83 http://burgues.svt.pagesperso-orange.fr/cycle_central/machine_terre/localisation_volcans.html

Distribution of volcanoes
Several volcanoes are at the plate boundaries (ridge and subduction volcanism),
but also within the plates (intraplate volcanism, such as hotspot volcanoes).

Ocean Rift
Subduction zone

Subduction
Transform zone
Volcanism of
fault
subduction zone
Ridge Volcanism Volcanism of
subduction zone
Hotspot Volcanism

84 https://www.bing.com/images/search?q=volcans+des+points+chauds+images&id=836F09
F176B0387A2CE0DF0EA0189CA562D3E317&FORM=IQFRBA
Volcanism of ridge or subduction zones

http://slideplayer.fr/slide/1288713/3/images/3/Volcans+actifs+dans+le+monde.jpg85

Hotspot volcanism
} Hotspot volcanism is an intraplate
volcanism, found mostly on oceanic plates.
} When in the mantle, an excessive increase
of heat produces a partial fusion of the
material, it creates a hotspot within a plate.
} Melted material at the hotspot being less
dense than the surrounding material, it rises
to the surface through the lithosphere to
form a volcano.
} As the plates move over the mantle plumes,
the melted mantle rock rises to create chains
of volcanoes.
} Many of these volcanoes are found in the
Pacific Ocean. They can form archipelagos,
like the Hawaiian Islands. Hot spots can Source: Krauskopf, Konrad B., and Arthur Beiser. "The physical
remain active up to 100 M.A. universe." (2011).

86
Types of Rocks and Rock cycle
} Minerals come together to form the rocks that are divided into three main
types forming the earth's crust:
} Eruptive or magmatic rocks that crystallize from magma (a melted mixture
of mineral matter and gas). This crystallization leads to the formation of a
series of silicate minerals.
} Eruptive rocks are divided into:
} volcanic or extrusive rocks when cooling is rapid outside the globe (eg basalt)
} plutonic or intrusive rocks when the cooling is slow inside the globe (eg Granite)
} Sedimentary rocks formed on the surface of the Earth result either from the
precipitation of elements dissolved in water or the accumulation of debris
from the erosion of surface rocks.
} Metamorphic rocks, which come from the transformation in depth, under
the effect of the increase of temperature and pressure, of the two other
groups of rocks, with crystallization of new minerals.

87

Types of Rocks and Rock cycle

transport
Sedimentary rocks
(deposited)
erosion
Diagenesis
metamorphism
erosion

Metamorphic rocks Sediments

(transformed) Fused
rocks
transport

metamorphism
erosion
http://www.geologues-
prospecteurs.fr/documen
Igneous rocks ts/cycle-roches/
(transformed)
88
Types of rocks and rock cycle
} These three groups of rocks are united in a cycle called rock cycle.
} Magma is at the starting point and end point of the cycle.
} The first phase of the cycle is the crystallization of the magma which is at
the origin of the formation of the Earth's crust.
} On the surface of the Earth, rocks are altered and disintegrated into particles
of various sizes.
} Under the effect of erosion, water, ice and wind transport the particles to
form a deposit called “sediments”. The latter is progressively transformed
by diagenesis (compaction and cementation) into a sedimentary rock.
} By metamorphism, igneous and sedimentary rocks are transformed into
magmatic rocks.
} All these rocks eventually return to the starting point by fusion.

89

Deformation of rocks
} When subjected to stress, the earth's crust is deformed:
} plastic deformation (such as a ball of modeling clay that is crushed)
} brittle deformation (such as breaking glass)

} Parameters are to be considered when applying stress-strain concepts to

materials of the Earth's crust: pressure (which increases in depth),
temperature, time, and the composition of the rock; some rocks are of a
brittle nature (like limestones, sandstones, granites), others more plastic
(like clay rocks).

90
Deformation of rocks - constraints
Tension
} Three important types of constraints deform
rocks:
} Tension constraints have the effect of
stretching the material. Compression

} Compression constraints where forces

converge.

Shearing

} Shear stresses that push a rock in two

opposite directions, causing a breakage or a
change of shape.

91

Rock deformation - folds

} Folds are formed by a slow and continuous
movement.
} They are produced by compression forces.
} Folds are most visible in rocks containing
layers.
} For plastic deformation of the rock to occur,
a number of conditions must be met,
including: Anticline
} The rocky material must be able to deform
under pressure and heat.
} The pressure must not exceed the internal
force of the rock. Otherwise, fracturing
occurs.
} Two examples are shown on the right, an
arch-shaped anticline and a syncline in
reverse form. Syncline
Source: http://www.physicalgeography.net/fundamentals/10l.html

92
 Rock deformation - faults
} A fault may be due to stress of tension,
compression or shear.
} The two compartments on either side of the
fault can move. The block above the fault
plane is called the hanging wall and the one Normal fault
below it is footwall.
} In a normal fault, the hanging wall slides Hanging
downward (result of tension). Wall
Footwall
} In a reversed fault, the footwall slides Fault
l
downward (result of compression). plane Reversed fault

} In a strike-slip fault there is horizontal sliding

of the two blocks with respect to each other.

Strike-slip fault

93

Erosion et isostatcy
} Erosion by runoff, ice and wind tends to flatten continental landforms
towards a basic profile that is the sea level.
} According to the principle of isostacy, the removal of a quantity of materials
on the surface of a continent leads to a rebalancing of the masses by the rise
of the continental lithosphere.
} Thus, the continental crust gradually grows thinner; it tends towards the
peneplain.
} Oceanic lithosphere overloaded by the addition of sediment sinks by
subsidence.
Mountain range
Continental peneplain
Oceanic sediments
crust
crust

Lithosphere (mantle part)

Isostatic adjustment
94
Source: http://www2.ggl.ulaval.ca/personnel/bourque/s3/erosion.isostasie.html
 Formation of fossil fuels
} Coal
} Coal deposits are made from terrestrial plants that accumulate in anoxic
areas, such as lakes or large swamps around which abundant vegetation
grows.
} With stacking and burial under sediments, volatile materials (oxygen,
hydrogen and nitrogen) are released and carbon is increasingly
concentrated.
https://comitemeac.com/dossiers-
} At 50% carbon, we have 2/dossiers/capsules-energetiques-
introduction/comment-se-sont-formes-les-
peat, at 72% its lignite, at combustibles-
fossiles/https://www.bing.com/images/search?q=form
85% its bitumen, then at ation+charbon
Peat
93% its anthracite, coal
itself. Coals are mainly used
in thermal power plants and
steel plants. burial
95

Formation of fossil fuels

depth
Depth Organic matter
Organic matter
} Oil
Biochem
Biochemical ical
degradation Substraction
} Oil is formed primarily from phytoplankton in degradation
oxygen-poor waters and with rapid burial in Kerogen
the presence of fine clay particles.
Thermal degradation
Thermal degradation
} In the sediment, the little free oxygen that may
be present is rapidly consumed by the
oxidation of a part of the organic matter. Thus,
the conditions become anoxic in the sediment.
Oil
Oil
} Organic matter composed of C, H, O, N is
then protected from oxidation but not from the Gas
action of anaerobic bacteria that use the Residue
oxygen and nitrogen of the organic matter for
their metabolism leaving the carbon and the
hydrogen. This is the biochemical degradation
of organic matter leading to kerogen. Generated
Generatedhydrocarbons
hydrocarbons
http://ornoir-ou-ordure.e-monsite.com/pages/i-
formation-et-composition/formation.html

96
Formation of fossil fuels
} Carbon and hydrogen unite to form Hydrocarbons (HC).
} One of the first molecules to form is CH4, methane (natural gas) that forms
in the upper layers of the sediment.
} As the sediment settles, HC molecules are brought to higher temperatures
and pressures, it is thermal degradation and hydrocarbon molecules become
more complex.
} Part of the initial organic matter is thus transformed into oil. The oil droplets
are formed in a rock called the parent rock.

97

Source: https://eapsweb.mit.edu/news/2016/study-pinpoints-timing-of-oxygens-
first-appearance-in-Earths-atmosphere

The Atmosphere and its dynamics

Role of the atmosphere, its origin, its chemical

composition, atmospheric layers, energy balance,
global atmospheric circulation and greenhouse effect
What is the Earth's atmosphere?
} The Earth's atmosphere is unique among the atmospheres of other planets in the
solar system.
} The atmosphere is an extremely thin gaseous envelope surrounding the globe.
} It is held by gravity around the rotating Earth.
} Its pressure and density decrease with altitude.
} From a physical point of view, and since it is a fluid, the atmosphere obeys the
same laws as those of water.
} It is of high importance for the Earth's climate and for the biosphere with which
it interacts.

99

Role of the atmosphere

} The atmosphere is the source of air we breathe, it provides the oxygen that
allows us to live.
} It controls the surface temperature on Earth because of the gases and
particles it contains that interact with radiation (e.g. CO2, reflective
particles).
} It protects living beings against external aggression:
} It is a shield against meteorites and space debris that enter the atmosphere
every day and burn there.
} Its ozone layer protects the Earth from dangerous solar radiation
(ultraviolet).
} It is a reservoir for natural substances but also for substances coming from
human activities.
} The atmosphere and all the chemical and physical processes it is involved in
can affect the climatic system.

100
Origin and evolution of the atmosphere
} The composition of the Earth's atmosphere has evolved since the formation
of the Earth, 4.5 billion years ago in 3 stages.
Composition of the atmosphere (in% of main gases)

carbon dioxide CO2

water vapour Oxygen O2

Appearance of life Time

(in billion years)
Formation of the oceans
Formation of the Earth
Source: https://leclimatdanstoussesetats.wordpress.com/2015/02/01/de-
101
latmosphere-primitive-a-latmosphere-actuelle/

Origin and evolution of the atmosphere

Primary atmosphere:
} Composition: He (Helium) and H (Hydrogen)
But this atmosphere does not last long. Why?
1. The first reason is that H and He are light gases,
Source:
Earth's gravity is not strong enough to hold them https://scijinks.gov/atmosphere
-formation/

2. Second, after 30 million years of Earth's formation, the Earth collided with a
body of the size of Mars, resulting in the formation of the Moon and the escape
of the H and He from the primitive atmosphere.

102
Origin and evolution of the atmosphere
Secondary atmosphere:
} Composition: mainly H2O and CO2, some nitrogen
and other gases.
} Volcanic activity was intense causing the release of
gas trapped inside the Earth.
Source:
} Oxygen is almost absent in the secondary https://scijinks.gov/atmosphere
atmosphere so no ozone. -formation/

} The CO2 present in large quantities in the atmosphere warms the Earth by
greenhouse effect and prevents its glaciation.
} The Sun’s brightness back then was lower than its current brightness.
Without CO2 to warm the atmosphere, the temperatures would have been
much lower.

103

Origin and evolution of the atmosphere

Secondary atmosphere:
} With progressive cooling, atmospheric water vapor condenses to form the
oceans.
} The rainwater charged with CO2 is acidic, it erodes volcanic rocks taking
off calcium, silicon ... Then calcium carbonates and clays formed on the
surface of Earth...
} These processes reduced CO2 and H2O content and reduced the greenhouse
effect caused by these gases thus, decreased temperature.
} Nitrogen became the major constituent of the Earth's atmosphere.
} Life appeared as photosynthetic (anaerobic) cyanobacteria 3.5 billion years
ago.
} O2 produced by cyanobacteria initially oxidized, inorganic matter such as
iron.

104
Origin and evolution of the atmosphere
The current atmosphere. From 2 billion years ago
until today:
} Composition: 78% N2, 21% O2, 0.041% CO2, H2O
(variable)
} The presence of O2 in the atmosphere allows the
Source:
diversification of life forms. https://scijinks.gov/atmosphere-
formation/
} The percentage of O2 in the atmosphere comes from the combined action of
green plants and aerobic living beings and reaches equilibrium.
} The ozone layer (O3) is formed under the action of solar radiation on oxygen
molecules.
} The absorption of certain UV for the formation of these ozone molecules,
prevents them from reaching the ground, thus allowing life to come out of the
oceans.

105

Thermal profile of the atmosphere

} The Earth's atmosphere is

composed of different layers
that can be defined according to
the temperature of the air.
} The Troposphere
} The Stratosphere
} The Mesosphere
} The Thermosphere

106
Source: https://atmos.washington.edu/2007Q3/101/LINKS-html/layers.html
The atmospheric layers
The Troposphere
} 80% of the mass of the atmosphere
} Variable thickness between 8 and 16 km
} Temperature: decreases with altitude of 6 ° C / km until reaching - 56 ° C at
its upper limit
} Its upper limit is the tropopause
} Location of accumulation of clouds, precipitation, and significant variations
in pressure.
} Contains convection cells that cause weather phenomena.

107

The atmospheric layers

The Stratosphere
} Extends from tropopause to 50 km altitude
} It contains the Ozone layer, which protects living beings on Earth from
harmful UV radiation.
} Temperature: it increases to 0 ° C at the level of the stratopause because of
the presence of ozone molecules.
} The air is much more stable than in the troposphere
} Its upper limit is the stratopause

108
The atmospheric layers
The Mesosphere
} Extends from stratopause to 80 km altitude
} Temperature: begins to decrease with altitude to reach -90 ° C at an altitude
of about 80 km.
} The dust and particles that come from space (the meteors) ignite when they
enter it because of the friction of the air (shooting stars).
} Its upper limit is called mesopause.

109

The atmospheric layers

The Thermosphere
} reaches up to 700 or 1000 Km altitude
} Temperature: increases with altitude to reach hundreds of °C and will even
reach 2000 to 3000 ° C.
} The pressure there is almost nil
} The lower part is called the ionosphere, a name that comes from the fact that
the nitrogen and oxygen atoms are ionized by solar UV. Parts of this area
also allow radio communications.
} The thermopause separates the thermosphere from the exosphere.

110
Actual composition of the atmosphere
Here are the eleven most abundant gases found in the lower atmosphere of the
Earth. Among them, nitrogen, oxygen, water vapor, carbon dioxide, methane,
and ozone. These gases play an important role in the terrestrial biosphere.

Gas Chemical formula Percentage by volume

Nitrogen N2 78.08%
Oxygen O2 20.95%
Water H2 O 0 to 4% Percentage of gases in the
Argon Ar 0.93% atmosphere

Carbon dioxide CO2 0.041%

Neon Ne 0.0018%
Helium He 0.0005%
Methane CH4 0.00019%
Hydrogen H2 0.00005%
Source:
Nitrous oxide N2 O 0.00003%
http://la.climatologie.free.fr/atmospher
Ozone O3 0.000004% e/atmosphere2.htm
111

Atmosphere and energy

} The factors that influence the temperature on Earth are numerous and
complex:
} Astronomical factors
} The main source of energy for the Earth's atmosphere is the sun.
} The Earth revolves around the sun in 365 days and a quarter in an almost
circular orbit and rotates around itself in 24 hours on an axis inclined at
23.5°. In addition the Earth is round shaped, and thus receives solar rays in
different angles depending on the latitude.
} These astronomical features of our
planet are the reason we have different Autumn Equinox
seasons in different periods of the year September 21st

and different climatic zones in Sun

Winter solstice Summer solstice
different latitudes. December 21st Jun 21st

} Some very slow variations of these Autumn Equinox

March 21st
features through Earth geological times
have modified the climate on Earth.
112
Source: http://saison.s.a.pic.centerblog.net/31utlih8.gif
 Atmosphere and energy
} Physico-geographical factors
} The energy sent by the sun to the Earth does not reach the ground entirely.
This is due to the following factors:
} The composition of the atmosphere:
Some components will reflect sunlight (clouds) while other will absorb
them.
} The ground cover:
The color and texture of the soil influence the temperature on the surface of
the Earth. So snow, vegetation, bare soil will behave differently to solar
radiation.

113

Atmosphere and energy

} The value of the
average energy received
at the top of the Reflected energy
atmosphere is 342 W.m-
2.

Top of the atmosphere

} Of this energy, 102
W.m-2 is reflected back
to space and only 240 absorbed by the
atmosphere and the
W.m-2 is absorbed by clouds

the atmosphere and the cloud

Earth's surface.

Land surface Absorbed on the surface

114
Atmosphere and energy
} The Earth heats up and re- Radiative balance at the top of the atmosphere (W / M2)
emits energy. The resultant
between absorption and Terrestrial
emitted
emission varies with Excess heat
latitude. Solar absorbed
Heat
TRANSPORT deficit
} This results in a Heat
deficit
} Excess heat in the tropical
band
} Heat deficit at higher latitudes
} It is the atmospheric and
oceanic circulation that
distributes excess energy
from low latitudes to high Meridian transport of energy (W)
latitudes. Source: http://planet-terre.ens-lyon.fr/article/repartition-energie.xml

115

Atmospheric circulation
Simple model of global circulation: Hadley's
cell:
} When the air reaches the equator, it is heated,
converges through the convection processes
and is lifted vertically.
} When it reaches the top of the troposphere, it
starts flowing horizontally again from the
equator to the poles.

Source:The Atmosphere, 8th edition,

Lutgens and Tarbuck, 8th edition, 2001
} At the poles, the air is cooled in the upper atmosphere then descends to the
surface of the Earth to complete the flow cycle.
} If there was no rotation of the globe, this simple model would work and we
would have a single convection cell between the equator and each pole but
the Earth rotates...
116
 Atmospheric circulation
} The model that takes into account the rotation of the Earth
(coriolis force) defines 3 different cells in each hemisphere:
} Hadley cell (0 ° - 30 °) with the trade winds.
} Ferrel cell (30 ° - 60 °) with westerlies.
} Polar cell (60 ° - 90 °) with the polar easterlies.
} These cells generate regions of low atmospheric pressure LP
(ascending air masses) and high atmospheric pressure HP
(descending air mass).

117

Atmospheric circulation
North Pole
Polar
CELLULE
cell
POLAIRE

Ferrel
CELLULE
Cell
FERREL

CELLULE
Hadley
HADLEY
Cell
Source:
http://eduscol.education.fr/obter/a
ppliped/circula/theme/atmos32.ht
m

118
South Pole
Atmospheric circulation
} Hadley's cell: it is characterized by the strong ascending (LP) hot and humid
equatorial air and the descent (HP) of dry air around the latitude 30 of the
tropics. At ground level, an atmospheric return air consisting of dry air
passes from tropical areas to the equatorial zone. These are the Trade winds.

} Ferrel's cell: Part of the tropical air continues its path north to latitudes 60,
where it encounters a cold polar front. The warm tropical air passes over the
cold and heavy polar air and its temperature drops. Latitudes 60 are LP
areas. At ground level, the Ferrel cell is characterized by Westerlies between
latitudes 30 and 60.

} The Polar Cell: it is characterized by the upward current (LP) at latitudes 60

which descends at the poles (HP). On the ground, a cold, dry air flow
connects the pole to the latitudes 60. These are the Polar Easterlies.

119

The greenhouse effect

Sun

Incident solar radiation (UV,

white light, IR) Emitted IR in space
Solar radiation
reflected by clouds,
atmosphere and soil

IR absorbed by
GHG
Cloud
Greenhouse
G r see effect
IR emitted by the ground

Earth
Source: http://www.developpement-durable-en-bilingue.eu/fileadmin/_migrated/pics/effet-de-
120 serre.png
The greenhouse effect
} The Earth's surface receives, in addition to direct solar radiation, an infrared
flux emitted by the lower layers of the atmosphere. It's the greenhouse
effect. Without it the temperature of the Earth would be much lower.
} Soil emits infrared rays that certain gases, GHGs (greenhouse gases)
intercept and re-emit to the ground, thus increasing the temperature.
} GHGs can be either naturally occuring or coming from human activities.
The main GHGs are:
} H2O mainly of natural origin, it constitutes the most abundant GHG
} CO2 from combustion, deforestation (in addition to natural sources)
} CH4 from agriculture (in addition to natural sources)
} N2O from agriculture (in addition to natural sources)
} CFCs from aerosol cans and previously used as refrigerants (no natural sources)

121

Source: http://www.un.org/fr/sections/issues-depth/oceans-
and-law-sea/

The hydrosphere and its dynamics

The water reservoirs, the water cycle, the oceans

(composition and characteristics), the oceanic
circulation
Distribution of water in reservoirs
} Our planet, the "blue planet", is the only one of the solar system where the
conditions of temperature and pressure allow the presence of water in its three
forms: liquid, solid, gaseous.
} The Earth water mass is gigantic : 1.4 x109 Reservoirs Percentage
km3 Oceans 97.25
} Water is found in seas, oceans, lakes, rivers, Cap and Glaciers 2.05
groundwater and in the cryosphere. Underground
0.68
} Seas and oceans store more than 97% of water
the waters. lakes 0.01

} 2% of total water is immobilized in Moisture of the

0.005
soil
glaciers and ice caps
Atmosphere 0.001
} Water is also found as a small percentage Rivers 0.0001
in the atmosphere and the soil and the
biosphere. Biosphere 0.00004

123

The water cycle

124 USGS Georgia Water Science Center Illustration by John M. Evans, Howard Perlman, USGS French translation by Monika Michel,
Agence de l'Eau Artois-Picardie, France — http://ga.water.usgs.gov/edu/watercyclefrenchhi.html
The water cycle
} Du to the effect of solar radiation, oceans provide about 90% of the
evaporated water that enters the water cycle. Part of it comes also from the
evaporation of the water of the continents and from the perspiration of the
plants.
} The vapor thus formed is driven by ascending air currents in the
atmosphere. At altitude, there is condensation of water vapor in clouds that
cause precipitation .
} Some precipitations fall as snow and can accumulate as ice caps and
glaciers.
} When the snow melts and the water runs off, water flows on the surface or
infiltrates the soil.
} Surface flow and seepage feed lakes and rivers.
} A lot of the infiltrated water goes down even deeper and is stored for long
periods.

125

The oceans
} The Earth appears blue because large bodies of saline water known as
oceans dominate the surface covering 70.8%. The oceans contain 97% of
the available water of our planet.
} The average depth of the oceans is about 3.8 kilometers. Maximum depths
may exceed 10 kilometers in a number of areas called ocean trenches.
} Oceans play an important role in climate regulation. They carry the energy
from the equator to the poles.

http://www.un.org/fr/sections/is
sues-depth/oceans-and-law-sea/

126
 Dissolved gas in seawater
} Seawater is composed of around 95% pure O2 ppm
water and a variety of dissolved substances 0 1 2 3 4 5 6 7
and suspended particles. 0
} When the temperature of the solution
increases: 1
if the solute is solid, the solubility

Depth (Km)
}
increases
} if the solute is gaseous, the solubility 2
decreases
Dissolved gases: 3
} Dissolved gases are in a very different ratio
from that of dry air.
4
} In ocean surface water: N2: 64%, O2: 34%, 44 46 48 50 52 5 56 58
CO2: 1.8% (60 times more than in air) CO42 ppm

127

Salinity of sea water

} Six ions make up about 99% of the marine salts: chloride (Cl-), sodium
(Na+), sulphate (SO42-), magnesium (Mg2+), calcium (Ca2+) and potassium
(K+).

} The relative abundance of major salts in seawater is constant regardless of

the ocean. Only the amount of water in the mix varies because of the
differences between the ocean basins.

} The chlorine ion constitutes 55% of the salt in the seawater.

} Salinity of seawater is defined as the weight in grams of the dissolved

inorganic matter in one kg of water (part per 1000 or ‰).

} Typically, seawater has a salinity of 35 parts permil (35 ‰).

128
Salinity of sea water
Salt sea water
chlorine
water

Salt
other
er constituents
Quantity for 1 kg or 1 L of seawater

Source: Hannes Grobe, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany; SVG version by Stefan
Majewsky ; translation by Korrigan — Translation in French of Image:Sea salt-e hg.svg, CC BY-SA 2.5,
https://commons.wikimedia.org/w/index.php?curid=3158453

129

Origin of salts in seawater

Two origins of seawater elements
} Continental: the supply of continental waters that leach rocks and soils is
loaded with different ionic species (calcium, sodium, chlorine, magnesium,
sulfates). E.g:
} NaCl Ú Na+ + Cl-
} CaCO3 + H2O + CO2 Ú Ca2+ + 2HCO3-
} CaSO4 Ú Ca2+ + SO42-

} Hydrothermal + submarine volcanism (especially for Hydrogen

Chloride): Hot hydrothermal vents are located in the vicinity of oceanic
ridges

130
Variation of surface salinity
} Surface salinity varies with latitudes
} Surface salinity is affected mainly by the following processes:
} evaporation and precipitation
} Melt and formation of ice
} Flow of freshwater from streams
} It is highest in the subtropical region where evaporation outweighs precipitation.
} Near the poles where evaporation is low and rainfall is high, the salinity is
relatively low.
} As for closed seas, they undergo a high rate of evaporation resulting in high
salinity (E.g.: 40 ‰ in Red Sea and 335 ‰ in Dead Sea!).
} On the contrary, salinity is weak in estuaries of great rivers or near the polar
areas due to melting ice.

131

Variation of surface salinity

Source: World Ocean Atlas, 2005

132
Variation of salinity with depth
} Halocline = water layer where 34,3 34,7 35,1 35,5 35,9
salinity changes rapidly 0

} Salinity values vary slightly halocline

between surface and deep 1
waters.

Depth (km)
} In depth, salinity is uniform
except for the waters near the 2
mid-ocean ridges.

3
Salinity ‰
Low and
medium High
latitudes latitudes

133

Variation of surface temperature

} Surface water temperature is related to solar irradiance.
} It is high at low latitudes (equator and tropics) where solar radiation is
direct. The tropical waters can reach the temperature of 30 ° C.
} It is low at the poles because the same radiation is very oblique and the
water temperature can go down to -2 ° C (without freezing because the it is
salty). The further we go to the poles, the less the rays arrive
perpendicular to the surface. The rays are less
numerous per unit area, so they heat up less.

At the equator, solar rays strike the surface of

the Earth perpendicularly. There is a greater
concentration of rays per unit area. The warming
of the surface is much more important.
Source: http://meteocentre.com/intermet/temperature/diff_temp2.htm
134
Variation of temperature with depth
} A surface layer or mixing layer T ºC
(200 m) is defined in which: 0 a b
} The temperature vary little with c d
depth during winter.
0,5 thermocline
} Temperature and extension of depth seasonal

Depth (km)
of the mixing level show seasonal
variations at mid-latitudes.
Permanent
} Between this level and the depth 1 thermocline
1000 m, there is a layer of water
where the temperature gradient is Deep water
important: it is the permanent 1,5
thermocline. a- Winter c-Effect of wind in the spring
b-Spring d-Summer
} Beyond 1000 m depth temperatures are stable and low.
135

Buffering capacity in oceans

} Water has a great capacity to absorb
CO2.
} In water, CO2 reacts with water and
produces carbonic acid:
CO2 (aq) + H2O(l) à H2CO3- (aq)
} Carbonic acid can give the
bicarbonate ion :
H2CO3 à HCO3- + H+
} Bicarbonate ion can give
carbonate ion: HCO3- à CO32- + H+
Source: http://arcticocean.globaloceanexploration.com/?p=104

This system tends to be in balance.

136
Oceanic surface circulation
Surface currents
} Their circulation depends essentially on:
} differences in surface temperature
} wind regimes
} the shape of ocean basins
} the Coriolis force
} Their role is to regulate atmospheric temperatures by bringing warm water
warmed by solar radiation from tropical areas to high latitudes and vice
versa.
} Scientists believe that the contrasts between climates would be even more
pronounced if these currents disappeared. The temperatures at the poles
would be lower and those at the equator would be even higher.

137

Oceanic surface circulation

Par Dr. Michael Pidwirny (see http://www.physicalgeography.net) — http://blue.utb.edu/paullgj/geog3333/lectures/physgeog.html,

138 [http://skyblue.utb.edu/paullgj/geog3333/lectures/oceancurrents-1.giforiginal image], Domaine public,
https://commons.wikimedia.org/w/index.php?curid=37108971
Deep ocean circulation (thermohaline)
} Deep currents are slow (loop = 1000 years)
} They are controlled by two factors that influence the density of water:
temperature and salinity
} This continuous loop circulation begins in the North Atlantic where the
cold, salty, dense and well oxygenated waters sinks to the depths

} These waters then circulate towards the South Atlantic along the bottom

} The waters then separates into two branches: one goes to the Indian Ocean,
and the other goes to the North Pacific, to resurface, cold and poorly
oxygenated.

} These waters close to the surface rise in temperature and becomes rich in
oxygen while returning from the Pacific to the Atlantic,

} Cooled again in the North Atlantic, they sink to resume the loop again.
139

Deep ocean circulation (thermohaline)

hea
heat
eatt di
ea distributed
is
istribute
ed
d to
the
hee atmosphere

Hot surface
surfac
urfacee
currentt
ntttxxx

Atlantic
antic
Ocean
eannX

Indian
an
n Ocean
ean
nX

Pacifiic
fiic Pacifiic
fiic
Ocean
eannX Ho
Hot
ott sur
o surface
urrfaaceexxx
xx Ocean
eannX
currentt
ntttxxx

Coldd water
wateter Deep
ep circulation
sinking
ngg areas xDeep
ep cold
old current

Source: PEDLOVSKY (1996) - Ocean circulation theory. Springer.

140
Coastal currents
} Coastal currents are parallel to the coast
} These currents are created by the waves, themselves created by the wind.
They can strike the shoreline at a certain angle and cause the water to pile
up, which will cause it to move in the same direction as the spread of the
wave, parallel to the shore.

} The sand of the beach is

constantly transported by
this type of currents. Coastal
current

141 Source: http://www2.ggl.ulaval.ca/personnel/bourque/s3/littoral.html

Turbidity currents
} A turbidity current is a rapid downward flow of water caused by increased
density due to the presence of large amounts of sediment.
} It is the transport mode of very fine sediments in the seabed forming very
large sedimentary cones at the mouth of the canyons.

} At the margin of the continental Turbidity

shelf, sedimentary masses in fragile currents
equilibrium accumulate. An
Earthquake or simply overload
breaks the equilibrium, leading to
turbidity currents and resulting in
large masses of sediments that
settle further away.

Source: http://www2.ggl.ulaval.ca/personnel/bourque/s3/littoral.html

142