GEO610 Module I.pdf

Amity Institute of Environmental Sciences
Earth and
Environment
(GEO 601)
Dr. Anamika Shrivastava
AIES

Module I
Concept of Minerals
and Rocks; Rock
types – igneous,
metamorphic and
sedimentary
Origin and evolution
of the earth
Geological time scale
Primary
differentiation and
formation of core,
mantle, crust
Atmosphere and
hydrosphere and
elemental
abundance in each
constituent

Origin and Evolution of Earth

Solar System
• Only planetary system know to us.
• Congregation of stars and planets.
• Planets are non-luminous bodies whereas stars are luminous bodies.
• Our solar system is having a disc-like shape with 8 planets and numerous
planetoids or asteroids.
• The Planets

Origin of the Earth

Scientific Concepts on the Origin of
Earth
Hot origin concept
• Origin of solar system and earth is believed to have
been formed from the matter which was either hot or
was heated up in the process of the origin of earth.
Cold origin concept
• Our solar system and earth was formed of the matter
which was initially either cold or always remained cold.
• After formation, earth might have been heated up due
to the presence of radioactive elements or interior might
have been heated up due to extreme pressure.

On the basis of Heavenly bodies
•involving only one
heavenly body
Monistic Concept
•involving only two
heavenly bodies
Dualistic Concept
•involving more than
two heavenly bodies
Binary Star
concept or
trihybrid concept

On the basis of Heavenly Bodies
• Gaseous Hypothesis of Kant
• Nebular Hypothesis of Laplace
Monistic Concept - involving
only one heavenly body
• Planetesimal Hypothesis of
Chamberlin
Dualistic Concept -
involving only two heavenly
bodies
• Binary Star Hypothesis of Russel
• Supernova Hypothesis of Hoyle
Binary Star concept or
trihybrid concept - involving
more than two heavenly
bodies
The Big Bang Theory

Dualistic Concept
(involving only two heavenly bodies)

Planetesimal Hypothesis of Chamberlin
Origin of Earth
• The solar planetesimal system (and hypothesis the earth) envisaged with the help origin
of two of heavenly bodies (stars) in the universe - ‘proto-sun’ and its ‘companion star’.
• Proto-sun - It was formed of very small particles which were cold, solid and circular in
shape.
• Another star, termed as 'intruding star' or "companion star' which was destined to pass
very close to the proto-sun.
• When the intruding star came very close to the proto-sun infinite number of small
particles were detached from the outer surface of the proto-sun due to massive
gravitational pull exerted by the giant intruding star termed as ‘planetesimals’.
• These larger planetesimals became nuclei for the formation of future, possible planets.
• Remaining proto-sun changed into the present-day sun.
• The satellites of the planets were created due to the repetition of the same processes and
mechanisms.
• The main force of the ejection of small jets or planetesimals from the proto-sun was the
tidal force exerted by the approaching or intruding star on the outer surface of the proto-
sun.

Planetesimal Hypothesis of
Chamberlin
Evolution of Earth
First
Stage
‘the period of planetesimal accession’ or ‘the period of
acquisition of present shape and size by the earth’
Second
Stage
‘the period of dominant vulcanism’ or ‘the period of the
evolution of earth’s interior and the evolution of continents
and ocean basins’
Third
Stage
‘the actual geological period’ or ‘the period of the formation
of the folds and faults, mountains and plateau etc.’

Planetesimal Hypothesis (contd….)
• 1. Period of planetesimal accession
 Evolution of the earth's atmosphere
 As the earth grew in size it captured 'atmospheric material and elements' by gravitational force
which was continuously increasing due to ever increasing size of the earth. The earth's atmosphere
was formed from two basic sources. (1) External Source-When the earth grew in size it became
successful in capturing free atmospheric molecules. (2) Internal sources provided carbon dioxide,
water vapour and nitrogen gases.
 Origin of heat
 Heat was originated due to mutual collision of planetesimals during the phase of their active
accretion.
 Some amount of heat was also generated by the re-arrangement of different molecular compounds
• 2. Period of dominant vulcanism
 Evolution of continents and ocean basins
 the primitive oceans were first formed under the fragmented and crevice-ridden outer
permeable zone of the earth's surface. Later on the crevices were cemented and thus water
derived through the condensation of water vapour accumulated in these crevices and volcanic
craters and the earth's surface
• 3. Actual geological period

Evaluation
• According to many astronomers the planetesimals would have so volatilized
(converted into gaseous mass from the solid state) due to excessive heat of friction
and collision at the time of their ejection from the 'proto-sun' that it would have
been impossible for them to condense in the form of orbits around the 'protosun'
without being diffused violently in the universe.
• Why only nine planets were formed? Why one more or one less?
• According to the planetesimal hypothesis, the planets always remained in solid
state (if we assume that Chamberlin proposed such situation only for the planets
of the inner circle of the solar systems). According to many scientists the planets
of the inner circle of the solar system (Mercury, Venus, Earth and Mars) were
initially in liquid state. There is no explanation in Chamberlin's hypothesis about
the planets of the outer circle which are of very low densities and are in gaseous
state.
• The infinite space of the universe makes such a close encounter between the stars
a remote possibility.

Binary Star concept or
trihybrid concept
(involving more than two heavenly bodies)

Binary Star Hypothesis of Russell
• There were two stars near the primitive sun in the universe. In the beginning the
‘companion star' was revolving around the primitive sun.
• Later on, one giant star (the third one) named as 'approaching star' came near the
companion star but the direction of revolution of the approaching star was opposite to
that of the companion star.
• There would have been no effect of tidal force of the giant approaching star on the
primitive sun but large amount of matter of the companion star was attracted towards
the giant approaching star because of its massive tidal force gravitational pull).
• As the giant approaching star came nearer to the companion star, the gravitational and
tidal force continued to increase and hence the bulge on the outer surface of the
companion star started growing towards the giant approaching star.
• When the giant approaching star came nearest to the companion star, large amount of
matter was ejected from the companion star due to maximum gravitational force exerted
by the giant approaching star.
• Planets were formed from the ejected matter.

Evaluation
• Russell did not throw light on the fate of the remaining portion of the
companion star. What happened about the residual part of the
companion star?
• Russell did not elaborate the process and mechanism through which
the planets, after their formation, were brought within the
gravitational field of the sun.

Supernova Hypothesis of Hoyle
• According to Hoyle initially there were two stars in the
universe viz. (i) the primitive sun and (ii) the companion
star.
• The companion star was of giant size and later on became
supernova due to nuclear reaction.
• With the passage of time all of the hydrogen nuclei of the
companion star were consumed in the process of nuclear
reaction and it collapsed and violently exploded.
• The violent explosion of the companion star (now supernova)
resulted into the spread of enormous mass of dust which
started revolving around the primitive sun.
• The gaseous matter coming out due to violent explosion of
the companion super-nova star changed into a circular
moving disc which started revolving around the primitive
sun. Thus, the matter of this disc became building material
for the formation of future planets.

Evaluation
• It fails to explain the peculiar arrangement of the planets on the basis
of their size, similar direction of rotation as well as the plane of
revolution and path of the planets and the lighter constituent
elements of the planets of the outer circle of our solar system on the
other hand.

Big Bang Theory

Big Bang Theory
• The Big Bang Theory postulated in 1950's and 1960's and validated in 1972
(May).
• The origin of universe and everything in it including ourselves on the premise
that the universe contained many million of gallaxies, each one 'having thousands
of millions of stars and each star having numerous planets around them
.According to this theory every universe emerged from a point known as
‘Singularity’ 15 billion years ago. The galaxies moved one another as the empty
space expanded. In the beginning the much smaller as there was less space
galaxies.
• "As the universe expanded for 15 billion years, the hot radiation in the original
fireball also expanded with it, and cooled as a result."
• 'There were already wispy clouds of matter stretching across vast distances,
upwards 500 million light years across. As those clouds collapsed in upon
themselves, pulled together by their own gravity, they would have broken up and
formed clusters of galaxies with the galaxies themselves breaking up into stars
like those of the Milky Way' (John Gribbin). The stars might have broken up to
form their planets as our earth.

Evolution of the
Earth

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

About 4.5 billion
years ago, Earth
formed out of
nebula of gases and
dust that were to
become the solar
system
Small objects--called
planetoids-- accreted or
combined together to build
larger objects…such as planets

Gravity reshapes the
proto-Earth into a
sphere. The interior of
the Earth separates into
a core and mantle.
Forming the planets from planetesimals:
Planetessimals grow by continuous
collisions. Gradually, an irregularly
shaped proto-Earth develops. The
interior heats up and becomes soft.

Geologic Time

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

Formation of the Moon
The Giant Impact Hypothesis
predicts that around 50 million
years after the initial creation of
Earth, a planet about the size of
Mars collided with Earth
This idea was first proposed
about 30 years ago, but it took
calculations by modern high-
speed computers to prove the
feasibility

This collision had to be very spectacular!
A considerable amount of material was blown off into
space, but most fell back onto the Earth

Part of the material from the collision remained in orbit around the
Earth
By the process collision and accretion, this orbiting material merged
into the Moon
The early Moon orbited very close to the Earth

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:

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

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

Chemical Composition of Earth
Whole Earth:
Fe+O+Si+Mg = 93%
Crust:
Si+O+Al = 82%
Each of the major layers has a distinctive
chemical composition, with the crust being
quite different from the Earth as a whole

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
Composition of Earth

Continents: Formed from solidified magma that
floated up from the Mantle
Chemical Composition of Earth
Oceans and Atmosphere:
Fluid and gaseous outer
layers believed to have
been created by out-
gassing of gases and fluids
from volcanic eruptions (in
a process called volatile
transfer)

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

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

These would include:
Water vapor (H2O)
Sulfur dioxide (SO2)
Hydrogen sulfide (H2S)
Carbon dioxide (CO2)
Carbon Monoxide (CO)
Ammonia (NH3)
Methane (CH4)
Note that oxygen (O2) gas is not created by
volcanic eruptions

It is hypothesized that water vapor escaping from the
interior of the Earth via countless volcanic eruptions
created the oceans (this took hundreds of millions of
years)
Creating the Oceans

Creating the Oceans
The earliest evidence of surface water on Earth
dates back about 3.8 billion years

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
Today our atmosphere
is 21% oxygen

By 3.5 billion years ago, the Earth also had
extensive oceans and seas of salt water, which
contained many dissolved elements, such as iron

But most important, by 3.5 billion years
ago, there was life on Earth

The Continents
By 2.5 billion years ago, the
continents had been formed
The density of the continental
crust (2.8 gr/cm3) is lighter that
the crust found on ocean
bottoms (3.2 gr/cm3), so the
continents rise above the ocean
floor
A question that remains
unanswered is, when did plate
tectonics start?

Structure of the Earth

Why is the Earth (near) spherical?
• Accretion: the gradual addition of new material
• When the Earth first accreted, it probably wasn’t
spherical
• What happened?
HEAT was generated and retained

Sources of Internal Heat
• Accretionary Heat
Proto-earth
1) Gravity attracts
planetesimal to the proto-
earth
2) Planetesimals accelerate
on their journey, gaining
kinetic energy (KE=1/2mv2)
3) They strike the proto-earth
at high speed
4) Their kinetic energy is
converted to thermal energy
(HEAT)

• Accretionary Heat

• Radioactive Decay
 The natural disintegration of certain isotopes to form new nuclei
 Time for nuclei to decay given by a “half-life”
Radioactive decay is an
important source of the
Earth’s internal heat

• Radioactive decay
 Short-lived Isotopes
26Al → 26Mg + Energy + … (t1/2 = 0.72 x 106 yrs)
129I → 129Xe + Energy + … (t1/2 = 16 x 106 yrs)
 Long-lived Isotopes
40K → 40Ar + Energy + … (t1/2 = 1270 x 106 yrs)
232Th (t1/2 = 1400 x 106 yrs)
235U (t1/2 = 704 x 106 yrs)
238U (t1/2 = 4470 x 106 yrs)

The Differentiated Earth
The earth differentiated into layers by density:
1) Crust
2) Upper Mantle
1) Lithospheric
2) Asthenospheric
3) Lower Mantle
4) Outer Core
5) Inner Core
Least Dense
Most Dense
Because different minerals have
different composition and
densities, physical partitioning of
the earth led to:
chemical differentiation
High Si
High Fe
Low Si
Low Fe

The Differentiated Earth
Whole Earth Density
~5.5 g/cm3
Surface Rocks
2.2 - 2.5 g/cm3
Core: Nearly
pure Fe/Ni
Mantle: Fe/Mg
rich, Si/Al poor
Crust: Si/Al rich,
Na/K/Ca rich

Another Source of Internal Heat
• Residual heat from the formation of the core
Gravitational Settling
E=GMm/r (gravitational potential energy)
• To understand:
 A 1-kg ball of iron, settling from the surface to the center of the
earth produces enough energy to heat a 10-kg piece of rock
(granite) to 750°C, where it would begin to melt.
 Heat capacity of granite = 840 J/kg K

The Crust
Continental Crust
• 35 - 40 km
• Less Dense
Oceanic Crust
• 7 - 10 km
•More Dense

The Mantle
The asthenosphere may contain a
few percent molten rock, but the
mantle is by and large solid
Despite this, given time, it will
flow

Loss of Internal Heat
All celestial bodies lose heat
There are three main mechanisms
•Conduction
•Convection
•Radiation
Conduction is the transfer of heat without
movement of material

Temperatures in the Earth
The geotherm is the description of how the temperature of the earth
increases with depth.
Near the surface
(to 8 km depth):
2-3 °C/100 m depth
Heat loss by conduction!

Core & Earth’s Magnetic Field
The core is almost completely Fe/Ni alloy. The outer core is liquid,
while the inner core is solid.
Convection of the outer, liquid core gives rise to the Earth’s magnetic
field

Evolution of Earth’s Atmosphere

https://www.youtube.com/watch?v=l0h_-
3M0Pso&ab_channel=Cognito

About 4.5 billion
years ago, Earth
formed out of
nebula of gases and
dust that were to
become the solar
system
Small objects--called
planetoids-- combined together
to build larger objects…such as
planets

The First Atmosphere
• The early atmosphere would have been similar to the Sun-
-mainly hydrogen and helium, but this atmosphere was
lost quickly for two reasons:
 (1) The gravity of the modest size earth was not strong enough to
prevent such light gases from escaping to space. Particularly since
the early earth was hot!
 (2) It appears that around 30 million years after the earth’s
formation, it was struck by a large object…the size of Mars. The
result: the origin of the moon and loss of earth’s early H, He
atmosphere.

Earth as Hell
• The surface of the earth during
this period was extremely hot
with numerous volcanoes
• The earth was under near
constant bombardment by
objects of varying sizes
• Slowly, the earth started to
cool down and the second
atmosphere began to form.

Earth’s Second Atmosphere
• A new atmosphere was established by
the outgasing of volcanoes…the
mixture of gases was probably similar
to those of today’s volcanoes:
• H2O vapor (roughly 80%)
• CO2 (roughly 10%)
• N2 (few percent)
• Small amounts of CO, HCl, H2S
(Hydrogen Sulfide), SO2, CH4
(Methane), Ammonia (NH3), and
other trace gases.

Earth’s Second Atmosphere
The apparent reason: so much CO2 so there was a very strong greenhouse effect.
At that time the sun was about 30% weaker than today…why didn’t the earth freeze over?
With a huge influx of water vapor and the cooling of the planet, clouds and earth’s oceans formed.
Thus, no ozone layer, so ultraviolet radiation flooded the earth’s surface.
Virtually no oxygen in that second atmosphere.

The Rise of Oxygen and the Third
Atmosphere
• In the first two billion years of the planet’s evolution, the
atmosphere acquired a small amount of oxygen, probably by the
splitting of water (H2O) molecules by solar radiation.
• The evidence of this oxygen is suggested by minor rust in
some early rocks.
• The oxygen also led to the establishment of an ozone layer that
reduced UV radiation at the surface.
• With the rise of photosynthetic bacteria (cyanobacteria) and early
plants, oxygen levels began to rise rapidly as did indications of rust
in rocks
• Between 2.5 billion years ago to about 500 bya, O2 rose to near
current levels.

The Third Atmosphere
While O2 was increasing, CO2 decreased due to several reasons:
(1) In photosynthesis CO2 is used to produce organic matter, some of
which is lost to the system (e.g., drops to the bottom of the ocean or is
buried)
(2) chemical weathering, which removes CO2

Chemical Weathering
• H2O + CO2 --> H2CO3 (carbonic acid)
• CaSiO3 + H2CO3 --> CaCO3 + SiO2 + H2O
Silicate Rock Carbonate
• At first this happened without life, but the process was sped up
tremendously by living organisms
• Marine organisms would incorporate carbonate into their
shells, which would fall to the ocean bottom when they died---
thus, removing them from the system for a long time.
• The bottom line…CO2 was being removed from the
system.

More Changes
• Sulfur compounds were taken out of the atmosphere as acid rain
and were deposited on the ground as sulfates.
• N2 gas increased slowly but progressively since it was relatively
inert.
• Current composition of the atmosphere was established
approximately a billion years ago.

A Problem
• With lower CO2 levels the earth became more susceptible
to ice ages when solar radiation decreases due to orbital
variations,
• It appears that around 750-550 million years ago the
earth cooled down and became nearly entirely glaciated.
• Note: one can get into a feedback with snow reflecting
solar radiation, producing cooler temperatures and more
snow, leading to less radiation, etc.

How Did We Get UnFrozen?
Volcanoes were still putting CO2 into the atmosphere
Weathering was greatly reduced…since little liquid
water.
So, CO2 increased until the greenhouse effect was so
large the earth warmed up.
Once warming started it would have happened very
rapidly.

The Last 500 million Years
The climate has not been constant, with warm periods
interrupted by ice ages.
Much of the variability forced by changing solar
radiation due to periodic changes in the earth’s orbital
characteristics and tilt and major volcanic eruptions
(putting out massive CO2 that caused warming.

Variability: Milankovitch Cycle
• The shape of Earth’s orbit, known as eccentricity;
• The angle Earth’s axis is tilted with respect to Earth’s orbital plane, known as
obliquity; and
• The direction Earth’s axis of rotation is pointed, known as precession.

The Biological Era - The Formation of
Atmospheric Oxygen
• This era of evolution of the atmosphere is called the "Biological Era”.
• The biological era was marked by the simultaneous decrease in atmospheric
carbon dioxide (CO2) and the increase in oxygen (O2) due to life processes.
• The build up of oxygen had three major consequences that we should note here:
 Firstly, the eukaryotes came about as a consequence of the long, steady, but less efficient
earlier photosynthesis carried out by Prokaryotes.
 Oxygen increased in stages, first through photolysis of water vapor and carbon dioxide by
ultraviolet energy and, possibly, lightning:
H2O -> H + OH
CO2 -> CO + O
O + OH -> O2 + H
 Secondly, once sufficient oxygen had accumulated in the stratosphere, it was acted on by
sunlight to form ozone, which allowed colonization of the land.
 Thirdly, the availability of oxygen enabled a diversification of metabolic pathways,
leading to a great increase in efficiency. The bulk of the oxygen formed once life began on
the planet, principally through the process of photosynthesis:
6CO2 + 6H2O <--> C6H12O6 + 6O2

Introduction to the Present
Atmosphere
The earth's atmosphere is the gaseous envelope surrounding the planet.
The earth's atmosphere figures centrally in transfers of energy between the
sun and the planet's surface and from one region of the globe to another;
these transfers maintain thermal equilibrium and determine the planet's
climate.
The earth's atmosphere is unique in that it is related closely to the oceans
and to surface processes, which, together with the atmosphere, form the
basis for life.

Composition of the Atmosphere

Structure of the Atmosphere Contd…

Troposphere
• The region of the atmosphere from the
surface up to about 11 km contains all of
the weather we are familiar with on
earth.
• Also, this region is kept well stirred by
rising and descending air currents. Here,
it is common for air molecules to circulate
through a depth of more than 10 km in
just a few days.
• This region of circulating air extending
upward from the earth’s surface to where
the air stops be coming colder with height
is called the troposphere— from the
Greek tropein, meaning to turn, or to
change.

Tropopause
• Just above 11 km the air temperature normally stops
decreasing with height. Here, the lapse rate is zero.
This region, where the air temperature remains
constant with height, is referred to as an isothermal
(equal temperature) zone.
• The bottom of this zone marks the top of the
troposphere and the beginning of another layer, the
stratosphere.
• The boundary separating the troposphere from the
stratosphere is called the tropopause.
• The height of the tropopause varies.
• It is normally found at higher elevations over
equatorial regions, and it decreases in elevation as we
travel poleward.

Why does all weather phenomena take place in the troposphere?
• Most of the weather phenomena, systems, convection, turbulence and clouds
occur in this layer, although some may extend into the lower portion of the
stratosphere.
• It contains about 70 to 80 per cent of the total mass of the Earth's atmosphere
and 99 per cent of the water vapor.
• The layer where most of the water vapor exists, as well as it is the layer where
the greatest energy imbalance between the surface and the atmosphere exists. As
a result, nature tries to restore energy balance in that layer by various means,
such as convection, and the effects of those processes we call weather. And hence
all the weather phenomena take place in the troposphere

Stratosphere
• In the stratosphere at an altitude near 20
km, the air temperature begins to
increase with height, producing a
temperature inversion.
• The inversion region, along with the
lower isothermal layer, tends to keep the
vertical currents of the troposphere from
spreading into the stratosphere.
• The inversion also tends to reduce the
amount of vertical motion in the
stratosphere itself; hence, it is a stratified
layer.

Mesosphere
• The mesosphere comes from the Greek
word mesos: middle.
• The air here is extremely thin, and the
atmospheric pressure is quite low.
• With an average temperature of –90°C,
the top of the mesosphere represents the
coldest part of our atmosphere.

Thermosphere
• The “hot layer” above the mesosphere is
the thermosphere.
• In the thermosphere, there are relatively
few atoms and molecules. Consequently,
the absorption of a small amount of
energetic solar energy can cause a large
increase in air temperature that may
exceed 500°C, or 900°F.

Exosphere
• At the top of the thermosphere, about 500
km (300 mi) above the earth’s surface,
molecules can move great distances
before they collide with other molecules.
• Here, many of the lighter, faster-moving
molecules traveling in the right direction
actually escape the earth’s gravitational
pull.
• The region where atoms and molecules
shoot off into space is sometimes referred
to as the exosphere, which represents the
upper limit of our atmosphere.

The Ionosphere
• The ionosphere is not really a layer, but
rather an electrified region within the
upper atmosphere where fairly large
concentrations of ions and free electrons
exist.
• The lower region of the ionosphere is
usually about 60 km above the earth’s
surface. From here (60 km), the
ionosphere extends upward to the top of
the atmosphere.
• The ionosphere plays a major role in
radio communications.

Atmospheric Pressure and
Temperature
• The amount of force exerted over an area of surface is called atmospheric pressure or, simply, air pressure.
• Air pressure decreases rapidly at first, then more slowly at higher levels
• At sea level, the average or standard value for atmospheric pressure is
1013.25 mb = 1013.25 hPa = 29.92 in. Hg.
• The rate at which the air temperature
decreases with height is called the
temperature lapse rate.
• The average (or standard) lapse rate
in this region of the lower atmosphere
is about 6.5 degrees Celsius (°C) for
every 1000 meters (m) or about 3.6
degrees Fahrenheit (°F) for every
1000 ft rise in elevation.
• Occasionally, the air temperature
may actually increase with height,
producing a condition known as a
temperature inversion.

Significance of the Atmosphere
1) Crucial Part of the Water Cycle
2) Indispensable for Life of Earth
3) Ozone Layer Makes Life Possible
4) Moderates Earth’s Temperature

1. Crucial Part of the Water Cycle

2. Indispensable for Life of Earth
• Atmospheric gases, especially carbon dioxide
(CO2) and oxygen (O2), are extremely
important for living organisms.
• Photosynthesis is responsible for nearly all of
the oxygen currently found in the
atmosphere.
• By creating oxygen and food, plants have
made an environment that is favorable for
animals.

3. Ozone Layer Makes Life Possible
• Ozone is a molecule composed of three
oxygen atoms, (O3).
• Ozone in the upper atmosphere absorbs
high energy ultraviolet (UV) radiation
coming from the Sun. This protects living
things on Earth’s surface from the Sun’s
most harmful rays.
• Without ozone for protection, only the
simplest life forms would be able to live on
Earth.

4. Moderates Earth’s Temperature
• The atmosphere keeps Earth’s
temperatures within a tolerable
range.
• Greenhouse gases trap heat in the
atmosphere so they help to moderate
global temperatures.
• Without an atmosphere with
greenhouse gases, Earth’s
temperatures would be frigid at night
and scorching during the day.
• Important greenhouse gases include
carbon dioxide, methane, water
vapor, and ozone.

Geological Time Scale

Precambrian
Time

• The Precambrian Time was the earliest time of formation of Earth and first form
of life on it.

Rocks

Rocks and Rock types
•Form by solidification of molten rock (magma)
Igneous
•Form by lithification of sediment (sand, silt, clay, shells)
Sedimentary
•Form by transformations of preexisting rocks (in the solid
state)
Metamorphic
An aggregate of one or more minerals; or a body of undifferentiated
mineral matter; or of solid organic matter (e.g., coal)
 More than one crystal
 Volcanic glass
 Solidified organic matter
 Appearance controlled by composition and size and arrangement
of aggregate grains (texture)

Igneous Rocks
Intrusive
Extrusive

Intrusive (plutonic)
 Form within the Earth
 Slow cooling
 Interlocking large crystals
 Example = granite

Extrusive (volcanic)
 Form on the surface of the Earth as a result of volcanic eruption
 Rapid cooling
 Glassy and/or fine-grained texture
 Example = basalt

Sedimentary Rocks

Origin of sediment
 Produced by weathering and
erosion or by precipitation from
solution
 Weathering = chemical and mechanical
breakdown of rocks
 Erosion = processes that get the weathered
material moving
Sediment types
 Clastic sediments are derived from
the physical deposition of particles
produced by weathering and
erosion of preexisting rock.
 Chemical and biochemical
sediments are precipitated from
solution.
Clastic
Chemical/biochemical

Lithification
The process that converts sediments into solid rock
Compaction
Cementation

Metamorphic Rocks

Types of Metamorphism
Regional
Metamorphism
burial ocean-ridge orogenic
Contact
Metamorphism

The Rock Cycle

Rock Cycle
https://www.youtube.com/watch?v=a3olYeNUVM0&ab_ch
annel=AmitSengupta

Summary

Minerals

Minerals are mined for our use
Magmatic copper, magnetite, uranium

Humans cannot survive without minerals
• 16 minerals needed for
humans to survive
• 0.03% of what we eat but
we would not survive
without the minerals
• Sodium, potassium,
calcium, magnesium,
copper, phosphorous

Salt
• Early people collected salt
before they understood
how important the mineral
is for survival
• Mediterranean-salt cakes
were used as money
• Greeks traded salt for
slaves

Glass is made from 6 minerals
• Silica
• Limestone
• Magnesium
• Boric acid
• Soda
• Aluminum

Criteria for Minerals
Solid
Naturally
occurring
Inorganic
Fixed
chemical
formula
Specific
atomic
arrangement

Minerals
https://www.youtube.com/watch?v=8a7p1NFn64s&ab_cha
nnel=MikeSammartano

Eight elements make-up 99% of the
Earth’s crust
Silicon and oxygen make-up 70 % of the Earth’s crust

Mineral Formation
Precipitation from aqueous solution (i.e., from hot water flowing underground, from
evaporation of a lake or inland sea, or in some cases, directly from seawater)
Precipitation from gaseous components (e.g., in volcanic regions)
Metamorphism — formation of new minerals directly from the elements within existing
minerals under conditions of elevated temperature and pressure
Weathering — during which minerals unstable at Earth’s surface may be altered to other
minerals
Organic formation — formation of minerals within shells (primarily calcite) and teeth and
bones (primarily apatite) by organisms (these organically formed minerals are still called
minerals because they can also form inorganically)

Mineral Formation
• Cooling of magma:
crystallization
• Evaporation: salt
• Hydrothermal

Minerals can be identified by physical properties
• Crystal form
• Cleavage
• Fracture
Quartz has a conchoidal fracture Mica has a single, perfect cleavage
Equant garnet: same dimension in all directions

Color
malachite
sulfur
apatite

Hardness
How the mineral can be
scratched
• Fingernail
• Penny
• File or knife

Streak
• Minerals leave a distinct
residue on a porcelain plate

Luster
• Metallic or non-metallic

• The ratio of the density of the mineral to
the density of water (1 g/cm3)
• If a mineral has a specific gravity of 5
that means it is 5 times as dense as water.
Specific Gravity

Classification of Minerals based on
composition
• Rock forming minerals
contain silicon and oxygen
are the SILICATE
MINERALS
The silicon
tetrahedron

Minerals are the building block of rocks
Feldspar crystal
Biotitie
Quartz
Hornblende

Silicate minerals are the building block
of igneous rocks
Mountains, British Columbia
Granite: individual minerals
make-up the rock

Mineral Classification: based on
dominant element
Pyrite: fool’s gold; FeS2
Sulfides: contains the element sulfur
Galena: PbS; important ore of
lead

• Carbonates: contains calcium carbonate; CaCO3
Mineral Classification: based on
dominant element
Calcite: CaCo3
Dolomite: CaMg(CO3)2

Economic Minerals
Energy minerals are used to produce electricity, fuel for transportation, heating for
homes and offices and in the manufacture of plastics. Energy minerals include coal, oil,
natural gas and uranium.
Metals have a wide variety of uses. For example, iron (as steel) is used in cars or for
frames of buildings, copper is used in electrical wiring, and aluminium is used in aircraft
and to make drink cans. Precious metals are used in jewellery and mobile phones.
Construction minerals include sand and gravel, brick clay and crushed rock aggregates.
They are used in the manufacture of concrete, bricks and pipes and in building houses and
roads.
Industrial minerals are non–metallic minerals used in a range of industrial applications
including the manufacture of chemicals, glass, fertilisers and fillers in pharmaceuticals,
plastics and paper. Industrial minerals include salt, clays, limestone, silica sand,
phosphate rock, talc and mica.

That’s All…

GEO610 Module I.pdf

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