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E A R T H : I N T R O D U C T I O N T O P H Y S I O G R A P H Y

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Earth: A Living Planet

Harun Yahya (2001), in the following article, presents the conditions that make earth, not just a livable planet, but a living planet. The writer contends that “the conditions essential for life are too complicated to have been formed „on their own‟;” hence, somebody greater than earth has authored earth. He further intones that “God has created the universe with infinite wisdom and power and designed the earth especially for human life.” The article clearly attempts to explain that the existence of the universe, of which the earth is a part, is not a result random process; instead, the observable universal elements around us are “proofs” that our world was planned by a superior being.

he earth is a living planet where many complex systems run perfectly without stopping

at all. When compared to other planets, it is evident that in all its aspects the earth is

specially designed for human life. Built on delicate balances, life prevails in every spot

of this planet, from the atmosphere to the depths of the earth. Exploring only a few of

the millions of these delicate balances would be sufficient to show that the world we live in is

specially designed for us.

One of the most important balances in our planet is revealed in the atmosphere that

surrounds us. The atmosphere of the earth holds the most appropriate gasses in the most

appropriate ratio needed for the survival not only of human beings, but also of all the living

beings on the earth.

The 77% of nitrogen, 21% of oxygen and 1% of carbon dioxide as well as other gasses

readily available in the atmosphere represent the ideal figures necessary for the survival of

living beings. Oxygen, a gas that is vital for living beings, helps food to be burned and

converted into energy in our bodies.

If the oxygen percentage in the atmosphere were greater than 21%, the cells in our body

would soon start to suffer great damages. The vegetation and hydrocarbon molecules needed for

life would also be destroyed. If this percentage were any less, this would cause difficulties in

our respiration, and the food we eat would not be converted into energy. Therefore, the 21% of

oxygen in the atmosphere is the most ideal quantity determined for life.

No less than oxygen, other gasses like nitrogen and carbon dioxide are also arranged in

the ideal quantity for the needs of living beings and the continuity of life. The amount of

nitrogen in the atmosphere has the ideal ratio to balance the harmful and burning effects of

oxygen. This ratio represents the most appropriate value required for photosynthesis, which is

essential for life's energy supply on the earth. Moreover, the amount of carbon dioxide has the

most appropriate value that is needed to maintain the stability of the surface temperature of the

earth and to prevent heat loss especially at night time. This gas, comprising 1% of the

Chapter

4

T

LESSON OBJECTIVES 1. Explain the effects of the sun’s light to the earth’s surface. 2. Describe the size, structure, and shape of the earth. 3. Analyze the theories postulating the origin and formation of

oceans and seas. 4. Explain how rivers contributed to the emergence of civilizations

in different locations across the globe. 5. Explain how landforms developed on the earth’s crust. 6. Discuss the effects of internal and external forces shaping the

earth on human beings.


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atmosphere, covers the earth like a quilt and prevents the loss of heat to space. If this amount

were greater, the temperature of the earth would increase excessively, causing climatic

instability and posing a serious threat against living beings.

These proportions remain constant, thanks to a perfect system. The vegetation covering

the earth converts carbon dioxide to oxygen, producing 190 billion tons of oxygen every day.

The proportion of other gasses is always kept constant on the earth by the help of interconnected

complex systems. Life is thus sustained.

In addition to the establishment of the ideal gas mixture required for life on the earth, the

mechanisms needed to preserve and maintain this order are created alongside with it. Any break

in the balance, though instantaneous, or any change in the ratios even for a very short time

period, would mean the total destruction of life. Yet, this does not happen. The formation of

these gasses in the atmosphere just in the amount people need, and the constant preservation of

these ratios indicate a planned creation.

At the same time, the earth has the ideal size in terms of magnitude to possess an

atmosphere. If the mass of the earth were a little less, then its gravitational force would be

insufficient and the atmosphere would be dispersed in space. If its mass were a little greater,

then the gravitational force would be too much and the earth would absorb all gasses in the

atmosphere. There is an incredibly high number of conditions required for the formation of an

atmosphere such as the one our world currently has and all of these conditions should exist

altogether to be able to talk of life.

The creation of these delicate proportions and balances in the sky is mentioned in the 7th

verse of Surat ar-Rahman:

"He erected heaven and established the balance." [Ar-Rahman 55:7]

The majority of people spend their lives without being aware of the delicate balances

and subtle adjustments in the gas composition of the atmosphere, the distance of the world to the

sun or the movements of planets. They are ignorant of the great significance of these balances

and adjustments to their own lives. However, even a minor deviation in any one of these

arrangements would create very severe problems regarding the existence and survival of

humankind.

There are many other balances established on earth for the continuity of life. For

instance, if the surface gravity were stronger than its current value, the atmosphere would retain

too much ammonia and methane gasses, which would mean the end of life. If it were weaker,

the planet's atmosphere would lose too much water, and life on earth would be impossible.

The thickness of the earth's crust constitutes another one of the delicate balances in the

earth. If the earth's crust were thicker, too much oxygen would be transferred from the

atmosphere to the crust and this would have severe effects on human life. If the opposite were

true, that is, if the earth's crust were thinner, volcanic and tectonic activity would be too great to

permit life on earth.

Another crucial balance for human life is the ozone level in the atmosphere. If it were

greater than its current value, the surface temperatures would be too low. If it were less, surface

temperatures would be too high, and there would be too much ultraviolet radiation at the

surface.


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In fact, the absence of even a single of these balances would set the end to life on earth.

However, God has created the universe with infinite wisdom and power and designed the earth

specially for human life. Despite this fact, the majority of people lead their lives in total

ignorance of these events. In the Qur'an, God reminds people of His blessings in the 13th verse

of Surat al-Fatir:

"(God) makes night merge into day and day merge into night, and He has made

the sun and moon subservient, each one running until a specified time. That is

God, your Lord. The Kingdom is His. Those you call on besides Him have no

power over even the smallest speck." [Al-Fatir 35:13]

It is sufficient look at millions of dead planets in space in order to understand that the

delicate balances required for life on earth is not a result of random coincidences. The

conditions essential for life are too complicated to have been formed "on their own" and at

random, and these conditions are specially created for life alone. These balances we have briefly

described so far are only a few of the millions of intricate, interrelated balances and orders

established so that people can live in peace and safety on the earth.

Examining only a part of the balances and harmony on the earth is enough to

comprehend the superior being of God and grasp the existence of a planned creation in every

detail of the universe. It is no doubt impossible for a person or any other living being to build

such an enormous balance and order. Nor are the components of this order such as atoms,

elements, molecules, and gasses capable of establishing an order based on such intricate and

extremely delicate calculations and measurements, and such fine tunings. This is because

activities like planning, ordering, arranging, calculating, and proportioning can only be realized

by beings that possess wisdom, knowledge and power. The Exalted Being Who orders, plans

and balances the entire universe to be fit for life of human beings on a planet like earth and Who

sustains it with dramatically delicate measures and balances is God, Who has Infinite Wisdom,

Knowledge and Power.

In the Qur'an, it is stated that those people who are able to realize these facts are only

"people with intelligence":

"In the creation of the heavens and the earth, and the alternation of night and day,

there are Signs for people with intelligence: those who remember God, standing,

sitting and lying on their sides, and reflect on the creation of the heavens and the

earth: 'Our Lord, You have not created this for nothing. Glory be to You! So

safeguard us from the punishment of the Fire." [Al-i-'Imran 3:190-191]

Earth: Outside and inside features

1. The Solar System. The Solar System mainly consists of the sun and the nine planets

revolving around it. It also includes a group of planetary fragments known as asteroids, and of

comets and meteors. The nine planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus,

Neptune and Pluto [Note: Pluto has been declared by scientists as no longer a planet]) revolve

around the sun following an elliptical orbit and are held in their paths by a balance of two

forces—gravitational attraction and centrifugal force. (Agno and Juanico, 1987)


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THE SUN is the most important to the earth and to geographic study, since the sun is

the source of solar radiation or sunlight, which allows life to exist on earth through the

process of photosynthesis—a process where carbon dioxide, water and chlorophyll

(green substance in plants), when all acted upon by sunlight, will produce

carbohydrates plus oxygen. (Agno and Juanico)

Location of the earth in Space. The earth is the third planet from the sun after Mercury and

Venus is located at a mean distance of 150 million kilometers from the sun. Its farthest

distance from the sun (aphelion) occurs on July 4 (151. 1 million km) and its nearest distance

(perihelion) occurs on January 3 (147. 2). Earth’s closest neighbor is its own satellite, the

moon. The significance of the earth’s distance from the sun is that such proper distance is just

right for the life forms and systemic process that need it to exist. (Agno and Juanico)

Earth Motions: Revolution and Rotation. The movement of the earth around the sun

following its orbit is termed as revolution. The earth revolves at a speed of 29.8 km/second

and it requires 365 ¼ days to complete this movement around the sun—marking the duration

of one year. The direction is eastward, i.e., from west to east. The other basic movement of the

earth is rotation, which means the uniform spinning of the earth on its axis (an imaginary line,

and is the earth’s shortest diameter running through the North and South Poles), which is

inclined at an angle of 23 ½ degrees from imaginary plane created by the earth’s orbit. This

rotation is from west to east. One complete rotation is equivalent to 24 hours or one day.

(Agno and Juanico)

The Solar System. [Source: kwizNET.com, http://www.kwiznet.com/p/takeQuiz.php?ChapterID=13&CurriculumID=7&

Num=3.2]


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Earth Attitude: Inclination and Parallelism. Inclination is the tilting or angle of tilting of the

earth’s axis from the line perpendicular to the plane of its orbit. Tilting is placed at 23 ½

degrees, and is always parallel to any of its position as it revolves around the sun. Inclination

and parallelism, in effect, cause the phenomenon called seasons. (Agno and Juanico)

Seasons of the Earth: Agno and Juanico explain that the basis is the Northern Hemisphere

since most of the north is inhabited by people. The earth’s four seasons are:

A. Summer (May-July): Summer Solstice (June 21); ―Solstice‖—standing still of the

sun; marks the longest day in the Northern Hemisphere and the longest night in the

Southern Hemisphere.

B. Autumn/Fall (August-October): Fall equinox (September 22); ―Equinox‖—equal

day and night; there is an equal length of day and night in both North and South

Hemispheres; marks the increase of nighttime period in the North and increase

daytime period in the South.

[Source: National Weather Service Weather Forecast Office, Albuquerque

http://www.srh.noaa.gov/abq/?n=clifeat

ures_summersolstice2010]


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C. Winter (November-January): Winter Solstice (December 22); marks the longest

night in the North and longest day in the South.

D. Spring (February-April): Spring/Vernal Equinox (March 21); there is equal day and

night in both hemispheres; signals the increase of daytime period in the North and

increase of nighttime period in the South.

Earth-Sun Relationship: Lower latitudes, near the earth’s equator, receive a greater

concentration of incoming energy than higher latitudes. This is because at higher

latitudes, the same amount of incoming energy is spread over a larger area of the earth than at lower latitudes. (Source: ARTICLE—Cooperative Extension University of

Arizona,2008, http://ag.arizona.edu/watershedsteward/resources/module/Climate/

climate-intro_pg2.htm; PHOTO—NASA, http://virtualskies.arc.nasa.gov/weather/2.html)

Source: Research Institute for Sustainable Development, http://www.rise.org.au/info/Tech/house/index.html


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Special Parallels—mark certain conditions and outcomes of the relationship between earth

and the sun

A. Tropic of Cancer (23 ½ degrees north of equator)—marks the northernmost limit

of the sun’s direct vertical rays (June 21—summer solstice)

B. Tropic of Capricorn (23 ½ degrees south of equator)—marks the southernmost

limit of the sun’s direct vertical rays (December 22—winter solstice)

C. Arctic Circle (66 ½ degrees north) and Antarctic Circle (66 ½ degrees south)—

mark the limit of the sun’s tangential rays in the northern and southern hemispheres

on two occasions (June 21 and December 22)

2. Structure of the Earth: Size, Structure and Shape. The earth is essentially a sphere with an

approximate diameter of 12, 874 km, a maximum circumference of 40, 232 km, and an area of

510 million km. In comparison to the sun, the earth is just like the size of a pea if the sun

would be a sphere of 30 inches in diameter. Thus, the sun is more than 100, 000 times that of

the earth. (Agno and Juanico, 1987). The earth has three layers. These are:

1. CRUST—is the outermost layer. It is rigid and thin as compared with the other layers.

Beneath the oceans, the crust generally extends to about 5 km only. Beneath the

continents, the crust’s thickness averages about 30 km; under large, mountain ranges

such as the Alps, the base of the crust can be as deep as 100 km. Like an egg’s shell,

the crust is brittle and can break. (USGS, 2002)

Mohorovicic Discontinuity –boundary between the crust and the mantle;

more often known as MOHO LAYER


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2. MANTLE – is the layer below the crust. It is a dense, hot layer of semi-solid rock

approximately 2, 900 km thick. It is made up of iron, magnesium, and calcium. In

comparison, it may be likened to the white of a boiled egg. (USGS, 2002) The upper

layer of the mantle is cooler and more rigid than the lower mantle and it behaves like

the overlaying crust. The crust and the upper mantle make up a rigid layer of rock

called lithosphere. (USGS)

Lithosphere. Averaging at least 80 km in thickness, the lithosphere has

been broken up into the moving plates that contain the world’s continents

and oceans. (USGS)

Asthenosphere. Below the lithosphere, scientists believe is a relatively

narrow, mobile zone in the mantle called the asthenosphere. This zone is

composed of hot, semi-solid material, which can soften and flow when

subjected to high temperature and pressure over geologic time. On this

slowly flowing asthenosphere, the lithosphere is believed to float or move

about. (USGS)

3. CORE – is the centermost layer of the earth. It is nearly twice as dense as the mantle

because of its metallic composition, which is mostly nickel and iron. It is made up of

two distinct parts: a 2, 200 km-thick liquid outer core and a 1, 250 km-thick solid inner

core. As the earth rotates, the liquid outer core spins, creating the magnetic field of the

earth. (USGS)

3. Bodies of water and landforms

Bodies of water


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Oceans and seas. About two-thirds of the Earth’s surface lies beneath the oceans [and

seas]. Before the 19th century, most people believed that the ocean floor was relatively flat

and featureless. For the next centuries, oceanic exploration dramatically improved our

knowledge of the ocean floor. In the 1950’s data gathered by oceanographic surveys led to

the discovery that a great mountain range on the ocean floor virtually encircled the earth.

This immense submarine mountain chain—more than 50, 000 km long and, in places,

more than 800 km across—zigzags between the continents, winding its way around the

globe like the seam on a baseball (USGS). The earth’s oceans and seas are shown in the

map below

NOTE: The body of water surrounding Antarctica has been designated as the

Southern Ocean or Antarctic Ocean

Origin of the Oceans? In Scienceclarified.com’s webpage, it is posted that:

One scientific theory about the origin of ocean water states that as Earth formed

from a cloud of gas and dust more than 4.5 billion years ago, a huge amount of

lighter elements (including hydrogen and oxygen) became trapped inside the molten

interior of the young planet. During the first one to two billion years after Earth's

formation, these elemental gases rose through thousands of miles of molten and

melting rock to erupt on the surface through volcanoes and fissures (long narrow

cracks). Within the planet and above the surface, oxygen combined with hydrogen

to form water. Enormous quantities of water shrouded the globe as an incredibly

dense atmosphere of water vapor. Near the top of the atmosphere, where heat could

The World’s Oceans & Seas

[Source: WorldAtlas.com]


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be lost to outer space, water vapor condensed to liquid and fell back into the water

vapor layer below, cooling the layer. This atmospheric cooling process continued

until the first raindrops fell to the young Earth's surface and flashed into steam. This

was the beginning of a fantastic rainstorm that, with the passage of time, gradually

filled the ocean basins.

(Read ―Asteroid Provides Clues to Earth's Oceans‖ on http://www.astrobio.net/ for

another theory of the earth’s oceans)

Lakes and Rivers. The main accessible sources of fresh water on the earth's surface are rivers

and lakes. Rivers have also played a significant role in the history of mankind. Some of the

greatest ancient civilizations arose around rivers and human settlement flourished in the river

valleys of some of the greatest rivers of the world. Below is a map showing the world’s major

rivers.

EnchantedLearning.com (2007) gives us more information about rivers:

Rivers are flowing bodies of waters. There are rivers on every continent (except

Antarctica). Rivers are an important part of the Earth's water cycle and the

RIVERS OF THE WORLD [Source: EnchantedLearning.com]


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sculpting of the Earth's topography as they carry huge quantities of water from

the land to the sea.

The Course of a River. Rivers generally start at a source, like a snow melt

(such as a glacier) or a natural spring. Most rivers flow into a larger body of

water, like an ocean, sea, or large lake.

The early course of a river is often in steep, mountain areas, with rapidly-

flowing cold water. As a river continues along its course (which is always

changing), the surrounding terrain flattens out and the river widens. Rivers

often meander (follow a winding path) along their middle course. Tributaries

(smaller rivers or streams) and runoff flow into the river, increasing the river's

volume (the amount of water it has). Rivers often have increased volume and

water speed in the spring, as snow at the river's source melts.

Most rivers end when they flow into a large body of water. The end of the river

is called the mouth. At the mouth, there is usually a river delta, a large, silty

area where the river splits into many different slow-flowing channels that have

muddy banks. New land is created at deltas. Deltas are often triangular-shaped,

hence the name (the Greek letter 'delta' is shaped like a triangle).

The Water in a River. At the source of a river, the water is relatively pure. As

the water flows downstream, it picks up silt and minerals (including mineral

salts) from the soil and rock in the river bed. Many other chemicals enter river

water as it flows downstream, including animal waste, human sewage,

agricultural (farm) runoff, urban runoff, and mining/factory effluent.

Landforms. Landforms are features that make up the Earth's surface. Some basic

landform types are:

Mountains - high, steeply sloped areas of the Earth's surface formed by the

upward movement of rock. Mountains are found on land and on the ocean

floor.

Plains - low areas of the earth that have been eroded nearly level or formed of

flat-lying sediments.

Plateaus - high, nearly level uplifted areas composed of horizontal layers of

rocks.

Volcano - is a mountain or hill formed around a crack in the earth's crust. This

crack allows molten rock and other hot materials to be thrown out from the

earth (www.mcwdn.org, no date)

Canyon - A narrow, deep, steep-sided opening in the earth's surface with steep

cliff walls, cut into the earth by running water; a gorge.

Delta - a fan shaped deposit of earth materials at the mouth of a stream.


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Hill - an isolated elevation in the land, usually no more than 30 meters from

base to peak.

Mesa - a broad, flat-topped elevation with one or more cliff-like sides, common

in the southwest United States

Mouth - a natural opening, as the part of a stream or river that empties into a

larger body of water or the entrance to a harbor, canyon, valley, or cave.

Valley - a low area between hills and mountains where a stream often flows

Sand dunes - hills left behind by the wind.

Fault - a fracture, or crack, in rocks along which movement has taken place.

Internal and External forces shaping the earth

1. Internal forces: Plate tectonics. Plate Tectonics is the study of the formation and

movement of plates [in geologic terms, these are large slabs of solid rocks] [See fig. 9]

(USGS, 2002 and Spaulding and Namowitz, 1997). The theory of plate tectonics states that the

Earth’s outermost layer is fragmented into a dozen or more large and small plates that are

moving relative to one another as they ride atop hotter, more mobile material. A precursor of

this theory is Alfred Wegener’s Continental Drift Theory, which states that the present-day

continents were the fragmented pieces of pre-existing larger landmasses that trace their origin

to a single ―supercontinent,‖ the Pangaea [See figure below]. (USGS, 2002)


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THE TECTONIC PLATES and their MOVEMENTS. Tectonic plates (also called

lithospheric plates) are massive, irregularly shaped slabs of rock, generally composed of both

continental and oceanic lithospheres. The sizes and thickness of plates vary; the Pacific and

Atlantic plates are the largest. Most of the boundaries between individual tectonic plates are

hidden beneath the oceans; thus, they cannot be seen. These plates may have developed in the

Earth’s 4.6 billion-year history, and they have been drifting about on the surface ever since.

(USGS) Scientists now have a fairly good understanding of the plates move and how such

movements relate to earthquake activity. Most movement occurs along narrow zones between

plates where the results of plate-tectonic forces are most evident. The four types of plate

boundaries are (USGS):

Divergent—where new crust is generated as the plates pull away from each other

Convergent—where crusts are destroyed as one plate dives under another

Transform—where crust is neither produced nor destroyed as the plates slide

horizontally past each other

Plate boundary zones—broad belts in which boundaries are not well defined and the

effects of plate interaction are unclear

THE PANGAEA, began to break

up about 225-200 million years

ago, eventually fragmenting into

the present-day continents

Divergent Boundary


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TECTONIC PLATES OF THE EARTH [Source: USGS, 2002]

Convergent Boundary

Transform Boundary

PLATE BOUNDARIES [Source: Agno and Juanico]


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2. External forces: Weathering and Erosion

Weathering refers to physical and chemical processes that change the characteristics of

rock on or near the earth’s surface. Weathering occurs slowly over many years and even

centuries. Weathering processes create smaller and smaller pieces of rock called sediment.

Sediment is mostly identifiable as mud, sand, or silt, which are very fine particles of rock.

(Arreola, Deal, Petersen, and Sanders, 2003).

Mechanical weathering --- involves the processes that break rock into smaller

pieces. This weathering process does not change the composition of the rock—

only its size. For example, when ice crystals build up in the crack of a rock,

they can actually create enough pressure to fracture the rock into smaller

pieces. All sorts of agents can break apart rocks. Frost and even plant roots dig

into crevices in the rock, splitting it. Human activities like road construction or

drilling and blasting in mining are also mechanical weathering forces.

Eventually, the smaller broken material will be combined with organic material

to become soil. (Arreola, et. al., 2003).

Chemical weathering — occurs when rock is changed into a new substance as

a result of interaction between elements in the air or water and the minerals in

the rock. (Arreola, et. al.) Decomposition or break up can happen in several

ways. Some minerals react to oxygen in the air and begin to crumble. That is

what happens when iron rusts, for example. Other minerals break down when

combined with water or carbon dioxide, which form weak acids within rock.

When sulfur and nitrogen oxides mix with water, acid rain is formed. Acid rain

speeds up decomposition. Climates too, have great effect on how rocks

decompose. (Arreola, et. al.)

Erosion. Erosion occurs when weathered material is moved by the action of wind, water,

ice, or gravity. For erosion to occur, a transporting agent, such as water, must be present.

Glaciers, waves, stream flow, or blowing winds cause erosion by grinding rock into smaller

pieces. Material moved form one location to another results in the lowering of some

locations and increased elevation in others. Erosion in its many forms reshapes landforms

and coastal regions, as well as riverbeds and riverbanks. (Arreola, et. al.)

Water Erosion—occurs as water flows in a stream or river. The motion picks

up loose material and moves it downstream. The greater the force of water, the

greater the ability of the water to transport tiny rock particles, or sediment.

Wind Erosion—is similar to water erosion because the wind transports and

deposits sediment in other locations. The greater the speed of the wind, the

larger the particles moved. Dust storms are capable of carrying as much as 6,

000 tons of sediment per cubic mile of air. As the wind slows, the sediment is

dropped.


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Glacier Erosion—is a large, long-lasting mass of ice that moves because of

gravity. Glaciers form in mountainous areas and in regions that are routinely

covered with heavy snowfall and ice. In mountain regions, glaciers move down

slope as a result of gravity.

[Source: CartoonStock.com, http://www.cartoonstock.com/directory/e/erosion.asp]

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Earth: A Living Planet - tecs onlinetecsonline.weebly.com/uploads/2/6/8/2/26827965/chapter_4.pdf · surrounds us . The atmosphere ... of the ideal gas mixture required for life on