TOPIC 2: EARTH SYSTEM – ADVANCED PHYSICAL GEOGRAPHY

TOPIC 2: EARTH SYSTEM – ADVANCED PHYSICAL GEOGRAPHY

SUB-TOPICS:

1. Earth as a system.
2. Atmosphere.
3. Layers of the atmosphere.
4. Interactions among earth’s spheres.

THE EARTH AS A SYSTEM

“System” is a collection of things and processes connected together and operating as a whole. Earth’s environmental spheres operate and interact through a complex of Earth systems. For example; soil, which is composed largely of bits of mineral matter (lithosphere) but also contains life forms (biosphere), along with air (atmosphere), soil moisture (hydrosphere), and perhaps frozen water (cryosphere) in its pore spaces.

SOLAR ENERGY

Sun is the main source of energy which power the Earth systems as it drives many of the environmental processes of the earth’s system. Sunshine is the light we get from sun rays. There is less light on earth when there are clouds in the sky. Sun rays is also called solar radiation or Insolation.

What is the Insolation?

Insolation is the amount of solar energy received on the earth surface. The energy has greater impact on atmospheric weather.

What is Temperature?

Temperature refers to a degree of hotness or coldness of a body in the atmosphere. It is influenced by the amount of solar radiation. High insolation means high temperature while Low insolation means low temperature.

HOW SOLAR RADIATION IS EMITTED INTO THE ATMOSPHERE

The solar energy is emitted to atmosphere through radiation called short waves radiation or solar radiation.

What is radiation (emission)?

Radiation or emission is the process by which electromagnetic energy is emitted from an object.

So the term “radiation” refers to both the emission and the flow of electromagnetic energy. All objects emit electromagnetic energy, but hotter objects are more intense radiators than cooler objects. In general, the hotter the object, the more intense its radiation.

How many processes occurs during emission of solar radiation?

There are three processes may occur during emission of solar radiation to the atmosphere. These are:-

1. Absorption:

Is the process in which solar radiation is retained by a substance and converted into heat. OR Is the process whereby electromagnetic waves striking an object may be assimilated by that object. OR Is the consumption of solar energy by various atmospheric components such as water vapour, clouds cover, and carbon dioxide gas.

2. Reflection:

Is the process whereby sunlight is redirected back after it strikes an atmospheric particles. OR

Reflection is the ability of an object to repel (“bounce back”) electromagnetic waves that strike it.

It occurs when the radiation hits the particles like clouds that are available in the atmosphere.

3. Scattering:

Is a process whereby sunlight is diverted from its straight path on striking obstacles like dusts, gases molecules and water vapour. OR

Is the process whereby gas molecules and particulate matter in the air can deflect light waves and redirect. Its takes place in all direction, where by light wave change direction but no change in wavelength.

Importance of solar energy

In general, importance of solar energy are like as follows:

1. It provides heat for drying clothes and crops.

2. Morning sunshine is a source of Vitamin D, which is necessary for human health.

3. It is used to generate electricity (called solar power).

4. Plants use sun-light in making food through the process known as photosynthesis.

5. It facilitates rain formation through evaporation and transpiration.

GLOBAL DISTRIBUTION OF INSOLATION/AMOUNT OF SOLAR RADIATION/TEMPERATURE

Basically, the amount of insolation received at the earth surface vary from one place to another. Its decreases outward the equator and increases inward to the equator.

The globe is divided into three zones of insolation basis on the amount received in a year. These zones are: –

1. Low latitude zone (Tropical zone):

This zone extends between tropic of cancer and tropic of Capricorn as well as the equator.

Every place in this zone receive maximum and minimum insolation twice a year.

2. Middle latitude zone (Temperate zone):

This zone extends between 23¹/₂⁰ and 66¹/₂⁰ latitude in both hemispheres.

Within this zone every place receives one maximum insolation during summer and one minimum insolation during winter.

3. High latitude zone (Frigid zone):

This zone extends from 66¹/₂⁰ and 90⁰ latitude in both hemispheres (north and south).

It is also receiving one maximum insolation during summer and one minimum insolation during winter, but sometime insolation become zero (nil) due to absence of day sun rays and obliqueness of the area to the sun especially at 90⁰N.

FACTORS AFFECT THE DISTRIBUTION OF INSOLATION

The amount of energy received by the Earth is determined by different factors including astronomical factors such as angle of incidence, length of the day, transparency of the atmosphere, variations in the distance between the earth and sun, and solar constant (the quantity of radiant). In general, these factors can categorized into three parts. These are: –

I. LONG TERM FACTORS;

1. Height above the sea level

2. The angle between sun rays and earth surface (Altitude of the sun) iii. The nature of the earth surface (land and sea).

3. Ocean currents

4. Prevailing winds

II. SHORT TERM FACTORS;

1. Seasonal change

2. Length of the day and night

III. LOCAL FACTORS;

i. Aspect

ii. Cloud cover

iii. Urbanization

Factors affecting insolation

In general, there are several factors affecting insolation like as follow: –

1. The angle between sun rays and earth surface:

The angle at which sun rays from the sun strike the earth’s surface called angle of incidence, it determines the amount of insolation received.

Insolation is maximum in the area receiving vertical angle of sun rays (Sun is directly overhead, has an angle of incidence of 90°) example Equator because the sun ray concentrates in a small area at this place.

On the other hand, region receiving oblique angle of sun rays (angle of incidence smaller than 90° or angle of incidence is 0°) normally experience minimum insolation example polar regions because the energy is spread out over a larger portion of the surface.

2. Length of day:

The length of the day varies in all places except in the equatorial area. The long duration of the sunshine during the day and the short period of night means that area of longer day receives maximum insolation example during 21^st June solstice in northern hemisphere where by Artic region (90⁰N) experience 24 hours of daylight and 18 hours for middle latitude (60⁰N), while the area with shorter day and longer night time receives minimum insolation example during 21^st December solstice for northern hemisphere the region experiencing 24 hours of darkness. This also referred as solstices and equinox.

NB:

Equinox: Spring equinox (21^stMarch in the N/Hemisphere and 23^rdSeptember in the S/Hemisphere) and Autumn equinox (.23^rdSeptember in the N/Hemisphere and 21^stMarch in the S/Hemisphere).

Solstice: Summer solstice (21^stJune in the N/Hemisphere and 22^ndDecember in the S/Hemisphere) and Winter solstice (22^ndDecember in the N/Hemisphere and 21^stJune in the S/Hemisphere).

MONTHS	SEASONS
	N/HEMISPHERE	S/HEMISPHERE
1. Febuary, March and April	Spring	Autumn
2. May, June and July	Summer	Winter
3. August, September and October	Autumn	Spring
4. November, December and January	Winter	Summer

3. Distance between sun and earth (Influence of aphelion and perihelion)

The earth at the time of perihelion that is nearest to the sun (147 million kilometers) each year on the 3^rd January receive maximum insolation, while during aphelion that is farthest to the sun (152 million kilometers) each year on 4^th July, the earth receives minimum insolation. But this condition varies between Equator and Poles.

4. The transparence of the atmosphere (nature of atmosphere):

The incoming solar radiation has found difficult to pass thick layer of the earth’s atmosphere made up by several components like dust particles, clouds, atmospheric gases, etc. So, during the transmission of solar radiation partly is absorbed (23%) by dust, ozone, clouds and water vapour, partly 40% loss through reflected and scattered by dust particles, earth surface and clouds to the atmosphere and other port radiated to the surface as incoming solar radiation. Therefore, the number of components is determining the amount of insolation, if the open sky there is maximum insolation eg. Desert areas, while closed sky by number of components is minimum insolation eg. In tropical areas.

5. The nature of the earth surface:

Generally, land surface and water differ in several properties. The amount of heat received by the land is high but quickly reflected to the atmosphere. On the other hand, water body receive the same amount of insolation but the low reflection, but absorption capacity is high. Therefore, there is maximum insolation on surface made up by water bodies and minimum insolation on the surface without water bodies.

6. Latitudinal position:

The impacts of latitude on the insolation is greater, since the low latitude zone such as equatorial experience overhead sun and thus affect the day and night time. In this case, they receive the high amount (maximum) insolation. Country to the middle and high latitude zones, where the sun rays strike more in oblique and have to travel at greater distance. Therefore, this place receives minimum insolation.

7. Elevation and aspects:

This factor affects the amount of insolation like as follow; For the case of aspects, the slope facing the sun receive maximum insolation compared to the slope facing away from the sun. For example, the southern slope of mountain Kilimanjaro in Tanzania more insolation than the southern slope facing Kenya.

On the other hand, the high elevated land there is coldness due to low insolation controlled by altitude their minimum insolation while there is maximum insolation toward the low elevated surface.

THE EARTH ALBEDO

What is the albedo?

Albedo is the ratio between the totally solar energy falling up on the surface and amount of it reflected.

What is the earth albedo?

Earth albedo is the capacity of earth surface to reflect the incoming short-wave rays (solar radiation) of the sun. OR

Is the percentage evaluation of insolation received and it reflection back to atmosphere. OR

Is the ratio between incoming solar radiation and the amount of it reflected, expressed as percentage. The earth albedo is expressed as decimal or percentage example earth average albedo from 30% (0.3) to 40% (0.4).

Therefore, temperature is marked higher of the place of low albedo than the place of high albedo. Example land albedo is lower than water albedo while land store heat during the day and quickly reflect it during the night while water store it greater capacity and little reflected back to atmosphere.

THE AMOUNT OF ALBEDO FOR DIFFERENT KIND OF SURFACES

	SURFACE	PERCENTAGE OF ALBEDO (%)
	Snow cover Sand Grass Dry ground Wet ground Forest Water Thick cloud Thin cloud x. Black soils	70 – 90 20 -30 – 37 -35 10 5- 10 3 – 5 70 – 80 25 – 50 8 – 14

N.B: High albedo = Low Temperature; while Low albedo = High temperature

ATMOSPHERIC HEAT BUDGET (GLOBAL HEAT BUDGET)

What is the heat budget?

Heat budget or heat balance is the existing mechanisms between the incoming and outgoing radiation creates a natural balance.

What is the atmospheric heat budget?

Atmospheric heat budget is the balance between the amount of solar radiation received by the earth’s surface, atmospheric component and the amount of heat lost by outgoing terrestrial long wave radiation from the earth’s surface and loose of heat from the atmosphere.

The global heat budget is evaluated by considering what happen to solar and terrestrial radiation.

There are two heat balance that are; Positive heat balance at the tropics, and Negative heat balance at both high latitude (Polar Regions) and high altitude.

The atmospheric heat balance controlled by both long waves heat (outgoing or infra-red) radiation from the earth surface, and short waves radiation from the sun. For example, the incoming solar radiation is 100%.

The 54% of incoming solar radiation was not reached to earth surface due 19% absorbed by water vapour, dust and ozone, 4% absorbed by clouds, 8% scattered by air, 17% reflected by clouds, and 6% reflected by surface.

Due to effect of absorption, reflection and scattering, solar energy accounts for 46% of the solar radiation that passes through the atmosphere to become available on the earth’s surface. Only 24% of incoming radiation reaches the earth’s surface directly and 22% arriving at ground level as diffuse radiation by the earth long wave radiation.

The incoming radiation is converted into heat energy when it reaches the Earth’s surface. As the ground warms, it radiates energy back into the atmosphere where 94% is absorbed by water vapour and carbon dioxide (greenhouse effects) and only 6% is lost to space. Without the natural green house effects the which traps so much outgoing radiation the world temperatures would be over 33⁰C and the life become impossible on the earth.

At the outer limit of the atmosphere the solar radiation consists of visible rays of about 41% in total, gamma rays, alpha rays, x-rays and ultraviolet rays of about 9% and the longer infrared and heat rays of about 50%

HEAT TRANSFERS

Heat transfer refers to the vertical and horizontal flow of heat energy along the thermal gradients normally resulting from differential heating.

Heat transfer is done in order to avoid overheating and overcooling of the surface of the earth.

WAYS OF HEAT TRANSFER

There are two main ways of heat transfers. These are: –

1. Atmospheric heat transfer (Atmospheric circulation)
2. Oceanic heat transfer (Oceanic circulation)

I: ATMOSPHERIC HEAT TRANSFER (ATMOSPHERIC CIRCULATION)

What is the atmospheric circulation?

Atmospheric circulation is the large scale movement of air and the means by which thermal energy is distributed on the surface of the earth.

MECHANISM OF ATMOSPHERIC HEAT TRANSFER

In atmosphere the heat can transfer either in horizontal or vertical like as follow;

a) Horizontal heat transfer.

This transferred of heat in horizontally away from tropics to polar ward. It is takes place to prevent equator become hotter and polar to be colder. These achieved through the following means;

• Winds. The winds are responsible for about 80% of this kind of heat transfer.
• Ocean currents. The ocean currents account for only 20% for heat transfer.

b) Vertical heat transfer

Is the transferred of heat in vertically upward from the low altitude to the high altitude. It is takes place to prevent the earth’s surface from becoming warm and the atmosphere to become colder.

These achieved through the following means;

i. Radiation. Is the transfer of heat energy between two objects by electromagnetic waves. Solar radiation in the atmosphere is absorbed by gases, water vapour, particles, while on the earth’s surface it is absorbed by trees, flowers, soils and water bodies which then warm up.

ii. Conduction. Is a mechanism of heat transfer in the atmosphere whereby the heat moves from areas of much more heat to areas of less heat by direct contact of molecules. Warmer molecules vibrate rapidly and collide with other nearby molecules leading to the transfer of their energy.

iii. Convection. Is the transfer of heat through movement of water or air molecules. This type of heat transfer can occur in liquids and gases because their free movement of the molecules, making it possible to set up warm or cold currents. Convection occurs naturally in the atmosphere on a sunny day.

iv. Latent heat. Latent is from the Latin, “lying hidden”.

Latent heat is the amount of energy needed to change the state of a substance without affecting its temperature. i.e ice changes to liquid water, liquid water changes to water vapor, and so forth.

The two most common phase changes are evaporation and condensation. During the process of evaporation, latent heat energy is “stored” and so evaporation is, in effect, a cooling process. On the other hand, during condensation, latent heat energy is released and condensation is, in effect a warming process and atmosphere is warmed.

Atmospheric circulation creates latitudinal circulation features where by categorised into three (3) cells. These are; Hadley cells (0⁰ – 30⁰N/S), Polar cells (30⁰ – 60⁰N/S), and Ferrell cell (60⁰ – 90⁰N/S).

2: OCEANIC HEAT TRANSFER (OCEANIC CIRCULATION)

What is the oceanic circulation?

Oceanic circulation is the large scale movement of waters in the ocean basins. It is associated by winddriven circulation (winds and Coriolis effects) or thermohaline circulation (density and temperature).

MECHANISM OF OCEANIC HEAT TRANSFER In the ocean, the heat transfer through the following ways; such as Salinity; Water temperature; Surface winds as well as Coriolis effects.

REVISION QUESTIONS ON INSOLATIONS

1. What are the factors that affect the amount of insolation on the earth’s surface (Necta 1978 and 1996)

2. Write an essay on insolation in temperate areas (Necta 1982)

3. Write an essay on heat budget (1987)

4. Describe the factors which affect the amount of insolation on the earth’s surface. (Necta 2010)

COMPONENTS/ PARTS OF THE EARTH AS A SYSTEM

The earth is an integrated system that can be divided into five (5) main interrelated components. These are: –

1. Atmosphere:

Stands like envelope of transparent odorless gases held on the earth by gravitational attraction.

It extends up from the earth surface for several hundreds of kilometers.

2. Biosphere:

A life supporting layer which surrounds the earth and makes plants and animals life possible without any protective device.

3. Geosphere:

It includes the rocks and minerals on earth from the molten rocks and heavy metals on the deep interior of the planets to the sand on beaches and peaks of mountain. Thus, includes all minerals, rocks and soils.

4. Hydrosphere:

Is the sphere that covers total amount of water on a planet earth. It includes water available on the surface of the earth, underground and in the air.

5. Cryosphere:

It is derived from Greek words “Kryos” which means “cold” and “sphere” which means

“layer”. Therefore, cryosphere is the frozen places of the earth. It encompassing all portions of the earth’s surface where water is in solid form, including sea ice, ice sheets, lake ice, snow caves, glaciers, ice caps, and frozen grounds.

QUIZ: “Planet earth is regarded as an integrated and interrelated system”. Discuss

EXTERNAL STRUCTURE OF THE EARTH

The external structure of the earth consists of hydrosphere, cryosphere, biosphere, and atmosphere.

I: HYDROSPHERE

Hydrosphere is the area that includes all earth’s water in the state of liquid, frozen or floating ice in the upper part or beneath the soil. It is comprised by all water bodies. It is estimated that, the water surface makes up 71% the total water of the earth surface. While the surface (continents and islands) make up the remaining 29% of the total area of the earth.

The hydrosphere constitutes all water bodies such as oceans, seas, rivers, lakes, ponds, underground water, etc.

The oceans and seas make up 97% of the all total water bodies while the fresh water bodies constitute only 3%. Hydrosphere is referred to as a major setting of the earth’s hydrological cycle. Hydrological cycle is the continuous movement of water from the atmosphere to the land and toward the sea or oceans then back to the atmosphere.. OR Is the continuous movement of water in the air, on the surface and below the earth’s surface, to the ocean and back to the air..

II: BIOSPHERE

Is the part of the earth external structure dealing with description on the totally of world living organism.

There are different types of living organisms (species) some live in the water, on the land and some live in the air.

The organism ranges from microscopic single cell plants and animals to giant trees and animals. Scientists estimates that about one (1) million of different species of animals and perhaps three (3) thousand million species of plants have existed since life began on earth.

CHARACTERISTICS OF LIVING ORGANISMS

i. Biological characteristics. Examples all living species respire excretion, reproduction, etc.

ii. They can adapt to many different environments, some can survive in the coldest and hottest desert, and few can survive in deep sea trenches.

iii. They have special adaptive mechanism enabling them to survive in their environment. Example fish have scale, date palm have long roots, etc.

iv. They are ecological interdependence. Example primary producer, etc

III: CRYOSPHERE

It is derived from Greek words “Kryos” which means “cold” and “sphere” which means “layer”.

Therefore, cryosphere is the frozen places of the earth. It encompassing all portions of the earth’s surface where water is in solid form, including sea ice, ice sheets, lake ice, snow caves, glaciers, ice caps, and frozen grounds.

The cryosphere is central to the daily lives of people, animals, and plants. Also, it has a great impact on the global cooling and great impact on the global cooling and distribution of cold winds. Cryosphere is a place where water is in solid form due to frozen.

Cryosphere occurs in polar regions like north pole and south pole, the Artic region, the Antarctic region, and also in high elevation regions like top of Mount Kilimanjaro in Tanzania, high mountain in United states, as well as in the northern reaches of Canada, China, and Russia. The cryosphere expands during the cold winter months. Seasonal areas of the cryosphere include places where snow falls, and where soil, rivers, and lakes freeze.

IV: ATMOSPHERE

The word atmosphere is the combination of two Greek words; “Atmos” meaning “vapour” and “sphaira” meaning “sphere” it is a layer of a gases surrounding a planet earth.

Atmosphere is the blanket of air that envelops the earth. OR Is an envelope of transparent, odorless gases held to the earth by gravitational attraction. OR Is the mixture of gases surrounding the earth held on it by the gravitational attraction.

Thickness of atmosphere is not really known but it is estimated to reach 32,000km. However, researches on exactly height of atmosphere are going on.

COMPOSITION OF ATMOSPHERE

There are two main components of atmosphere; such as Biotic components (living organism) and Abiotic components (non-living organism); generally; the atmosphere composed several gases, and both living and non-living organisms like as follow: –

1. Mixture of gases:

Several mixtures of gases like nitrogen 78%, oxygen 21%, carbondioxide 0.03%, Argon 0.009% and other gases to a minimal amount such as Xenon, ozone, neon, helium, and krypton. Also, there are several pollutant gases like chlorofluorocarbon, Sulphur dioxide, nitrous oxide etc. Their amount very according to the nature of places.

These gases are very important to atmosphere and living organisms like as follow;

Nitrogen gas (N2): 78% dilutes oxygen and prevents rapid burning at the earth’s surface. Living things need it to make proteins.

Oxygen gas (O₂): 21% used by all living things, essential for respiration. It is necessary for combustion or burning.

Carbon dioxide (CO₂): 0.03% plants use it to make oxygen. Acts as blanket and prevents the escape of heat into outer space.

Argon (Ar): 0.93% used in light bulbs, etc.

2. Water vapour and clouds:

Water vapour is the gaseous forms of water which suspended in the air driving through evaporation.

The condensed water vapour forms clouds as a result of precipitation.

In the atmosphere these components (water vapour and clouds) are uneven distributed. There is large amount in humid areas and along the large water bodies, but there is less or no in desert areas. Climatologically water vapour composed 0.20% to 4.0% and used for rainfall formation, albedo effects, and also for prevents heat loss from the earth.

3. Dust particles:

There are also dust particles both large enough to be visible, and smaller particles which invisible to the naked eye, may remain suspended in the atmosphere for months or even years. The solid and liquid particles found in the atmosphere are collectively called particulates or aerosols.

They have innumerable sources; Some natural sources such as Volcanic ash, windblown soil and pollen grains, meteor debris, smoke from wildfires, and salt spray from breaking waves. Others coming from human sources such as industrial, automotive emissions, and smoke and soot from fires of human origin.

These tiny particles are most numerous near their places of origin like above cities, seacoasts, active volcanoes, and some desert regions. They may be carried great distances, however, both horizontally and vertically by the restless atmosphere.

They affect weather and climate in two major ways:

1. Act as hygroscopic nuclei which water vapour condenses. This accumulation of water molecules is a critical step in cloud formation.
2. Also, act as albedo effects by either absorb or reflect sunlight, thus decreasing the amount of solar energy that reaches Earth’s surface.

4. Bacteria and viruses (organism):

They are commonly found in the tropical areas due to humid conditions. Example in West Africa, etc.

THE FUNCTIONS OF ATMOSPHERE TO THE UNIVERSE

1. It is an insulator:

Atmosphere act as blanket, hence moderates temperatures at night and during winter. The atmosphere permits short entry of heat waves and also hinders the escape of long radiated waves. The effect known as the greenhouse effect.

2. It is a filter:

The atmospheric water filters solar insolation and prevent ultra-violet rays (UVR’s) of a certain length. This protective screen is made up of ozone layer about a mile up which is referred to as a shield of life.

3. Hydrological function:

The surface water evaporation, condensation, and precipitation formation take place in the atmosphere. Solid dust particles act as nuclei for rain droplets formation. Humidity brings about precipitation. Excess water vapour brings about precipitation inform of rainfall, snow, hail, and sleet. When water vapour is present in the atmosphere in small quantity lead to extreme dryness of air which cause occurrence of hot desert.

4. Life support function:

Gas like oxygen are important in living organisms. Air has weight which contribute to the atmospheric pressure variations and breathing would be impossible without pressure variation. Wind movement and direction that balances temperature, humidity and precipitation also result from pressure variations. Carbondioxide is important for plant growth through photosynthesis.

5. It is scientific field:

Atmosphere is a field through which scientists do the experiments and observation. Example; ionosphere reflects some electromagnetic waves and radio signal back to the earth. Scientific developments like television, radio, radar, and others telecommunication and air transport are done in the atmosphere.

6. Protective function:

The atmosphere protects us from objects falling towards the earth from outer space meteoroid enter the atmosphere and burn up before reaching the earth due to friction with air.

VERTICAL DIVISION OF ATMOSPHERE

The exactly thickness of atmosphere is not known, but it is estimated to be 10,000 kilometers and most of its mass is concentrated at very low altitudes. However, the research still continues in this phenomenon.

The atmosphere broadly divided into two (2) parts. These are; Homosphere and Heterosphere. These division are based on physical (based on temperature variations) and chemical properties (how gases mix up in the layers). These division are like as follow:-

I: HOMOSPHERE

This also referred as low atmosphere. In this atmosphere air mix up. It has begun from the surface of the earth upward to the height of 80km (50miles).

The Homosphere has subdivided into three (3) based on the temperature changes. These are; Troposphere, Stratosphere, and Mesosphere.

A. Troposphere

This is the lower most layer of Homosphere in which temperature decrease with increasing altitude called temperature lapse rate. The rate of temperature decreasing is 0.6⁰c per 100m or 0.65⁰c per 100m or 6⁰c per 1km (1000m) or 3.5⁰F per 1000feets.

The troposphere is beginning at the ground surface to the height of 17km (10miles) from the or 10km (5miles) from poles. It is the layer in which living organisms live and depend on it.

This has the following characteristics; temperature decrease with increasing height (environmental lapse rate), pressure falls with height increasing due to effect of gravity decrease, wind speed usually low due to friction but their speed increases with height increase, and there is unstable conditions due to formation of humidity, cloud cover and precipitation. This layer separated to stratosphere by thin layer called Tropopause.

B. Stratosphere

The stratosphere begins above the tropopause upward to the height 50km (30miles) from ground surface. The exactly thickness of this layer is only 20 miles. The temperature inversion is characteristics of this layer where by temperature increasing from -63⁰C at tropopause to 0⁰C at upper stratosphere.

At the lower stratosphere there is Ozone layer (Ozonosphere) with impacts of absorbing dangerous ultra-violet rays from the sun (UVR’s) reaching to the ground.

In this layer temperature become constant for a distance upward before starting to increasing with height increasing.

The characteristics of this layer are; temperature increasing with height increasing (temperature inversion), wind speed is high due absence of friction as a result of horizontal high-speed wind like jet stream wind, pressure continues to fall with height increase, and there is stable condition due to absence of cloud and precipitation.

This layer separated to mesosphere by thin layer called stratopause.

C. Mesosphere

This layer begins above stratopause upward to the height of 80km (50miles) from ground surface. The exactly thickness is 20 miles. In this layer the temperature become constant for a distance upward then starting to decrease with height increasing from 0⁰C at the stratopause up to -83⁰C at the upper mesosphere. At the upper mesosphere there is IONOSPHERE layer. The characteristics of these layer are; the temperature decrease with height increase as leading to lowest atmospheric temperature, there is stable conditions (no clouds and precipitation), the winds speed is very strong to about 3000km/hr, and the pressure continues to fall with increase height.

This layer separated to thermosphere by thin layer called Mesopause.

II: HETEROSPHERE

This layer also known as upper atmosphere. It is starting above the Homosphere at mesopause (50km) up ward to the height estimated above 32,000km from the ground surface.

This layer subdivided into; Thermosphere, and Exosphere like as follow;

A. Thermosphere

This layer starting from mesopause at 80km upward to 500km. The temperature increases with height increase from -83⁰C at the mesopause upward to the between 1100⁰C and 1600⁰C at upper thermosphere.

The characteristics of thermosphere are; temperature inversion up to 1500⁰C, pressure fall with height increase, wind speed is very high, and it is absorbing sun energy and creates moderate temperature to the surface. Thermosphere subdivided into D, E, and F layers. At the lower thermosphere there is layer called IONOSPHERE.

Ionosphere:

The ionosphere is a deep layer of electrically charged molecules and atoms (which are called ions) in the middle and upper mesosphere and the lower thermosphere, between about 60 and 400 kilometers (40 and 250 miles).

The ionosphere is significant because it aids long-distance communication by reflecting radio and TV waves back to Earth. It is also known for its auroral displays, such as the “northern lights” that develop when charged atomic particles from the Sun are trapped by the magnetic field of Earth near the poles. In the ionosphere, these particles “excite” the nitrogen molecules and oxygen atoms, causing them to emit light, not unlike a neon lightbulb.

B. Exosphere

This is the highest and top layer of the earth’s atmosphere. It starts at 500 km high and marks the edge of space. These are very few molecules layer mainly composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen, and carbondioxide. This layer is the earth’s first line of defense against the harmful sun rays. Also, it is the first layer to come into contact and protect the earth from meteors, asteroids and cosmic rays.

NB:

Therefore, “top of the atmosphere” is a theoretical concept rather than a reality, with no true boundary between atmosphere and outer space.

REVISION QUESTIONS: ATMOSPHERE

1. Describe and explain the composition of the atmosphere (Necta 1987)

2. Examine the vertical structure of the atmosphere (Necta 2008)

3. Form Five students from school X were heard saying that, the end of the sky is the end of atmosphere. Address such misconception by properly classifying the structure of the atmosphere. Support your answer with a diagram. (Necta 2023)

4. Examine six consequences brought by depletion of the ozone layer in the atmosphere. (Necta 2019)

5. Examine four layers of the atmosphere and in each give three characteristics. (Necta 2018)

6. Describe the composition of the atmosphere and its functions to the universe (Necta 2015)

7. Discuss the environmental impacts of greenhouse effects on global warming. (Necta 2012)

8. The World is in crisis of climate changes which are associated with global warming. According to National center for Environmental information on statistical analyzing, the year 2022 is very likely to be ranked in among ten warmest years on the records. Examine four consequences brought by condition and four measures to the problem. (Songwe mock, 2023)

9. “Atmosphere is the sphere of all sphere”. Discuss …….answer; all layers of atmosphere

10. The earth is an integrated system, which can be subdivided into five main interrelated components. Each component has its own collection of materials and process. Justify this statement with five points. (TAHOSSA ANNUAL FORM 5 2023)

10. With examples, account for the usefulness of hydrosphere in the life of living organisms. Give six points.

11. “Atmosphere is the vacuum place”. Discuss …….answers: Components of atmosphere

INTERACTION AMONG THE EARTH’S SPHERES

There are several and complex interaction among the atmosphere, biosphere, and geosphere.

The most six forms of interactions includes the following;

i) Atmosphere-biosphere interactions ii) Biosphere-hydrosphere interactions iii) Hydrosphere-geosphere interactions iv) Geosphere-atmosphere interactions

v) Atmosphere-hydrosphere interactions

vi) Geosphere

– biosphere interactions

1: ATMOSPHERE-BIOSPHERE INTERACTIONS

Atmosphere-Biosphere interaction interact with each other, however, these interactions are numerous and complex. A few examples of these interactions are the exchange of gas and the deposition of particulates. They can be described as follows;

(a) Exchange of gases;

Earth system as a set of interacting spheres involves constant cycling or movement of gases through different media such as the atmosphere, geosphere, hydrosphere, and biosphere, collectively known as biogeochemical or nutrients cycles.

It includes elements such as nitrogen, hydrogen, carbon, phosphorous and Sulphur. These elements are important in existence of life on the earth. Living organism depend on air or gas for survival. Example, human and other animals inhale oxygen from the atmosphere and exhale carbondioxide back to atmosphere during respiration. On the other hand, plants absorb carbondioxide from the atmosphere and releases oxygen gas. These exchange are what make the gas cycle continuos and mainatain the life on earth. Furthermore, the decomposition of vegetations such as trees and grasses release gases like carbondioxide, methane and others into the atmosphere.

These gases exchanges can be demonstrated in different cycles as follows;

(b) Carbon cycle

Element of carbon are available in the atmosphere in the form of carbon dioxide. Plants receives one quarter of the carbon dioxide from the atmosphere which supports in photosynthesis. It helps plants to create carbohydrates in the form of food which is used as food by all living organism. Carbon dioxide dissolving (absorbed) in the water bodies such as lakes, oceans, and sea through direct air water exchange is again collected in the form of lime on the earth. After dissolution of limestone, carbon dioxide reaches the atmosphere again through a process called carbonization.

Furthermore; carbon dioxide is also added to the atmosphere naturally. When animals respire, living organisms decompose or decay and through human activities such as the burning of fossil fuels like coal, petroleum and natural gases. This is a continuous process through which carbondioxide circulates between the four subsystem of the earth. [Observe a diagram below]

(c) Oxygen cycle

The oxygen cycle is the process through which oxygen is produced and reused in the atmosphere. Oxygen which is the second most abundant gas in the atmosphere is produced by plants through photosynthesis with the support of sunlight. Through photosynthesis, plants convert carbondioxide and water into oxygen and releases it into the atmosphere. The released oxygen is used by human beings for burning fuels such as wood, coal and gas. The oxygen cycles occurs due to the exchange between the atmosphere and the oceans. The cycling of oxygen is also accomplished by the weathering of the carbonate rocks. [Observe a diagram below]

(d) Nitrogen cycle

Nitrogen is an important element for life and the largest constitute of the gaseous envelope that surrounds the earth. The main source of nitrogen are the nitrates present in the soil. From the atmosphere, nitrogen enters bio-components through biological and industrial process. Regardless of the process involved, nitrogen gets to plants through biological nitrogen fixation (BNF). It involves the incorporation of nitrogen gas into the roots of some plants, such as legimes, cloves, alfalfa, soybeans, peas, peanuts and beans.

The bacteria living in the nodules around these plants root chemically convert nitrogen in the aitr to form nitrates (NO₃) and ammonia (NH₃) and make it available to plants. Nitrogen compounds available int plants are transferred to animals through food chain. Animals that feed on the plants ingest the nitrogen and release it in organic wastes. Bacteria decompose dried plants and dead animals and produce nitrogen gas which goes back into the atmosphere. In this way, a continuous cycle of nitrogen gas is completed. [Observe a diagram below]

(b) Decomposition of particluates

As human beings engage in various activities such as agriculture, mining and transportation, they may inadvertently produce fumes and aerosols that have a significant impact on the environment. These emissions can contribute to the decomposition of particulates, which in turns affect atmospheric conditions.

2: HYDROSPHERE-BIOSPHERE INTERACTIONS

It share a complex relationship that impacts the environment. Their interplay can significantly influence the distribution and abundance of living organisms, as well as the state of the hydrosphere. The following are various interaction between hydrosphere and biosphere;

(i) Life support; all living organism depend solely on water. Plants require water during photosynthesis and for growth, while animals depend on water for hydration and other bodily functions.

(ii) Habitat; many plants and animals live in the hydrosphere, including aquatic plants like water hyacinths and animals like fish and crocodile.

(iii) Water cycle; The biosphere plays a crucial role in supporting the water cycle. For instance, plants release water vapour into the atmosphere through transpiration. Although human actions such as environmental conservation and management aid in evapotranspiration; unfortunately, deforestation practices by humans especially on a large scale, negatively impact the water cycle.

(iv) Energy; the hydrosphere is an abundant source of energy for all life on earth; especially humans. Through the use of water, humans can generate energy for a variety of purposes such as cooking, heating, transportation and lighting. In Tanzania, kidatu, kihansi, mtera, new Pangani, and Hale waterfalls have been the primary sources of hydropower for some years.

However, with the completion of the construction of the Julius Nyerere hydroelectric station (JNHS) at Stiegler’s Gorge in Morogoro region the country is ensured sufficient energy supply.

3: ATMOSPHERE-HYDROSPHERE INTERACTIONS

The earth is fundamentally a water planet, defined by the intricate interplay between its atmosphere and hydrosphere. These two subsystems are deeply interconnected and their interaction takes on many different forms. Examples of forms of interaction between these spheres includes the following;

Atmospheric water circulation

The hydrosphere, consisting of rivers, streams, seas and oceans, contributes water vapour to the atmosphere through evaporation. This water vapour then undergoes condensations to form clouds, ultimately resulting in precipitation that replenishes the evaporating surfaces.

Carbon sink

The ocean serves as a crucial carbon sink, as it can absorb more than 31% of the carbondioxide gas (CO₂) present in the atmosphere. However, as atmospheric carbon dioxide levels tend to follow suit, Chemical reactions occurs when carbondioxide is absorbed by the ocean, leading to an increase in acidity levels. This process is commonly refered to as ocean acidification.

Temperature regulation

It is also called heat sinking. It is a vital component in maintaining a balanced environment. Both the atmosphere and hydrosphere work together to achieve this; in instances where the atmosphere is warmer than the ocean surface, heat energy is transferred from the air to the ocean. Conversely, when the air is cooler heat energy is released from the ocean into the air.

4: GEOSPHERE-BIOSPHERE INTERACTIONS

They are interconnected through the processes suh as the carbon cycle and denudation. Example; (i) Biological weathering;

Biosphere and Geosphere interact through weathering and erosion. Living organism like animals and plants which form biosphere can break down rocks in the geosphere to form sediments. This is not only affects the landscape but also releases nutrients into the soil.

5: HYDROSPHERE-GEOSPHERE INTERACTIONS

They work together in a way that supports the hydrological cycle and sustains life in the biosphere. Some of interactions that occur between the hydrosphere and geosphere are;

(i) Chemical weathering

Overtime, water can weather down rocks through a natural process of erosion. This happens when rain water comes into contact with minerals forming the rock and breakdown the rock into sediments. The sediments or broken rocks can then be transported by winds, water or ice, eventually setting in a different location. This can result in a change in the landscape’s shape.

(ii) Water storage

Water is a vital component of earth’s subsystems, as it continuously circulate through the atmosphere, biosphere and geosphere. When surface water enters the soil, it forms underground water that flows down to the wate table due to grsvity. Large portion of water is stored on the earth’s surface as a surface water and into the ground as ground water.

6: ATMOSPHERE-GEOSPHERE INTERACTIONS

While the atmosphere amd hydrosphere are distinct, they are closely interconnected and they impact one another in numerous ways;

Energy exchange

The atmosphere provides the geosphere with the necessary heat and energy for weathering and erosion. For example; wind blowing leads to erosion. Conversely, the geosphere release back into atmosphere via conduction.

Water vapour

In the atmosphere water vapour condenses to form clouds that eventually result in precipitation. This precipitation falls onto the geosphere, contributing to the formation of water bodies which fin part of the hydrological cycle.

REVISION QUESTIONS

1. Results from current research activities show that ozone layer is continuously destroyed by human development activities. As an expert of Earth system interaction, explain how you can contribute on the protection of ozone layer.

2. Explain how the interactions among the Earth’s spheres support lives of human beings and other living organism?

3. Explain how human actions alter the natural interactions of the Earth’s sphere and outline the possible consequences of such alteration to human development.

4. With examples, argue for or against the statement that, “the atmosphere is never stable”

5. Substantiate the statement, “humans impact all spheres of the earth”

6. Why is the earth considered to be a system?

7. Explain the earth’s surface as a whole does not accumulate too much heat.

8. Although ozone layer is located in the atmosphere, approximately 16-50km above the earth’s surface, it plays a crucial role in supporting life on the earth. Discuss its importance to life on earth’s surface.

9. How is the studying layers of the atmosphere useful in the aviation sector?

10. How does the atmospheric radiation process support sustenance and flourishing of life on earth?

11. How does human beings influence the radiation processes on the earth system?

NECTA GENERAL TOPIC REVISION QUESTIONS

NECTA – 1987; Describe and explain the composition of the atmosphere. NECTA-2008; Examine the vertical structure of the atmosphere.

NECTA- 2015; Describe the composition of the atmosphere and its function to the universe.

NECTA-2018; Examine four layers of the atmosphere and in each give three characteristics.

NECTA – 2023; Form Five students from School X were heard saying that, the end of the sky is the end of the atmosphere. Address such misconception by properly classifying the structure of the atmosphere. Support your answer with a diagram.

NECTA 2024

1. With examples, analyze six factors that determine the degree of hotness or coldness of an area.
2. With examples, analyze five human activities that pollute the air and four measures to address the problem.

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