Chapter One: Introduction to Geography
Introduction
Earth is our home, the Mother Nature where all human beings and other living things live. While living on the planet Earth, we have to study and understand our environment. We must seek to understand how geographical phenomena happen, where they are found, why they are there, and how they develop and change over time and space. To understand all these things, you need to study Geography. In this regard, this chapter introduces you to the concept of Geography, branches of Geography, and the importance of studying Geography. Also, you will learn about the relationship between Geography and other disciplines. The competencies developed will enable you to appreciate the importance of Geography, and apply the knowledge to other disciplines. This will enable you to solve problems associated with natural and man-made processes and activities.
Think
Man's survival in the environment
Concept of Geography
Activity 1.1
Search for information from the library and other reliable online sources on the meanings of Geography. Make short notes, then develop your own definition of Geography.
The word 'geography' comes from two Greek words geo which means the Earth and graphein or grapho which means to draw, describe or write. The two words are joined to form one word "geographia", which means "writing about the Earth."
Therefore, Geography is the science that describes the Earth.
The term 'geography' was first used in 240 B.C by a Greek philosopher Eratosthenes who is regarded as "the father of geography". He published a book about the Earth and named it Geography. According to Eratosthenes, geography is defined as writing about the planet Earth. The book contributed a lot to the understanding of the Earth and the universe. Based on that origin, Geography has been understood as the study of man and his surroundings. It is concerned with the study of the size, shape, and movements of the Earth in relation to other heavenly bodies. Also, Geography deals with landmasses, water bodies, climate, vegetation, human activities, and events in different places of the world. Geography focuses on the description of the Earth and its features, and the distribution of life on it. This includes human life and the effects of human activities on the Earth. Therefore, Geography is the scientific study of physical characteristics of the Earth and their influence on human life and activities.
Activity 1.2
Search for information about physical features including simulations, videos, or animations from other reliable sources, and note down any features observed.
Branches of Geography
Activity 1.3
(a) Visit a nearby area of your school or home environment and observe different physical, social, economic and cultural features.
(b) Create a table to classify whether the features observed fall into physical geography or human geography.
Every day, man explores different things, including the earth's landscapes, climate, people, and places as he or she navigates through wide and varied aspects of geography. The exploration allows man to know different regions, countries, continents, and the amazing physical and man-made features. Geography opens up a world of endless exploration from understanding the wonders of nature like mountains, rivers, and forests. Furthermore, Geography renders the exploration of economic activities, population and man-made creations such as cities. Therefore, this exploration enables man to make a clear distinction between the physical aspects and human aspects.
Geography has two major branches, namely physical geography and human geography. Physical geography is involved with the study of natural features of the Earth. It focuses on the structure of the earth, atmospheric processes, and the formation and distribution of landforms such as mountains, valleys, and plateaus. It also studies the distribution of plants and animals (flora and fauna) on the earth's surface.
Human geography is concerned with the study of man-made features found on the earth's surface. It also deals with the interaction between human beings and the environment. Furthermore, it studies human population aspects such as population structure, distribution, growth, settlement, and human activities.
The two major branches of geography need geographical skills and techniques that are covered under the technique known as practical geography. Practical geography deals with geographical techniques, which support scientific approaches to collecting, recording, storing, analysing and interpreting geographical data. It is potential in understanding physical and human geography through the study of cartography, photography, Geographical Information System (GIS), research, survey, remote sensing, and statistics. Practical geography also helps learners acquire skills that enhance their curiosity and ability to understood both physical and human geography (Figure 1.1).
Physical
- Focuses on Earth's natural environment
- - Landforms
- - Water features
- - Plants
- - Animals
- Studies the processes that shape the physical environment
Interaction between people and the environment
Human
- Studies the distribution and characteristics of the world's people
- Examine how people make and trade the things they need to survive
- Studies where people live and work
Figure 1.1: Branches of Geography
Activity 1.4
Search for information from the library and other reliable online sources on the main branches of Geography, namely physical geography and human geography. Then, write a short essay on what each branch is concerned with.
Exercise 1.1
- With examples, differentiate natural features from man-made features within your surroundings.
- How does physical geography contribute to our understanding of the Earth?
- Why is practical geography important in studying physical geography and human geography?
Importance of studying Geography
Activity 1.5
Read from different reliable online sources, about the importance of studying Geography to human life. Write a summary on the importance of Geography to human life.
The study of Geography is important because it increases awareness of our country as our national heritage, including its boundaries and resources. It helps to develop the basic skills of observation, measurement, recording, storing, analysing, and interpreting geographical phenomena. These skills help to generate scientific knowledge that enables us to predict outcomes of different processes and activities for appropriate decision making. Geography also helps us understand our culture and how it differs from other cultures. This can help us be more tolerant and cope with others nationally and internationally. Also, by studying the geography of other countries and their human interactions, it can help us gain knowledge and skills for improving ways of utilising our resources for our development. Moreover, Geography equips man with skills for environmental conservation and management. These skills are for appropriate use of environmental resources and methods for managing associated problems for the wellbeing of the present and future generations. Geography gives us practical skills and knowledge, which are relevant in various fields, like map-making (cartography), teaching and researching, surveying, land use planning, natural resources management, conducting environmental and social impact assessment, aviation, navigation, surface transport, and tourism. Furthermore, Geography helps to realise how natural resources are distributed over the country. For instance, by studying maps of natural gas reserves in Tanzania will help us understand how much gas we have, how long it will last, and decide on investing on alternative energy sources. Geography helps to realise why some areas are highly populated while others are sparsely populated, and why some economic activities are mostly found in certain areas than in others.
Activity 1.6
Prepare a morning speech to be presented before your fellow students regarding the problems that may arise if one lacks geographical knowledge and skills.
Exercise 1.2
- Explain how Geographical knowledge helps us protect the environment in our local community.
- How does geographical knowledge help us in travelling and tourism?
- In what ways can geography help us make appropriate decisions about land use and development?
- Explain how human geography helps in undertaking different social and economic activities in Tanzania.
- Explain the activities you do in your daily life that uses the geographical knowledge you have learnt in school.
The relationship between Geography and other disciplines
Geography as a subject is related to other disciplines. Geography as an integrative discipline relates to serves several other disciplines. Such disciplines include Mathematics, Geology, Biology, Astronomy, Physics, Chemistry, Political science, Economics, and Agriculture. For instance, Astronomers who study about heavenly bodies like stars, planets, comets, galaxies, and the moon use geographical knowledge and skills to undertake their explorations. When studying about soil science and geology, Geography gives a basis for understanding and analysing the type, structure, and compositions of soils and rocks. Moreover, while studying about forces of gravity in Physics, scientists use geographical knowledge to explain these forces.
Sometimes as an interdisciplinary field, Geography provides a base for understanding other concepts in social sciences. For example, when studying human culture, Geography provides a basis for understanding spatial distribution and how people interact with the environment. Geography is also related to political science, especially when describing political boundaries, regions, population size and distribution of resources in different locations. Figure 1.2 illustrates the relationship between Geography and other disciplines.
[Diagram showing Geography at the center with connections to various other disciplines]
Figure 1.2: Relationship between Geography and other disciplines
Activity 1.7
Visit a nearby area and observe different activities carried out. Make a list of activities, then:
(i) Explain how such activities relate with geography.
(ii) Indicate under which disciplines such activities fall.
Exercise 1.3
Answer the following questions.
- Hekima is a Form One student interested to be a pilot. His teacher encourages him to study hard and ensure he performs well in Geography, Physics, Mathematics and language subjects. Hekima's friends also advise him that, besides being a pilot, he can also become a cartographer, surveyor, environmental expert, geologist, astronaut, astronomer, or meteorologist. Write an essay to explain Hekima's interest in becoming a pilot in relation to the Geography subject.
- Give reasons why the following career paths require specific geographical knowledge?
- Weather forecasting
- Map making and interpretation
- Planning and organisation of cities
- Aviation
- Photographer
Revision exercise 1
- Study the pictures (a) to (f) and explain how they relate to the use of geographical knowledge.
- Read the following statements carefully, then group them into branches of Geography:
- Studying the behaviour of stars in the sky.
- Analysis of population structure and migration.
- Studying about manufacturing industry in Tanzania.
- Understanding physical features and their change in time and space.
- Mention two geographical techniques that help geographers to conduct their practical work.
- Explain how geographical knowledge influences people's settlements.
Chapter Two: The Planet Earth
The planet Earth is part of a dynamic solar system, interacting with a variety of celestial bodies like asteroids, meteorites, comets, and the moon. The origin of the Earth along its entire system has been researched for hundreds of years. Various scholars have developed different theories and arguments on how the planet Earth evolved and changed over time. In this chapter you will learn about the Earth. You will focus on its origin, position in the solar system, shape, and size. The competencies developed will enable you to describe these aspects of the earth and apply, the knowledge to understand and explain the nature and behaviour of phenomena on the earth's surface.
Think
Origin of the planet Earth
Origin of the Earth
Activity 2.1
(a) Use various reliable online sources to search for simulation videos or animations about the origin of the Earth.
(b) Focus your search on the Big Bang theory, Nebula hypothesis, then Inter-stellar dust hypothesis, and prepare a summary of what you have searched.
The Earth is the only known planet in the solar system that supports life. Its surface is made up of land and water bodies. The evolution of the Earth can be traced through various assumption, including both theories and hypotheses, which explain about the origin of the universe. A number of ideas, principles, and assumptions have been developed by various scholars to trace the origin of the universe from which the planet Earth is found. These assumptions have examined various processes through which the universe, galaxies, stars, and planets were formed, and the changes that are still taking place over time (Figure 2.1).
[Image showing the origin of the Earth in the universe]
Figure 2.1: Origin of the Earth in the universe
Some of the assumptions that explain about the origin of the Earth include the Big Bang theory, Nebula hypothesis, Interstellar dust hypothesis, and the Creation theory. However, various critiques have emerged against these theories, and hypotheses, though they remain important for understanding the evolution of the universe and the planet Earth in particular.
This is an hypothesis that explains about the origin of the Earth. The hypothesis was proposed by Immanuel Kant in 1755. This hypothesis states that solar system was formed from cold spinning cloud of gases called the Solar nebular. It resulted from uneven distribution of gases throughout the universe in the Milky Way Galaxy. As the gravitational pull began to condense the gas towards the centre, the speed of the rotation increased. This caused the cloud to flatten, and created an accretion disk. Matter continued to collect as the force of gravity toward the centre increased. Eventually, the gas warmed from increasing pressure. As the mass further increased, also the gravity increased, and the temperature continued to rise. A ball of hot gas formed in the centre of accretion disk, creating a protostar, also known as the Sun.
Finally, when enough gas gathered in the centre of the protostar, the pressure generated enough heat to fuse the atoms to form a star. Outside the star, matter was forming into clumps of gas, dust and rocks, which created protoplanets that are believed to give rise to the planets. The theory was modified by Pierre Laplace in 1796. The critiques of the theory were put forward by Pierre Laplace who challenged Immanuel Kant through the following: large amount of heat cannot be generated due to the collision of cold particles of primordial matter as claimed by Kant. Also, mutual collision of particles cannot generate motion in the primordial matter. Moreover, the random motion of the particles cannot generate circular motion in the primordial matter. On top of that angular velocity of rotary speed of the nebular cannot increase due to increase in size of the nebular as assumed by Kant.
This theory was proposed by Lemaitre Georges and Edwin Hubble in the 1920s. The Big Bang theory explains that about 15 billion years ago, a great explosion occurred. This explosion caused the expansion of universe expand. This explosion is known as the big bang. At the time of this event, all matter and energy in space were contained in one point. The explosion pushed matter and energy outward expanding in all directions, forming a collection of dust, gas, and stars held together by gravitational attraction. Later, the sun, gas, and dust collided and aggregated into small grains, eventually forming larger bodies called planetesimals (very small planets).
Some of these small planets reached diameters of several hundred kilometres, and later formed the current eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune) and their satellites. However, scientists and institutions such as NASA (National Aeronautics and Space Administration) are still investigating to find out if there is existence of other planets in the outer space. The critique of the theory is that it appears all galaxies emerged at the same time; therefore, they could potentially have at least the same age. However, but this has not been the case. In fact, current astronomical researchers have found that while other galaxies are very old, there are many young galaxies around and far from the Earth.
In 1943, a Russian scientist Otto Schmidt proposed a theory known as Inter-Stellar dust hypothesis. The theory explains the complex problems of the origin and characteristics of the solar system and the Earth. According to the Inter-Stellar dust hypothesis, the Sun, during its 'galactic revolution, captured the dark matter of the universe. The dark matter (Inter-Stellar dusts) of gaseous cloud and dust particles had their own angular momentum. The dark matter after being attracted by the sun during its 'galactic revolution' started revolving around the primitive rotating sun. The intense heat from the sun dispersed the gaseous particles towards the margins of the disk. Collision among the dust particles started the process of aggregation and accretion around the bigger particles which became the essentials of the future planets. With the passage of time, these embryos captured more and more matter and grew in size to become asteroids. Furthermore, these asteroids grew in size due to continuous acceleration of nearby matter around them; thus, they became planets. The hypothesis has been criticised that gravitational force of the primitive sun was incapable of capturing dark matter scattered in the universe. The second critique of this hypothesis is that some astrophysicists believe that meteorites and asteroids were formed from disintegration of planet. Thus, so they reject the idea that the planets were formed out of meteorites and asteroids.
Activity 2.2
Search for information on the creation theory from the library or other reliable online sources. Then, prepare points to either oppose or propose the theory in relation to other theories you have studied.
Exercise 2.1
- How do you relate the sun, moon, stars, and other objects you see in the sky with the origin of the Earth?
- Using the theories that you have identified regarding the earth's origin, complete the provided matrix.
Name of the theory Key assumptions Critique - Do you think that knowledge about the earth's origins has significance in your everyday life? Provide reasons to support your answer.
Position of the Earth in the Solar system
Activity 2.3
Utilise materials readily available in your local area to design a model illustrating the solar system, displaying all the planets and their orbital paths.
According to the origin of the universe, the solar system is found in one arm of the Milky Way galaxy in the universe. The Milky Way is a galaxy with a spiral arm structure and a central bar-shaped region composed of stars, gas, dust, and dark matter. The name "Milky Way" arises from its appearance as a hazy band of light stretching across the night sky. This band is composed of countless distant stars and other celestial objects. This band is most visible from the Earth in areas with minimal light pollution. It is the galaxy that contains our solar system, where the Earth is found. The Milky Way contains billions of stars. A galaxy is a vast and immense system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. These components are held in a specific, organised structure that can take various forms, including spiral, elliptical, or irregular shapes. Galaxies come in a wide range of sizes, with some containing just a few million stars, while others, like the Milky Way, host hundreds of billions of stars. Additionally, galaxies can exist in isolation or be part of larger groups or clusters of galaxies.
The universe is teeming with galaxies and they are the basic building blocks of the cosmic structure. They serve as focal points for astronomical study and are integral to our understanding of the larger cosmos. Each galaxy, in turn, can be home to its own planetary systems, which may include planets, moons, asteroids, and comets. The Milky Way is just one of billions of galaxies in the universe. It plays a fundamental role in our understanding of the cosmos and it is a subject of extensive study in the fields of astronomy and astrophysics.
Solar system is composed of a set of different types of planets, moons, asteroids, comets, meteorites, interplanetary dusts and gases. Planets are arranged from the outer gas giants which consist of Jupiter, Saturn, Uranus, and Neptune to the rocky inner planets which comprises of Mercury, Venus, Earth and Mars. The inner planets are smaller, hotter, and solid than the outer planets which are large, cold, and gaseous in nature.
The Earth is the third planet in position from the Sun (Figure 2.2). Making life possible is the distinctive features of planet Earth among other planets in the Solar system. The planet Earth is located about 150 million kilometres from the sun. The Earth supports life due to presence of water. Water exists in three states: liquid, solid, and vapour. It has an atmosphere which contains different gases such as oxygen, carbon dioxide, hydrogen, nitrogen, and ozone gas. All these gases are essentials for life on Earth. Also, the Earth has important nutrients found in the soil, air, and water, which are essential for living things. Furthermore, the position of the Earth in the Solar system makes its temperature suitable for plants and animals.
Due to this, it is evident that the planet Earth is a unique and precious celestial body in the universe. It is the only known celestial body that supports life. Despite this, still the Earth faces numerous challenges, such as climate change, pollution, deforestation, loss of biodiversity, and overconsumption of natural resources, which are associated with unsustainable human exploitation of resources. Increasingly, the challenges are threatening life on the planet.
[Diagram showing the position of Earth in the solar system]
Figure 2.2: The position of Earth in the solar system
Exercise 2.2
- Explain why the orbit of the Earth around the Sun is not a perfect circle?
- What is the significance of the distance of the Earth from the Sun?
- What is the impact of the Earth's position in the Solar system on weather elements?
Shape and size of the Earth
Activity 2.4
In a dimly lit room, shine a flashlight towards a spherical object resting on a flat surface like a table. Make sure the flashlight is switched on and is casting a beam of light on the spherical object. Observe the shadow that appears on the wall.
The Earth is the fifth largest planet in the solar system in terms of size and mass. Its shape is like a flattened sphere known as an oblate spheroid (geoid). The flattening of the Earth is very slight as shown by the measurements of the North-south and East-west distances in Figure 2.3. The distance through the centre from the North Pole to the South Pole is approximately 12713 kilometres, whereas the distance through the centre of the Earth at the Equator is approximately 12757 kilometres. The circumference of the Earth at the equator is about 40085 kilometres while the polar circumference is 39955 (Figure 2.3).
[Diagram showing the size and shape of the Earth]
Figure 2.3: Size and shape of the earth
However, the earth's axis is not upright. It is tilted relative to the plane of its orbit. The axial tilting of the Earth refers to the angle between the earth's rotational axis and a perpendicular to the plane of its orbit around the Sun. The earth's axis of rotation is an imaginary line that runs from the North Pole to the South Pole. This tilting is approximately 23½° angle. The tilt of this axis is responsible for the changing seasons and variations in daylight hours throughout the year. It is significant in shaping the earth's climate, seasons, and overall environmental conditions.
Activity 2.5
(a) Use reliable online sources to search for videos or animations of the Earth's appearance. Study them and comment on the shape of the earth and its horizon.
(b) Relate your observations to the evidence that support the shape of the Earth.
The Earth has an oblate spheroid shape. There are several pieces of evidence to justify the spherical shape of the Earth. Such pieces of evidences include the following:
(i) Sunrise and sunset
The Sun rises and sets at different times in different places of the Earth. People in the East see the sun earlier than those in the West due the spinning of the Earth on its own axis from West to East (Figure 2.4 a). If the Earth was flat, the whole world would have sunrise and sunset at the same time (Figure 2.4 b).
[Diagrams showing sunrises on spherical and flat Earth]
Figure 2.4 (a and b): Sunrises on the spherical and flat Earth
(ii) Circumnavigation of the Earth
If you travel from a certain point on the Earth by going in a straight line around it, you will eventually come back to the point of origin. This concept was proved by the first navigator Ferdinand Magellan who sailed around the world from 1519 to 1522. Magellan in his voyage did not encounter any abrupt edge on earth's surface over which he would fall. This journey around the earth is called circumnavigation of the Earth (Figure 2.5).
[Diagram showing circumnavigation of the Earth]
Figure 2.5: Circumnavigation of the Earth
(iii) Aerial photograph of the Earth
Several vertical photographs taken from an airplane or images captured by artificial satellites from great heights show that the Earth is curved (Figure 2.6).
[Aerial photograph of the Earth]
Figure 2.6: An aerial photograph of the Earth
(iv) Ship's visibility
When watching an arriving ship from the coast, the visibility of the ship, which is far away, starts with the flag, then the mast, and eventually the whole ship is seen as it approaches the coast. When the ship moves away, it gradually disappears starting with the ship, then the mast, and finally the flag. If the Earth was flat, the whole ship would appear or disappear at once (Figure 2.7 a and b).
[Diagrams showing ship's visibility on spherical and flat Earth]
Figure 2.7 (a and b): Ship's visibility on the spherical and flat Earth
(v) Lunar eclipse
When light from the Sun is obstructed, a circular shadow is observable. For example, during the eclipse of the moon, the shadow of the Earth on the moon appears spherical (Figure 2.8).
[Diagram showing lunar eclipse]
Figure 2.8: Lunar eclipse
(vi) Earth's curved horizon
The Earth appears to have a curved horizon when viewed from a high cliff, a plane or a high building. The earth's curved horizon widens as the observer's altitude increases until it becomes circular (Figure 2.9).
[Diagram showing Earth's curved horizon]
Figure 2.9: The earth's curved horizon
Exercise 2.3
- Give evidence to justify that the Earth is not a flat surface.
- How does the Earth's shape affect the occurrence of day and night?
Revision exercise 2
- Differentiate the following;
- (a) Inter-stellar dust hypothesis and Nebular hypothesis
- (b) Planet and Milky Way Galaxy
- Match the item in Column A with their corresponding response in Column B
Column A Column B (a) Evidence to prove that the shape of the Earth is a slightly flattened sphere (i) Earth (b) The fifth largest planet in the solar system (ii) Orbit (c) It generates heat and light that are essential for life (iii) Sun (d) Jupiter, Saturn, Uranus, and Neptune (iv) Circumnavigation (e) Mercury, Venus, Earth and Mars (v) Solar eclipse (vi) Gas giant planets (vii) Rocky planets - In which ways does the Earth sustain life by considering the role of soil, water, sunlight, and various gases like oxygen, carbon dioxide, hydrogen and ozone in the process?
- Planets are positioned in different locations in the solar system; they all revolve around the sun. Give reasons why they do not experience collisions.
- Assume the distance between the Earth and the sun is reduced by half; explain what is likely to happen to living organisms on the Earth.
- Explain with examples the consequences for living organisms, if the Earth were situated at a different position within the solar system.
Chapter Three: Movements of the Earth in the Solar System
Our planet Earth is not static. It is constantly in motion, which makes it dynamic in nature. This motion affects the Earth as a planet and all other life forms found on it. Therefore, in this chapter, you will learn about the movements of the Earth in the solar system and their effects. Such movements include rotation and revolution of the Earth. Also, you will study about the imaginary lines on the earth's surface. Such lines include parallels and meridians. The competencies developed will enable you to understand the natural world and inform many aspects of our daily life. It will also help you to monitor and predict different events of the Earth as a celestial body, as well as to plan different activities according to time and seasons of the year.
Think
Earth's movement in the solar system
Rotation of the Earth
Activity 3.1
Read from library and other reliable online sources and search for simulation videos on the meaning of the earth's rotation, then make short notes.
How the Earth rotates
When travelling in a fast-moving vehicle, while looking outside, the trees and other objects outside the vehicle appear to move in the opposite direction. This observation is similar to the movement of the Earth in relation to the sun. Based on this scenario, the one moving is the person in the moving car not the trees or objects outside the vehicle. This is just like the rotation of the Earth; it is the Earth that rotates, not the Sun. The term rotation means spinning of a body on its axis. An axis of the Earth is an imaginary line joining the North and South Poles through the centre. The earth's axis is tilted making an angle of 23½° from the perpendicular. The earth rotates on its axis in an anticlockwise direction, from West to East through 360° in 24 hours (Figure 3.1). This means that, the earth takes 1 hour to rotate through 15°, which is equal to 4 minutes for every 1°.
[Diagram showing Earth's rotation]
Figure 3.1: Earth's rotation
Exercise 3.1
- Explain the concept of the earth's rotation.
- Explain the importance of the earth's rotation in your daily life.
- Differentiate between the earth's axis and the earth's line of perpendicular.
Evidence of the earth's rotation
Activity 3.2
Search for evidence of the earth's rotation from library and other reliable online sources.
The earth's rotation changes from no movement at the poles to very fast movement at the equator. We do not feel the motion because we move with it. At the equator every point of the earth's surface moves eastwards at about 1600 kilometres per hour. We do not feel this motion because we move with the earth's movement at a constant speed. At latitude 40°, the speed is about 1280 kilometres per hour. In the meantime, at the poles, the speed is zero (0) kilometre per hour. There are several pieces of evidence which show that the Earth is rotating. These include:
Sunrise and sunset
The Sun is located at the centre of solar system; it does not move. Instead, as the earth rotates from the West to the East, the Sun appears to rise from the East and set to the West. It is this movement of the Earth which explains sunrise and sunset.
Day and night
The most apparent evidence of the earth's rotation is the cycle of day and night. The Earth is a sphere. As it spins on its axis, different parts of the planet face the Sun at different times, resulting into daylight in one area and darkness in the other.
Shape of the Earth
The Earth is not a perfect sphere. It is slightly flattened at the poles due to the absence of centrifugal force and strong gravitational pull. Meanwhile it bulges at the equator because of strong centrifugal force and weaker gravitational pull.
Star Trails
When you look at the night sky, stars appear to make a circular movement around the North or South Poles, from East to West. In fact, the stars do not move, this happens because the Earth is rotating on its axis from the West to East.
Time Zones
The division of the Earth into different time zones (24 hours) is based on the earth's rotation. As the Earth spins on its axis, different regions experience daylight and darkness at different times.
Coriolis Effect
The Coriolis Effect causes moving objects, like winds and ocean currents to curve or be deflected due to the Earth's rotation. This effect influences the direction of wind patterns and ocean currents.
Exercise 3.2
- Why do we experience sunrise and sunset?
- What is the impact of the Earth's axis tilting to an angle of 23½°?
- The sun does not move instead the Earth moves, explain.
- Explain the consequences of the earth's rotation to stop suddenly. How would this influence different aspects of life on Earth?
- Why the speed of the earth's rotation is zero (0) kilometres per hour at the poles?
The effects of rotation
Activity 3.3
Using a flashlight and a globe, demonstrate how the earth's rotation causes day and night. Turn on the flashlight on the globe to represent the Sun's light, while you rotate the globe to simulate its rotation. Then, present what you have observed.
Rotation of the earth has the following effects:
(i) Day and night
The change between day and night is caused by the rotation of the Earth on its axis. The side that faces the sun experiences the light from the sun (day) whereas the side that is not facing the sun at that time is in darkness (night).
(ii) Differences in time
Rotation of the Earth causes differences in time in places located at different longitudes. Places on the same longitude have the same time. The Earth is divided into 24 time zones, each with approximately 15 degrees of longitude width.
(iii) Gain or loss of a day
This effect is primarily related to crossing the International Date Line. One will lose a day when crossing the IDL from the East to the West, and will gain a day when crossing the IDL from the West to the East.
(iv) Deflection of winds and ocean currents
The earth's rotation causes deflection of planetary winds and ocean currents. The planetary winds and ocean currents are deflected to the right in the northern hemisphere and to the left in the southern hemisphere.
(v) Tides
Ocean tide is the rising and falling of water level in oceans. This is caused by gravitational attraction exerted largely by the moon and partly by the Sun upon the rotating earth.
Exercise 3.3
- Explain the factors that affect the deflection of winds and ocean currents.
- What is the importance of knowledge of deflection of winds and ocean currents in your daily life?
- Do tides happen in lakes and rivers, or just in the ocean? Why?
- What is the importance of the low and high tides to your life?
Revolution of the Earth
Activity 3.4
(a) Search for videos, simulation, or animations from reliable online sources on how the Earth revolves around the Sun and how the Moon revolves around the Earth;
(b) Observe what happens during the movements, and record your observation; and
(c) Draw an illustration of what you have observed.
The Earth revolves around the Sun following its orbit. It revolves around the sun in an elliptical path, completing one full revolution in approximately 365¼ days or one year. However, a normal year has 365 days. The fraction days are not counted every year but are added once in 4 years to make a leap year of 366 days. The leap year occurs once in every four years, when the month of February has 29 days instead of 28. The speed of the earth's revolution is about 29.6 kilometres per second which is estimated from the earth's travel about 940 million Kilometres.
Effects of the earth's revolution
The revolution of the Earth around the sun and tilting on its axis has the following effects:
(i) Seasons of the year
A season is the main period of the year with a particular type of weather. Seasons are caused by the tilt of the earth's axis and the earth's revolution around the sun.
(ii) Changes of overhead sun
The position on Earth where the Sun is directly overhead changes throughout the year due to the tilt of the earth's axis and its elliptical orbit around the Sun.
(iii) Varying lengths of day and night
The lengths of day and night are not the same across the world because the earth's axis is inclined to its plane at an angle of 66½°.
(iv) Aphelion and Perihelion
The Earth revolves around the sun in an elliptical orbit. Due to the elliptical shape of the earth's orbit, the Sun is closer to the Earth at one point of the year than at the other.
(v) Eclipses
An eclipse is a total or partial obstruction of light from the sun by either the earth or the moon. This occurs when the earth or the moon intercepts light from the sun.
Summer
Warmest season
Spring
Growth season
Winter
Coldest season
Autumn
Harvest season
Exercise 3.4
- Discuss the effects of the earth's revolution in your area.
- Explain the common economic activities carried out in your area in different seasons of the year.
Parallels and Meridians
Activity 3.8
(a) Take a ball and draw a horizontal line that divides the ball into two equal halves, the hemispheres.
(b) Draw another line that divides the ball into two equal halves, vertically connecting top and bottom sides of the ball.
(c) Add more lines that circle the ball horizontally and vertically.
(d) Name the horizontal and vertical lines you have drawn in relation to parallels and meridians.
(a) Latitudes
Latitudes also known as or parallels are imaginary lines parallel to the Equator joining all the places at an equal angular measurement. The equator divides the Earth into two equal parts called hemispheres. The two hemispheres are the Northern Hemisphere and the Southern Hemisphere. The North Pole has a latitude of 90° North, and the South Pole has a latitude of 90° South.
(b) Longitudes
Longitudes are also known as meridians. They are angular distance measured in degrees West or East of the Prime Meridian. They are imaginary lines which run from the North Pole to the South Pole East or West of the Greenwich meridian (0°).
Calculating local time using longitudes
The Earth rotates on its own axis from West to East once after every twenty four hours (one day). This means that the Earth turns through 360° in 24 hours. It rotates 15° in one hour or 1° in 4 minutes.
60 minutes ÷ 15° = 4 minutes per degree
Example 1
The local time of Tunis located at 10°E is 03:00 pm. What is the local time of Mtwara, Tanzania located at 40° E?
Solution:
Difference in longitude: 40° - 10° = 30°
Difference in time: 30° × 4 minutes = 120 minutes = 2 hours
Since Mtwara is east of Tunis, add 2 hours: 03:00 pm + 2 hours = 05:00 pm
Exercise 3.7
- Name the two most common great circles and explain their importance on the Earth.
- Calculate the longitudinal position keep of town H whose time is 10:00 am, when it is 3:00 pm in Town G whose longitude is 5° W.
- Calculate the longitudinal position of a town whose local time is 7:00 am while GMT is 5:00 pm.
- Kalunde starts his trip at longitude 0° at 12:00 noon-moving towards town Y at longitude 45° E. Calculate the time that Kalunde arrives at his destination.
- If the time in Town Z located at 75°W is 5:00 pm on Friday, calculate the time and day Town K located at 120° E.
Revision exercise 3
- "The variation in daytime and night-time experienced throughout the day is caused by rotation of the Earth". Explain.
- Describe how movements of the Earth and moon relate in regard to the position of the sun.
- What are the effects of perihelion and aphelion on our life?
- Why all meridians are great circles?
- Imagine you are at the beach during different times of high and low tide. What would you observe?
- Calculate the local time in New York (USA) located at 75° W, when it is 10:00 am in Lagos, Nigeria located at 15° E.
- What is the time at 120° E when it is midnight at Greenwich?
- If it is 4:15 am in a Village A located at 20° E, calculate the local time of a Village B located along the following longitudes:
- (a) 50° E
- (b) 65° E
- (c) 75° E
- (d) 90° E
- If the time at town A located along the meridian 40° E is 10:00 am, calculate the time along the following meridians:
- (a) 55° W
- (b) 10° W
- (c) 60° W
- (d) 0°
- If the time of town B located at 120° E is 12:00 (noon), calculate the longitude of the following recorded times:
- (a) 5:30 pm
- (b) 5:30 am
- (c) 12:00 noon
- (d) 3:45 pm
Chapter Four: Major Features of the Earth's Surface
People live on the earth's surface, which hosts a variety of features and serves as the primary habitat for all forms of life. The existence of land, water, and vegetation plays a central role in sustaining human and other living organisms on our planet. In this chapter, you will learn about major features of the earth's surface such as continents and their features. You will also learn the major water bodies such as oceans and seas, major features of the ocean floor, as well as large inland water bodies such as rivers and lakes. Moreover, you will learn about vegetation zones on the earth's surface and their importance to human life. The competencies developed will enable you to use and manage resources sustainably in different places.
Think
Features seen on the Earth's surface
Earth's Surface
Activity 4.1
(a) Observe the appearance of your school compound and the nearby areas.
(b) Analyse the features that you have observed and note them down.
Earth's surface refers to the outermost layer of the Earth, including both the landmasses (continents and islands) and the water bodies (oceans, seas, lakes, and rivers). It is the part of the Earth that we interact with directly and where all terrestrial life exists. It is made up of continental landmasses, which cover about 29% of the earth's surface, and water bodies, which cover about 71% of the earth's surface. The landmasses comprise of continents and vegetation. The water bodies consist of oceans and seas, and large inland water bodies such as rivers and lakes.
Continents and Oceans of the World
Activity 4.2
Explore information from library and other reliable online sources about the continents of the world, focusing on their cultural diversity, climate, geographical features, and significant historical events.
In the beginning the earth's surface was a single giant landmass called Pangaea that was surrounded by a single superocean called Panthalassa. Over millions of years, the geomorphic processes caused the Pangaea to break up into two big landmasses. The northern landmass was called Laurasia, and the southern landmass was called Gondwana. The two landmasses were separated by Tethys Sea. The two supercontinents broke into present continents whereby Laurasia included present-day North America, Europe, and Asia while Gondwana comprised of present-day Africa, South America, Antarctica and Australia.
A continent is a major landmass rising from the ocean floor. Continents are usually surrounded by a large mass of water bodies such as oceans and seas. Islands adjacent to continents are part of them because they contain rock structure similar to that of the continent. In general, there are seven continents on the Earth, namely: Asia, Africa, South America, North America, Australia, Europe and Antarctica. Among the seven continents, five continents are separated by oceans and seas, except Europe and Asia, which are separated by the Ural Mountains.
[Map showing distribution of continents and oceans]
Figure 4.1: Distribution of continents and oceans
Activity 4.3
(a) Prepare a well labelled sketch map of a world showing the seven continents.
(b) Give at least one fact about the continent identified, including the name of a country or a major city located on the continent.
The continents of the world are arranged by size starting with the largest to the smallest. They can also be arranged from the smallest to the largest continent depending on the purpose. Therefore, the following is the description of continents based on the size from the largest to the smallest.
Asia
Size: 44.6 million km²
Location: 10°S to 78°N, 30°E to 180°E
Features: Largest continent, covers more than one third of Earth's land surface
Africa
Size: 30.3 million km²
Location: 35°S to 37°N, 15°W to 50°E
Features: Crossed by Equator, Tropic of Cancer, and Tropic of Capricorn
North America
Size: 24.7 million km²
Location: 10°N to 80°N, 60°W to 160°W
Features: Bordered by Pacific, Atlantic, and Arctic Oceans
South America
Size: 17.8 million km²
Location: 10°N to 50°S, 35°W to 80°W
Features: Separated from North America by Panama Isthmus
Antarctica
Size: 14 million km²
Location: Around South Pole
Features: Not inhabited by humans due to extreme cold
Europe
Size: 10.1 million km²
Location: 40°N to Arctic Circle, 10°W to 60°E
Features: Separated from Asia by Ural Mountains
Australia
Size: 8.5 million km²
Location: 10°S to 40°S, 115°E to 150°E
Features: Smallest continent, "island continent"
Exercise 4.1
SECTION A: Fill in the blanks with the correct names of the continents of the world
- The largest continent, both in terms of land area and population, is ______.
- ______ is recognised as the smallest continent, and it is commonly referred to as the "island continent."
- ______ is the only continent that lies in both the Northern and Southern Hemispheres.
- The continent that is located entirely in the Southern Hemisphere and covered mostly by a massive ice sheet is ______.
- ______ is the continent where you can find the Sahara, which is the world's largest hot desert.
- The continent with countries such as Canada, United States of America (USA), and Mexico is ______.
SECTION B: Answer the following questions.
- Give a short description of how continents were formed.
- Describe the geographical features of Africa.
- Which continent do you currently reside in? Describe its geographical location.
- Provide five benefits of geographical position of Tanzania within its continent.
Major Relief Features of the Continents
Each continent has its unique geographical features. The surface of any continent is not regular in shape and elevation. The height above the sea level (altitude) and slope (degree of steepness of the land) give rise to different relief features. In this regard, the main relief features of the continents include Plains, plateaus, mountains, and basins. Other relief features include hills and valleys.
Plains
Continuous stretches of comparatively flat lands that do not change much in elevation. Examples: Serengeti plains (Tanzania), Siberia (Asia), North European plains.
Plateaus
Extensive high altitude area with more or less uniform summit level. Examples: South African plateau, Arabian plateau, Deccan plateau (India).
Mountains
Parts of the earth's surface that rise abruptly to greater height, usually above 300 metres from the surrounding level.
Basins
Natural depression or bowl-shaped hollow on the earth's surface, formed when part of the land sinks due to earth's movements.
Fold Mountains
Formed by folding or wrinkling of the earth's crust due to compressional forces.
Examples: Himalayas, Rockies, Andes, Alps
Block Mountains
Upland areas bordered by faults, formed when crustal rocks break and central part is uplifted.
Examples: Uluguru, Usambara (Tanzania), Ruwenzori (Uganda)
Volcanic Mountains
Cone-shaped mountains formed from cooling and solidification of lava during volcanic eruptions.
Examples: Kilimanjaro, Oldonyo Lengai (Tanzania)
Residual Mountains
Formed by weathering and erosion of weaker rocks, leaving behind resistant rocks.
Examples: Sekenke Hills (Tanzania), Ahaggar Mountains (Sahara)
Exercise 4.2
- With examples explain the economic and social importance of the following relief features to the community:
- (a) Mountains
- (b) Plains
- (c) Plateaus
- (d) Basins
- (e) Hills
- (f) Valleys
- Explain how a rift valley differs from other valleys.
- With examples, describe the processes of mountain formation.
- Describe human activities on mountains.
Water Bodies on the Earth's Surface
A water body is a mass of stationary or moving water which occupy the surface of the Earth. Water bodies can be salty or fresh, large or small. Water occupies about 71 percent of the earth's surface. There is more water surface in the southern hemisphere than in the northern hemisphere. Some of the major water bodies are rivers, lakes, seas, and oceans.
Rivers
Mass of fresh water flowing by gravity in a definite channel from source to mouth.
Major Rivers: Nile (6,650 km), Congo (4,700 km), Amazon (6,400 km)
Tanzania: Rufiji, Ruvuma, Kagera, Pangani
Lakes
Hollow or depression in the earth's surface that contains fresh or salty water.
Tanzania: Victoria, Tanganyika, Nyasa, Rukwa
Types: Natural lakes, Man-made lakes, Rift valley lakes
Seas
Large body of salty water that is surrounded in whole or in part by land.
Examples: Mediterranean Sea, Red Sea, South China Sea
Salinity: Varies with temperature and fresh water input
Oceans
Large body of salty water surrounding the landmass of the Earth.
Major Oceans: Pacific, Atlantic, Indian, Southern, Arctic
Largest: Pacific Ocean (168.7 million km²)
The Ocean Floor and its Features
Ocean floor (sea-bed) refers to a landscape found at the bottom of the ocean. The ocean floor is made up of various features. The major features of the ocean floor include the continental shelf, the continental slope, oceanic ridges, deep sea plain, ocean deep (trench), ocean plain, oceanic island, and submarine plateaus.
Continental Shelf
Gently sloping margin of a continent occupied by shallow waters (up to 200m depth). Excellent fishing grounds.
Continental Slope
Steep slope found where continental shelf meets the ocean basin.
Mid-Ocean Ridge
Raised part of the ocean floor, sometimes appearing as oceanic islands.
Ocean Deep (Trench)
Long narrow steep sided depression plunging to depths of 10000+ metres.
Vegetation
Vegetation refers to a community of plants, trees, shrubs, grasses, mosses, ferns, and other green species that grow in a particular area. Vegetation gives an area a distinct character. It forms the natural landscape of a place. It is an important feature that forms an essential part of the earth's surface. Vegetation supports various animal species, maintains ecological balance, and contributes to the overall health of the environment through temperature regulation, rain formation and soil protection against erosion.
Types of Vegetation
Natural Vegetation
Grows without direct human influence, adapting to natural environmental conditions.
- Woodlands
- Forests
- Grasslands
- Desert vegetation
- Swamp vegetation
Planted Vegetation
Also known as artificial or man-made vegetation, intentionally planted for specific purposes.
Tanzania Examples: Mufindi, Makete, Lushoto, Rongai soft wood forests
Factors Influencing Vegetation Zones
Climatic Factors
- Temperature
- Precipitation
- Sunshine
- Wind
Topographical Factors
- Relief (elevation)
- Slope
- Aspect (direction)
Edaphic Factors
- Soil type and quality
- Soil depth
- Nutrient content
Biotic Factors
- Human activities
- Animal interactions
- Pollination and seed dispersal
Importance of Vegetation to Human Life
Oxygen Production
Plants produce oxygen through photosynthesis
Carbon Absorption
Vegetation absorbs CO₂, reducing climate change impacts
Food Source
Primary source of food for humans and animals
Soil Conservation
Prevents soil erosion and conserves soil
Medicine Source
Many plant species have medicinal properties
Income Generation
Agriculture and forestry provide employment
Habitat Support
Provides habitat for numerous animal species
Climate Regulation
Influences rainfall patterns and temperature
Exercise 4.5
- Explain the role of water bodies in the distribution of vegetation zones in Tanzania
- Explain how topography and climate in Tanzania give rise to different vegetation zones
- Why do we have different economic activities related to vegetation in different parts of Tanzania?
- What economic activities related to vegetation zones can be conducted in places like Lushoto, and the Southern highlands in Tanzania?
- What would have happened if Tanzania did not have the vegetation covers found in Serengeti, Ngorongoro, Manyara, and Mikumi national parks?
- Why is vegetation important to human kind?
Revision Exercise 4
SECTION A: Multiple Choice Questions
- Which of the following is an example of a major fold mountain in the world?
- (a) The Himalayas in Asia
- (b) Ruwenzori in East Africa
- (c) Vosges and Black Forest in Europe
- (d) Sekenke in Tanzania
- (e) Kilimanjaro in Tanzania
- From the following pairs of mountains, which one represent block mountains:
- (a) Himalaya and Vosges
- (b) Alps and Usambara
- (c) Alps and Andes
- (d) Uluguru and Usambara
- (e) Kilimanjaro and Vesuvius
SECTION B: Short Answer Questions
- With examples, state the importance of having large continents.
- Give the economic importance of the following:
- (a) Lakes
- (b) Rivers
- (c) Plains and plateaus
- (d) Continental shelf and continental slope
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