Geography and Environment

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  Geography and Environment

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• Unit 1: Introduction to Geography

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• Unit 2: Elements of a map

  

  By the end of this unit, you must be able to interpret the essential elements of a map and draw sketch maps

  Unit objectives

  By the end of this unit, you must be able to:
  (a) define a map
  (b) identify the various elements of a good map
  
  (c) identify and interpret symbols and signs on a map
  
  (d) draw sketch maps
  (e) state indicators of relief on a physical map
  
  (f) define a map and an aerial photograph
  
  (g) define an atlas index.

  What is a map?
  

  A map is a representation of the features of an area of the earth on a flat surface.  The area could be on land or sea. A map usually shows physical features such as cities and roads. This representation is usually done on a flat surface or piece of paper.

  There are several types of maps. In this topic, we will use topographic maps for our study.
  
  Topographic maps are also called relief maps. These are maps that show both natural and artificial features of a given area.   The maps are drawn to scale. This means that they are reduced so that large areas are represented on small sheets of paper.

  

  Read this passage and answer the questions that follow.

  Gahigi wanted to go to a place far away from his home. He had been invited by his friend Uwase to go on an expedition.  Early one morning, he set out on his journey. His friend had told him that they would meet under a certain tree. She gave him a list of physical features to look out for on his way.
   
  He was to cross a river and then turn right. After going down a valley, he was supposed to turn left and wait for his friend under a big tree with many leaves.
  
  (a) If you were Gahigi, what would you have done?
  
  (b) Do you think Gahigi got to his destination?
  
  (c) Name the tool that Gahigi needed for him to get to his destination quickly.

  

  Study the map of Rwanda below, and answer the questions that follow. Write your answers in your notebooks.
  
  
                                                                                 Fig 2.1
  
  
  1. (a) What is the title of the map?
      (b) What is the main information represented by the map?
  
      (c) Why do you think it is important for such a map to have a title?
  
  2. (a) Name other elements of maps that have been shown on the map.
  
     ( b) Give the importance of the elements you have identified on the map.

      (c) Which element helps a map reader to understand the meaning of various symbols and signs            used on a map?
  3. Suppose Miss Tumusiime wishes to use the above map, which tool would help her to locate              Kigali City? .

             
  Elements of a good map

  

  In groups, study the map of Africa below and answer the questions that follow.       

                          

    1. Name the elements of a good map marked:
         (a) (i), (ii), (iii), (iv) and (v).

         (b) Explain the purpose of each element mentioned in (a) above.

  2. Give the direction of tropical rain forests from Lesotho.

  A good map has specific features. These features are commonly referred to as the elements of a map.The elements of a map are not part of the information that is represented in a map. They are therefore usually placed at the margins.

  The following are the major elements of a good map.

  Table 2.1 Elements of a good map.
  
  
  

  Element	Description
  Title	This shows the information that is contained in a map.
  Frame	This is a line that surrounds a map showing its limitation.
  A key	This is a tool that is used in maps. It helps a map reader to understand the symbols, colours and signs used. A key is important since it helps one to understand the contents of a map in detail.
  A compass	This shows the direction of various features that are shown on map. The directions are usually in relation to the cardinal points of a compass. They are North, South, West and East.
  Scale	This is the ratio of the size of a map to the ground area represented on it. A scale helps cartographers to draw a large area of the earth’s surface on a small sheet of a paper.

  
  
  
  In groups, use the elevation map shown below to answer the questions that    follow.  

  Physical features of Rwanda
  

  

                                          Fig 2.3  

  1. Which physical feature is found to the north-western part of the map?
  
  2. Name the lake that is found to the western side of the map.
  
  3. Give the direction of Birunga Mountains from the Eastern plains.
  
  4. Your teacher has organised a trip for you to the Rusumo falls.  Identify its direction from Kigali city.

  Symbols and signs used on maps

  A symbol is something that is used for or regarded as representing something else.In map work, a key usually shows different symbols.It also gives their meanings. The symbols are usually in the form of shorthand characters, pictorial presentations or colours. In most cases, they show the activities, towns and other physical features. This is done purposely to avoid overcrowding
  a map with a lot of information that would make it look untidy.

  

  In groups, use the map extract provided below.

  1. Identify the symbols used to represent various features on the map.

  
  
  2. Use the map key to identify the symbols used.
  
  3. Give the meaning of each of the symbols and signs used on the map.

  Some of the features represented on a key are given in Table 2.2:

  Table 2.2 Symbols used in maps

  Feature	Symbol used
  Road
  Railway line
  Airstrip (airport
  Religious centre
  Village
  Town
  Mineral works/mining
  Power transmission line
  Mosque
  Hut
  Bridge
  River
  Lake
  School
  Hospital
  Antiquity
  Swamps
  Telephone lines
  Trigonometrical station (Primary
  Trigonometrical station (Secondary)
  Foot path
  Brown lines (contours)

  
  The features shown in Table 2.2 are only a few of the features that are represented
  on maps. It is important that you go to the library and find out other symbols used to represent the features that are shown in maps. The symbols used on maps are usually given in the key of a map. It is important to study the key of a map.
  
  Drawing sketch maps
  
  
  
  Do the following under the guidance of your teacher.
  
  1. Collect drawing materials: pencils,paper, a ruler and an eraser.
  
  2. Go outside your classroom and carefully observe your school surroundings.
  
  3. Draw a map showing your school surroundings. Your teacher will show you how to come up with and use different scales, for example  1:100,000
  
  4. On the map, use symbols to represent features such as buildings, vegetation and roads.
  
  
  5. Include all the elements of a good map on the map that you draw. This include; a title, a frame, a key, a scale and a compass.
  
  A sketch map is an outline map that is drawn from observation.It does not use exact measurements. It only shows the main features of an area.
  
             Below is an example of a sketch map of Mt. St. Helens
  
                           Fig 2.5 Sketch map.
  
  .Characteristics of sketch maps
  Sketch maps have the following features that distinguish them from other maps.
  
  • They are drawn roughly.
  • They are not drawn to the scale.
  • They represent few features for the interests of the user.
  
  • They are less detailed as compared to topographical maps.
  
  • They are simple and hence easy to understand.
  
  • They have the elements of a good map such as the title, key, frame and compass.
  
  Steps involved in drawing a sketch map
  There are five steps in the designing and drawing of a sketch map.
  
  1. Identify and point out the features to be represented. For instance,landforms such as hills, mountains,lakes and rivers. Remember to also include land use such as construction,mining and farming. Transport facilities such as roads, railway lines and airports should also be included.
  
  2. Place the identified elements in order according to the divisions of the landscape.
  
   These include the background, middle ground and the fore ground. This is important because it ensures that each feature is rightly shown where it is supposed to be.
  
  3. Draw the actual sketch map,representing it in a simple way.
  
  4. Select a suitable title that accurately shows the purpose of the sketch map,for instance, what the map is about.
  
              Sketch map of a school
  
          Fig 2.6 (a) Sketch map of a school.
  
  Sketch map of a school
  
  
                Fig 2.6 (b) Sketch map of a school.
  
  
  1. Draw a sketch map of your homestead with all the features that are in it.
  2. In your sketch map apply the elements of a good map.
  3. Use a scale of 1:24000.
  4. Present your work for assessment by your teacher.
  
  Task 2.1
  1. Explain the meaning of a map.
  2. Which of the following combination comprises of elements of a good map?
  
  A. Title, roads, key
  B. Title, key, relief
  C. Title, key, compass direction
  3. Give other elements of a good map that are not listed in the combination in Question 2.
  
  4. State the difference between a topographical map and a sketch map.
  
  5. Explain the main steps involved in drawing a sketch map.
  
  6. Describe the characteristics of a sketch map.
  
  Indicators of relief on maps
  
  
  In groups, use the map extract provided below to answer the questions that follow:
  
  
                                                 Fig 2.7
  (a) Identify the vegetation type of the area represented.
  
  (b) Identify two natural features on the map.
  
  (c) Describe the economic activity of the people in the area.
  
  

  The term relief in geography refers to the nature and outlook of a landscape. Relief usually refers to the highest and lowest elevation points in an area.
  
   Mountains and ridges are the highest elevation points, while valleys are the lowest. Relief describes the horizontal and vertical dimensions of a land surface.This is also known as terrain.
  
  Relief features are visible on physical maps.This is because these maps emphasize the height of the land. This is usually shown with differences in colour and shading. This is done for different heights.The earth’s surface is made up of various relief features. These features have varying altitudes, characteristics and origins that shape their appearance. The relief features represented on maps include the following:
  
   • mountains
  • hills
  • rivers
  • lakes
  • plains (low land areas)
  • escarpments/rift valley
  • fault lines
  • swamps.
  It is important to study relief in geography because of the following reasons.
  
  • The terrain of an area is one of the main determinants of its suitability for human settlement. Rocky and steep areas are not favourable for human settlement. Flat plains that have alluvial soils are suitable for settlement.
  
  • Understanding an area’s relief helps town planners to understand the drainage of an area.Relief maps help planners to locate watersheds and to determine where water moves. It also helps to predict how human activity is likely to affect water quality over time.
  
  • Knowing the relief of the land also helps with planning for soil conservation. Soil conservation is important in agriculture.This helps to inform the farmers about practices like contour ploughing.

  • Knowing the terrain of an area makes the difference between a smooth landing and a difficult one, for aircrafts.

  

  Do this in groups with the guidance of your teacher.
  
  1. Go for a field study in the area around your school.
  
  2. Study the relief of the area. Observe both the artificial and natural features.
  
  3. Study the relationship between the artificial and natural features.
  
  4. Write down your observations in a notebook.
  
  5. Explain how human activities have affected the environment.
  
  6. Explain the ways humans can use their surrounding in a sustainable way.
  
  Methods of presenting relief on maps

  Physical maps show the location of landforms like deserts, mountains and plains. Topographical maps are detailed, accurate graphic representations of features that appear on the Earth’s surface. These features include:
  
  • roads, buildings, urban development, railways and airports.
  
  • geographical features, administrative boundaries, state and international borders and reserves
  • lakes, rivers, streams, swamps and coastal flats
  • mountains, valleys, slopes, depressions and plains
  • forested and cleared areas.
  A map key lists the features shown on the map, and their symbols. There are many ways of representing relief on topographical maps. They include:

  (a) use of colour
  (b) trigonometric stations 
  (c) spot heights
  (d) contours
  (e) pictorials
  (f) hachures
  (g) shading
  
  Layer tinting

  This is the use of colour to show different relief features in relation to various heights.The colour or shade used varies from dark to light shades.
  
           Fig 2.8 Coloured representation of relief.
  
  The dark shades of colour are used for areas of higher altitudes. Areas with lower altitudes
  are shaded using lighter shades of colour. For example, areas with ice or snow are shown
  in white. Dark brown represents mountains, light green shows low lying areas and light brown colour represents hilly areas. Depths of oceans and seas are shown in shades of blue from light to dark. This means that as the height increases, the shade deepens and becomes darker.

  
  
  Do this in groups.
  1. Study the map of Figure 2.9.

  

                                      Fig 2.9

  2 Identify the relief features shown.
  3. Describe the height of the features presented on the map.
  4 Present your findings to the rest of the class.

  Trigonometric stations

  These are fixed surveying stations that are used for land surveys. A trigonometric station is also known as a trig point. Many trigonometric stations are located on the top of hills. This is done so that they can top of hills. This is done so that they can easily be spotted from many directions Trigonometric stations are shown on maps using a triangle. In some instances, the
  actual heights of specific spots where the triangles are placed are given beside the triangle. The stations are important in the construction of modern infrastructure such as land boundaries, roads, railways and bridges. Table 2.3 shows the types of symbols for trigonometric stations.
  
  Table 2.3 Symbols showing trigonometric stations.

  
  
  
  Do this in groups.
  Study the map of Figure 2.10.

  
                                                 Fig 2.10
  
  1. Using the map extract provided, state the highest points in metres.
  2. Describe the terrain of the area represented on the map.
  3. Draw a sketch map of the landscape around your school. Use colour to show the
  important features.

  Spot heights

  These are dots used to represent specific areas on a topographical map. They show the
  actual heights of given areas. For example, • 2015 • 2001 • 560 • 675.

  

     Fig 2.11 Spot heights on an extract of a topographical map.

  

  Do this in groups of three.
  1. Identify the spot heights indicated on the map of Figure 2.12.

  

                                             Fig 2.12

  2. Describe what they represent.

  Contours
  Contours are lines drawn on maps joining areas with the same height above sea level.
  They show both the height and steepness of a place. Height is usually represented in metres or feet. The contour lines are usually drawn at intervals called contour intervals. The contour lines never cross each other. The lines are usually brown in colour. In steep areas, the lines are very close to each other. In areas with gentle gradients, the lines are far apart. Contours are mostly used in representing relief on topographical maps.
  
  
  
           Fig 2.13 Contour lines used on a map.

  Characteristics of contour lines used on maps
  • They have the height number written on them.
  • They are drawn based on a specific and uniform interval.

  
  
  In pairs, do the following with the guidance of your teacher.
  1. Study the picture below.

  
                                  Fig 2.14
  
  2. Which side of the hill is shown in Figure 2.14?
  3. Sketch contour lines representing this side of the hill.
  4. Give reasons for your choice of sketch.

  Interpretation of contours on a topographical map

  various landforms. Some of the landforms
  include:
  • conical hills
  • flat-topped hills
  • ridges
  • hills with depressions
  • craters
  • slopes
  • plateaus

  • spurs
  • low lands
  • river valleys.

  Conical hills

  

     Fig 2.15 A conical hill .

  tops with slopes that are similar in gradient and appearance. The contours representing conical hills are of the same size. They also have uniform spacing between them. This means that the lines are evenly spread.They usually have a circular arrangement as shown in Figure 2.16.

  
     Fig 2.16 Contour lines representing a conical hill.

  
  The top part of the hill is represented by contour lines which are close together. As you move away from the top, the space between the lines are widely spaced on the slopes of the hill. This is due to the gentle gradient of the slopes. If a hill has the same gradient in all its slopes, it is represented by the contour lines shown in Figure 2.17.

  
  Fig 2.17 Contour lines representing a conical hill with an even gradient

  
  Flat-topped hills

  These differ from the conical hills as their tops are generally flat. The contour lines representing flat-topped hills are wide apart at the top, but start getting close together towards the lower parts of the hills.
  
  
       Fig 2.18 Flat topped hill.

  
  

  Fig 2.19 Contours representing a flat topped hill.
  
  Hills with depressions

  These are hills which have depressions at their tops. They are represented by contours that are ring shaped. The depression is represented by pictorial symbols.
  
     Fig 2.20 A hill with a depression on its top.
  
  
  Fig 2.21 Contours representing a hill with a depression.

  Depression craters

  
  
  Work in groups of three. Use geographical documents and other resources.
  
  1. Find out information about
  (a) depression craters
  (b) ridges
  (c) escarpments.
  2. Write short notes about each feature.
  3. Present your findings in a class discussion.
  
  Depression craters are hills or mountains that have deep depressions usually containing water. An example is Mt. Bisoke in Rwanda. Such hills or mountains are represented on a topographical map with ring-shaped contour lines.
  
  
  
    Fig 2.22 The crater lake on Mt. Bisoke

  
  Fig 2.23 Contours representing a depression crater

  
  Ridges

  A ridge is an elongated or stretched out hill,or a range of hills that are close together. The contour lines representing ridges are elongated or sometimes oval shaped. In some instances, the hills that make up a ridge are separated from each other by gaps called saddles which are broad gaps or cols which are narrow gaps.
  
  
         Fig 2. 24 A ridge.
  
  Fig 2.25 Contours showing a ridge with cols and saddles.
  
  Escarpments

  These are physical features that have two distinctively different slopes. One side is steeper than the other. The steep side is called a scarp slope while the gentle side is known as the dip slope. The contour lines representing the dip slope are far apart from each other while those representing the scarp slope tend to be close together.

  
  Fig 2.26 An escarpment and contour lines representing it.
  
  
  
  Your teacher will take you to a hill near your school. Do this in groups.
  
  1. Observe and describe the nature of the hill.
  
  2. Identify the scarp slope and the dip slope.
  
  Slopes

  A slope refers to the surface of the earth whereby one end is at a higher level than the other.
  
                  Fig 2.27 A slope.
  .

  Types of slopes and how they are represented on topographical maps

  
  

  1. Your teacher will take you for a field visit to an area near your school.
  
  2. Carefully study the hilly areas and the slopes and draw them in your exercise book.
  
  3. Describe the difference in the gradients of the slopes you have drawn.
  
  Concave slope
  
  The contours that represent this slope are close together towards the top. They are
  wide apart towards the base of the slope.This is because the land is steep at the top
  and gently slopes towards the base.
  
            Fig 2.28 (a) A concave slope.

  
  
      Fig 2.28 (b) Contours representing a concave slope
  

  Convex slopes

  This is a slope that is gentle towards the top and steep towards the base. The contours are widely spaced at the top. Towards the base where the land is steep, they are closely spaced.
  
            Fig 2.29 (a) A convex slope.
  
  
                  Fig 2.29 (b) Contours representing a convex slope.
  
  Steep slopes

  

  
  Do this is in groups of three. Use Figure 2.30 below to answer the questions that follow.
  
  
  .                   Fig 2.30
  
  1. Describe the nature of the landscape shown.
  2. Explain the gradient or nature of the slope.
  3. Suppose you lived in such an area, how would you use the land sustainably?
  
  A steep slope is represented on a topographical map by contours that are very close together. This is due to the uniform steepness of the slopes or land.
  .

                    Fig 2.31 (a) A steep slope

  
  

                  Fig 2.31 (b) Contours representing a steep slope.

  Gentle slopes

  A gentle slope is represented on a topographical map by contours that are uniformly spaced. This is because the slope is uniformly gentle.

  

                 Fig 2.32 (a) A gentle slope.

  

                      Fig 2.32 (b) Contours representing a gentle slope.
  
  Flat land or plains

  This is represented on a topographical map by contours that are uniformly widely spaced. Such areas are associated with other features such as swamps.
  
  
             Fig 2.33 (a) A flat land

  
           Fig 2.33 (b) Contour lines on a relatively flat land.
  
  Even slope

  This is a slope where the land has an almost similar gradient. When being represented on a topographical map, contour lines with same distance between the lines are drawn. Thecontour lines are equally spaced.
   
  
           Fig 2.34 (a) An even slope.
  
       Fig 2.34 (b) Contours showing an even slope.
  
  

  Work in groups.
  Do the following.
  1. Describe the nature of the land shown by the contour lines.
  2. Identify some of the landforms on the map represented by the contour lines.

  

  

  There are other indicators of relief used on maps. They include the following.

  Hachures

  Hachuring is one of the commonly used methods of representing relief on topographical maps. This method is used to show the altitude of a given area. It is used
  more in places with steep gradients. They are represented using short parallel lines.The steepness or gentleness of a slope is shown using lines with varying lengths and thicknesses. It is very important to note that hachures do not reveal the actual heights of areas represented as is the case with contour lines.

  

       Fig 2.36 Hachures.

  Table 2.4: Interpretation of hachure lines.

  Nature of the lines	interpretation
  Lines drawn very close to one another in a compacted way.	Represent a very steep slope or gradient such as a cone volcano.

  
  

  Lines drawn widely apart and less compacted or not congested (thin in nature).	Represent a very gentle gradient or a gently sloping area.

  
  Pictorial method
  
  This method uses symbols based on the appearance of the features. It shows how features appear from above. For example, mountains are raised while valleys are sunken. When showing height, very short thick lines which have thick heads and tails are used. The sharp point of the symbol points towards the lowland part of a feature while the thick head points to the
  high altitude.
  
  Hill shading
  
  This method of representing relief is about careful use of light and shadow. It is imagined that light over a given area brings variations in shading. The intensity of light keeps on reducing depending on the nature and angle of the slope and the gradient. The darker expressions are used to represent the steep slopes. Bright expressions are used to represent hill tops, areas with gentle gradients such as valley bottoms and plain or flat lands.
  
  
                                       Fig 2.37 Hill shading.
  
  Do this in groups. Study the map extract provided below, and answer the questions that follow.
  
                                                 Fig 2.38
  1. Give the grid reference of Lac Nyakuzi.
  2. Mention the relief indicators that have been used to represent relief features on the map.
  
  
  
  Do the following in groups, with the help of your teacher.
  1. Draw a sketch map showing the landscape of the area around your school.
  2. Using different colours, shade the map illustrating variations in light. Ensure that you bring out        the gradient expressions.
  3. Present your drawings to the rest of the class for discussion.
  
  Maps and aerial photographs
  
  
  1. Study Figures 2.39 and 2.40. Give a name to each one of them
  
                                                        Fig 2.39
  
                                 Fig 2.40
  2. Describe the features of each one of them.
  
  As earlier explained, a map is a representation on a flat surface of a whole or part of an area. Maps represent parts of the earth’s surface drawn to scale. Figure 2.41 shows a map of Rwanda
  
  
   Fig 2.41 A map showing the districts of Rwanda
  
  A photograph is a picture created using a camera and stored digitally. Photographs are usually in the form of a print or a slide. A photograph could be a picture of a person,a scene or a physical feature on earth or space.The sizes of photographs vary. There is
  no relationship between the size of a photograph and the size of the object represented.
  An aerial photograph is a picture of the earth’s surface taken from above. The picture is usually taken from an aircraft. Aerial photographs are often used as data for geographers. They are also used for locating geographic features as well as for interpreting environmental conditions.
  
  
  Fig 2.40 An aerial photograph of Mt. Bisoke in Rwanda
  
  Your teacher will provide you with copies of maps and a variety of aerial photographs.
  1. Study the documents carefully
  2. Identify maps and photographs. Do this by separating them accordingly.
  3. Give reasons why you have classified them the way you have.
  4 Present your work to the rest of the class members.
  
  Differences between maps and aerial photographs
  
  Aerial photographs and maps are used by geographers. Cartographers sometimes
  use aerial photographs when designing and preparing maps.
  
  
  Under the guidance of your teacher, do the following.
  1. Draw a sketch map of your school. Include all the elements of a good map in your drawing.
  2. Your teacher will help you take ground photographs of your school using a camera.
  3. Compare the photographs you have taken with the aerial photographs that you had studied before.
  4. Note the differences that you can observe between the two types of photographs. Write them in your exercise books.
  5. Note down the differences between the aerial photographs and the map that you have drawn.
  6. Present your findings in class.
  
  The table below shows the difference between maps and aerial photographs.
  
  Table 2.4 Differences between maps and aerial photographs.
  
  

  Maps	Aerial photographs
  A map is a representation of a part of the earth’s surface.	An aerial photograph is a picture taken from a raised platform representing a small part of the earth’s surface
  They are drawn to scale.	Not taken to scale.
  A map can represent a relatively large area.	An aerial photograph only covers a small area or object.
  The features used on a map are interpreted by use of symbols.	The features are clearly seen without the use of symbols. They appear as they are in their natural form.
  A map is sometimes difficult to interpret.	An aerial photograph is easy to interpret.
  A map only shows specific information that is needed. It is thus prepared selectively.	An aerial photograph shows all features that are near a place, whether they are useful or not.
  A map is difficult to come up with. It requires a wide range of skills such as cartographic techniques.	It is relatively easier to take a photograph. It only requires one to have a camera and to know how to use it.
  A map has a key that helps readers to interpret and understand it.	An aerial photograph has no key. To understand it, one only has to keenly look at it.
  A map has no skyline. It does not show the horizon which can be used to determine the relief of an area. It instead uses contours to represent relief.	An aerial photograph has a skyline especially the high oblique aerial photographs. This makes it easy to determine the relief and climate of the area represented.
  A map has a compass that shows the direction of various parts on it. This is done in relation to the actual areas being represented.	An aerial photograph does not have a compass to aid in determining the direction of the features in it.

  
  Atlas index
  
  
  
  

  Work in groups. Your teacher will give you atlases.
  1. Read the contents on the last page of the atlas.
  2. Write down your observations in your exercise book.
  3. Using the Internet and your textbook, find out the meaning of an atlas index.
  4. Identify its main characteristics.
  5. Write down the findings in your exercise books for class presentation.

  An atlas is a collection of maps of the Earth or regions of the Earth. However, there are atlases of other planets too. An atlas is usually a bound book with a collection of maps. However, there are atlases in multimedia formats

  

         Fig 2.43 An atlas book

  Atlases usually present geographical features, political boundaries, geopolitical, social, religious and economic statistics. They also have information about maps and places in them.
  An atlas index is a detailed alphabetical listing of names, places and topics. In some cases, an atlas index follows numerical listing. The list is accompanied by the numbers of the pages on which they are mentioned or discussed. The atlas index is usually found at the end of the atlas.

  

  1. Your teacher will provide you with an atlas. Find the index page and comment on the following.
  • Content of the index.
  • The position of the index.
  • The arrangement of content of the index.
  2. Present your findings in class.

  

  

                  Fig 2.44 Sample of an open atlas index.

  Elements of an atlas index

   The atlas index shows various topicsband names of places.
   The index is at the last pages of the atlas.
   The index lists a summary of the specific contents of the atlas.
   The index acts as a pointer. It directs the reader to specific pages where given topics can be             found inside the atlas.
   The index follows a systematic alphabetical or numerical order.The following are the elements of      an atlas index.

  Did you know?

  • No one knows the exact date when the first map was created.
  • People who create maps are known as cartographers.
  • Some of the first detailed maps were made by armies.
  • It is impossible to create a map with a perfect scale.
  • The first aerial photographs were taken by French map makers in 1858.

  

  1. (a) Define the term relief.
  (b) Name six the features that are represented on a topographical map.

  2. (a) Name the seven different ways that can be used to represent relief on topographical maps.
  (b) Muhire wants to indicate the height of a specific spot of an area on a map. Suggest to him two methods that he can use.
  3. (a) Distinguish between an trigonometric station and a spot height.
  (b) Name two types of trigonometric stations.
  (c) Show the symbols used for each.
  4. (a) Explain the difference between hachures and hill shading methods of representing relief.
  (b) Give the appropriate illustration for each.
  5. (a) Define contours.
  (b) Explain the main characteristics of contours in map work.
  (c) Describe types of slopes and explain how they are represented on topographical maps.
  6. Using illustrations, explain how the layer tinting method can help geographers to represent relief on a map.
  7. Explain five differences between a map and an aerial photograph.
  8. (a) Give the meaning of an atlas index.
  (b) Describe the characteristics of an atlas index.

• Unit 3: The Earth in relation to the universe

  
  

  By the end of this unit, you must be able to analyse the impact of the earth’s position and movements in the solar system.

  Unit objectives

  By the end of this unit, you must be able to:
  (a) identify different components of the universe
  (b) describe the earth and the solar system
  (c) state the earth’s movements and their consequences
  (d) show the relationship between longitude and time
  (e) define latitude and longitude.

  Components of the universe

  

  Do this in groups of four under the guidance of your teacher.
  1. Go outside your classroom for five minutes.
  2. Observe the sky.
  3. Write down what you have observed.

  4. Let each group member say what is seen in the sky at night.
  5. Write down your points.
  6. Compile your points and share them with other members in a class presentation.

  

  Do this individually and share the findings with other members of your class.

  Study the pictures shown below.

  

                  Fig 3.1
  

                   Fig 3.2

  1. Compare the two pictures showing the sky at different times.

  2. Write down the differences that you can observe.
  3. Explain why you think there is a difference in the sky at night and at day time.
  4. Share your findings with the rest of the class.

  Definition of the universe

  The term universe refers all of space including everything that exists in it. This includes the stars, the galaxies, the planets, matter and energy . It also has empty space with particles and interstellar gas. The universe is also known as the cosmos. During day time, it is common to see the sun. This is one of the heavenly bodies that exist in space. However this depends on one’s geographical location. The universe has no specific shape. It is endless space. Scientists have not fully explored the universe due to its vast and seemingly unending nature. They are still making discoveries in order to understand the universe better.

  

  Do this in groups of five.
  1. Use the Internet, geography textbooks and photographs to find out the elements that constitute the universe.
  2. Write down notes on your findings.
  3. Choose a group leader who will share the findings of your group with other class members in a class presentation.

  Components of the universe

  
  

  Do this in groups of three.
  1. Using the Internet and geography textbooks, find out other heavenly bodies found in the universe.
  2. Write them down in your notebooks.
  3.The universe is made up of planetary bodies that move or revolve around the sun. They
  include the following. Present your findings in class.

  • Stars
  • The sun
  • Clusters
  • Galaxies
  • Planets
  • Earth
  • Moons
  • Asteroids
  • Meteors
  • Comets

  (a) Stars
  Stars are luminous heavenly bodies that give out light. In most cases, stars have very
  high temperatures. There are many stars in the universe. Each star is associated with planets and moons.

  

       Fig 3.3 Stars in the sky at night

  (b) The sun
  The sun is one of the stars that are found in the universe. It is the only star that gives out its own light. Other stars in our universe reflect light from it. It is located in the middle of the solar system. The sun is near the earth’s atmosphere. All the known planets and other heavenly bodies revolve
  around it. The planets and heavenly bodies revolve around the sun following specific paths
  known as orbits. This revolution occurs because the sun pulls them towards it. They also use their own gravitational force to pull towards their centres and end up being in a circular motion.

  

  Fig 3.4 The earth orbits the sun

  (c) Clusters
  Star clusters are a group of stars that share a common origin. They are held together by
  the force of gravity.

  

         Fig 3.5 A cluster of stars.

  (d) Galaxy
  A galaxy is a large collection of gas, dust and billions of stars held together by gravity. One galaxy can have hundreds of billions of stars and be as large as 200,000 light years across. These stars are still held together by the force of gravity. For example, our planet, Earth is found in the Milky Way galaxy. It derived its name from its milky, appearance of a dim glowing band arching across the night sky. There are also other galaxies in the universe.

  

       Fig 3.6 The Milky Way galaxy.

  (e) Planets
  These are heavenly bodies that revolve around a star following specific orbits.

  

             Fig 3.7 Planets in the solar system

  The solar system consists of eight planets and the sun. The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The Earth is the only planet that has been known to support life. 

  

  Work in pairs.
  1. Go outside the classroom. Describe what you can see on planet earth that makes it able to support life.
  2. Write down your findings in your notebooks.

  3. Present your work in a class discussion.

  (f) Moons
  The moon is another heavenly body that is found in the universe. It is a natural satellite of the earth. There is only one moon that attends to our planet Earth. Other planets also have satellites that attend to them. It is estimated that there are about 179 satellites that attend to all the planets and planetoids. These satellites form part of the universe.

  

    Fig 3.8 The moon as observed from the earth

  (g) Asteroids
  Asteroids are small, airless rocky bodies revolving around the sun between Mars and Jupiter. They are too small to be called planets. This is because they never fully developed into planets. They are sometimes referred to as planetoids or dwarf planets. They range in size from tiny particles to large bodies hundreds of kilometres in diameter. It is not easy to see the smallest asteroids. Since they have little gravity, they are irregular in shape. Asteroids are minor members of the solar system. They form part of the universe.

  

        Fig 3.9 Asteroids in space

  Meteors
  Meteors are fragments of rock and metal that fall to Earth from space. They are known to fall as they break away from other bodies such as asteroids. They are of different sizes. Some are as small as a fraction of a millimetre. Others are as big as a football pitch or bigger. The Earth’s gravitational force causes the meteorites to accelerate to over 11.2 kilometres per second. As they enter Earth’s thick atmosphere, they rapidly slow down due to the friction. They then glow, flashing across the sky like fireworks, before finally crashing to the ground.

  Meteors are popularly known as shooting stars. When they enter the Earth’s atmosphere, they appear as short-lived long thin lines of light. This light suddenly disappears into vapour or ash.
  This happens before the meteors reach the Earth’s surface. The bright light is formed out of friction between the meteor and the atmospheric air. Meteors are minor members of the solar system. They form part of the universe.

  

      Fig 3.10 Meteors in outer space

  Meteors that fail to vapourise or burn up reach the Earth’s surface as rocks. They are referred to as meteorites. Some hit the Earth’s surface with a great impact forming craters. When meteorites reach the Earth’s surface, they cause great damage. However, in most
  case the meteors fail to enter the Earth’s atmosphere. This is because of the following
  reasons.

  • Most of them burn up before they reach on the Earth’s surface. This is due to the high speeds and powerful friction.
  • The moon safeguards the Earth from meteoroids. Therefore, most of them land onto the moon’s surface. This is why there are many craters on the moon’s surface.
    

  

  Do this in groups of three.
  1. Using space photographs, the Internet and textbooks, find out what would happen to our environment if meteors hit the Earth’s surface.
  2. Come up with appropriate measures that humans could take to ensure that we protect our  environment should that happen.

  (i) Comets

  Comets are small heavenly bodies that revolve round the sun along very elongated orbits. They are made up of frozen gases, ice and lumps of rocks. Comets cross the orbits of other planets as they move towards the sun.

  

           Fig 3.11 Comets in space.

  When they get closer to the sun, the heat vapourises the frozen gases. This produces a glowing head called coma and a tail.The tail extends for millions of kilometres. This tail points away from the sun. As thencomets move away from the sun, the gases condense and the tail disappears.

  Task 1.

   (a) Define the term universe.
  (b) Outline the components of the universe.
  2. (a) Describe the phases of the moon.
  (b) Explain the meaning of a satellite.
  3. (a) What is an orbit?
  (b) Why should planetary bodies revolve around the sun?
  5. Describe the difference between the sun and other stars.
  6. (a) With specific examples, define the term planet.
  (b) Explain the characteristics of the moon that is attendant to planet Earth.
  7. Describe the following terms as used in geography.
  (a) Asteroids       (b) Planetoids
  (c) Meteors        (d) Meteorites
  (e) Comets         (f) Shooting stars

  Constellations and galaxies

  

  Work in pairs. Your teacher will provide with two photographs.
  1. Using the Internet and geography textbooks, find out the meanings of the following:
  (a) constellations
  (b) galaxies.

  2. Look at the photographs that yourbteacher provided you with and state the differences between the two.
  3. Write down the differences in your notebook.
  4. Present your findings in class.

  Constellations

  A constellation is a group of stars that forms a pattern in the sky. This is as seen when viewed from the earth.
  There are 88 constellations in our solar system. The Southern Cross commonly referred to as a Crux is the brightest while Hydra is the biggest. The following pictures show different constellations and their appearances in the sky.

  

        Fig 3.12 The big dipper

  

           Fig 3.13 Orion.

  

  

  

  

  Do this in groups of four.
  1. Go outside the classroom.
  2. Using threads and short sticks, demonstrate the patterns of the following constellations:

  (a) The big dipper
  (b) The Southern Cross (Crux)
  (c) Orion
  (d) Pegasus.

  Galaxies

  

  Do this in groups of three. Use the Internet, geography textbooks and journals to do the
  following.
  1. Define the term galaxy.
  2. Name and describe different galaxies.
  3. Find out whether the Milky Way galaxy is spiral, elliptical or irredula.
  4. Write down your findings in your notebook.
  5. Share your findings in a class discussion.

  As you learnt earlier, galaxies form part of the universe. A galaxy is a big collection of gas, dust and billions of stars held together by gravity. One galaxy can have hundreds of billions of stars. It can also be as large as 200,000 light years across.
  (a) The Milky Way galaxy – This galaxy has a bright central core with a high density of stars and a flattened disk surrounding it. Its name “milky” is derived from its appearance as a dim glowing band
  arching across the night sky. This galaxy contains our solar system.

  

             Fig 3.20 The Milky Way galaxy.

  (b) The Andromeda galaxy – This galaxy gets its name from the area of the sky in which it appears, the constellation of Andromeda. It is the closest big galaxy to the Milky Way.

  

         Fig 3.21 The Andromeda galaxy.

  (c) Black Eye galaxy – It has a spectacular dark band of absorbing dust in front of the galaxy’s bright nucleus, giving rise to its nicknames of the “Black Eye” or “Evil Eye” galaxy.

  

         Fig 3.22 The Black Eye galaxy.

  (d) Bode’s galaxy – This is named for Johann Elert Bode who discovered this galaxy in 1774.

  

           Fig 3.23 The Bode’s galaxy.

  (e) Cartwheel galaxy – Its visual appearance is similar to that of a spoked cartwheel.

  

         Fig 3.24 The Cartwheel galaxy.

  (f) Cigar galaxy – This galaxy appears similar in shape to a cigar.

  

  Fig 3.25 The Cigar galaxy

   (g) Comet galaxy – This galaxy is named after its unusual appearance, looking like a comet.

  

           Fig 3.26 The Comet galaxy.

  Tadpole galaxy – The name comes from the resemblance of the galaxy to a tadpole. This shape resulted from tidal interaction that drew out a long tidal tail.     

  

               Fig 3.27 The Tadpole galaxy .

  (i) Whirlpool galaxy – From the whirlpool appearance this gravitationally disturbed galaxy
  exhibits.      

  

            Fig 3.28 The Whirlpool galaxy

  Task 3.2

  1. What is a constellation?
  2. Give the names of the following.
  (a) The brightest constellation.
  (b) The biggest constellation in our solar system.
  3. Give the names of specific examples of constellations.
  4. Define a galaxy.
  5. Name any three examples of galaxies.

  The earth and the solar system

  

  Do this in pairs.
  1. Go outside your classroom and observe the sky.
  2. Record what you see in your notebook.
  3. Explain the importance of the sun to human beings and to the environment.
  4 Share your findings in a class discussion.

  When you go outside, you can see a bright heavenly body that gives us light. The heavenly body is known as the sun. We have already learnt that we have stars in the universe. The most important star is the sun. Plants, animals and human beings all depend on the energy provided by the sun. The sun is a star that is at the centre of the solar system. It is the only star that gives out its own light.

  

  Do this in groups of three.
  1. Discuss the importance of the sunshine.
  2. Explain what would happen to our environment if:
  (a) the sun did not produce light
  (b) the sun gave too much heat.

  The solar system

  

  Work in pairs.
  1. What is the meaning of the solar system?
  2. Name the components of solar system.
  3. Name the heavenly body that holds planets in the solar system.

  The word solar is derived from a Latin word sol that means the sun.

  

                        Fig 3.29 The composition of the solar system.

  The solar system is a composition of the sun, the eight planets and other heavenly bodies. In the solar system, the planets and the heavenly bodies revolve around the sun. The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. They occur in that order from the sun. Jupiter is the largest planet while Mercury is the smallest. Other heavenly bodies are
  smaller than the planets. They include; satellites, meteors, asteroids, satellites, comets and meteorites, gas and dust. The solar system exists in the universe. It is one of the components of the universe.

  The sun
  The sun is a star. A star has a bright sphere of hot gas. There are millions of stars in the space. The sun was formed about 4 to 6 billion years ago. It forms the central part of the solar system. All the bodies of the solar system revolve around the sun. The gravitational field of the sun holds elements of the solar system in orbit. The sun rotates in an anticlockwise direction on its axis. It takes about 25 days to complete a rotation at the equator. It also takes about 34 to 35 days to rotate at the poles. The sun is mainly made up of hydrogen and helium which are burning gases.
  The planets.

  The planets

  

  Work in groups.
  1. Go outside your classroom to the playground.
  2. Draw eight different circles on the ground using chalk. The circles should be inside each other with spaces of about 2 metres apart.

  3. Choose some students to run as they go round the circles in an anticlockwise direction. They should begin at a slow speed and increase the speed gradually.
  4. Observe what happens. Explain why the above learners did not collide as they ran around.
  5. What is the geographical name given to the paths that the learners followed?
  6. What do you think would happen if the learners did not have specific paths to follow?

  A planet is a heavenly body which:
  (a) is made up of rocky solids
  (b) is oval in shape
  (c) is suspended in space
  (d) rotates on its own axis
  (e) revolves around the sun.
  The planets are grouped into two:

  (a) The inner planets: These are also referred to as the terrestrial planets. They are made up of silicate rock mantles. Their cores are composed of iron. They are the planets that are nearer the sun.They are:
  . Mercury           .Venus
  
  . Earth               . Mars

  (b) The outer planets: They are also called Jovian planets. They are:

              Jupiter        Uranus
              Saturn        Neptune
  

  Jupiter and Saturn are composed of gas while Uranus and Neptune are composed
  of ice. The planets revolve around the sun in an anticlockwise direction along paths known as orbits. The orbits are oval or elliptical in shape. Different planets take different lengths of time to make complete revolutions round the sun. This is because of their various distances from the sun. The period taken by a planet to make a complete revolution round the sun is known as a year. The earth takes 365 ¼ days to make a complete revolution round the sun. This period is one year on the Earth. Mercury takes 88 days to make a complete revolution round the sun. This is because it is near the sun. This is the shortest time taken by a planet to go round the sun. While revolving around the sun, the planets also rotate on their own axes. The planets and heavenly bodies are held in place by the gravity of the sun.

  

  (a) Name the planets in the solar system.
  (b) Which planet supports life?
  (c) Suggest ways that humans can make planet Earth fit for human habitation.

  Table 3.1 The known planets of the solar system.

  Planet	Key features
  Mercury	• It is the smallest planet. • It is the nearest planet to the sun. • It completes its revolution in 88 days. • It is moonless. • It is about 70 million kilometres from the sun when it is at its farthest. When it is closest to the sun , it is at 47 million kilometres away.
  Venus	• It is slightly smaller than planet earth. • It is one of the brightest planets in the universe. • It is almost similar to the earth. • It is moonless. • It is 108.9 million kilometres from the sun. • It takes 225 days or 0.165 Earth years to complete its revolution around the sun.
  Earth	• It is the third planet from the sun. • It is the only planet known to support life . • It is 146 million kilometres from the sun. • It has one moon. • It takes 365 days to complete a revolution around the sun.
  Mars	• It is slightly cooler than other planets. • It is 228 million kilometres from the sun. • It has 2 moons. • It takes 686.971 Earth days to complete a revolution around the sun.
  Jupiter	• It is the largest planet. • It has 63 moons. • It takes 12 Earth years to complete one revolution round the sun. • It is 779 million kilometres from the sun.
  Saturn	• It has a ring around it making it unique. • It has 62 moons. • It is 1.4 billion kilometres from the sun. • It takes 29.4 Earth years to complete a revolution around the sun.
  Uranus	• It is the 7th planet in the universe . • It is the 8th 2.5 billion kilometres from the sun. • It has 27 moons. • It takes 84.3 years to complete a revolution around the sun.
  Neptune	• It is the 8th planet from the sun. • It is 4.5 billion kilometres from the sun. • It has 13 moons. • It takes 164.79 Earth years to complete a revolution around the sun.

  
  (c) Satellites
  
  
  Your teacher will provide you with photographs of satellites.
  (a) Classify the satellites as natural or artificial.
  (b) Write down the differences between the two in your notebook.
  (c) Share your findings with your classmates in a class presentation.
  

  • A satellite is an object that moves around a larger object. The moon is a satellite because it moves around Earth. Some planets are moonless meaning they have no satellites while others have many moons. In total, the solar system has 179 satellites. There are two types of satellites in our universe.
    
  • (a) natural satellites
    
  • (b) artificial satellites.
    
  • 
    
  • Natural satellites
    
  • 
    
  • These are heavenly bodies that float around planets passing through specific paths called orbits. They occur naturally in the outer space. A good example is the moon. It is a natural satellite.
    
  • 
    
  • 
    
  •         Fig 3.30 The moon is a natural satellite.
    
  • 
    
  • Artificial satellites
    
  • 
    
  • These are smaller objects in the outer space made by humans. They move around planets or moons. They are mostly used for scientific research, communication, weather monitoring and military purposes.
    
  • 
    
  • 
    
  •         Fig 3.31 An artificial satellite in space.
    
  • 
    
  • 
    
  • Use the Internet and geography textbooks:
    
  • 1. Find the relationship between the solar system and the universe.
    
  • 2. State the importance of the solar system in the universe. Write down your findings in your notebook.
    
  • 3. Share your findings with the rest of the class.
    
  • 
    
  • Task 3.3
    
  • 
    
  • 1. Explain what a planet is.
    
  • 2. Distinguish between the inner planets and outer planets.
    
  • 3. List examples of terrestrial planets and explain why they are called so.
    
  • 4. With the aid of a diagram, list the planets of the solar system in order of occurrence.
    
  • 
    
  • The moon
    The moon is a natural satellite of the earth.Moonlight is the illumination of the sun’s light. The moon does not produce any light of its own.
    
  • 
    
  • The moon’s diameter is approximately 3,476 kilometres. It is egg-shaped with the smaller end pointing towards the earth. It rotates on its axis. It also revolves round the earth in 27 days, 7 hours and 43 minutes. It takes 29 days, 12 hours and 44 minutes to get to a new moon. The moon therefore, completes its rotation and revolution at about the same time
  • 
    
    
• Phases of the moon
  
• 
  
• 
• 
  
• 
  
• Do this in pairs.
  
• 1. From your own observation, how would you describe the changing appearance of the moon at different times ? Write these down in your notebook.
  
• 2. Share with your classmates in a class discussion.
  
• 
  
• The moon has different phases. These phases refer to the different shapes of the illuminated part of the moon. These phases are as seen from Earth. The moon changes its phase in relation to the reflected sunlight depending on its position.
  
• 
  
• The following are the main phases of the moon.
  
• 1. Primary phases.
  
• • New moon
  
• • First quarter
  
• • Full moon
  
• • Last quarter
  
• 
  
• 2. Intermediate phases.
  
• • Waxing crescent
  
• • Waxing gibbous
  
• • Waning gibbous
  
• • Waning crescent
  
• 
  
• New moon
  The new moon is completely dark on the first day. This happens when the side of the moon that receives sunlight faces away from the earth. The new moon appears when the moon is aligned with the sun and the Earth. During this period, the sun and the moon rise and set about the same time. The new moon is usually dark.
• 
  
  
• 
  
•      Fig 3.32 The new moon.
  
• 
  
• Waxing crescent moon
  
• 
  
• Between the 1st and the 6th day after the new moon, the moon changes. The part that faces the earth begins showing a silver bright crescent shape. This happens to the moon as it moves around the earth.This shape continues to increase in size as days go by.
  
• 
  
• 
  
•         Fig 3.33 Waxing crescent moon.
  
• 
  
• The first quarter moon
  
• 
  
• Seven days after the new moon, the moon completes a quarter of its journey around the earth. This is when we are able to see the half of it that receives sunlight. This happens when the moon is at a 90° angle to the earth and sun. This is the part that is illuminated. The other half is in theshadow. 
  
•    
•      Fig 3.34 The first quarter moon.
  
• Waxing gibbous moon
  
• This is the moon that appears between day 8 and 13. This phase appears when the part of the moon that receives sunlight grows bigger.




     Fig 3.35 The waxing gibbous moon.



At this point, we view a bigger bright part of the moon as illustrated in Figure 3.35.

Full moon

Fourteen days after the new moon, the moon completes half of its revolution around the earth. During this phase, we see a complete circle of the moon exposed to sunlight





          Fig 3.36 The full moon.



Waning gibbous moon


This phase appears between 15 to 21 days after the first phase of the new moon. From the earth, we see the lit disk of the moon decreasing or waning. This continues to decrease as days go by.





     Fig 3.37 Waning gibbous moon.



Last quarter



This phase appears three weeks after the new moon. From the earth, we see half of the moon that is lit and half that is completely dark.







Waning crescent



This phase occurs 23 to 28 days after the new moon. In this phase, the dark part of the moon is bigger than the lit side. From the earth, a bright crescent is seen. It keeps on decreasing until the whole disk of the moon is dark. This leads to day 0 when another new moon occurs.





     Fig 3.39 Waning crescent moon.





                  Fig 3.40 A summary of the phases of the moon.





Do this in pairs.

1. Collect a used DVD disk and a torch.

2. Hold the disk as you face your classmate.

3. Ask your classmate to hold a brightly lit torch pointing towards the disk.

4. Continue changing the position of the disk as you observe the light.

5. Note down your observations.

6. Discuss your observations with your classmate.

7. Compare this to the different phases of the moon.



Characteristics of the moon







Do research in pairs. Use the Internet and other geographical documents.

1. Find out the unique characteristics of the moon as a component of the universe.

2. Write down your findings in notebooks.

3. Share your findings in a class presentation.



The moon has the following characteristics.



(a) It has a cold surface. Although it gives out light, the temperatures on its surface are so low. It does not produce its own light. It reflects light from the sun that is projected onto planet Earth.



(b) It is a dry globe. It has neither rain nor water bodies. This means it has no moisture in its environment.

(c) Its surface is dominated with craters.Craters are depressions or holes. They are caused by other heavenly objects that fall on it with great force.



(d) Its landscape is made up of rocks and dust. When other heavenly objects fall onto the moon, they break the rocks on the surface. As they break,they are crushed into dust.



(e) It has no or low gravitation force. On most parts of the moon, there is very little gravity. On other parts, there is no gravity at all. The gravitational force of the moon causes periodic rising and falling of sea and oceanwaters. This causes tides.



(f) Its atmosphere is very limited.This means that there is little air surrounding it.





Fig 3.41 The surface of the moon is full of

craters.



Eclipse





Do this in groups of three.

(a) Collect a torch and a football. The ball represents a heavenly body while the torch represents the sun.

(b) One of you should hold the ball and the other one the lit torch.

(c) Hold the lit torch and the ball aligned in a straight line.

(d) Note down your findings.

(e) One group member should stand in front of the source of the lit torch.

(f) Observe what happens to the ball.

(g) Write down your observation in your notebook.

Answer the following questions in your group.

     (i) What happened to the ball when the torch was lit?

     (ii) What happened when an obstacle came in between the source of light and the ball?



The answers to the questions in Activity 3.20 explain what happens between the sun, moon and the earth. This happens when the moon moves around the earth. The word eclipse comes from the Greek word ekleipsis which means abandonment.

An eclipse is the blocking off of the light of a heavenly body. This light is blocked by another heavenly body that passes in front of it.

An eclipse occurs when the sun or moon is hidden from an observer on earth. The sun is larger than the earth and the moon.

This results in the formation of zones of shadows. The inner total shadow is called the umbra. The outer partial shadow is called the
penumbra.



Types of eclipse



There are two types of eclipses.

•  The eclipse of the moon (lunar eclipse).
•      The eclipse of the sun (solar eclipse).
  
Eclipse of the moon (lunar eclipse)


This occurs when the earth comes between the moon and the sun. The earth blocks the sun’s light from reaching the surface of the moon. The earth casts its shadow on the moon, making it
completely dark.
During the eclipse, the moon may be visible but without its bright illumination. The moon remains in darkness for about two hours. This is because the earth is larger than the moon. It therefore takes a longer period to move the path of the sunlight. Lunar eclipses take place at night and only during
the full moon.

 


Eclipse of the sun (solar eclipse)


This eclipse occurs when the moon comes between the earth and the sun. The moon casts its shadow on the Earth’s surface. It obscures or hides the Earth from the sunlight. Only a small section of the Earth experiences a total solar eclipse. It lasts for about seven and half minutes. The solar eclipse occurs at daytime.



             Fig 3.43 (a) A drawing showing the lunar eclipse.

                  Fig 3.44 (b) An illustration of the solar eclipse.









Do this in pairs. Use the encyclopedia, the Internet and geography textbooks.
1. Carry out further research on the occurrence of the solar and lunar eclipses.
2. Compile a report of your findings.
3. Share your findings in a class presentation.


The characteristics of the Earth

The Earth is one of the eight planets in the solar system. It is the third planet after Mercury and Venus. It is believed that the earth was formed about 4,600 million years ago. It was formed when
hot gaseous material broke away from the sun. When this happened, the denser materials consolidated first. They collected at the centre to form a core. The less dense materials collected around the core to form the mantle and the crust. The crust cooled at a faster rate than both the mantle and the core. It therefore hardened. The interior of the earth still maintains very high
temperatures.
The earth is surrounded by a thin layer of gases that is called the atmosphere. The atmosphere is held into place by gravity.About 71% of the total surface of the Earth is occupied by water. Only 29% is occupied by land.


Elements of the earth



Do this in pairs.
1. Use the Internet and geography textbooks to critically study the components of the earth.
2. Compare them with those of other planets in the solar system.
3. Find out the components that make the earth unique.
The earth is made up of the following.
• The core
• The mantle
• The crust
• The atmosphere
• The hydrosphere

The core

The core of the earth is made of dense material. This material collected during the formation of the earth. The core consists of an outer and an inner core.


The mantle

This part lies between the crust and the core. It consists of hot, dense, semi-solid rock. It is about 2,900 kilometres thick.


The crust

It is the outermost layer of the earth. It is made of a variety of igneous, sedimentary
and metamorphic rocks.

The atmosphere

This is the thin layer of gases that surrounds the earth. It is held onto the earth by the force of gravity. It consists of a mixture of gases like nitrogen, oxygen, water vapour and carbon (IV) oxide.

The hydrosphere

This is composed of all the water on the earth’s surface. The oceans and seas cover 71% of the earth’s surface. This accounts for about 97% of the total waters on earth.



Uniqueness of the earth

The earth is the only planet that is known to support life. This is because it has liquid water
on its surface. The water is in amounts that are conducive to life evolving. The earth has plates that move over an underlying mantle.
It also has an atmosphere. The atmosphere shelters it from the sun’s rays. These attributes make it unique among the other planets.



Do this in groups of three.
1. Go outside the classroom.
2. Identify evidences of the factors that support the Earth’s uniqueness.
3. Suggest ways in which humans can conserve the environment to make the Earth remain habitable.
4 Use the findings of your discussion to make a class presentation.


The shape of the earth

Do this in groups of five.
Your teacher will provide you with whole pumpkins. Follow the instructions given below. After the activity, write down the findings in your note book for class discussion.

1. Cut off the top and bottom parts of the pumpkin. Name the top part North Pole and the bottom part South Pole.

2. Use a thread and ruler to measure the circumference of the pumpkin. Record your findings.


3. Measure the latitudinal distances around the pumpkin, 5 cm from each pole.

4. Determine the middle part of the pumpkin and draw a line using a marker. This represents the equator. Measure its distance from the poles and note down your findings.

5. From your findings, state the similarities and the differences between the two parts of the
pumpkin.

6. Use your findings to describe the shape of the earth.


In the past, the shape of the earth was thought to be flat. Later on, scientific studies showed that it is almost spherical in shape.
However, the shape of the earth does not make a perfect sphere. It is oblate spheroid or a geoid. It is flattened along the polar regions and bulges along the equator. It is therefore not an actual sphere.
The dimensions of the Earth along the equator, the poles and the meridians give a hint about the shape of the Earth.

Evidence to show that the shape of the Earth is not a perfect sphere

(a) The polar diameter (12,722 km) is shorter than the equatorial diameter which stands at 12,762 kilometres.

(b) The circumference of the polar and equatorial areas differ. The circumference at the equator is bigger than that at the polar regions.

(c) There is great gravitational pull at the poles than at the equator. This is because areas along the equator are far from the centre of the Earth.

(d) Modern satellites show that the Southern Hemisphere is slightly larger than the northern hemisphere.


Evidence to show that the earth is not flat

Do this in pairs.
1. Describe the shape of each of the following:
(a) Eggs
(b) Oranges
(c) Watermelon
(d) Football
(e) A square wooden board

2. Write down your points for a class discussion.
3. Which one of the above items perfectly represent the shape of the earth?


The above activity should help you prove that the shape of the Earth is spherical. The evidence listed below show that the Earth is not flat.
(a) Aerial photographs taken using satellites from high altitudes show the earth is round.

(b) The shadow cast onto the moon during the lunar eclipse shows the earth is round.
(c) Several voyages taken around the earth have all proven that the earth is round. Movement on the earth along a straight path in one direction brings you to your starting point from the opposite direction.
(d) Places on the Earth’s surface do not receive sunshine at the same time.
(e) The sun keeps changing its altitude at different times of the day. In the morning and evening, the sun seems to be at a low altitude. At noon, the sun’s altitude is at a high altitude. This is illustrated below:




       Fig 3.47 The sun at various altitudes.


(f) The Earth’s horizon is curved. This is evidenced by approaching ships. The smoke, funnels and mast appear on the horizon, before the rest of the ship is seen from the coast.

(g) The polar star looks bigger at the poles and smaller away from the poles.
All the planets in the solar system are spherical. The Earth being one of the planets has a similar shape.


The size of the earth
Earth is the fifth largest planet in the solar system. It has a surface area of 510 million square kilometres. It is a member of the terrestrial planets and is the largest in the group. It is also the densest planetary body in the solar system. Table 3.2 shows the dimensions of the earth.


Table 3.2 Dimensions of the earth.


Measurement	Kilometres
Equatorial diameter	12,762 km
Equatorial circumference	40,075.16 km
Polar diameter	12,722 km
Meridional circumference	40,009 km
Surface area	510,000,000 km2

Position of the earth in the solar system

As you earlier learnt, the Earth is the third planet in the solar system. It is about 150,000,000 million kilometres from the sun. It lies between Venus and Mars. It is the largest of the four terrestrial planets.



Do this in pairs.
1. Using the Internet, encyclopaedias and other geography textbooks, describe other characteristics of the earth.
2. Write down your findings in your notebook.
3. Present your findings in a class discussion


The Earth’s movements and their consequences

There are mainly two types of the Earth movements.
(a) Rotation of the Earth.
(b) Revolution of the Earth.


Rotation of the Earth on its axis

Do this in pairs. You will require an orange and a sharp stick. You can also use a globe if it is available.
1. Hold the orange in your hand.
2. Pierce the sharp stick through it. Ensure that the stick goes through both ends of the orange.
3. Hold the stick with the orange on hand. Rotate it in a west to east direction.
4. Compare this with the rotation of the earth on its axis.
5. If you use a globe, rotate it to a west to east direction. Observe what happens.


Definition of rotation


Rotation is the act or process of turning around a centre or an axis. The earth is not static. It is always moving round its axis. The earth rotates in an anticlockwise direction from west to east. It rotates at a speed of 1680 kilometres per hour or 28 kilometres per minute.
The earth’s axis is an imaginary line believed to cut across the centre of the earth. It cuts from the North Pole to the South Pole. The earth’s axis is inclined at 23° perpendicular to its orbital plane. The axis has two ends, namely:
(a) North Pole
(b) South Pole.



        Fig 3.48 Rotation of the earth.
The earth’s rotation takes 24 hours in which it is able to complete 360°. This means that
for every 1° , the earth takes 4 minutes. This is calculated practically as shown below.
360°=24 hours

Therefore, the Earth completes one degree in 4 minutes.



The consequences of the earth’s rotation

The rotation of the earth has the following effects.
(a) Day and night.
(b) The rising and falling of ocean tides.
(c) Differences in time between longitudes

(d) The deflection of winds and ocean currents.
(e) Variations in atmospheric pressure over the earth’s surface.
(f) It influences the revolution of the moon round the earth.

Day and night



You will require a torch and a ball or globe.
1. One of you should hold the ball or globe and the other one the torch.
2. The student with the lit torch should focus the light to one spot . You can focus it to the centre of the ball or globe.
3. The student with the ball or globe should rotate the ball in a slow motion.
4. Observe what happens and write it down.
5. Present your findings in a class discussion.


You will observe that the side of the ball facing the light is bright. The other parts facing away from the light are dark.



This is exactly what happens as the earth rotates.
The side of the earth that faces the sun receives sunlight and thus experiences daytime. The opposite side of the Earth experiences darkness in the form of night.


The rising and falling ocean tides

A tide is defined as a rhythmic rise and fall of the sea level. This is caused by gravitational
forces between the moon, the sun and the earth.


When the earth is rotating, areas facing the sun are pulled by the sun’s gravitational force. However, the solid parts of the earth do not positively respond to this force. The mobile elements of the earth respond in particular the hydrosphere or water bodies. It influences the water levels causing sea levels to rise. When these specific areas move away from the sun, the sea levels go
back to normal. These are referred to as solar tides.


Parts of the earth that face the moon at night are subjected to the moon’s gravitational force. This causes lunar tides.
At times, the moon and sun are aligned at the same position in a linear order. At such times, strong tides called spring tides are formed.
The occurrence of tides can be observed at a shore. At high tide, the ocean water rises and covers most of the shore. At the low tide, the water flows back into the ocean. 
Time differences between longitudes Longitudes are imaginary lines drawn on a map from the North Pole to the South Pole. They are geographic coordinates that specify the east–west position of a point on the earth’s surface. Longitudes are sometimes referred to as meridians. They
are measured in degrees east or west of the Prime or Greenwich Meridian. This is a line that is marked 0° up to 180° both to the west and east.


Longitudes are expressed in degrees. They cover 3600 of the globe. The difference
between longitudes is 150 which is equivalent to 1 hour.
The major longitudes are:
(a) Prime or Greenwich Meridian
(b) International Date Line.

How to determine local time using longitudes

The Prime Meridian is important in determining the local time. This is in reference to the usage of other longitudes. Calculation of time is in reference to Greenwich. Therefore, when calculating
time away from the Greenwich Meridian, it is important to know the time at Greenwich.


Example

Calculate the time at Alexandria located
at 30° east when the time at Greenwich is noon.

Solution

Step 1:

Determine the difference in degrees between the two longitudes.
The Prime Meridian and 30°.
0° + 30°= 30° east.



Step 2:

Find the time based on the difference in degrees between the two longitudes. In this case, if the earth takes 360° to make a complete rotation in 24 hours, then:


 360°= 24 hours
15° = 1 hour
15°= 60 minutes
1° = 4 times
Therefore, 30° = 30° X 4 minutes
=120 minutes
Convert the 120 minutes into hours.
1 hour = 60 minutes



Step 3:

Alexandria is located east of Greenwich. This implies that the time there is ahead of that
at Greenwich. Therefore;2 hours + time at Greenwich 
2 hours +12:000 GMT =14:00 hrs (24 hour clock) or 2:00 p.m (12 hour clock)


The time at Alexandra is 14:00 hrs (24-hour clock) or 2:00 p.m (12-hour clock) when it
is noon at Greenwich.



Do this individually.
Determine the time of various places using the longitudes given.
(a) It is 2:00 pm at Greenwich, what is the time at Kinshasa which is located at 15° east?


(b) It is 4:00 am at Greenwich; calculate the time at Mogadishu which is located at 45° east?


The standard time and time zones


The standard time
This is the time recorded by all the countries found in the same geographical region. It is
a time that is agreed by all the countries in a given region. For example, Uganda, Tanzania and Kenya have the same time. Standard time is important for the following reasons:
(a) It helps in making schedules of transport systems.
(b) It helps in creating schedules of meetings.
(c) It gives a country a standard time that it is known for internationally


Time zones
A time zone is a region that observes a uniform standard time. This is important for legal, commercial, and social purposes. Time zones follow the boundaries of countries and their subdivisions. This is because it is convenient for areas close to each other to keep the same time.
Each time zone is 15 degrees of longitude wide (with local variations). The local time is one hour earlier than the zone immediately to the east on the map. There are 24 time zones in the world.


The International Date Line 


As earlier discussed, the longitudes are measured from 0° (Greenwich) to 180° east or 1800 west. International Date Line refers to an imaginary line of longitude on the earth’s surface. It is located at about 180 degrees east (or west) of the Greenwich Meridian. It marks the change from one calendar day to the next. At any moment, there are two days on earth with the same time. A new day begins at midnight on the International Date Line. If one travels across the International Date Line, the date would change either forward or backward.

At 12:00 a.m at Greenwich on Monday, it will be 12.00 a.m on Tuesday across the 180° east longitude. On the other hand, the time at 180° west would be 12:00 a.m on Sunday. In other words, time does not change; what changes is the date. When going to the east, one adjusts the clock by
adding 24 hours to the time. When going west, one adjusts the time by subtracting 24 hours to the time.


The deflection of winds and ocean currents

The earth’s rotation from west to east results in winds and ocean currents changing direction. This change of direction is referred to as deflection. 
Ocean currents are streams of water flowing in a horizontal direction. They are usually associated with seas and oceans.


        Maximum deflection at pole

Fig 3.50 Deflection of winds and ocean currents in the North and South Hemispheres.
Winds and ocean currents change direction to the left in the Southern Hemisphere. They deflect to the right in the Northern Hemisphere.


Variations in atmospheric pressure over the earth’s surface

When the earth rotates, it causes the air at the poles to move towards the equator. As this air crosses latitudes that are becoming wider, it spreads out over a larger area. It creates low pressure at latitudes 60° north and south.

Air moving from the equator towards the poles spreads over latitudes which are becoming shorter. As the surface area reduces, the air molecules contract hence having contact with each other. This builds high pressure at latitudes 30° north and south of the Equator. The earth rotates in an anticlockwise direction. It moves from west to east through 360° in 24 hours. In 1 hour, the earth covers 15°. To go through 1° it takes 4 minutes.


The revolution of the moon round the earth

Do this in groups of three in the library. Use the Internet, encyclopedias and geography textbooks:
1. Find out why the position of the sun keeps changing as the day progresses.
2. Relate this to the rotation of the Earth on its axis.
3. Write down your findings.
4. Share your findings in a class discussion.


The rotation of the Earth round the sun leads to the revolution of the moon round the earth. As the Earth rotates on its axis, it produces a centrifugal force which causes its satellite to move in a circular motion.
This leads to revolution of the moon around the Earth.


The revolution of the earth around the sun



1. Take a globe and rotate it to fully cover 360° in a west to east direction.
2. Observe what happens.
3. Compare this to the revolution of the earth round the sun.


Definition of revolution
Revolution refers to the motion of the earth on its orbit around the sun. The earth revolves round the sun from west to east.
The earth takes one year or 365 ¼ days to complete its revolution round the sun. This happens in a normal year. A leap year occurs once after four years where the earth takes 366 days to complete one revolution. The earth is inclined at an angle of 66½°.


The consequences of the earth’s revolution
The earth’s revolution results in the following.
(a) The occurrence of the four seasons.
(b) Varying lengths of day and night.
(c) Changes in the position of the overhead sun.

                     Fig 3.51 Earth’s revolution round the sun.
The four seasons

Do this in groups of four.
(a) Analyse and discuss the climate of Rwanda.
(b) Note down the rainy and dry periods.
(c) How many climatic seasons does Rwanda experience?
(d) If you lived in Europe, write down the seasons you are likely to experience


Seasons are climatic changes that occur in different zones of the earth. They occur due to temperature changes that result from the earth’s position as it revolves around the sun. The earth’s axis is tilted at an angle of 66½°.
This tilt brings about variations in the sunlight received at different latitude areas on earth. The revolution of the earth also brings variations in the sunlight received at different latitude areas. The seasons are mostly experienced in high and mid-latitude
regions of the world. They are:


      (a) Summer                 (c) Winter
      (b) Autumn                  (d) Spring

On 21st March, the sun is overhead at the equator. This time is the start of the spring season in the Northern Hemisphere. During the same period, it is autumn season in the Southern Hemisphere.
On 21st June the sun is overhead at the tropic of cancer. This time is the start of summer in the Northern Hemisphere. During the same period, there is winter in the Southern Hemisphere.

On 22nd December, the sun is at the overhead position at the tropic of Capricorn.
This is summer time in the Southern Hemisphere and winter in the Northern Hemisphere.

On 21st March and 23rd September the sun is overhead at the equator. During this period,
days and nights are equal. This is called the equinox.
The summer season is characterised by warm to hot temperatures because of the long durations of sunlight.
The winter season is characterised by cool to cold temperatures because nights are longer.
Spring and autumn are short seasons that mark the changes between winter and summer.
The order of seasons is such that autumn comes before winter and spring before summer.
The seasons determine the type of activities that take place at a given time. In winter for example, snow falls covering the ground making it frozen. People engage in indoor activities. Plants also remain dormant throughout winter. However, sports such as skiing and ice skating take place.


Spring time comes immediately after winter. This is when temperatures begin to warm up springing everything back to life. Leaves sprout on trees, grass and flowers begin to grow and hibernating animals become active.
The summer season which follows spring is full of activities. Plants and animals become active. Fruits and grains mature and ripen for harvest before autumn sets in.
In autumn, plants begin to shed their leaves and animals begin to hibernate in preparation for winter.
These four seasons occur in the temperate zones. These are the regions between the
tropics and the Arctic and Antarctic circles.

        Fig 3.52 The four climatic seasons in the Northern and Southern Hemispheres.


Table 3.2: Description of seasons


Season	Description
Winter	• Very low temperatures • Severe cold • Land mostly covered by snow in some areas
Spring	• Occurs after winter • Temperatures begin to increase leading to summer conditions
Summer	• A lot of sunshine • High temperatures
Autumn or Fall	• Occurs when summer is ending • Temperatures start falling and decreasing towards very cold conditions

Task 3.4
1. What is the meaning of the term season?
2. Name the seasons experienced in Europe.
3. On which date(s) is the sun overhead the equator?
4. Mention the date(s) when the sun is overhead at the Tropic of Cancer and Tropic of Capricorn.
5. Explain the meaning of equinox.
The varying lengths of days and nights
The earth’s revolution leads to differences in the lengths of days and nights. During summer, longer hours of sunshine are experienced. Longer hours of darkness are experienced during winter . This means that in summer there are more days of sunshine than darkness. It also means that in winter,
there are more days of darkness than days of sunshine.

For example, in December, hours of darkness increase in the Northern Hemisphere. At the same time in the Southern Hemisphere, hours of sunshine increase. As one goes beyond the Arctic circle 66° north, there are days of total darkness.


Changes in the position of the overhead sun

The sun’s altitude is the height of the sun above its nearest horizon. The sun changes its altitude in relation to the earth’s revolution as seen in Figure 3.52.

           Fig 3.53 Changes in the position of the overhead sun.
Task 3.5
1. List and explain the effects of the earth’s revolution round the sun.
2. Define the following terms:
   (a) axis           (b) tides.
3. What is the difference between standard time and time zone?
4. Give the meaning of International Date Line.
5. What are ocean currents?
6. Differentiate between the earth’s revolution and earth’s rotation.
7. State and examine the effects of the earth’s revolution


Latitudes and longitudes


Do this in pairs.
You will require a globe or a ball, thread of different colours and a ruler.
1. Tie a red thread round the globe or ball. The thread should run vertically from the top to the bottom.
2. Make 24 other vertical runs of thread of different colours round the globe or ball. Ensure that the space between one thread and the next is equal. Use a ruler to obtain exact measurement. You can use sellotape or glue to ensure that the threads stick in place.


3. Get a strand of the red thread that you had used before. Determine the centre of the ball or globe using the ruler. Tie the thread horizontally across the ball or globe.
4. Use threads of a different colours and pass them horizontally round the globe. Ensure that the spacing between one thread to the other is equal. Use the ruler to ensure this. You can use sellotape or glue to ensure that the threads stick in place.
5. Differentiate between the vertical and the horizontal threads.
Latitude
A latitudes is the angular distance of a place north or south of the earth’s equator Latitudes range from 0° at the equator to 90° north or south at the poles. They are measured in degrees, minutes and seconds north or south of the equator. On a map, latitudes are drawn horizontally from west
to east. Lines of latitudes are referred to as parallels.
Distance between lines
The distance on the earth’s surface for each degree of latitude or longitude is about 111 kilometres. This is achieved if you divide the circumference of the earth by 360°.
It is important to note that this distance reduces as you move towards the poles.This is the direction towards north or south of the equator.

          Fig 3.54 A map of the Great Lakes countries showing latitudes and longitudes.
Longitude
A longitudes is the angular distance of a place east or west of the Greenwich Meridian. Longitudes are measured in degrees, minutes and seconds east or west of the Greenwich Meridian. They
are imaginary lines drawn on a map, from north to south. Lines of longitudes are also referred to as meridians. They help us to determine the time of a given place and locations of different places.
Latitudes and longitudes are used together on a map. They help in finding the exact locations of places and features easily. In Activity 3.33 on page 88, the vertical threads that you tied on the globe represent the longitudes. The red middle thread represents the Greenwich Meridian which
is a very important longitude.
The horizontal threads that you tied represent the latitudes. The red thread that you tied across the globe or ball represents the equator. The equator is a very important latitude. When reading the coordinates on a map, remember the following tips.
• Latitude is always given before longitude (49° N 100° E).
• Latitudes are parallel, but longitudes are not.
• Degrees west and south are sometimes referred to as negative degrees (–12° –23° is the same as 12°S 23°W).
• The latitude of a place affects its climate, but its longitude does not.
• Key longitude lines are the Prime Meridian (0°) and the International Date Line (180°).
• Key latitude lines include the Equator (0°), Tropic of Cancer (23° 26’ N), Tropic of Capricorn (23° 26’ S), the Arctic Circle (66° 33’ N) and the Antarctic Circle (66° 33’ S).

Use an atlas to do the following.
1. Distinguish between latitudes and longitudes.
2. Find the location of Kigali City on a map of Rwanda using latitudes and longitudes.
3. Determine the coordinates of the location where you were born on a map of Rwanda.
4. Find the location of Kigali City on a world map using latitudes and longitudes.
5. Present your work to your teacher.


Earlier in this unit, you learnt that the rotation of the earth causes differences in time between longitudes. You learnt how to determine time using given longitudes. This is in relation to the Greenwich Meridian.
In this sub-topic, you will learn how to determine the longitudes of different places. This is done using time in relation to the Greenwich Meridian.
How to determine the longitude of a place using time

It is also possible to determine the longitude of a given place using time.

Do this individually. Make reference to a globe, a map or an atlas.
1. Determine the longitude of Taipei in Taiwan whose local time is 8:00 p.m when the local time in London is 12 noon.
2. What is the longitude of Nairobi whose local time is 8:00 a.m, when it is 5:56 a.m in Accra?
3. Mr. Kamari took a flight from London at 12 noon to Honiara Island that is located at 159°E. What time did he arrive at Honiara?
4. It is noon at Manaus in Brazil which is situated at 60°W. What would be the
time in Dhaka located at 90°E?
This is done in reference to the time at Greenwich and the specific area. Study the
example shown below.
Example
Calculate the longitude of place X whose local time is 10:00 p.m when the local time
at Greenwich is 1:00 p.m.
Step 1:
Find the difference in time between two longitudes.
Time at Greenwich is 1:00 p.m.
Time at location X is 10:00 p.m
1:00 p. m - 10:00 p. m = 9 hours
Step 2:
For every hour, the earth rotates through 15°. Therefore, in 9 hours the earth will have
rotated through 15 × 9 =135°
Step 3:
The time at Greenwich is behind that of location X. This means that location X is east
of Greenwich by 135°. Therefore location X is 135° east of Greenwich.


Did you know?
• A huge part of the universe is made up of things we cannot see.
• The solar system was formed approximately 4.6 billion years ago.
• The formation of the solar system was by the collapse of a giant cloud.
• 99.86% of the solar system’s mass is found in the sun.
• A person would weigh much less on the moon than on earth.

1. (a) What is the universe?
(b) List the components of the universe.
2. Using examples, distinguish between a constellation and a galaxy.
3. Describe the composition of the solar system.
4. List four characteristics of the moon.
5. (a) Name two earth movements.
    (b) Discuss the consequences of the rotation of the earth.
    (c) Discuss the consequences of the revolution of the Earth.
6. Distinguish between a latitude and a longitude.
7. With the use of well-labelled diagrams, describe the main types of eclipse.



Planet	Key features
Mercury	• It is the smallest planet. • It is the nearest planet to the sun. • It completes its revolution in 88 days. • It is moonless. • It is about 70 million kilometres from the sun when it is at its farthest. When it is closest to the sun , it is at 47 million kilometres away.
Venus	• It is slightly smaller than planet earth. • It is one of the brightest planets in the universe. • It is almost similar to the earth. • It is moonless. • It is 108.9 million kilometres from the sun. • It takes 225 days or 0.165 Earth years to complete its revolution around the sun.
Earth	• It is the third planet from the sun. • It is the only planet known to support life . • It is 146 million kilometres from the sun. • It has one moon. • It takes 365 days to complete a revolution around the sun.
Mars	• It is slightly cooler than other planets. • It is 228 million kilometres from the sun. • It has 2 moons. • It takes 686.971 Earth days to complete a revolution around the sun.
Jupiter	• It is the largest planet. • It has 63 moons. • It takes 12 Earth years to complete one revolution round the sun. • It is 779 million kilometres from the sun.
Saturn	• It has a ring around it making it unique. • It has 62 moons. • It is 1.4 billion kilometres from the sun. • It takes 29.4 Earth years to complete a revolution around the sun.
Uranus	• It is the 7th planet in the universe . • It is the 8th 2.5 billion kilometres from the sun. • It has 27 moons. • It takes 84.3 years to complete a revolution around the sun.
Neptune	• It is the 8th planet from the sun. • It is 4.5 billion kilometres from the sun. • It has 13 moons. • It takes 164.79 Earth years to complete a revolution around the sun.