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Sunday, March 24, 2019








3.  Description of  the internal structure of the earth and its well labeled diagram.

Earth is the planet we live on, the third of eight planets in our solar system and the only known place in the universe to support life.

- The  internal structure of the earth includes the crust, mantle and the core.



This is the thinnest layer and forms the outer shell on which life exists. It varies in thickness from just 1km in some places to more than 80 kilometres in others. It is known as Lithospere, It is largely composed of igneous rocks. Other types of rocks also exist as a result of changes on the earth’s surface. The rocks are crystalline, hard and brittle. Bacause of being brittle they tend to break when subjected to stress or forces especially the compressional forces. The crust also consist of two layers are sial and sima layers.

a) Sial
Is the outer layer of the crust which rich in silica and Aluminium minerals. The sial for the basis of the continent. The presence of silica and aluminium minerals collectively form SIAL layer.

a) Sima  
Is the layer which found beneath the sial. It is the inner layer of the crust which separated from sial layer by the zone called Conrad discontinuity line. The sima layer is composed by silica and magnesium. It forms the basis of ocean floor. 
Note: Sial and sima layer together forms the crust.

2. MANTLE                                                                                                    
Mesosphere or mantle which found between the crust and core. It lies beneath the crust. It separated from the crust by the zone of separation called Mohorovic discontinuity or moho. It extends downward to about 2900 km (1800 miles) where the temperatures may reach about 50000c. It consist of pale green minerals called Olivine (Ferromagnesium silicate) in form of ultra basic rock.It consists of lower and upper mantle. The upper mantle is rigid and crust to form a large layer called lithosphere.

The lower mantle is less rigid and forms the moltern layer within the earth’s interior called asthenosphere. Asthenosphere is the molten layer layer which responsible for the balancing movement of the earth’s material called isostatic readjustment. Asthenosphere has been investigated is found between 100 to 200 km below the upper surface.


The core is the innermost zone of the internal structure of the earth. It is also called barysphere or centrosphere. It has diameter of about 6900 km (4300 miles) density of about. The core is also classified into two parts i.e. the outer and inner core. It separated from the mantle by zone of separation called Gutenberg discontinuity.

1. The Outer Core
It is liquid in nature due to high temperature of up to 37000c, and consist of nickel and iron (NIFE) . It is estimated to be 2100 km with density of about 10.5 gms/cc.

2. The Inner Core is thought to be solid in nature because of high pressure exerted from different parts toward the center - It composed mainly by iron. It has diameter of about 2600 – 2700km. (1600 – 1700 miles)

Internal Structure of the Earth

4. (a) 
 Potato production (“000”)


A compound bar graph to show the production of Irish potatoes in the three villages.

(b)  Three advantages of the compound bar graph are

       (i) It is easy to read and interpret as the totals are clearly shown. 

       (ii) It gives a clear visual impression of the total values.

       (iii) It clearly shows the rise and fall in the grand total values.

  Two disadvantages of the compound bar graph are

       (i) The graph is very difficult to construct and interpret.

       (ii) It is not easy to represent a large number of components as this would involve very long bars with many segments.

(c) 0ther methods which could be used to present the data provided in the table are comparative bar graph, divergent bar graph, group line graph, divergent bar graph and compound line graph.

5. (a)  An interview  is the verbal communication/interaction between the interviewer and interviewee, designed to list the information, opinions and feelings they have on their own. It can be through by two ways - Face to face interview or telephone interview.

(b)  Five things to be adhered to for a researcher to have a successful interview are

       (i)  Create friendly atmosphere where two people can talk easily.

       (ii)  Maintain warmth and friendliness. It enables respondent to express in detail their thought and feelings.

       (iii)   Be neutral in note and don’t suggest any answer.

       (iv)   Instill confidence and trust to the respondent by assuming his/her information given would be confidential.

        (v)  Explain briefly the purpose of the interview.

6. (a) (i)  Chain survey is the surveying method in which linear measurements of an area are taken.

         (ii) Four principles of chain survey are

·         Stations should be established first by placing ranging rods (later by pegs if permanent is required) after preliminary reconnaissance survey of the site has been done.

·         Obstacles, steep and uneven slopes should be avoided as far as possible.

·         The triangles should have angles lying between 30° and 120° so as to given clear intersection and check lines must be provided for all independent figures.

·         Field notes should contain a free hand sketch of the area to be surveyed and a neat booking of measured distances.

  (b)  One reason for each of the following are

         (i) Ranging pole has a pointed metal end because it used formarking out key points for measuring.
         (ii) Note book is important during field study because it used for the recording of work done in the field.

         (iii) Back bearings are taken during compass survey because it used to identify the location of an object.
          (iv)  During surveying, measurements are called back by the booker because booker need to record correctly measurements without contain any errors during surveying.

7. (a) Two ways that have been used to show relief on the map are

           (i) Contour and form lines.
           (ii)  Trigonometric Station.

     (b) Relief section to connect Nyabubele Hill at 383834 and Bungwe Hill at 430825.

     (c)  To measure the length of the all­weather road in km from grid reference 315844 to 443940 using a sheet of paper.

               By using a piece of paper the map distance of all­weather road is 32.8Cm.

               Scale on map = 1:50000
               Change. 1:50000 into kilometers.

                1km  = 100000cm
                    X   = 50000cm

         100000x = 50000x1

                      x = 50000/100000

                      x =1/2 km (one a half)

    So.        1Cm = 1/2 km
                  32.8= X

                       X=32.8x 1/2
                       X= 16.4 km

  Therefore length of the all­weather road is 16.4 km

    (d) The bearings of Chabulongo Hill at 367917 to a school at Nyamahuna 349818 is 190° SSW

8. Carefully study the photograph given below then answer the questions that follow:

a) Name the type of photograph 
    Low Oblique Photograph due to the following reasons: 
    - The image on the photo shows both top and side views  
    - Foreground objects look larger than middle and background
    - The horizon is not easily seen at the backward of the photograph

b) Describe the relief of the area  
    Relief of the area is:        
    - Mountainous areas  
    - Highlands with various hills at the backward

c) Giving two reasons, describe the scale of production of the crop in the photograph 
      Small Scale Agriculture   
      - Size of the farm, the area of the farm look small    
      - More than one crop grown in the farm as it is seen at the backward

d) Explain two uses of the crop (maize) in the photograph
    - Providing food to the human beings   
    - Feeding animals like pigs, cattle and poultry
Corn silk (maize long shiny fibers) is used for bladder infections, inflammation of the urinary system, inflammation of the prostate, kidney stones, and bed wetting. 
It is also used to treat congestive heart failure, diabetes, high blood pressure, fatigue, and high cholesterol levels.

e) Describe three conditions necessary for the production of the crop  
    - Moderate rainfall of about 896 mm especially in the growing period   
    - Temperature of about 18°c
    - Soilthe best suitable soil for maize is deep and rich soils of the sub-tropics

9. A cash crop is an agricultural crop which is grown for sale to return a profit

    Cash cropping in the United States rose to prominence after the baby boomer generation and the end of World War II. It was seen as a way to feed the large population boom and continues to be the main factor in having an affordable food supply in the United States.

    Six contributions of cash crops production of the economy of United States of America are

       (i)  Availability of land in U.S.A
       (ii) Availability of capital in U.S.A

       (iii) Availability of labour in U.S.A

       (iv)Supply of market

       (v)  Availability of transport and communication network in U.S.A

       (vi)Availability of water supply in U.S.A

10. Rufiji river basin is a river basin found in Tanzania which the government of Tanzania organized the development of Rufiji river basin to support economic activities of the people.

      Six potentials of the Rufiji river basin are

        (i)  It has promoted the market for the Hydro Electric Power (HEP) from Kidatu power plant.

        (ii)  It control floods.

        (iii) The scheme has stimulated the development and maintenance of the railway lines and roads.

        (iv) It has lead to the creation of employment opportunities in the valley.

        (v)  It has promoted living standards of people through employment.

        (vi)  The development of villages and towns, for example new towns like Kidatu,   Makambako and Mikumi.

11. Death rates is the ratio of total deaths to total population in a specified community or area over a specified period of time. The death rate is often expressed as the number of deaths per 1,000 of the population per year. It is also called fatality rate.
       Five reasons for decreasing death rates in many parts of the world are

       (i) Improvement and expansion of health services such as building of new hospitals and expansion of immunization programs.

       (ii)  Family planning programs which have led people to bear few children they can raise.

       (iii)  Improvement of agriculture which has led to increase in food production.

       (iv)  Improvement of transport and communication systems which led to easy distribution of food from areas with surplus to areas with food deficit hence reducing death due to famine.

        (v)  Increase in awareness of importance of personal hygiene.

12. A settlement is a place where people live. A settlement may be as small as a single house in a remote area or as large as a mega city (a city with over 10 million residents), settlement may be permanent or temporary.

      Six factors affecting growth of settlements in Africa are

        (i) Availability of water example places such as Rungwe in Mbeya which has plenty of water have high growth of settlement while areas such as Longido which is arid has low growth rate of settlement

        (ii) Availability of land for agricultural activities For example areas along Kilimanjaro slope which is fertile due to volcanic soil have high growth of settlement compared to areas such as Mpwapwa which is infertile due to soil erosion which low growth rate.

        (iii) Relief of the area

people prefer in areas which are have gentle slopes and tend to avoid settling in areas which have steep slopes due to difficult in establishing infrastructure and thin soil found in the steep slopes. Also people tend to avoid settling in flat areas susceptible to flooding. For example in Katumba Songwe in Kyela  people avoid to settle due to floods from river Kiwira.

        (iv) Availability of social services

people prefer to live in areas which have social services such as education, water and electricity and avoid settling in areas which lack social services. For example many rural areas in African continent low settlement growth rate  due lack of social services while urban areas such as Dar es salaam have high settlement growth rate due to abundance of  social service.

        (v) Climatic condition

areas which have adequate rainfall tend to have high growth of settlement due to high agricultural production while areas which experience low rain fall tend to have low growth of settlement due to shortage of water and poor agricultural production.

        (vi) Government policy

government can affect the growth of settlement by forcing people to settle in certain area or persuade people to settle in certain area by supplying social services and other incentives. Also government policy affect settlement growth through town and land use planning. For example there has been a rapid growth of settlement in kinyerezi area on the outskirt of Dar es salaam city due to government decision to allocate that land to settlement and supplying social services.