Physical Environment - Class 8 Social Studies Revision Notes

• Physical Environment
  
  • Types of Environment
• Map Reading And Intepretation
  • Elements of a Map
    • Use of Elements of a Map
  • Map Reading
  • Features That Can Be Interpreted From a Map
    • Human Activities Commonly Found in a Map
    • Features on a Map That Represents Administration
    • Features That Show Drainage Systems on a Map
  • Human Settlement on the Map
    • Types of Settlement
  • How to Identify Functions of a Town on a Map
• Physical Features
  • Effects of Physical Features of Human Activities
  • Negative Effects of Physical Features
• Climate
  • Traditional Methods of Observing Weather
  • Observation, Measurement and Recording of Weather Elements
    • Wind
    • Air Pressure
    • Rainfall
    • Temperature
  • Factors Influencing Climate Change
  • Impact of Climate Change on Human Activities
• Soil
  • Major soil types in Kenya
  • Characters of types of soil
    • Volcanic Soil
    • Clay(Black Cotton) Soil
    • Sandy Soil
    • Loamy Soil
    • Alluvial(Young) Soil
  • Major causes of soil erosion
  • Effects of Soil Erosion on Human Activities
  • Soil Conservation Measures

 

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Physical Environment

What is Environment?

The things around us or in our surrounding make up the environment.
Examples

1. Trees
2. Animals
3. Water etc.
4. Grass
5. Rivers
6. Buildings
7. Birds

Types of Environment

1. Natural environment
   These were things that were made by God. E.g Mountains ,Lakes, Rivers, Vegetation etc.
2. Human environment
   These are things made through man`s efforts e.g Dams, buildings, roads, etc.
3. Physical environment
   The non – living part of the environment which consists of Soils, air, rocks, water, hills, mountains, rivers and lakes form the physical environment.

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Map Reading And Interpretation.

A map is a drawing on a flat surface that represents a whole part of the earth.

Elements of a Map

Elements of a map helps a reader to understand the information on a given
map.
The main element of a map are:

1. Title
2. Key
3. Compress
4. Frame
5. Scales

Uses of Elements of a Map

ELEMENT	USE(S)
Title	It is the name of the area represented by the map and the information it contains.
Frame	It shows the extent of the area represented by a map. It is also known as the borderline of a map.
Key	It contains the signs or the symbols which represents various features represented in a map.
Compass Direction	Helps to find direction of a position or features in relation to others
Scale	Helps the map reader to know the actual distance on the earth`s surface as reprtesented on the map

Map Reading

This is the ability to read, understand, and interpret information given on a
map.
Symbols of a map contained in the key should be fully understood and
interpreted correctly.

Features That Can be Interpreted From a Map

1. Relief and drainage patterns in the area.
2. Human and economic activities in the area.
3. Types of climate experienced in the area.
4. Transport facilities in the area.
5. Vegetation found in the area.
6. Human settlement pattern in the area.
7. Administrative boundaries in the area.
8. Social activities (services) found in the area.

Human Activities Commonly Found in a Map

Economic activities are the objectives that people carry out in order to get
income (money).
Examples

Economic activity	Evidence
Crop farming	Crops e.g coffee, tea, sisal, sugarcane, cotton, pyrethrum, wheat and cotton ginneries, factories, plantations, mills.
Forestry	Presence of saw mill, timber yard, forest guard, posts.
Livestock farming	Presence of cattle dips, butcheries, slaughter houses, cattle boma, dairy farms, creamery, veterinary offices, ranches, beef factories, trough.
Tourism	Presence of national parks, game reserves, camping sites, picnic sites, hotels, lodges, museums, pre-historic sites.
Fishing	Presence of fish ponds, fishing villages, a fish factory, fish traps, fisheries departments.
Mining	Presence of quarry, symbols of mines, name of the mine like Salt mining works.
Trade	Presence of markets, shops, trade license office, trading centers, warehouses, stores, towns, custom offices
Industry	Manufacturing factories, bakeries, refineries, rolling mills, ginneries, saw mill.
Transport and communication	Roads, railway lines, airports, airstrips, ports, post offices, telephone lines.

Social Activities on a Map

1. Religious activities : Churches, mosques, temples, shrines.
2. Medical services : Clinics, dispensaries, health centers, district hospital, provincial hospitals and National hospitals.
3. Education: Schools, colleges, polytechnics, universities.
4. Recreation : Cinema halls, Social halls, play grounds, theatres.

Features on a Map That Represents Administration

1. Government offices e.g. Assistant chief`s offices or chief`s camp.
2. Police post.
3. Administrative boundaries.

Features That Show Drainage Systems on a Map

Drainage features	Interpretation
Boreholes and wells	Areas of low and unreliable rainfall.
Permanent rivers	Areas that receive high rainfall.
Seasonal rivers	Areas of low rainfall.
Waterfall	Areas of hard and soft rocks.
Many swamps	Clay soils, poorly drained areas.
Tributaries	Direction of the flow of the river

Human Settlement on the Map

Settlement is the pattern of population distribution in an area shown by dots and black shades.

Types of Settlement

How to Identify the Functions of a Town on a Map

Functions of the urban centre	Identification symbol
Administrative centre	Government offices, chief`s camp, law courts, police posts, prisons, administrative boundaries.
Commercial centres	Shops, markets, road functions, trading centers, towns, cities, warehouses, stores, trade licensing offices.
Social centres	Schools, colleges, mosque, churches, theatres, sports, grounds, hospitals, cinema halls.
Mining centres	Mining works, quarries, named mines.
Agricultural centres	Food stores, Large estates, or plantations, processing factories, dairy, creameries, cattle ranches, cattle dips, dairy farm.

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Physical Features

These are things we see on the surface of the earth. They include natural physical features and man-made(human)

Natural features: Mountains, plateaus, hills, plains, valleys, rivers, lakes, etc.

Man-made: dams, lakes etc.

The Effects of Physical Features on Human Activities

Physical features	Human activities
Lakes, oceans, rivers	Fishing-( food income) Electricity production Supply of water   Transport-income Sporting activities
Ocean, lakes
Snow capped mountains	Tourism
Rift valley
Beautiful water falls
Sand beaches
Hot springs
Homa hills(limestone)	Mining	Minerals
Lake Magadi(Soda ash)		Income
Indian ocean(salt)		Creating employment

Negative Effects of Physical Features

1. Flooding.
2. Water borne diseases e.g. Malaria and Bilharzia.

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Climate

Traditional Methods of Observing Weather

1. Observing the sky
   • Thick grey clouds: rain.
   • Certain stars arranged in a particular manner: dry spell.
2. Phases of the moon
   • New moon: rain.
   • Full moon: It would rarely rain.
3. Appearance of the rainbow
   • Some communities believed that it would not rain if the rainbow appears in the sky when it was about to ran
4. Condition of the environment
   • Very hot and humid: Coming of the rain.
5. Blowing of wind
   • Strong winds blowing after a dry weather: Showed the coming of the rains
   • Wind blowing during the rainy season: Meant chasing away of the rain to give way to a dry spell.
6. Behavior of birds:
   • Happy and playful birds in the sky would signify the coming of rains.
7. Trail of ants: Signified the coming of rains.
8. Croaking of frogs: Signified the coming of the rain.
9. Appearance of toads: Signified the coming of the rains.
10. Behavior of cattle: Coming of the rains(showing happiness by jumping up and down)
11. Shedding of leaves after a rainy season: This Signified a dry spell.

Observation, Measurement and Recording of Weather Elements

What is meteorology?

It is the science of observing and measuring weather elements.

1. Wind

   
   
   
   
   

2. Air Pressure

   
   
   
   

3. Rainfall

   
   
   The raingauge is dug into the ground as shown above.
   
   

4. Temperature

   
   
   1. Minimum and maximum thermometer
      
      
      Used to measure temperature for the day.
      It is U-shaped.
      Minimum records coldest temperature.
      Maximum records warmest temperatures.
      
      
   2. Single-tube thermometer
      
      
      Used to measure coldness and / or hotness of the air.
      It is marked in o Celsius.
      It may contain alcohol or mercury.

Factors Influencing Climate Change

Climate change is the occurrence of unexpected change of climatic condition in a particular region. The main factors influencing climate change include:-

1. Deforestation
   Cutting down of trees leads to reduced amount of rainfall.
   It creates desert – like conditions in the areas previously occupied by forests.
   It contributes to increased carbon dioxide in the atmosphere.
   
   
2. Afforestration and re-afforestration
   Planting of more trees will increase the amount of rainfall.
   Both afforestration and re-afforestration reduce soil erosion and evaporation, hence protecting water catchment areas.
   
   
3. Industrialization
   Heat and smoke from industries cause pollution and increase temperature in the atmosphere.
   
   
4. Excess use of chemicals
   Such as fertilizers causes atmospheric change due to the gasses they produce.
   The growing of rice under irrigation contributes to warming of the atmosphere. The rice in water release a gas known as methane, which
   contributes to global warming. The same applies to the use of fertilizers.
   Global warming is also caused by the use of petroleum to run vehicles .Machines give off a gas known as carbon monoxide, which makes
   the air warmer.
   
   
5. Clearing of vegetation for agriculture
   This exposes the soil to agents of soil erosion.
   
   
6. Building of dams
   Human-made lakes which form behind the dam modify the climate.
   
   
7. Ocean currents
   These leads to temperature change along the coastal areas.

Impact of Climate Change on Human Activities

Positive effects

1. Increase in food production due to increased amount of rainfall
2. Increased generation of hidro-electric power due to high rainfall.
3. Promotion of fishing due to adequate water in rivers.

Negative effects

1. Low agricultural production due to lack of rains.
2. Displacement of people due to floods.
3. Global warming as a result of general increase in temperature worldwide.
4. Increase of water-borne diseases such as malaria and bilharzias due to increased rains.
5. Damage of transport systems e.g. roads.
6. Migration of people migration of people to favourable climate.
7. Death of human beings.

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Soil

Soil is formed through a process called weathering. Soil contains:

1. Organic matter
2. Rock particles
3. Humus
4. Air
5. Minerals
6. Water
7. Living organisms

Major Soil Types in Kenya

1. Volcanic soils.
2. Clay (black cotton) soil.
3. Sandy soil.
4. Loamy soil.
5. Alluvial (young) soil.

Characteristics of Types of Soil

Volcanic Soil

1. Red in colour.
2. Deep fertile and well-drained.
3. Occur in layers.
4. Medium – sized soil particles.
5. Mainly found in the highlands.

Clay( Black Cotton) Soil

1. Small – sized particles.
2. Dark in colour
3. Deep and fertile
4. Poorly drained.
5. Muddy and sticky during the rainy season.
6. Big cracks during dry seasons.

Sandy Soil

1. Large soil particles.
2. Shallow and dry.
3. Contains a lot of air.
4. Water seeps through them fast.
5. Low water retention capacity.
6. Loose nutrients mainly through leaching.

Loamy Soil

1. It has a mixture of small, medium and large soil particles.
2. It retains a reasonable amount of water fertile, deep and well drained.
3. Appears in different colours e.g. light grey, dark brown and dark grey.

Alluvial (Young) Soil

1. They are found in river valleys and flood plains.
2. They are made of slits.
3. Soil particles are of medium size.
4. Have a smooth texture.
5. They are deep and fertile.

Major Causes of Soil Erosion

Soil erosion is the natural displacement of soil from the original place of formation to another by agents of erosion like wind, water and human beings.

The major causes of soil erosion are as follows:

1. Deforestation- Cutting down of trees which exposes the soil to agents of soil erosion.
2. Overstocking- Keeping large herds of livestock beyond the capacity of land leading to overgrazing
3. Overgrazing-Livestock grazing on all pasture (vegetation) leaving the ground bare.
4. Monocropping-Growing of one type of crop on the same peace of land year after year exhausts soil fertility.
5. Over-cropping-Growing of many different types of crops which compete for nutrients. The soil finally becomes loose and infertile
6. Up-the-slope (hill) cultivation-This promotes gulley erosion.
7. Mining and quarrying-Results to displacement of soil.

Effects of Soil Erosion on Human Activities

1. Destocking (reducing the number of livestock on the farm)
2. Application of fertilizers to the soil in order to increase its fertility.
3. Introduction of afforestration and re-afforestrationprogrammes
4. Promotion of agriculture in the flood plain where fertile soil (alluvial) is deposited.
5. Adoption of good farming methods to reduce soil erosion.
6. Additional expense to the government in building dams, dykes and canals.

Soil Conservation Measures

1. Afforestration :
   Planting of trees.
2. Re- afforestration:
   Planting of trees where they had been cut down.
3. Agro-forestry:
   Planting of trees together with crops.
4. Crop rotation:-
   Growing of different crops on the same peace of land in alternate planting seasons.
5. Mulching: The covering of the bare ground with grass to prevent moisture loss.
6. Cover cropping:
   Planting of perennial crops like coffee and bananas together with food crops likepotatoes, beans and maize.
7. Construction of gabions:
   Pilling up of stones in iron cages to prevent further movement of soil downhill.
8. Terracing:
   Making of horizontal steps on sides of hilly areas.
9. Fallowing:
   Leaving the land idle for some time in order to retain its fertility.
10. Creation of cut-off- drainage:
    This is the digging of trenches to divert water from hill tops
11. Controlled grazing:
    This is done by subdividing land into paddocks.
12. Use of fertilizers and manure:
    This helps the soil to regain its fertility.
13. Contour ploughing:
    This is ploughing of farm across the land guarded by the contours.

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