NYUMBA: FORM THREE - GEOGRAPHY DIRECTORY

FORM THREE - GEOGRAPHY DIRECTORY

SUBJECT MATTERS TO COVER

Structure of the earth
The earth’s crust, mantle and core
Types of rocks of the earth’s crust
Simplified geological time scale
Forces that affect the earth
Forces causing earth movements
Internal forces
Radial/vertical or lateral/horizontal movement
Vulcanicity
Earthquakes
External forces
Mass wasting
Weathering
Erosion and deposition by water, ice, wind and wave action
Artificial forces
Soil
Soil formation
Soil composition and properties
Soil profile and characteristics
Simple soil classification
Soil erosion
Elementary surveying and map making
Meaning and types of survey
Chain survey
Map reading and interpretation
Concept of map reading
Reading and interpreting topographical maps
Photograph reading and interpretation
Types of photographs
Reading and interpreting photographs
Application of statistics
Concept of statistics
Simple statistical measurement and interpretation

1. STRUCTURE OF THE EARTH

THE EARTH’S CRUST, MANTLE AND CORE

ORDER OF LAYERS :

- Lithosphere - Contains the crust

- > Mohorovic Discontinuity - Boundary between crust and mantle

- Mantle - Contains the Asthenosphere

- > Gutenberg Discontinuity - Layer of rocks between mantle and core

- Core (Barysphere) - Contains inner and outer core

- Sial and sima are the rocks that make up the outer crust of the Earth

Water Table

- Is the level at which the groundwater pressure is equal to atmospheric pressure and is the upper limit of the saturation of water in a saturated rock

Asthenosphere

- Is the region of the upper mantle of the Earth and balances the movements of Earths materials

Barysphere (Core)

- Scientific name for the core, made up of iron and nickel

Conrad Discontinuity

- Is the border between the upper continental crust and the lower one (sial and sima)

Core

- Interior layer of the earth which is subjected to great heat and pressure

Gutenberg Discontinuity

- The layer of rocks which separates the mantle from the core

Hydrosphere

- Is the combined mass of water found on, under, and over the surface of planet

Lithosphere

- The hardest part of the Earth’s crust (Litho means rock), geographical name of the crust

Mohorovic Discontinuity

- Is the boundary between the Earth's crust and the mantle

Sial

- Part of the Earth forming the upper part of the crust or continental blocks

Sima

- The lower part of the Earth’s crust

TYPES OF ROCKS OF THE EARTH’S CRUST

Conglomerate

- Is a rock consisting of finer-grained materials that have become cemented together

Igneous Rock

- Is formed through the cooling and solidification of magma or lava

Metamorphic Rocks

- Are formed by the transformation of a rock by pressure and heat inside the Earth

Sedimentary Rocks

- They are usually found in layers, important minerals can be found there, some are deposited by wind; they can be formed organically, chemically, or mechanically

Shale

- A sedimentary rock composed of rounded gravel-sized particles

Examples of metamorphic rocks

- Granite, slate, marble and gneiss

How sedimentary rock is formed

- Formed by cementation and compaction of sediments arranged in layers by deposition

Features of sedimentary rocks

- Usually found in layers, contain important minerals, can be deposited by water or wind, are formed organically/mechanically/chemically

Economic importance of rocks

- Provide building material, used for industry, formation of soil, storage of underground water, provides fuel (coal), manufacturing of cement, salt extraction, decoration in houses

Economic significance of sedimentary rocks

- Contain building material, used as decorative material, provide energy (coal), production of cement, formation of features in karst regions

- Quartz is a compound element of silicon and oxygen

- Granite and basalt are examples of igneous rocks

- Marble is metamorphized limestone

- The three main groups of rocks on the surface of the earth are igneous sedimentary and metamorphic and are classified according to how they were formed

- Igneous rocks are formed when molten rocks from the mantle cool and solidify

- Clay is classified as an impermeable rock

Simplified geological time scale

Order of time periods of the geological time scale:

Oldest

1. Paleozoic - Primary period

2. Mesozoic - Middle period

3. Cenozoic - Modern period

Youngest

Cenozoic Era

- The most recent of the three classic geological eras and covers the period from 65.5 million years ago to the present following the Mesoic Era

Geological Time Scale

- Is a chart which is used to date rocks to understand how landforms were created

2. FORCES THAT AFFECT THE EARTH

Forces causing earth movements

Internal forces

Internal forces operating in the Earth

- Diastrophic forces

Radial/vertical and lateral/horizontal movement

Features caused by faulting

- Formation of rift valleys (graben), horsts, plateaus, basins, block mountains, fault scarps, tilt block landscape, changes drainage and causing of earthquakes, occurrence of springs

River Valley (Graben)

- Is a depressed block of land bordered by parallel faults. A graben is the result of a block of land being downthrown producing a valley with a distinct scarp on each side. Graben often occur side-by-side with horsts

Horsts

- Is the raised fault block bounded by normal faults or graben. A horst is formed from extension of the Earth's crust. The raised block is a portion of the crust that generally remains stationary or is uplifted while the land has dropped on either side

Plateau

- An extensive elevated region with a gentle undulating surface with a uniform summit level

Spring

- Is a natural occurrence where water flows to the surface of the earth from below the surface. Thus it is where the aquifer surface meets the ground surface. Forms from a dyke cutting across a layer of permeable rock

Aquifer

- A natural outflow of water from the surface rock

Artesian Aquifer

- Is a confined aquifer containing groundwater that will flow upward through a well, called an artesian well, without the need for pumping

Types of earth movements (caused by either compressional or tensional forces)

- Vertical movements, lateral movements (orogeneses)

Types of folds

- Symmetrical, asymmetrical, over fold

Symmetrical Fold

- A fold produced with limbs of similar nature

Asymmetrical Fold

- A fold where one limb is steeper than the other, they are not similar

Overfold

- Fold formed when compressional forces push one limb of an asymmetrical fold over another

Types of faults - Normal faults, reverse faults, tear (transformation, shear) fault

Normal Faults

- Produced by tensional forces

Reverse Faults

- Caused by compressional forces

Tear Fault

- A vertical fracture produced when two blocks slide against one another

Examples of fold mountains

- Rocky mountains, Appalachian mountains, Alps, Andes, Atlas, Himalayas

How a graben (rift valley) forms

- Is formed when faults between two rocks sink down due to either compressional or tensional forces

Anticline

- Is a fold that is convex up and has its oldest beds at its core

Block Mountains

- Are formed when large areas of bedrock are widely broken up by faults creating large vertical displacements of continental crust

Compression Forces

- Causes a wrinkling of the Earth’s surface due to forces pushing towards each other

Exfoliation Joints

- Are surface-parallel fracture systems in rock often leading to erosion of concentric slabs

Fault

- Is a fracture in the crust due to stress or strain associated with rock displacement

Faulting

- Is the fracturing of the crust to form faults

Folding

- Is when one or a stack of originally flat and planar surfaces are bent or curved

Lateral Forces

- When two forces act away from each other laterally

Joint

- Is a crack in the rock due to stress but is not associated with rock displacement

Orogeny

- Refers to forces and events leading to a severe structural deformation of the earth's crust due to the engagement of tectonic plates

Range

- Chain of mountains bordered by highlands or separated from other mountains by passes or valleys

Set of fault types

- Normal fault, reverse fault, tear (symmetrical) fault

Syncline

- Is a downward-curving fold, with layers that dip toward the centre of the structure

Tectonic Plates

- Is a scientific theory which describes the large scale motions of Earth's lithosphere

The difference between faults and joints is that joints have no associated displacement

Fold mountains are caused by compressional forces

VULCANICITY

Features with volcanicity

- Caldera, craters, dyke, laccoliths, plug dome, solfatara, phacolith, lopolith

Caldera

- A feature formed as a result of a violent volcanic eruption and is shaped like a large basin or depression on the top of a volcano

Dyke - A vertical feature formed out of the solidification of magma within the Earths crust, forms across a bedding plane of bedrock

Laccolith

- Is a sheet igneous intrusion that has been injected between two layers of sedimentary rock

Lopolith

- Is a large igneous intrusion which is shaped like a lens with a depressed central region

Phacolith

- Lens-shaped strip of igneous rock formed if magma solidifies along anticlines or synclines

Solfatara (Fumarole)

- Is an opening in the Earth’s crust near volcanoes which emit steam and gasses

Features of intrusive vulcanicity

- Dyke, sill, laccolith, Lopolith, Phacolith, batholith

Sill

- Is a flat sheet intrusion that has intruded between older layers of sedimentary rock, beds of volcanic lava, forms along the bedding planes of bedrock

Batholith

- A large mass of solidified rock formed when magma cools in the heart of mountain ranges

Major extrusive volcanic features

- Caldera, crater, shield volcano, crater, ash and cinder cone (scoria cone), composite cone (strato-volcano), volcanic plug (plug dome volcano), acid lava cone

Crater

- A depression formed on the summit of the cone after the plug has been blown off

Shield Volcano

- A broad domed lava cone with gently sloping sides

Volcanic Plug

- The solidified volcanic feature within the vent that prevents an eruption

Ash and Cinder Cone

- A cone shaped accumulation of rock fragments around a vent

Composite Cone

- A large cone with alternate layers of fragments from ash or lava

Acid Lava Cone

- A dome shaped volcano with convex slopes formed when acidic lava solidifies around a vent

Minor extrusive volcanic features

- Solfatara, fumerole, hot springs, geysers

Hot Springs

- Spring caused by the emergence of heated groundwater from the Earth’s crust

Geyser

- Is a spring with an intermittent discharge of water ejected violently and accompanied by a vapour phase (steam)

Types of volcanoes

- Dormant, extinct, active

Dormant

- A volcano which has stopped erupting but can still erupt at any time

Extinct

- A volcano which has stopped erupting and will not erupt again

Active

- A volcano with erupts frequently

Lava

- Is molten rock expelled by a volcano during an eruption, is the name of magma on the surface

Magma

- Is a mixture of molten rock and solids that is found beneath the surface of the Earth

Volcanic Eruption

- The forceful emission of magma from the core of the Earth through a vent

Volcano

- Is an opening, or rupture, in a planet's surface or crust, which allows hot magma, ash and gases to escape from below the surface

Volcanism

- Refers to the range of processes by which molten material and gasses are either intruded into the Earth’s surface or extruded from the Earth’s surface

Characteristics of a shield volcano

- Forms from fluid lava which flows to cover a large surface area, formed by basaltic lava, lava flow is slow, not very tall but occupies a large surface area, crater is small due to slow rate of eruption

A volcanic eruption is most likely to be violent if the lava reaches the surface through a fissure due to high pressure inside the volcano

EARTHQUAKES

Causes and effects of earthquakes

- Causes: Tectonic forces (diastrophic forces), faulting of lithosphere, volcanism, mass movements, falling of meteorites, mans activities (e.g. quarrying, explosives), movements of large amounts of animals Effects: Death, destruction of property, formation of joints in the rocks, landslides, collapse of buildings, tsunamis, fires

Crest

- The upper part of a wave

Earthquake

- The sudden movement of the Earths crust along faulted and volcanic areas when tectonic plates collide with each other

Epicenter

- Is the point on the Earth's surface that is directly above the focus

Focus

- Is the point where an earthquake originates

Magnitude

- Refers to the total amount of energy released by an earthquake

Mercalli Intensity Scale

- Is a scale used for measuring the intensity of an earthquake

Richter Scale

- Measures the amount of energy released by an earthquake

Seismography

- Measures the intensity of an earthquake

Seismology

- The study of the Earths movements such as earthquakes or tremors

Trough

- The bottom part of a wave

External forces

External forces operating on the Earth’s surface

- Exogenic forces, denudational forces

MASS WASTING

- Is the geomorphic process by which soil, regolith and rock move downslope under the force of gravity. Is caused by the process of granular disintegration, tips electric polls and fences

Eluviation

- The process of the removal of materials from geological or soil horizons

Denudation

- The process of rock disintegration by means of erosion, weathering, or mass wasting

Forms of slow mass wasting

- Soil creep, talus (scree) creep, solifluction (sludging)

Soil Creep

- Slow movement of soil particles which can be recognized by bending of trees and fences

Talus Creep

- Very slow movement of waste rock of all sizes down a slope

Sludging

- The gravitational flow of soil mixed with gravel saturated with water down a slope

Forms of rapid mass wasting

- Earth flow, mudflow, avalanches, landslides, slumping, rockslide, debris slide, rock fall

Earth Flow

- A downslope viscous flow of fine grained materials that have been saturated with water, and moves under the pull of gravity

Mudflow

- The movement of large volumes of materials which are supersaturated with water as mud

Avalanches

- The sudden and catastrophic movement of materials down a slope with snow

Landslides

- Movements of materials which slip rapidly down a slope

Factors affecting mass wasting - Gradient(slope), climate, vegetation, nature of material and extent of saturation, endogenic forces (tectonic forces), human beings

Effects of mass wasting in our daily life

- Death, loss of property, soil erosion, formation of fertile soil, creation of lakes, creation of tourist attractions, land degradation

WEATHERING

Weathering - The destruction of rocks by climatic conditions such as rain or temperature change

Types of weathering

- Mechanical, chemical, biological (biotic)

Forms of mechanical weathering

- Exfoliation, granular disintegration, block disintegration, shattering

Exfoliation

- The peeling off of the outer layer of the rock due to high temperatures

Granular Disintegration

- The breaking up of rocks which consist of different minerals

Block Disintegration

- Takes place when a homogeneous rock breaks into blocks due to temperature, common in rocks that are well jointed

Frost Shattering

- Freezing and thawing causes the rocks to expand and contract until they break

Types of chemical weathering

- Oxidation, carbonation, hydration, hydrolysis, solution

Oxidation

- The process where minerals are oxidized when they combine with oxygen and water

Carbonation

- Takes place when a weak acid in rainwater reacts with rocks composed of calcium carbonate such as limestone

Hydration

- When certain minerals absorb water and swell causing fracturing of the rock

Solution

- The process where some soluble minerals dissolve e.g. rock salt

Factors affecting the rate weathering

- Nature of the rocks, climate, organisms, relief(slope)

Nature of the rocks

- Mineral composition, rock structure, colour

Climate

- Climatic variations increase or decrease the rate that rocks weather

Organisms

- Plants and animals can break apart rocks chemically or mechanically

Relief

- Steeper slopes can cause rocks to break apart

- Chemical weathering is the result of organic acid and weak carbonic acid

- Chemical weathering is most effective when it is hot and wet

Tors

- Rock outcrops formed by weathering which is usually found on near the summit of a hill, formed when joints develop in rocks

Wind Attrition

- The process by which rock particles rub or collide against each other when they are carried along with the wind

Wind Deflation

- The process by which the wind blows away loose rock waste and in doing so, lowers the desert surface producing depressions

Wind Abrasion

- The process by which small particles of rock are hurled by the wind against rock surfaces to blast away features

EROSION AND DEPOSITION BY WATER, ICE, WIND AND WAVE ACTION

WATER

Types of deserts

- Sandy, rocky (erg), badlands, mountainous

Erg

- A stony desert

Depositional features due to water action in deserts

- Alluvial fans, alluvial cones, bajadas (bahada), peripediment, playas (sebkhas/chotts) and Salinas(salars)

Alluvial Fans

- Fan-shaped features formed when large quantities of sediments are deposited at the foot of steep slopes

Alluvial cones

- Look like alluvial fans but consist of coarser material

Bajadas

- Continuous gently sloping features with an undulating surface formed when alluvial fans/cones coalesce during the deposition of more sediment at the foot of a steep slope

Playas/Salinas

- Are temporary salt lakes

Peripediment

- A gentle slope formed when alluvial deposits overlie the edge of the pediment surrounding the playa

Erosional features due to water action in deserts

- Rills, gullies, wadis (chebka), pediment, pediplains, inselbergs, mesas, buttes, dry river valleys

Rills

- Small, shallow grooves formed due to erosion by surface runoff

Gullies

- Deep, steep troughs produced when erosion in rills becomes larger

Wadis

- Steep-sided, deep and flat floored valleys formed due to severe erosion by water in the desert

Pediment

- Gently sloping platform formed when the edges of the desert and semi-desert highlands get pushed back by erosion and weathering

Pediplains

- Multi-concave features resulting from the coalescing of several adjacent pediments

Mesas

- Extensive flat-topped residual tablelands with resistant rock on the top

Buttes

- Small but prominent residual flat-topped hills capped with resistant rock which remain after denudation of a plateau in arid areas

Dry River Valleys

- River valleys which remain dry after streams of water dry during the dry season

Surface features of a karst region (limestone surface features)

- Scarps, hills and mountains, grikes (grykes), clints, swallow holes (sink holes or ponor), doline, uvala, polje, gorge, terra rosa

Terra Rosa

- A red clay which is found in floor of a polje

Scarps/Hills/Mountains

- Formed when there are hard rocks which have not been eroded away that remain standing as residual features

Grikes

- Gullies formed when water erodes the cracks on the surface before going underground

Clints

- Ridges or blocks in limestone rock separating grikes in a karst region

Sinkhole (Swallow Hole)

- A vertical hole produced when the joints are enlarged by water percolating into the rock

Doline - Is a large depression produced when several swallow holes coalesce (join together)

Uvala

- Is a large depression formed when Dolines coalesce

Polje

- A very large depression formed when several uvalas collapse

Gorge

- Steep sided trough lined by steep rocky cliffs which form when the roof of the cavern collapses

Karst

- A well developed surface of a limestone region where the rocks are well jointed

Limestone

- A soluble rock with jointed structures resembling a wall

Underground features of a limestone area (caves)

- Caverns, stalactites, stalagmites, underground river, natural pillar, anthodites, resurgent river

Caverns

- Underground chambers formed due to the solution of limestone rock underground

Stalactite

- Long needle like calcite rock that hangs downward from the roof of a limestone cave

Stalagmite

- Is a type of structure found on the floor of a limestone cave due to the dripping of mineralized solutions and the deposition of calcium carbonate

Underground River

- The river formed when water sinks underground through sinkholes and joints

Natural Pillar

- A natural column formed when a stalactite and stalagmite join together or when a stalagmite reaches the roof

Anthodites

- Delicate flower-like formations which are formed when calcite is deposited on the roof of caverns

Resurgent River

- An underground river that reappears on the surface somewhere

The amount of water that sinks into the ground from the surface depends on the underlying geological structure

Erosional features in the upper section of a river (young stage, river torrent, or river mountain)

- V-shaped valley, interlocking spurs, river capture, waterfalls, canyons(gorge), rapids, pot holes, plunge pool, boulders

V-shaped Valley

- A valley with a strong gradient which is formed due to the river’s high velocity

Interlocking Spur

- Is a natural geographical feature which occurs in a river's upper course, where vertical erosion is the dominant force in determining the river's course

River Capture

- Process where a stronger river captures a weaker river when the stronger river erodes its valley both vertically and headword at a faster rate and flows at a lower level than the weak river

Waterfalls

- Sudden downpours of water along a river due to the sudden drop of slope in the riverbed

Canyon

- A deep ravine cut between cliffs like mesas, buttes, or plateaus by a river in a desert climate

Rapids

- The sudden descent of the stream of water without a waterfall, the slope is not steep enough

Pot Holes

- Shallow depressions cut by pebbles as they are carried by swirling water on the riverbed

Plunge Pool

- A large deep depression that develops at the base of waterfalls due to abrasion by pebbles carried in the river

Boulders

- Large rocks broken up by river erosion that are too heavy to be taken downstream

Features resulting from river capture

- Elbow, pirate river, wind gap, misfit river

Elbow

- The bend produced where the river has been diverted

Misfit River

- Stream which lost headwaters due to its volume being capture by another river

Wind Gap

- The valley behind the misfit river in between the misfit river and the elbow

Pirate River

- The river which takes volume from the misfit river and is rejuvenated in the process

Features in the lower section (old stage, or flood plain of the river) of a river (depositional features)

- Flood plain, natural levees, ox-bow lakes (Cut-offs), deferred tributary, deltas, estuaries

Flood Plain

- A gently sloping area produced as a result of deposition of alluvium (silt and sand)

Levee

- Embankments produced as the result of deposition of sediments along the bank of the river in the flood plain. Also created by humans to prevent flooding

Ox-bow Lakes

- Cut-off meanders formed as the river cuts through the necks of the loops or well established river bends

Deferred Tributary

- A tributary in the lower course of a river that has been forced to flow alongside the main valley before joining the river

Deltas

- Low lying swampy plain formed as the result of accumulation of alluvium at the mouth of a river

Estuary

- River valley that has been drowned by a rise in sea level or the fall of the land along the coast

Basin lakes of Africa

- Victoria and Chad

Types of river rejuvenation

- Dynamic rejuvenation, static rejuvenation

Dynamic Rejuvenation

- Rejuvenation brought about by either sea level change or land level change

Static Rejuvenation

- Is the type of rejuvenation caused by the increase in the river volume due to heavy rainfall, melting of ice or river capture

Features due to river rejuvenation

- Knick point (rejuvenation head), paired terraces, incised meanders

Knick Point

- Break of the slope in the long profile of the river valley where the riverbed drops sharply

Paired Terraces

- Steps or benches on either side of a river valley formed as a result of undercutting of the river due to renewed erosion

Incised meanders

- Steep sided curved bends of the river valley produced as a result of the undercutting of the riverbed by the river along the meander

Rejuvenation

- The renewed activity of an ecological area such as a river or forest

Types of drainage patterns

- Dendritic pattern, trellised pattern (rectilinear pattern, rectangular pattern, radial pattern, annular pattern, centripetal pattern, and parallel drainage pattern

Dendritic Pattern

- Looks like a tree trunk with its branches as veins, possessing many tributaries

Trellised pattern

- Develops in areas with alternating hard and soft rock, the tributaries join the main river valley at almost right angles

Rectangular Pattern

- Its tributaries join the main river at a right angle

Radial Pattern

- The drainage pattern where streams flow outwards down flanks or slopes of a dome or cone such as a volcano e.g. Kilimanjaro

Annular Pattern

- A series of streams flowing in a spiral way forming concentric circles

Centripetal Pattern

- Streams flowing from all directions converge at the center in the basin

Parallel Drainage Pattern

- A series of streams running parallel to one another

Types of drainage systems

- Accordant drainage system, discordant drainage system

Accordant Drainage System

- The normal drainage system of a river, the water flows in accordance to rock structure and slope

Discordant Drainage System

- Does not flow in accordance with rock structure or slope

Accordant drainage systems are seen by the following drainage patterns

- Radial, trellised, rectangular, centripetal drainage patterns

Discordant drainage systems

- Antecedent, superimposed, anteposition

Antecedent

- A river maintains its course by eroding vertically up the land due to having enough velocity to go up the slope

Superimposed

- The opposite of an antecedent, the river maintains its course into a newly exposed rock layer without following the structure of the rock

Anteposition

- Develops as a result of the combination of antecedence and superimposition

Alluvium

- Loose soil or sediments, eroded, deposited, and reshaped by water on Earth’s surface

Deposition

- The laying down of rock particles on the surface

Importance of rivers

- Water supply, transport, hydroelectric power, sources of materials like sand/diamonds, fishing grounds, tourism, irrigation

Causes of river rejuvenation

- A fall in the sea level (eustatic change), land uplift and subsidence (isostatic change), increase in the river volume (discharge)

Conditions necessary for the growth of coral polyps:

1. Warm waters with temperatures between 20-30 degrees Celsius

2. Clear salty water, hence they do not occur at river mouths

3. Sunlight that penetrates to a depth of about 50m

4. Plentiful supply of plant food and oxygen

Types of coral reefs

- Fringing reef, barrier reef, atoll

Fringing Reef

- A reef attached to the coast with a shallow lagoon separating it from the mainland

Barrier Reef

- Similar to a fringing reef but the barrier reef is farther away from the coast and is separated from the mainland by a larger deeper lagoon

Atoll - Circular or elliptical shaped coral reef enclosing a lagoon found in mid oceans

Features of an ocean floor

- Continental shelf, continental slope, trench, plateau, basin, plain, deeps

Ocean Ridge

- Is an underwater mountain range, typically having a valley known as a rift running along its spine, formed by plate tectonics

The continental shelf is the best place for commercial fishing

Attrition

- Collision of loads with each other and broken down in a river

Cross profile of a river

- Distance between one side of a river and the next

Dendritic Drainage

- A drainage pattern which looks like a tree with its branches

Drainage Pattern

- Is the plan or layout of the river with its tributaries

Formation of a river delta

- First corrasion, then transport, then deposition

Hydraulic Action

- Wearing away of the sides and bottom of a river’s channel by the load carried by a river

Long profile of a river

- Stretch of the river from its source to its mouth

Meander

- Is the bend in a river as it courses downriver

Potholes

- Is a type of disruption in the surface of a roadway where a portion of the road material has broken away, leaving a hole

River Rejuvenation

- Is the renewal of the erosive activity of a river in its valley

River Valley

- A section of a river where erosion is pronounced and is characterized by a V-shaped valley

- The source of a river is the catchment area

- The erosive power of a river depends mainly upon its volume and speed

- River water can flow in the following two ways: Laminar and turbulent

WAVES

Features due to wave deposition

- Spit, tombolo, sand bar, mudflats, beaches, berms, cusps

Spit

- A low narrow ridge of sand attached to the land at one end with the other side ending in the sea

Tombolo

- Is a deposition landform in which an island is attached to the mainland by a narrow piece of land such as a spit or bar

Mudflat

- Are coastal wetlands that form when mud is deposited by tides or rivers. They are found in sheltered areas such as bays, bayous, lagoons, and estuaries

Beach

- Lies between the high and low water levels (tides), formed by deposition of sand along water

Berm

- A narrow ridge or shelf with a steep front which is found on the upper part of some beaches

Cusps

- A series of small, horn-shapes projections separated by shallow indentations that face seawards giving the beach a curved appearance

Sand Bar

- A ridge of material which lies parallel or almost parallel to the coast or across the estuary or bay between two headlands

Features due to wave erosion

- Cliffs, wave-cut platforms, bays, caves, blowhole (gloup), arch, geo, stack, stump, headland

Cliff

- Is a high perpendicular or steep rock face along a sea coast produced by waves below

Wave-Cut Platform

- A plateau like structure produced by continual undercutting of a cliff by waves

Headland

- Is a high promontory with a steep face which projects into the sea or a lake when less resistant rocks are eroded away

Bays

- A curved indentation of the sea into the land which is formed by the erosion of less resistant rock

Cave

- Is a tunnel-like opening at the base of a cliff face that forms where there is a weakness in the rocks (joint or fault) through constant wave erosion by abrasion and hydraulic action

Arch

- Is a roof-like structure formed as a result of a headland being eroded right through from one cave to the other side of the headland

Stack

- Is an isolated mass of rock near a coastline detached from the mainland by wave erosion which caused the collapse of an arch

Stump

- Is an isolated mass of rock which was formed as a result of a stack being considerably eroded

Blowhole

- Is a hollow structure nearly vertical on the land formed when erosion occurs along a vertical joint which passes from the land surface to the cave roof

Geo

- A long narrow inlet of the sea, penetrating cliffs that have been formed as the result of the collapse of the roof joining a cave and blowhole

Shore

- The land between the high tidal water level and the low tidal water levels

Shoreline

- The line where the shore and sea meet

Classification of Coasts

- Submergent coasts, emergent coasts, stable coasts, compound coasts

Submergent Coasts

- Result from the rise of the sea level or submergence of land

Emergent Coasts

- Result from the fall in sea level or uplift of land

Stable Coasts

- Coasts formed where there is little change

Compound Coasts

- Produced from the mixture of emergences and submergences

Types of submerged upland coasts

- Ria coasts, fiord coast, dalmation coasts (longitudinal coasts)

Ria Coast

- Formed when the highland area with river valleys is submerged and the lower parts of its river valleys become flooded by water from the sea

Fiord Coast

- Formed when glaciated U-shaped valleys are flooded after the submergence of the former coastal highland area

Dalmation Coast

- Form where a mountainous area which lies parallel to the coast is submerged, forms valleys called sounds

LAKES

Classification of Lakes

- Created by diastrophic movements, volcanic activity, erosion, deposition, man

Lakes caused by diastrophic movements

- Rift valley lakes, down-warped lakes

Rift Valley Lakes

- Formed when water occupies rift valleys formed as a result of faulting

Down-Warped Lakes

- Formed when water occupies basin-like depressions

Lakes due to volcanic activity

- Crater and caldera lakes, lava dammed lakes

Crater and Caldera Lakes

- Formed when water occupies a crater or caldera

Lava Dammed

- Formed when a river is blocked by lava that erupts and runs across the river

Lakes due to erosion

- Glacial lakes, trough lakes, rock basin lakes

Glacial Lakes

- Tarn lakes formed when water fills land occupied by cirques

Trough Lakes

- Lakes formed when water occupies hollows on the floor of U-shaped valleys

Rock Basin Lakes

- Formed when water occupies the depressions formed on the rock surface

Lakes due to deposition

- Glacial depositional lakes, moraine dammed lakes, kettle lakes, ox-bow lakes, delta lake, flood plain lakes, marine deposition, lucastrine

Lucastrine

- A delta which is found in a lake

Lakes which occur as a result of deposition

- Playa, Ox-bow, Delta, Lagoon

Playa - Is a desert basin with no outlet which periodically fills with water to form a temporary lake

Ox-bow Lake

- Is a waterhole that forms at the lower side of the river, where the river develops meanders while deposition is taking place

Delta

- A broad tidal channel where a river enters the sea

Lagoon

- Is a body of shallow sea water separated from the sea by some form of barrier

Lake

- Is a hollow or depression on the Earth’s surface where water has accumulated

Manmade Lakes

- Are formed as a result of the construction of a dam across a river

Ice

Sapping

- The breaking of rocks by the alternation between thawing and freezing of water at the bottom of cracks in glaciated land

Erosional features formed in a glaciated highland

- Truncated spur, U-shaped valley, pyramidal peak, arête, cirques (corrie/cwm), hanging valley, fjord, ribbon lake

Pyramidal Peak

- Mountaintop that has been carved by ice during glaciation and frost weathering

Cirque (Corries)

- Circular depressions which are formed by glaciations in the highlands

U-Shaped Valley

- A steep-sided, flat bottom, wide valley which contains features produced by both glacial erosion and deposition

Arête

- A steep ridge separating two cirques which is formed by cutting back of the walls of cirques

Truncated Spur

- Spurs whose ends have been cut off due to erosion as ice moves down the valley

Hanging Valley

- Is the tributary valley of the U-shaped valley which hangs above the floor of a U-shaped valley separated by an almost vertical slope. If there is a river a waterfall will form

Fjord (Fiord)

- Is a submerged glaciated U-shaped valley formed when the glacier has eroded its path by undercutting and been plunged into the sea

Ribbon Lakes

- Lake that occupies an elongated trough excavated by ice in a U-shaped valley

Tarn Lake

- Is a mountain lake or pool, formed in a cirque excavated by a glacier

Erosional features formed in a glaciated lowland

- Eroded plain, crag and tail, roche mountonée

Eroded Plain

- Is a rounded topography with a large area of bare rock scratched by boulders embedded in the base of the glacier

Crag and Tail

- Is a resistant mass of rock standing in the path of a moving glacier

Roche Mountonée

- Outcrop of resistant rock smoothed by a glacier into a gentle slope

Depositional features of a glaciated lowland

- Till plain (boulder clay plain), drumlin, erratics, kames, eskers, kettles, moraines, outwash plains, kame-terrace

Till Plain

- A long plain made of clay and boulders deposited by ice sheets and glaciers over a surface which contains features like erratics, drumlins, kames, eskers and kettles

Kettles

- Are the depressions formed after the melting of the ice block enclosed within the till

Erratics

- Are large boulders deposited by a glacier or ice sheets as they melt

Drumlin

- Elongated egg-shaped hills made of boulder-clay which occur in groups

Moraines

- Refer to the boulder clay deposits laid down in the lowlands to form ridges

Lateral Moraine

- Lines of glacial deposits along the sides of valleys

Medial Moraine

- Consist of rock fragments deposited in the middle of the valley which marks the point where two glaciers met

Terminal Moraine

- Refers to the ridge like feature found at the end of a glacier

Recessional Moraines

- Series of parallel terminal moraines that mark the retreat of glaciers

Esker

- Is a long winding ridge of stratified sand and gravel

Kame

- A feature of an irregular undulating mound of bedded sands and gravel

Kame-terrace

- Is a discontinuous ridge along the valley side formed by deposition of sands in narrow lakes between a glacier and the adjacent rock wall

Outwash Plain

- Is a wide gently sloping plain formed as the result of deposition of material by melt-water from the glacier

WIND

Erosional features due to wind in deserts

- Rock pedestals, zeugen, yardangs, blowouts (deflation hollows/pans), inselbergs, desert pavements, ventifacts (draikanter)

Rock Pedestals

- Tower like structures composed of alternate bands of soft and hard rock formed due to wind abrasion in the desert

Zeugen

- Ridges consisting of alternate layers of hard and soft rock formed in areas where rock layers lie horizontally and are characterized by joints

Yardangs

- Are the ridges consisting of hard and resistant rock bands standing either vertically or at an angle which run parallel to the direction of the prevailing wind

Blowouts

- These are hollows or depressions produced by wind deflation

Inselbergs

- Residual hills consisting of hard and resistant rocks left behind after the rest of the surface has been eroded away

Desert Pavements

- The horizontal areas of bare polished rock formed by the scouring action of quartz

Ventifacts

- Heavier rock blocks left behind after wind has carried away all of the material

Wind depositional features associated with deserts

- Sand dunes, seifs, barchan, ripples, loess

Sand Dunes

- Are hills of sand which have been deposited by the wind in a desert

Seifs

- Are long narrow ridges of sand which lie parallel to the direction of the prevailing wind

Barchans

- Crescent shaped sand dunes that are formed by an obstacle in the desert like a rocks

Loess

- Are a sediment formed by the accumulation of wind-blown particles that were carried by the wind beyond the desert limits

Ripples

- Small wavy structures commonly found between sand dunes

Formation of sand dunes (or barchans and seifs) are influenced by

- The extent of vegetation cover, the size of the sand particles, the relief of the desert, the velocity of the wind

3.2.4 Artificial forces

3. Soil

SOIL FORMATION

SOIL

- A natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics

PROCESSES OF SOIL FORMATION

- (1)Weathering of rock to produce regolith

REGOLITH

- Loose broken material due to weathering of rock or deposition of alluvium, drift loess and volcanic material

- (2)Formation of topsoil by adding water, gasses, living organisms, and decayed organic matter (humus)

FIVE MAJOR FACTORS OF SOIL FORMATION

- Time, parent materials, climate, living organisms, topography

SOIL COMPOSITION AND PROPERTIES

COMPONENTS OF SOIL

- Organic matter (biota, 45%), inorganic matter (5%), soil water (25%), soil air (25%)

ORGANIC MATTER

- Made of decomposed plant and animal remains (humus) and living micro-organisms

INORGANIC MATTER

- Provide minerals required for plant growth

SOIL WATER

- Derived from rainfall and is important for regulating temperature, dissolving nutrients

SOIL AIR

- Plants and animals gain oxygen for metabolism from soil air

SOIL PROFILE AND CHARACTERISTICS

CHARACTERISTICS OF SOIL ARE INFLUENCED BY

- Vegetation, parent rock, climate and weathering

PROPERTIES OF SOIL

- Soil profile, soil depth, soil colour, soil texture, soil porosity, soil structure

SOIL PROFILE

- A vertical cross-section of the soil showing its horizons

SOIL DEPTH

- Varying properties depending on the maturity of the soil and nature of rocks below

SOIL COLOUR

- Colour is determined by mineralogical composition of the soil

SOIL TEXTURE

- The degree of coarseness or fineness of a soil

SOIL POROSITY

- Total volume of pores or empty spaces between particles of soil material

SOIL STRUCTURE

- Refers to the arrangement of soil particles

SOURCES OF SOIL POLLUTION

- Atmosphere, daily human activity, industrial activity, farms

ATMOSPHERE

- Pollutants introduced through acid rain

DAILY HUMAN ACTIVITY

- Garbage like plastic, metals, bottles, cans are dumped on the soil

INDUSTRIAL ACTIVITY

- Chemicals, radioactive materials and industrial waste are dumped

FARMS

- Pesticides (DDT/fertilizers) and certain crops can damage the soil

WAYS YOU CAN COMBAT SOIL DEGRADATION

- Good agricultural practices, mixed farming, crop rotation, avoid soil pollution, education of land users, avoid bush fires, ensuring soil moisture, avoid mass wasting

FACTORS INFLUENCING SOIL FERTILITY

- Presence of mineral plant nutrients, presence of water, presence of air, soil pH, soil, presence of colloids, presence of organisms

LOSS OF SOIL FERTILITY

- Leaching, over-cultivation, monoculture, soil pollution, soil erosion, mass wasting, loss of water in the soil

SIMPLE SOIL CLASSIFICATION

PODZOL

- The group of soils which occur mostly in moist cool temperate climates

CLAY SOIL

- Is a naturally occurring material composed primarily of fine-grained minerals

HUMUS

- Refers to any organic matter that has reached a point of stability, where it will break down no further and might, if conditions do not change, remain essentially as it is for centuries, if not millennia

LATERITES (RED LATERIC SOIL)

- Are soil types rich in iron (causing red from oxidation) and aluminum, formed in hot and wet tropical areas

LEACHING

- Is the loss of plant nutrients from the soil, contributes to groundwater contamination

LOAM

- Is soil composed of sand, silt, and clay in relatively even concentration (about 40-40-20% concentration respectively)

RESIDUAL MOUNTAINS

- Owe their origin mainly to denudation

MULCHING

- The practice of covering the soil with a layer of grass or plant remains

ADVANTAGES OF MULCHING

- Helps to conserve moisture in the soil by preventing evaporation, reduces loss of soil by erosion, rotting mulch adds organic matter to the soil, helps control the spread of weeds

TYPES OF SOIL

- Azonal, intrazonal, zonal

AZONAL SOIL

- Are without well-developed characteristics due either to their youth or to some condition of relief or parent material which prevent soil development, Soils forming in recent eolian, alluvial and colluvial deposits are azonal

INTRAZONAL SOIL

- Have well defined soil profile characteristics that reflect the dominant influence of some factor of relief or parent material over the classic zonal effects of climate and vegetation

ZONAL SOIL

- Soils with clearly distinguishable horizons which occur in definite regions of climate and vegetation

SOIL EROSION

SOIL DEGRADATION

- Is the spoilage of the quality of soil through human activity. It is deterioration of the soil quality through loss of fertility, soil pollution, soil erosion and mass wasting

SOIL EROSION

- Is the physical removal of soil from one place to another by agents of erosion such as running water, wind, glacier, or waves

SOIL EROSION IS CAUSED BY MANMADE AND NATURAL CAUSES SUCH AS

- Sheet erosion, gully erosion, splash erosion, rill erosion, climate, nature of soil, vegetation cover, topography, cultivation, excessive mining, construction activities, excessive deforestation by man, bush burning

WAYS OF PREVENTING SOIL EROSION

- Contour farming, crop rotation, terrace farming, afforestation and reforestation, destocking, avoiding bush fires, growing cover crops

WAYS TO MANAGE SOIL EFFECTIVELY

- Education, training of farmers, planting better crops, afforestation/reforestation, reducing chemical use in farming/industry, recycling

4. Elementary surveying and map making

MEANING AND TYPES OF SURVEY

FORMS OF SURVEYING

- Chain/tape, prismatic compass, plane table, leveling, cadastral, geodetic

CHAIN SURVEYING

- Is a method of plane surveying which deals with the measurement of linear horizontal distances. The distances covered in chain surveys are normally short and straight

PLANE TABLE SURVEY

- Is the science of measuring and fixing positions of distant objects by intersection by considering the surface of the earth to be a plane (completely flat surface), curvature is ignored

PRISMATIC COMPASS SURVEY

- Is the fixing of an objects position in the field by measuring the angles of bearing between the line of magnetic north and the line of sight of the object

LEVELING

- Is the process of measuring height differences between points on the ground by determining the relative altitudes of the two points

CADASTRAL SURVEYING

- The kind of survey which collects data about the ownership of property

GEODETIC SURVEYING

- Precise type of surveying which covers large areas considering the curvature of the earth, uses triangulation/traversing/trilateration/leveling/astronomical direction fixing

LEVELING

- A process of determining the differences in elevation between two points

USES OF LEVELING

- Construct contour maps, find the best level at which you should erect a building, create longitudinal section of roads/railways/canals/pipes/sewers in urban areas, determine proper human settlements

TOOLS USED FOR LEVELING

- Leveling instruments (i.e. theodolite, abney level, clinometer, alidade, dumpy level, tilting level etc), leveling staff, chain or tape, pegs, field sheets

PURPOSE OF PLANE SURVEYING

- Determine horizontal distances between two or more points on the surface, to locate physical and nonphysical features on the surface, direction of various features of the surface, determine the area of a given region

TOOLS FOR A PLANE TABLE SURVEY

- Plane table, alidade, plumb bob, trough compass, spirit level, clinometer

ADVANTAGES OF A PLANE TABLE SURVEY

- It is the best kind of survey used to measure and fix positions of distant objects, it is quick/accurate and allows quick sketching of details, it can cover very large land areas, less accumulation of errors than chain surveying, uses instruments which are easy to use, useful for cartography, booking is not required

DISADVANTAGES OF A PLANE TABLE SURVEY

- Not suitable for a small area of land, not suitable for undulating surfaces, cannot be used during damp or rainy seasons, requires alidade which requires skills to use, a simple math error can cause all angle measurements to be incorrect, some instruments are expensive

EQUIPMENT USED FOR PRISMATIC COMPASS SURVEYING

- Two prismatic compasses, ranging poles, tape measures, chains, metal markers, chalk, field sheets

ADVANTAGES OF PRISMATIC COMPASS SURVEYING

- Rapid method, check can be made on all compass bearings, cumulative error is reduced/easily fixed, objects can be pin-pointed with accuracy, method can be combined with other methods

DISADVANTAGES OF PRISMATIC COMPASS SURVEYING

- Transport is needed if surveying over long distances, human error is involved in observations, magnetic rocks may affect readings

ALIDADE

- Is a device that allows one to sight a distant object and use the line of sight to perform a task such as to draw a line on a plane table

SURVEYING

- The science of measuring and recording distances, angles and heights on the Earth’s surface to obtain data from which accurate plans and maps are made

TOPOGRAPHIC MAPS

- colour contour maps showing the physical and manmade features such as rivers/roads/mountains/valleys/railways

TRAVERSING

- Consists of a series of lines whose lengths and directions are measured, connecting points whose positions are determined used to establish data benchmarks

TRIANGULATION

- Consists of a series of connected triangles which overlap each other, used to reduce the number of measurements that need to be taped or chained

TRILATERATION

- Is the use of electronic distance measuring equipment to directly measure the lengths of the sides of triangles from which angles can be calculated

- The three types of topographic surveying are chain surveying, prismatic compass surveying, and plane table surveying

BEARING

- The direction of a place in degrees from another place

Bearing of SW is - 225º

ESE - 112.5 º

CHAIN SURVEY

INSTRUMENTS USED IN CHAIN SURVEYING

- Chain, tape, surveyor’s band, ranging poles, cross staff, pegs, arrows, optical square, notebook

THE CHAIN

- This chain is made up of pieces of steel which are connected by rings

THE TAPE

- Used to measure horizontal distance on the ground

SURVEYOR’S BAND

- A long graduated strip made from steel or plastic, rolled in a metal frame

RANGING POLES

- Locates a place temporarily during the chaining process

CROSS STAFF

- Used to set a perpendicular line or right angles from the main line of survey

PEGS

- Their major function is to mark points permanently on the ground

ARROWS

- Steel skewers which mark and locate temporary positions on the surface

OPTICAL SQUARE

- Used for setting offsets from right angles from the line

NOTEBOOK

- Good notebook for recording or booking all fieldwork information

PREPARING A CHAIN SURVEY

- Must be well informed about the nature and location of the area, land configuration, presence of buildings or natural obstacles, preparation of instruments and personnel, prepare working schedule, transportation

ADVANTAGES OF CHAIN SURVEYING

- Used to map small areas on flat ground, simple to conduct, used to add details to existing maps, needs few people to set up, uses simple tools like pegs, applicable to compass surveying also, only survey for measuring distances (the others measure angles and heights), does not require a lot of mathematical calculations

DISADVANTAGES OF CHAIN SURVEYING

- Time consuming, subject to the accumulation of errors

5. MAP READING AND INTERPRETATION

CONCEPT OF MAP READING

(Not in study guide)

READING AND INTERPRETING TOPOGRAPHICAL MAPS

(Not in study guide)

PHOTOGRAPH READING AND INTERPRETATION

TYPES OF PHOTOGRAPHS

(Not in study guide)

READING AND INTERPRETING PHOTOGRAPHS

(Not in study guide)

6. APPLICATION OF STATISTICS

CONCEPT OF STATISTICS

IMPORTANCE OF STUDYING STATISTICS

- It helps to summarize massive data in simple figures, simplifies the process of data interpretation, helps to represent data in visual ways like charts and maps

SOURCES OF DATA

- Primary sources, secondary sources

PRIMARY DATA SOURCES

- Data collected directly from the field, also known as first hand data

SECONDARY DATA SOURCES

- Data obtained from other people’s findings i.e. from books, journals etc

CONTINUOUS DATA

- Are number that can be expressed with infinite figures of possible values that fall between any two observed values

DATA

- Exact numerical values collected and arranged for a certain purpose

DISCRETE DATA

- Consists of separate and indivisible categories of data

GROUP DATA

- Are values given in a range of numbers, data falls into certain classes

SINGLE DATA

- Are statistics or values given for each individual item in a sample

SIMPLE STATISTICAL MEASUREMENT AND INTERPRETATION

1. USE THE FOLLOWING DATA TO DRAW A GROUP BAR GRAPH:

Contribution of Agriculture to the Gross Domestic Product (GDP) in East Africa (in percentage)

- To draw this graph you must first think about what the x and y axes will be. The x axis will be years because this will group together the percentages from each country. The y axis will be percentage because this is the value being compared between the various countries. A grouped bar graph is chosen because it shows the difference between each country’s GDP by year clearly.

ADVANTAGES

- Enable easy comparisons, easy to interpret, no complicated calculations, detailed, contrasts clearly, gives visual impression about the totality

DISADVANTAGES

- Consumes time, does not give accurate impression of totals, erroneous conclusions can be made depending on the scale used, uses many colours

2. USE THE DATA BELOW TO DRAW A COMPOUND LINE GRAPH AND A COMPOUND BAR GRAPH

- To draw a compound line graph you first plot the x and y axes. You start with the smallest number to draw the bottom portion of the graph (in this example it is maize), then you choose the next lowest until you have drawn a line for each variable. After this you shade down to the next line until you have completed

ADVANTAGES OF COMPOUND GRAPHS

- Useful in comparing many variables, attracts readers with colours, detailed information is provided

DISADVANTAGES OF COMPOUND GRAPHS

- Needs knowledge of mathematics, needs more time to construct, if the same shading is used it may mislead the interpreter

3. USE THE DATA BELOW TO SHOW THE ENROLMENT OF FORM 5 STUDENTS USING A DIVERGENT LINE AND BAR GRAPH

- To construct a divergent line or bar graph you must first calculate the mean deviations. This is done by calculating the mean then finding the difference between the number of students and the mean deviation.

FINDING THE MEAN DEVIATION

Step 1: Find the mean

STEP 2: FIND THE DEVIATION FOR EACH DATA

Ex. 1981

150 - 191.7 = -41.7

Ex. 1983

200 - 191.7 = 8.3

- Since the answers are both negative and positive (because they lie on either side of the mean), you will use a graph that shows both positive and negative values, the divergent bar graph. You can also use a line graph, or a simple bar graph.

ADVANTAGES:

- It shows the increase or decrease of values over time, it is used for comparisons

DISADVANTAGES:

- It does not deal with real numbers but rather only with mean deviations, it also needs extra calculations and is difficult to construct.

4. CONSTRUCT A LINE GRAPH AND BAR GRAPH FROM THE DATA BELOW AND DISCUSS THE DEFINITION OF A LINE GRAPH AS WELL AS ITS MAIN TYPES

LINE GRAPH

- Is a graphical representation of data which uses a line to join the points of the data being represented

FOUR TYPES OF LINE GRAPHS

- Simple line graph, compound line graph, group line graph, convergent line graph

ADVANTAGES

- Easy to construct/draw, illustrates variations, no difficult calculations, easy to interpret/read, saves, simple visual impression, wide variety of uses, exact values are easily estimated
DISADVANTAGES
- Inaccurate deductions can be made, easy to confuse X and Y variables, little space where X and Y axes meet, cannot represent more than one item

5. CREATE A PIE CHART USING THE DATA BELOW OF CAR TYPES USED IN TANZANIA

- To create a pie chart you must calculate the degrees that each portion of the pie represents

STEP 1: CALCULATE THE SUM TOTAL OF ANGLES. ADD UP THE VALUES IN THE TOTAL ROW.

260 + 340 + 460 + 400 + 250 = 1710

STEP 2: CALCULATE ANGLES OF EACH CAR TYPE AND THEN DRAW THEM WITH A PROTRACTOR

ADVANTAGES

- Easy to interpret, easy to construct, illustrates statistical information accurately, gives a good visual representation, useful for comparing various commodities/sectors/items

DISADVANTAGES

- Difficult to read for getting exact values, trends and directions of change in value cannot be deduced from a pie chart, time consuming to calculate and construct, difficult to interpret or draw when there are numerous items

6. MAKE A POPULATION PYRAMID GRAPH FROM THE FOLLOWING DATA:

- Simply plot males on one side and females on the other with each row of the graph representing one of the columns of data. On the X axis you start with 0 in the centre and write marks on either side of it.

ADVANTAGES

- Enables one to analyze the structure of a given population, forms a basis for predicting population structure in the future, used to estimate or evaluate current/future needs, easy to construct and interpret, used to compare structure of different populations, used to compare between males and females
DISADVANTAGES
- Involves a lot of calculation, not easy to choose convenient horizontal scales, five year age groups generalize groups, can take a lot of space if there are too many age groups

7. A) FROM THE DATA BELOW CALCULATE THE MEAN, MODE, MEDIAN, MODAL CLASS, AND STANDARD DEVIATION

8, 22, 18, 20, 22, 8, 8, 13, 16, 21, 22, 30, 23, 16, 8, 4, 6, 2, 10, 12, 14, 15, 16, 22, 22, 27, 26, 22, 18, 4
FIRST ORDER ALL OF THE NUMBERS
2, 4, 4, 6, 8, 8, 8, 8,10, 12, 13, 14, 15, 16, 16, 16, 18, 18, 20, 21, 22, 22, 22, 22, 22, 22, 23, 26, 27, 30