FORM
THREE - GEOGRAPHY DIRECTORY
SUBJECT
MATTERS TO COVER
- Structure of the earth
- 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, arĂªte, 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
ArĂªte
-
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)
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:
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 femalesDISADVANTAGES
- 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
8.
B) FINDING THE MODAL CLASS AND STANDARD DEVIATION FOR THE ABOVE SET
OF NUMBERS
HOW
TO CALCULATE THE VALUES FOUND IN THE TABLE ABOVE:
FINDING
THE MODAL CLASS
The
Modal Class is the class with the highest frequency (F)
Class
20 - 24 has the highest frequency (F) of 9
CALCULATING
STANDARD DEVIATION
There
are two formulas for calculating standard deviation; the summations
come from the table above
see also :
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