312/1
GEOGRAPHY
PAPER ONE MARKING SCHEME
(Theory)
LAICOMET
FORM FOUR EXAM
312/1
GEOGRAPHY
PAPER 1 MARKING SCHEME.
SECTION A
1. a)mountain building period
-charnian orogeny
-harcynian orogeny
-caledonian orogeny
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-alpine orogeny
3x1=3mks
b) volcanic ejecta rocks
-pumice
-tuff
-tephra
-pyroclasts
2x1=2mks
2. a)reasons why there is no vegetation on top of mountain Kenya:
-very low temperature which inhibits plant growth
-thin soil which can not support growth
-presence of frozen surface
-precipitation in the form of snow
2x1=2mks
b) Characteristics of the vegetation found in the Nyika plateau
-tufted grass
-deciduous trees (some)
-some tress are evergreen
-some have thick barks
-some plants are short (stunted)
-some vegetation have thorns
-some plants have tap roots
-some plants have waxy needle like leaves
-some plants have swollen trunks
-some plants have thick leaves
3x1=3mks
3. a) (i) the rate of 0.60c / 100m at which temperature decreases with altitude in the lower
atmosphere is called environment lapse rate 1mk
(ii) Justification of the statement ‘the higher we go the cooler it becomes’ in the lower
atmosphere much heating of the lower atmosphere takes place through long radiation
from the ground
Density of the components of the lower atmosphere such as dust particles and gases
decreases with altitude immediately from ground surface
(More dense components near ground surface absorb and retain more heat)
b) Ways in which latitude determine the temperature of different places on the earth surface
-less area is heated on low latitude place than in high latitude places due to spherical shape off
the earth
-sun’s rays travels shorter distance before reaching places on low latitude places than high
latitude places
- sun’s rays reach places on low latitude places at right angles and thus short distances than
those reaching high latitude places that travel at acute angle hence loose some heat
2x1=2mks
4. a)mode of formation of the following lakes
(i)
Lake Victoria-downwarping
(ii)
Lake Nasser on river Nile-manmade
(iii)
Lake Bosumtwi in Ghana – falling of a meteorite to form a depression 3mks
b) two ways in which a lake may influence the micro-climate of the surrounding area
-evaporation from the lake can lead to convectional rainfall
-evaporation from the lake can increase the relative humidity
-lakes reduce flooding by holding excess water during rainy seasons
-lake breezes have a cooling effect hence lower the temperature
2x1=2mks
5. a) feature marked X is –fringing reef
(1mk)
b) formation of feature X
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-coral starts to grow from island or mainland seawards
-growth faster seawards then shorewards due to cleaner water
-eventually, the coral reef becomes higher seawards to enclose a shallow lagoon on the shore
side
-this coral ridge which is visible at low tide and parallel to the coast is a fringing reef
4mks
6. a) (i) 288548
2mks
(ii) 10km + or – 0.5
2mks
0
0
b) (i) 35 to 35 15
(ii)
a)
Jamji forest (2mks)
River itare (2mks)
All weather road (2mks)
(iii)
- meanders
- ox-bow lake
- swamp
- flood plain
c) (i) 2270+ or-1
(1x3=3mks)
(2mks)
(ii)
- tea growing – requires heavy rainfall
- presence of forest – thrive in areas of heavy rainfall
- many large permanent rivers
- area is densely populated
- coffee growing
d) - crop growing – tea estates, factories an nurseries
- transport – presence of roads, airstrips
- trade – presence of shops
- livestock rearing – veterinary livestock centre
7. a) (i) vulcanicity
- is the process through which molten rocks, ashes, steam and gaseous material are forced out
by pressure from the interior of the earth to the surface (2mks)
(ii) Causes of vulcanicity
- very high pressure in the mantle
- weight of overlying materials result to temperature and pressure
- horizontal earth movement
- water from the earth’s surface infiltrate into ground reaching the hot rock overlying the
mantle. It is superheated to appear on the surface as steam, gersers and hot springs
- the high temperature that heat the water to steam
3mks
b)(i) formation of intrusive volcanic features
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- magma moves upward but solidifies before reaching the earth surface
- magma lacks the required pressure to push through the existing lines of weakness of
overlying rocks
-magma gets trapped within the earth’s crust and cools
- cooling is slow hence formation of igneous rocks
(5mks)
(ii) Formation of a dyke
Low ridge
(dyke)
Crustal rock
Narrow trench
(dyke)
-is a vertical or inclined mass of intrusive rock that cuts across a bedding plane of
rock strata
-can be eroded to form an elongated, narrow trench if it is softer than the
surrounding rock
-if harder than the surrounding rock it forms a low ridge
(6mks)
Formation of a sill
sill
-is an intrusive feature formed when magma flows along a bedding plane. Sill becomes
exposed by denudation to form ridges low escarpment
(6mks)
c) Negative significance of vulcanicity
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-can cause death due to poisonous gas emitted
-causes great damages to property e.g settlements and infrastructure
-can trigger landslide which can destroy environment
-results to overheating of surface of water affecting marine life
-magma pushed near surface raise temperature leading to drying of crops (6mks)
8. a) (i) soil profile –verticle arrangement of soil in layers / horizons from the surface to the bed
rock
(1mk)
soil catena – arrangement of soil along a slope from hull top to bottom (1mk)
(ii) zone of eluviation
-largely decomposed organic matter
-soluble content at least partly removed by solution
-humus and fine clay available
-grey in colour
(2x1=2mks)
Zone of illuviation
-hard pan due to deposition of leached soluble materials from zone of eluviation
-possible iron accumulation and other oxides
(2mks)
b) (i)significance of humus in the soil
-contain organic colloids which increase water holding capacity
-helps improve soil structure (arrangement of soil particles)
-source of plant nutrients
-adds organic acids necessary for soil formation
(4mks)
(ii) Colour of the soil
Parent rock
-reddish brown soils have high concentration of iron and aluminium oxides
-grey / bluish soils have more silica
-yellow soil indicates presence of iron oxides
Organic matter
-dark soils have a lot of organic matter while light soils have less
Amount of moisture presence in the soil
-dry sol particle have faint / light colours which turns dark / clear with increase in
moisture
3x2 = 6mks
c) (i)soil degeneration – loss of soil fertility (1mk)
(ii) Natural ways of soil degeneration
-soil erosion (fertile top soil removed by agent of erosion)
-leading (soil nutrients dissolved and carried downwards to lower layers where the rate of
percolation is high)
-mass wasting (poor hill side soils covering fertile hill bottom soils)
2x2=4mks
Man made ways of soil degeneration
-mono – cropping can lead to exhaustion of some minerals as well as accumulation of pests and
diseases eventually making soil infertile
-burning of land (soil with burnt humus loses water, plants nutrients and micro-organisms)
-application of farming chemicals may change the PH making soil suitable for certain crops.
-mining, roads and houses construction, up and down ploughing or other man-made ways of soil
degeneration
2x2=4mks
9. (a) (i) wind erosional processes
-a brasion
- attrition
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-deflation
(ii) Features formed by wind erosion
-yardangs
-rock pedestals
-zengens
-deflation hollows
-mushroom blocks
-ventifacts
2x1=2mks
2x2=4mks
(b) Formation of a barchans
Leeward side
(steep slope)
Prevailing winds
Horns
Windward side
(gentle slope)
-sand deposits occur around a barrier like a rock or a piece of vegetation
-accumulation of sand leads to formation of a big mound of sand on the barrier
-wind transport some sand beyond the barrier edges to form the horn
-due to continued transportation the horn grows longer and longer
-finally a crescent shaped sand dune is formed
(c) Significance of desert land forms
-loess is fertile for agriculture
-deflation hollows may contain oasis which may contain water
-offer good site for testing military equipment / weapons
-some are tourist attraction e.g. zengens, yardangs, inselbergs etc
-some are used as homes/dwellings of people in china and Europe which are warmer in winter
and cooler in summer
-salt flats provide salt for industrial purposes
-the hot sun can be trapped for solar energy.
(d) (i)Route maps
-shows the routes to be followed during the study
-shows the distribution of major landforms which may be of interest
-helps in estimating distances to be covered
-helps to estimate the time required for the study
(ii)Recommendation to be given to the government
-dams should be constructed to harness rain water
-boreholes should be dug
-people to be advised to have water tanks to store water
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-seasonal streams should be dammed
(iii) Problems to be encountered
-might get tired walking long distances
-attack by wild animals
-the area may be too large to be studied adequately in the given time
-time may be inadequate to carry out the field study
-harsh weather conditions too hot or very strong winds
-inaccessibility of some areas due to physical barriers like mountains, hills, valley or wadis
-hostile people e.g. cattle rustlers
-lack of necessary data
10. a) causes of mechanical weathering
-changes in temperature
-effect of rain water
-freeze and thaw action of ice
-crystal growth
4x1=4mk
b) (i) carbonation process of chemical weathering
-rain water mixes with carbon dioxide in the atmosphere to form a weak carbonic acid
-weak carbonic acid reacts with limestone and chalk carbonates to form calcium bicarbonate
-the calcium bicarbonate is removed in solution form from the rock through the joints causing
the rock to disintegrate
3mks
(ii)-limestone rock
-chalk rock
(iii) Earth’s surface features formed due to carbonation process
-grikes –dints –uvalas –poljes
2x1=2mks
c) (i) an exfoliation dome is a rounded- off mass of rock left behind after peeling-off of outer
layer due to temperature changes 1mk
(ii) How an exfoliation dome is formed
-high temperature heat outer surface layer of rock during the day in hot and arid areas.
Outer layer expands at a faster rate than the inner layers.
-low temperatures during the night cause outer layer to contract at a more than the inner
layer due to cooling
-repeated expansion and contraction cause stress within outer layer of the rockmass causing
it to peel off as curved shells
3mks
d) Ways in which weathering positively influence mans activity
-formation of fertile soils for mans agriculture
-minerals - broken small rocks particles may contain valuable minerals such as iron ore,
manganese and nikel which can be exported for foreign exchange
-tourism, tors exfoliation domes, inselbergs attract tourists who in turn creates employment
-pottery,brick making industries use clay and bauxite produced by weathering
- Building and construction materials such as rocks and sand are more accessible where
weathering has taken place
-quarring and mining made easier for man by weathering
(3x2=6mks)
Negative effects of weathering
-destruction of landforms formed by faulting, folding and vulcanicity
-speeding up the process of erosion in which the landscape is worn out
-weathered landscape is unsuitable for man’s activities such as agriculture and transport where
features such as grikes and dints, poljes and uvalas may be formed
2x2=4mks
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