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2.
Study Figure 2 carefully.
Figure 2
(a) Name the plate margins marked X, Y and Z. Give examples.
(b) (i)
(6 marks)
Compare and explain the features of the plate margins X and Y. (6 marks)
(ii) Describe the processes taking place along margin Z.
(2 marks)
(c) Briefly describe the impact of crustal movements of peoples' lives and explain
why damage during crustal movements often varies in severity.
(6 marks)
3.
Figure 3 shows an ecocline in tropical rain forest leading from equator towards the
tropical desert.
Figure 3
(a) Briefly define the term "ecocline.
(2 marks)
(b) Describe the ecocline from the equator to the Tropic of Cancer.
(5 marks)
(c) Describe how vegetation changes along the ecocline and state what has caused
the change.
(8 marks)
(d) In what ways had man also played a part in changing the vegetation pattern in
this ecocline?
(5 marks)
4.
Table 4 gives a detailed description of an acidic soil. Study the table carefully before
answering.
Table 4
Horizon
A
(0-5 cm)
Morphology
B
(5-100 cm)
C
(100 cm +)
Main composition
Thin, dark, granular
structure, little fresh
litter on top
thick, red to reddishbrown, granular to
blocky structure,
well-drained
mineral mixed with
decomposed organic
matter
mainly kaolinite clay
mixed with oxides of
iron and aluminium
and some residual
minerals
(mainly
quartz grains)
varying thickness, red weathered rock with
to reddish-yellow,
some partly weathered
rock structure visible
minerals
(a) Name the soil.
Main Processes
Rapid decomposition
of organic matter,
humus formation
Very intense weathering,
strong leaching with
removal of nearly all
soluble ions (basses and
silica)
strong weathering,
reorganization of
minerals
soil
(2 marks)
(b) Describe the spatial pattern in the world distribution of such kind of soil.
(3 marks)
(c) Explain how the formation of this soil is influenced by
(i)
climate.
(4 marks)
(ii) topography, and
(3 marks)
(iii) organisms.
(3 marks)
(d) Name five human activities that could lead to changes in the characteristics of
this soil and explain how each one works.
(5 marks)
S.6 Geog. Final Exam. (2000-2001)
Suggested Answer
2.
(a) X shows the constructive plate margin/zone of spreading such as
(6 marks)
the Mid Atlantic Oceanic Ridge.
Y shows the destructive plate margin/zone of subduction such as the
Himalayas/the Andes/the Rockies.
Z shows the conservative plate margin such as the San Andreas Fault.
(b) (i)
X
- divergence of plates
- constructive plate margin
- processes of spreading/tension
- oceanic crust and oceanic crust
- creation of new earth crust in a spreading
zone
- forming oceanic ridges with volcanic
origin
- volcanism and shallow seismic activities
- basic volcanic materials
Y
(6 marks)
- 2 plates move towards one another
- destructive plate margin
- processes of collision/compression/folding
- formation of tectonic mountains
- intersections of oceanic crust and
continental crust
- destructive of earth crust
- subduction of ocean crust, formation of
ocean trenches
- benioff zone with deep-seated earthquakes
volcanism and volcanic mountains
- acidic volcanic materials
(ii) The Pacific Plate and the American Plate are moving alongside each other,
crust is neither destroyed nor created.
(2 marks)
(c) Beneficial impacts on man:
- fertile soils derived from volcanic ashed
- building materials
- formation of mineral ores
- geothermal energy
(2 marks)
Hazardous impacts on man:
Lithological hazards
e.g. seismic activies, tsunamis, avalanches and landslides, volcanic ash
eruptions
(2 marks)
Severity of damages depends on:
- the intensity and magnitude of crustal movements
- population density of the areas involved
- preventive measures adopted
- knowledge and perception
(2 marks)
3. (a)
Ecocline is a broad transition along which plant communities and environments
change.
(2 marks)
(b)
- it is hot and wet at the equator but hot dry at the Tropic of Cancer
- the amount of rainfall significantly decreases poleward
- the latitudinal variation in mean annual temperature nevertheless is small
- the zonal soil group in equatorial region are mainly lateritic red soil and
grey brown podsolic soil
- prairie soils, brown soils and desert soils occur in sequence towards the
Tropic of Cancer.
(5 marks)
(c)
Vegetation communities changes rapidly along the ecocline, indicating a steep
environment gradient exists.
Vegetation shows the following morphological changes towards the desert:
- a decrease in the height of vegetation,
-
a decrease in the percentage of surface coverage by plants,
a reduction in biomass / primary productivity,
increasingly poor in species,
both trees and shrubs adapt increasing xerophytic features:
a. deciduous forest first replacing the evergreen rainforest. Trees shed leaves
in the short dry season to conserve moisture.
b. In the savanna, trees become thorny and widely spaced. Some trees
develop bottle-like trunk to store water.
c. Shrubs replace trees as the dominant plant species in the drier end of the
ecocline.
d. Plants have long tap roots which penetrate deeper into the subsoil to reach
groundwater.
(8 marks)
(d) -
Ecocline from rainforest to desert demonstrate human influences on the
change in vegetation.
Forests reduce while grasslands expand.
Lumbering and frequent burning (by shifting cultivators) suppress the
growth of trees.
Trees take longer time to recover and therefore remain no longer the
dominant plant species.
They are replaced by grasses which recover faster on cleared sites.(5 marks)
-
4.
(a) Latosol, or lateritic soil, or ferralsol
(2 marks)
(b) - mainly found in the equatorial and tropical monsoon regions
- rainfall (up to 2000 mm)
- mean and monthly temperature are high and constant
- in North Brazil (the Amazon Basin), the West Indies, Central Africa (the
Congo Basin), South India
(3 marks)
(c) (i)
- high temperature, high rainfall, small seasonal variation
- rapid and intense decomposition and weathering, kaolinite and
sequioxides formed
strong leaching, nutrients washed away
organic matter breaks down rapidly, little litter or humus in topsoil
(4 marks)
(ii) -
steep slope- erosion, truncation of topsoil, soil development arrested
gentle slope- deep and mature soil
altitude- changes in climate and therefore soil-forming pressures.
(iii) -
Favourable environment for organisms to thrive - rapid growth, quick
cycling of nutrients
Abundant flora and fauna in soil assist decomposition of organic
matter and formation of structure.
(3 marks)
-
(d) - Deforestation - erosion, loss of topsoil and nutrients.
- Fertilization - change nutrient status and soil structure.
- Cultivation - structural change, flora and fauna changes.
- Harvesting - removal of nutrients, breakdown of closed nutrient cycles.
- Mining - removal of soil materials, dumping of soil materials on the
existing soil.
(5 marks)