The F.C.T (Abuja) is
almost predominantly underlain by high grade metamorphism and igneous rocks of
Precambrian age generally trending NN-E-SS-W, these rocks consists of gneiss,
migmatites, granites and schist belt outcrops along the eastern margin of the
area. The belt broadens southwards and attains a maximum development to the
southeastern section of the area where the topography is rugged and their
relief is high. In general the rocks are highly sheared (kogbe, 1978).the rocks
of the area can be divided into 5 major groups as follows.
·
Metamorphosed Supra Crustal
·
Exogenic Rock: mica schist,(sh), marble(m), amphibolite
and amphibole schist (a) fine medium grained gneisis.
·
Migmatitic Complex: migmatite (mi)migmatitic gneiss (mg),
granite gneisis, (gg), porphyroblastic granite gneisis (pg), leucocratic
granite gneiseis (lg),intrusive granite coarse grained granite (eg).
·
Minor Intrusion: Rhyolites (ry), quartz feldspar porphyry
(py), Daca titea and desties (an), dolerites and basalts (b).
·
Other Formations: quartzite (qz), pegmatite (p), quartz
vein (q).
RELIEF
The lowest elevation in the
Federal Capital Territory (Abuja) is found in the extreme southwest where the
flood plain of the river Guraja is at an elevation of about 10mabove sea level
from there, the land rises irregularly eastward, northwards and north
westwards. The highest part of the territory is in the northeast where there
are many peaks over 760m above sea level. Hills occurs either as clusters or
form long ranges.
The most prominent of these
include the Gawa range in the northeast, the Guarfata range southwest of
Suleja; the Bwari-Aso range in the northeast, the Idon-Kasa range north-west of
Kuje and the Wuna range north of Gwagwalada. Elsewhere in the territory, there are
many rather roundish isolated hills usually called ISELBERGS in between the
major hills are extensive plains, the most important of which are the Gwagwa
plains and the Rubochi plains. Indeed about 50% of the Federal Capital
Territory (Abuja) consists of plains. Out of these plains, the Gwagwa plain was
selected for the building of the Federal Capital Territory City (F.C.T).
2.2 CLIMATE
The F.C.T (Abuja) has 2 main
seasons, rainy (April – October) and dry (November – March) seasons. The high
altitude and undulating terrain of the territory act to provide a regulating
influence on its weather. During the dry season, the typical month being March,
the temperature varies between 300 C in the north east to about 370
C in the southwest. This period is characterized by high diurnal ranges
when drops as low as 170 C may be recorded between the highest and
lowest temperature in the dry season. During the rainy season, temperature drop
considerably due to dense cloud cover. The annual range also drops to around 70
C, especially between July and August. The F.C.T records a relative
humidity in the dry seasons of some 20% in the afternoon at higher elevations
and at more northern locations but also 30% in the extreme south.
2.3 soils and vegetation
The soils of territory (Abuja)
are generally shallow and sandy in November, especially on the major plains
such as iku-Gurara, Roboes and Roubochi. The high sand content makes the soils
to be highly erodible. The shallow depth is a reflection of the presence of
strong lower horizons. Those on the famous Gwagwa plains are however deep and
clayey, perhaps reflecting the influence of parent materials gabbro and fine to
medium textured biotite granite.
Thus, the soils rich of the Gwagwa plains are
the most fertile and productive. In addition, their being more or less from all
exposed interfluves summits, makes them ideal for urban development. The F.C.T
(Abuja falls within the guinea savanna vegetation zone of Nigeria.
Patches of rain forest,
constituting about 7.4% of the total mass of the vegetation, however, occurs in
the Gwagwa plains, especially in the gullied terrains to the south and rugged
southeastern parts of the territory. Patches of the rainforest certain trees
such as Antirisem Africana, Anthocleista noblis, ceiba, pentandra, cola the
gigantean, celtis spp, chotorophora excels, khaya grandifondlia , terminnala
superb, piptadenianum africanum, Triplochiton sceroxylon and Dracaena arborea.
The dominant vegetation of the territory is classified into 3 namely.
·
Park or grassy savanna – about 53%
·
Savannah woodland
- about 12.85%
·
Shrub savannah – occurs extensively in rough terrains
close to hills and ridges in all parts of the territory and covers about 12.9%
of the total area.