This question was attempted by few candidates and the performance of the candidates that attempted the question was poor. The answers that were required of the candidates were:
(i) Characteristics of gorges
-           also called ravines/cayons
-           elongated
-           steep sided
-           can be dry
-           favours the construction of dams
-           could be associated with faults
-           deep narrow river valley
-           can be found in limestone regions
-           can be found on dissected plateaux
-           found along rejuvenated rivers
-           formed where rivers cross outcrops of resistant rocks
-           very common in upper course of rivers
-           usually V-shaped
-           examples include the Rhine in Germany, Shiroro gorge on river Kaduna, Bumbuna gorge in Sierra Leone on River Rokel, Bui gorge on River Volta in Ghana, along River Indus in India, Ajena gorge on River Volta in Ghana etc
(ii) Mode of formation of gorges
-           formed mostly in the upper course of a river
-           formed where waterfall retreats upstream
-           formed along fault lines
-           presence of alternate bands of hard and soft rocks
-           formed where  rivers cut deeply along the lines of weakness vertically
-           further vertical erosion deepens the valley
-           this creates an elongated depression
-           the depression has steep sides due to minimal lateral erosion
-           the valley is called a gorge
-           could be formed where a river crosses a limestone region
-           also where a river incises itself into the land surface due to fall in sea level
(iii)       Characteristics  of seif dunes
-           found in arid regions
-           they are sand deposits
-           they are long and narrow ridges
-           lie parallel to the direction of prevailing winds
-           they lie parallel to each other
-           could attain 60 meters in height
-           could be over 100km in length
-           crests are characterized by peaks and saddles
-           they migrate and are therefore not stationary
-           they are separated from each other by a corridor
-           also known as longitudinal dunes
-           have steep sides
-           the crest line is serrated
-           examples are the Great Sand Sea of Egypt and Libya in the Sahara Desert, Northeastern Nigeria, Namib Desert, Thar Desert,  in West Australian Desert, Southern Persian Desert
(iv) Mode of formation of seif dunes
-           formed in desert areas
-           formed due to wind deposition
-           sand dunes are deposited parallel to the prevailing wind
-           winds  blow to clear the corridors between the dunes of sand
-           eddies blow towards the sides of the corridors
-           this results in long parallel mounds of sand called the seif dunes
-           may also be formed when wind breaks through barchans
-           the winds forming the barchans may change their direction
-           this results in removal of sand from the middle of the barchan
-           the removed sands are deposited at the horns to build up seif dunes
-           the crest of the sand dunes moves forwards as more sand is accumulated by wind action
-           sand is blown up the windward side
-           this action leads to dune advancement/migration