(a) With the aid of suitable diagrams, describe the appearance and formation of any two of the following landforms (i) delta (ii) river capture (iii) waterf...

(a) Appearance and formation of any two landforms

(i) Delta

• Appearance: a low, flat, roughly triangular or fan-shaped mass of alluvium at a river mouth, split by many branching distributaries and dotted with swamps, sandbars and lagoons.
• Formation: as a heavily laden river enters a sea or lake, its velocity is suddenly checked. It can no longer carry its load, so it deposits sand, silt and mud at the mouth. Where deposition is faster than the sea can remove it, the sediment builds up, splits the channel into distributaries and extends seaward as a delta (for example the Niger Delta).

(ii) Waterfall

• Appearance: a vertical or steep drop where a river plunges over a rock step, with a plunge pool at its foot and often a gorge downstream.
• Formation: where a band of hard rock lies across the course above softer rock, the river erodes the soft rock downstream faster. This leaves the hard rock as a step over which the water falls. The falling water erodes the soft rock at the base, forming a plunge pool and undercutting the hard band, which collapses. Repeated collapse makes the fall retreat upstream, leaving a gorge.

Inselberg (alternative): an isolated, steep-sided residual hill of bare, resistant rock (often granite) rising abruptly above a plain, formed when surrounding weaker rock is worn away by long-continued weathering and erosion, leaving the resistant mass standing.

River capture (alternative): the diversion of the headwaters of one river into the valley of a neighbouring, more powerful river. The stronger stream, eroding headward, breaks into the weaker stream's valley at an elbow of capture, beheading it and leaving a dry wind gap and a misfit stream.

(b) Importance to man (one for each chosen feature)

• Delta: the fertile alluvial soils and abundant water support intensive farming and fishing; deltas such as the Niger Delta also yield petroleum.
• Waterfall: provides a site for generating hydro-electric power and attracts tourists.
• Inselberg: serves as a defensive/settlement site and a source of building stone and tourism.
• River capture: the enlarged captor river gives a bigger water supply and power potential.