WAEC SSCE - Geography - 1990 (Objective)

The presence of gorges in the upper section of rivers is due to the fact that?

the rocks in the upper course are less resistant

the volume of the river is small

hanging valleys join the main valley as waterfalls to cause the gorges

the upper course has has a steep gradient Amsar da ta dace

the water contains chemicals which dissolve the rocks

Bayanin Amsa

The correct option is "the upper course has a steep gradient." This is because the upper course of a river is the section closest to its source, and it usually has a steep gradient. The steep gradient causes the water to flow rapidly, eroding the bed and banks of the river channel. As a result, gorges are formed as the river cuts through hard rocks in the upper course, creating narrow and deep channels with steep sides. The other options, such as the volume of the river being small, rocks in the upper course being less resistant, hanging valleys, and chemicals in the water, may also contribute to the formation of gorges, but the steep gradient is the main cause.






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