Which one of the following pairs (River – Direction) is not correctly matched ?

Question

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Correct — D, Mekong river – South-West. The Mekong is the odd one out because it runs the other way along the east–west axis: it rises on the Tibetan Plateau in Qinghai, cuts south through Yunnan as the Lancang, then continues broadly south and south-east along the Myanmar–Laos and Laos–Thailand borders, through Cambodia, and ends in a delta in southern Vietnam that empties into the South China Sea. Every leg of that ~4,350 km course carries the water southward and eastward — never towards the south-west. A river flowing south-west from Tibet would have to head for the Bay of Bengal, which is the Irrawaddy and Salween story, not the Mekong's. So the pair 'Mekong – South-West' is the one that is not correctly matched, and (d) is the marked answer. The way to keep this straight is to fix the mouth rather than the middle: Amur → Strait of Tartary and the Pacific in the far north-east; Syr Darya → the shrunken northern Aral Sea in the north-west of its basin; Angara → the Yenisei, reached by first running due north out of Lake Baikal; Mekong → the South China Sea in the far south-east. Once the mouths are fixed, the compass directions follow without memorising them.

Why the other options are wrong — (a) Correctly matched, so it cannot be the answer. The Amur proper begins where the Shilka and the Argun meet on the Russia–China frontier. It first runs east, arcs south-east for a few hundred kilometres, and then — after the Songhua (Sungari) joins it and it passes Khabarovsk — turns decisively north-east, flowing north-north-east through a wide valley in eastern Russia before swinging east to its mouth at Nikolayevsk-na-Amure. From there it enters the Pacific through the Strait of Tartary, which links to the Sea of Okhotsk. Its net displacement from source to mouth is emphatically towards the north-east, which is exactly what the option says.  (b) Correctly matched. The Syr Darya is formed in the Fergana Valley where the Naryn and the Kara Darya, both fed by the Tian Shan, come together. From there it runs for about 2,256 km 'west and north-west' through Uzbekistan, the Sughd province of Tajikistan and southern Kazakhstan, ending in the northern remnant of the Aral Sea near Kazaly. It is the classic north-westward Central Asian river — its twin, the Amu Darya, does the same thing further south, and the two together once kept the Aral Sea alive.  (c) Correctly matched. The Angara is the single river that flows out of Lake Baikal — over three hundred streams feed the lake, but only the Angara drains it, leaving near the settlement of Listvyanka. It then runs north past Irkutsk, Angarsk, Bratsk and Ust-Ilimsk, crosses the Angara Range, and only in its final stretch turns west to join the Yenisei near Strelka. 'North' is therefore the right label for its dominant direction, and the later westward swing does not change that.

Concept: The direction a river takes is decided by the regional slope of the land, not by any preference of its own, so a river's compass heading is really a statement about the tilt of the continent it drains. Northern Asia tilts towards the Arctic, which is why the Ob, the Yenisei and the Lena — and the Angara that feeds the Yenisei — all run north. The Central Asian interior is a closed basin with no outlet to the sea, so the Amu Darya and the Syr Darya run inward and north-west to the Aral Sea and die there. The Far Eastern margin drains to the Pacific, taking the Amur north-east. And the Tibetan Plateau, the highest source region on Earth, sheds water in every direction — the Indus and Sutlej west, the Brahmaputra east then south, and the Salween, Mekong and Yangtze south and south-east through the deep parallel gorges of Yunnan.

State PCS 2024 Q77 — Geography PYQ with Answer

State PCS 2024 Q77 — Geography PYQ with Answer