Which is the longest river in the United States from the options below ?

Question

UnlockIAS · Accepted Answer

Correct — option (1), the Mississippi. The stem is careful to say 'from the options below', and that phrasing matters: of the four rivers offered, the Mississippi is by a wide margin the longest. It rises at Lake Itasca in northern Minnesota and runs roughly 3,766 kilometres south to its delta on the Gulf of Mexico, passing St Louis, Memphis and New Orleans. The next longest option, the Columbia, is little more than half that; the Snake is shorter still, and the Hudson is barely a seventh of the Mississippi's length. So the ranking within this option set is not close and the question turns on knowing the rough scale of each river rather than on any fine measurement. Two further facts make the Mississippi the natural answer to a question about American rivers. Its drainage basin is the third largest in the world after those of the Amazon and the Congo, gathering water from thirty-one states and two Canadian provinces — essentially the whole interior of the United States between the Rockies and the Appalachians. And with its great tributary the Missouri it forms a combined system among the longest on earth. That tributary is worth naming explicitly, because standard measurements make the Missouri itself marginally longer than the Mississippi and it is often listed as the longest single river in the United States; but the Missouri is not among the four options here, so it cannot affect this answer. Within the list the paper actually prints, the Mississippi stands alone at the top, and option (1) is right.

Why the other options are wrong — (b) The Columbia is a major river but a much shorter one, running about 2,000 kilometres from its source in British Columbia through Washington and along the Washington-Oregon boundary to the Pacific. It is the largest river by volume flowing into the Pacific from North America and is heavily dammed for hydroelectricity, which gives it a prominence out of proportion to its length and makes it a plausible-sounding answer. But volume of flow and economic importance are not what the stem asks about, and on length the Columbia is little more than half the Mississippi.  (c) The Snake is about 1,735 kilometres long and is itself a tributary — the largest tributary of the Columbia, which it joins in southeastern Washington after cutting Hells Canyon along the Idaho-Oregon boundary. A river that flows into another river in the same option list is very unlikely to be the longest in the country, and that structural observation alone should push it down the ranking. It is roughly half the length of the Mississippi and cannot be the answer.  (d) The Hudson is the shortest of the four by a very large margin, at roughly 500 kilometres from the Adirondack Mountains of New York south to New York Harbour. Its fame is historical and commercial rather than physical: it carried the early European settlement of the region, and with the Erie Canal it opened a route from the Atlantic to the Great Lakes. Prominence in American history is exactly what makes it a tempting name to a candidate guessing on recognition, and exactly why the question rewards a rough sense of each river's actual scale.

Concept: The drainage of the United States is organised by two mountain systems and the vast interior between them. The Rocky Mountains in the west and the Appalachians in the east enclose the Mississippi basin, which collects the runoff of the central lowland and carries it south to the Gulf of Mexico. The Mississippi itself flows from Lake Itasca in Minnesota to a birdfoot delta below New Orleans, and it gathers three great tributaries on the way — the Missouri from the northern plains, the Ohio from the Appalachian side, and the Arkansas from the south-west. Its basin covers about forty per cent of the conterminous United States and is the third largest drainage basin in the world. West of the Rockies the drainage is quite different: short, steep rivers reach the Pacific over a much shorter distance, the Columbia and its tributary the Snake being the largest of them, and they are valued more for hydroelectric power and irrigation than for navigation. On the Atlantic side the rivers are shorter still, the Hudson among them, because the Appalachian divide lies close to the coast.

State PCS 2024 Q28 — Geography PYQ with Answer

State PCS 2024 Q28 — Geography PYQ with Answer