UPPSC 2025 Prelims GS Paper-I · Question 85 of 150

Correct — B, (A) is true, but (R) is false. The Assertion is sound: the Australian interior — the 'outback' — is dominated by the Great Victoria, Great Sandy, Tanami, Gibson and Simpson deserts, and roughly seventy per cent of the continent is classed as arid or semi-arid. The Reason is false on its geography: northern Australia is not in the temperate zone at all. The Tropic of Capricorn (about 23.5 degrees South) runs right across the middle of the continent, passing near Alice Springs in the Northern Territory and Rockhampton in Queensland, so everything north of that line — Darwin, the Kimberley, Arnhem Land, Cape York — lies inside the tropical (torrid) zone and has a monsoonal wet-and-dry savanna climate. Australia's temperate belt is its SOUTH: Victoria, Tasmania, and the southern margins of Western Australia, South Australia and New South Wales. With the Assertion true and the Reason false, the answer is (b).

• (a)Both (A) and (R) are true, but (R) is not the correct explanation of (A) — This accepts the Reason, and the Reason is the one wrong statement in the pair. It is the option chosen by a candidate who spots that the two statements do not connect but never checks the factual claim about the northern zone.
• (c)(A) is false, but (R) is true — It inverts the truth values completely. The desert interior is one of the least disputable facts in world regional geography, and the temperate-north claim is simply wrong — the Tropic of Capricorn crosses the continent well south of Darwin.
• (d)Both (A) and (R) are true and (R) is the correct explanation of (A) — Doubly wrong. The Reason is false, and even if one granted it, a statement about the NORTH could not explain the aridity of the INTERIOR. The genuine causes are the subtropical high-pressure belt sitting over the middle of the continent, the rain shadow of the Great Dividing Range, sheer distance from the sea across a 4,000 km-wide landmass, and the cold West Australian Current offshore.

Australia is the driest inhabited continent. The Tropic of Capricorn bisects it, so the interior lies under the descending limb of the Hadley cell — the subtropical high-pressure belt of stable, subsiding, drying air that produces every major tropical desert, from the Sahara and Kalahari to the Atacama. Three further factors deepen the aridity: the Great Dividing Range along the east coast intercepts the moisture-bearing south-east trades and casts a long rain shadow inland; the continent's great east-west extent leaves the centre far from any moisture source; and the cool West Australian Current chills the western coastal air, suppressing convection and rainfall.

Latitudinal zones are the quiet half of this question. The torrid zone runs between the Tropic of Cancer and the Tropic of Capricorn, the temperate zones lie between each tropic and the corresponding polar circle, and the frigid zones lie beyond. Since the Tropic of Capricorn cuts through central Australia, the country is split: tropical in the north, temperate in the south. A candidate who mentally files 'Australia' as a temperate, European-settled country will accept the Reason without checking. The reliable habit is to place the country against the tropic lines before judging any climate statement about it. Also note the code ordering in this paper: option (a) is 'both true, no explanatory link' and option (d) is 'both true, R explains A' — the reverse of the ordering candidates usually see, so read the labels before marking.

• The Tropic of Capricorn (about 23.5 degrees S) crosses central Australia near Alice Springs and Rockhampton, placing northern Australia inside the tropical zone
• Northern Australia has a tropical monsoon and savanna climate with a marked wet season and dry season; the temperate belt is in the south (Victoria, Tasmania, southern WA/SA/NSW)
• Major interior deserts: Great Victoria (the largest), Great Sandy, Tanami, Gibson and Simpson
• Roughly 70% of the continent is arid or semi-arid, making Australia the driest inhabited continent
• Causes of the aridity: the subtropical high-pressure belt, the rain shadow of the Great Dividing Range, continentality, and the cold West Australian Current

• Assuming Australia as a whole is temperate; the Tropic of Capricorn splits it into a tropical north and a temperate south
• Accepting a false Reason because the Assertion is obviously true — always test the two statements separately before testing the link
• Attributing interior aridity to latitude of the north rather than to the subtropical high-pressure belt and the Great Dividing Range's rain shadow

UPPSC hides a latitudinal-zone error inside an assertion-reason on a well-known regional fact; UPSC prefers the direct forms — which countries the Tropic of Capricorn passes through, or which desert belongs to which country.

• practice — not a real PYQ

  The Great Victoria Desert is located in which country?

  • (a)South Africa
  • (b)Australia
  • (c)Argentina
  • (d)Mongolia

  Answer(b) Australia — it is the largest of the Australian deserts, in Western Australia and South Australia.

• practice — not a real PYQ

  Which one of the following best explains why the world's great tropical deserts occur on the western margins of continents between about 20 and 30 degrees latitude?

  • (a)Persistent onshore monsoon winds
  • (b)Subsiding air of the subtropical high-pressure belt, reinforced by cold offshore currents
  • (c)The rain shadow of young fold mountains alone
  • (d)Very high mean annual cloud cover

  Answer(b) Subsiding air of the subtropical high-pressure belt, reinforced by cold offshore currents — the mechanism behind the Sahara, Namib, Atacama and the Australian deserts alike.