UPSC Prelims 2013 · GS Paper I: Consider the following :1. Electromagnetic radiation2. Geothermal energy3. Gravitational force4. Plate movements5. Rotation of…

All six are correct (d). The Earth's surface is shaped by exogenic forces driven by solar radiation (1) and gravity (3): weathering, running water, wind, glaciers and mass movement. Endogenic forces come from geothermal energy (2) and plate movements (4): mountain building, volcanoes and earthquakes. Rotation (5) sets wind and ocean-current patterns through the Coriolis force and drives tides with the Moon. Revolution (6) brings the seasons, which change weathering, rivers and glaciers. So (a), (b) and (c) leave out real factors.

Notice the frame: geomorphology sees landforms as a balance between endogenic building and exogenic wearing down. Gravity also drives landslides on young slopes such as the Himalaya. Trap: rotation and revolution seem astronomical, but they shape climate and so the surface.

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Bahrain and Qatar must cross the Strait of Hormuz (b). The Strait of Hormuz, between Iran and Oman, is the only sea exit from the Persian Gulf. Items 1 and 3 are right: Bahrain and Qatar lie wholly inside the Gulf, so their ships must pass it. Item 2 is wrong: Syria is on the Mediterranean. Item 4 is wrong: Egypt reaches the Indian Ocean through the Suez Canal and the Red Sea. So options (a), (c) and (d) fail.

Notice its importance: about a fifth of the world's oil passes through Hormuz, and much of India's crude and LNG (Qatar is a top LNG supplier). Iran's threats to close it raise prices. The UAE's pipeline to Fujairah and Saudi pipelines to the Red Sea help bypass it.

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Tungurahua is in Ecuador (a). Tungurahua, meaning "throat of fire", is an active stratovolcano in the Andes of central Ecuador, above the town of Baños. UNESCO named the area around it a Global Geopark in 2025. Options (b), (c) and (d), Peru, Bolivia and Colombia, are wrong, though the Andes pass through all of them too.

Notice Ecuador's other famous volcanoes: Cotopaxi, one of the highest active volcanoes, and Chimborazo, whose summit is the point farthest from Earth's centre, because of the equatorial bulge. Ecuador also owns the Galápagos Islands. A Global Geopark honours geological heritage; India has none yet, though sites like Lonar have been proposed.

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Statements 1 and 2 are correct (b). Statement 1 is right: the islands lie close to the equator in the Bay of Bengal, so they are hot and humid all year, a tropical coastal climate. Statement 2 is right: they get rain from both the south-west and north-east monsoons, from about May to December. Statement 3 is wrong: January to April is the driest part of the year, so maximum rain is not between December and May. So options (a), (c) and (d) fail.

Notice the islands' features: Barren Island, India's only active volcano; Saddle Peak, the highest point; and Indira Point, India's southernmost tip. Rich tropical evergreen forests cover them, and cyclones often form nearby.

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Features 1 and 2 belong to the Peninsular Block (b). The Peninsula is an old, stable block. Item 1 is right: faulting submerged parts of the west coast. Item 2 is right: long erosion left residual hills such as the Veliconda and Mahendragiri. Item 3 is wrong: Peninsular rivers are mature, with broad, shallow valleys; deep V-shaped valleys belong to the young Himalayan rivers. So options (a), (c) and (d) fail.

Notice other Peninsular traits: Gondwana coal, Deccan Traps basalt, rift valleys of the Narmada and Tapi, which flow west into the Arabian Sea, and old block mountains like the Aravallis, among the world's oldest. Rivers here are rain-fed, not snow-fed.

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