Geography: UPSC Previous Year Questions (Prelims)

Explanation

A is matched with 3: The Deccan Traps are one of the largest volcanic provinces in the world, formed due to massive volcanic eruptions during the late Cretaceous and early Eocene periods (about 66 million years ago). These lava flows cover a vast part of western and central India. B is matched with 1: The Western Ghats, that include Sahyadri Hills, are part of the Late Cenozoic formations, meaning they formed relatively recently in geological history. These mountains are the result of faulting and uplift processes. C is matched with 2: The Aravalli Range is one of the oldest mountain ranges in the world, dating back to the Pre-Cambrian era. It is heavily eroded and was once part of a much larger mountain system. D is matched with 5: The river valleys of the Narmada and Tapi belong to the Pleistocene era (about 2.5 million to 11,700 years ago). They have alluvial deposits from recent geological periods due to sedimentation from river action.

Explanation

The 18°C January isotherm is used as the dividing line between the tropical and subtropical zones in India. This isotherm runs roughly along the Tropic of Cancer (23.5°N latitude) and helps distinguish the warmer tropical climate of southern India from the relatively cooler subtropical climate of northern India. Areas south of the 18°C isotherm (covering most of Peninsular India) experience tropical climate with higher temperatures, minimal winter, and a distinct monsoon pattern. Areas north of the 18°C isotherm (including northern states like Punjab, Haryana, and parts of Uttar Pradesh) fall under the subtropical zone, experiencing cooler winters and greater temperature variations between seasons.

Explanation

The Alamatti Dam is constructed on the Krishna River in Karnataka. It is a part of the Upper Krishna Irrigation Project and is located in Bagalkot district. The dam plays a crucial role in irrigation, hydroelectric power generation, and water management in Karnataka. It is one of the largest reservoirs in South India and helps regulate the flow of the Krishna River.

Explanation

The Farakka Barrage was constructed across the Ganga River in West Bengal with the aim of diverting water to the Hooghly River to ensure that the Kolkata Port remains navigable. The Farakka Feeder Canal is responsible for carrying the diverted water into the Hooghly River. Canal Capacity: The canal has a designed carrying capacity of 40,000 cusecs, which is the amount of water it can carry per second. This is an important feature of the Farakka Barrage, as it ensures the flow of sufficient water into the Hooghly River to prevent silting and to support the navigation in Kolkata’s port.

Explanation

Pair (d) is correctly matched: Sundari is a type of mangrove tree that is found in the Sundarbans region of West Bengal. It is well known for its role in the coastal ecosystem of the Sundarbans and is the dominant species in the mangrove forest. Pairs (a), (b) and (c) are incorrectly matched:

Teak is predominantly found in Tamil Nadu, Karnataka, and Kerala, not in Jammu and Kashmir. Jammu and Kashmir is known for coniferous trees like Chir Pine and Fir. Deodar (Cedrus deodara) is primarily found in Himachal Pradesh, Jammu and Kashmir, and Uttarakhand, not in Madhya Pradesh. Madhya Pradesh has a variety of other trees like Sal and Saja. Sandalwood (Santalum album) is native to Karnataka, Tamil Nadu, and Andhra Pradesh. Kerala is not popularly known for sandalwood cultivation, although the tree may grow there in some areas.

Explanation

Indian Standard Time (IST) is UTC +5:30 hours, based on the longitude 82°30’ E. The International Date Line (IDL) is at approximately 180° longitude. The difference in longitude between the IDL (180°) and the IST meridian (82°30’ E) is 97°30’ (180° - 82°30’). Time difference calculation: 15° of longitude corresponds to 1 hour of time difference. 97°30’ corresponds to 6 hours and 30 minutes (97.5° × 15° = 6.5 hours). Normal Earth Rotation (West to East):

When it is 12:00 noon at the IDL, it would be 05:30 AM (IST) (because IST is ahead of IDL by 6 hours 30 minutes). Reversed Rotation (East to West):

If the Earth rotates in the opposite direction, the time difference reverses. Instead of being ahead, IST will lag behind the IDL by 6 hours and 30 minutes. When it is 12:00 noon at the IDL, it will be 6:30 PM (18:30 IST).

Explanation

Option (d) is correct: The description refers to an extensive archipelago stretching from Aceh, a province on the northern tip of Sumatra Island in Indonesia, to the Torres Strait, which lies between Australia and Papua, near eastern Indonesia. The distance of about 5,000 miles and the mention of 14,000 islands align with Indonesia, the world’s largest archipe-lagic state, comprising over 17,000 islands. Major islands in this vast archipelago include Sumatra, Java, Borneo (Kalimantan), Su-lawesi, and New Guinea, which is shared with Papua New Guinea. Options (a), (b) and (c) are incorrect:

West Indies: The West Indies, an archipelago in the Caribbean Sea, consists of many islands, cays, and reefs. However, it is much smaller than Indonesia, with fewer islands and shorter distances from north to south. The islands also vary in size but are not as large as Indonesia’s biggest islands. Therefore, the West Indies do not match the description’s focus on vast distances and large island sizes. Japan: Japan, an East Asian archipelago, has a smaller land area and fewer islands than Indonesia. Its north-to-south span is much shorter than 5,000 miles, and its islands, though varied in size, do not include some of the world’s largest. Hence, Japan does not match the description as accurately as Indonesia. Philippines: The Philippines, an archipelago in Southeast Asia, has thousands of islands. However, it is smaller than Indonesia, with shorter distances between its northernmost and southernmost islands. While the Philippines have many islands, they lack the vast size and variety described, especially islands comparable to the world’s largest. Therefore, the Philippines do not match the description as closely as Indonesia.

Explanation

The "Diamond Ring" phenomenon is a striking optical effect observed during a total solar eclipse. It occurs when a small sliver of the Sun’s light is visible around the edge of the Moon, creating the appearance of a brilliant diamond resting on a luminous ring. This effect is typically seen moments just before the eclipse reaches totality or immediately after it ends.

Explanation

The Ionosphere ranges from approximately 60 kilometers (37 miles) to 1,000 kilometers (620 miles) above the Earth. It is characterized by the presence of ions and free electrons. These electrically charged particles are created by solar radiation (primarily ultraviolet and X-rays) that ionizes the atmospheric gases. The ionosphere plays a crucial role in radio wave propagation. It contains several layers (D, E, F1, and F2), each with varying densities of ions and electrons. These layers can reflect radio waves, allowing them to travel far beyond the horizon. The ability of the ionosphere to reflect radio waves depends on the frequency of the radio waves and the state of the ionosphere (which varies with time of day and solar activity).

Explanation

Option (a) is correct:

Assertion (A) is true: The regions near the equator (such as the tropics) generally receive consistent rainfall through-out the year. This is due to the Intertropical Convergence Zone (ITCZ), where the trade winds from both hemispheres converge, leading to frequent cloud formation and rain. The high temperatures and constant moisture availability near the equator contribute to year-round rainfall. Reason (R) is true: In equatorial regions, intense solar heating during the day warms the Earth’s surface, causing water to evaporate and warm, moist air to rise. As the air ascends, it cools, leading to the condensation of water vapor and the formation of cumulonimbus clouds. This process triggers convectional rainfall, which typically occurs in the afternoon. R is the correct explanation of A: The high temperatures and humidity near the equator lead to convectional rainfall, which contributes to the consistent precipitation observed throughout the year in equatorial regions.