UPSC Mains Answer PYQ 2025: Geography Paper 1 (Section- A)

Q1: Answer the following in about 150 words each:
(a) Explain the causes of glacial lake outburst flood.
Ans: Glacial Lake Outburst Floods (GLOFs) occur when moraine-dammed lakes in glaciated regions suddenly release large volumes of water. Causes include:

• Glacial melting: Accelerated by climate change, leading to lake expansion and overflow. For instance, Himalayan glaciers are retreating rapidly due to global warming, as seen in the 2023 Sikkim GLOF.
• Moraine dam failure: Weak dams made of ice, rock, and debris collapse under pressure from seismic activity, avalanches, or heavy rainfall.
• Triggering events: Earthquakes, landslides, or ice calving into the lake cause surges that breach dams.
• Human factors: Infrastructure like hydropower dams can exacerbate risks if not designed resiliently.

GLOFs devastate downstream areas, causing flash floods, erosion, and loss of life. Recent events in Bhutan and Nepal highlight the need for early warning systems amid rising temperatures up to 2025.

(b) What is solifluction? What are its impacts?
Ans: Solifluction is a slow downslope movement of saturated soil or regolith in periglacial environments, where the active layer above permafrost thaws seasonally. It occurs in Arctic and alpine regions with freeze-thaw cycles, causing soil to become waterlogged and flow like a viscous fluid at rates of 1-10 cm/year.

Impacts include:

• Landscape modification: Forms lobate or terraced features, altering topography and creating solifluction lobes.
• Infrastructure damage: Undermines roads, pipelines, and buildings; for example, in Alaska's permafrost zones, it contributes to structural instability amid climate-induced thawing.
• Ecosystem disruption: Affects vegetation patterns and soil stability, leading to erosion and habitat loss.
• Human risks: Increases landslide hazards in mountainous areas. With permafrost degradation accelerating due to global warming-projected to affect 20% more land by 2025-solifluction exacerbates challenges in polar regions.

Mitigation involves engineering solutions like insulated foundations.

(c) What geological and tectonic processes lead to the formation of nappes in orogenic belts?
Ans: Nappes are large, sheet-like rock bodies thrust over underlying strata in orogenic belts, formed during mountain-building processes.

Geological and tectonic processes:

• Plate convergence: Collisional tectonics, where continental plates collide, generate compressive forces. E.g., the India-Eurasia collision forming the Himalayas.
• Thrust faulting: Rocks detach along low-angle faults and slide over foreland basins due to shortening.
• Folding and overthrusting: Initial folding evolves into recumbent folds; continued compression causes overriding, creating nappes.
• Metamorphism and erosion: Heat and pressure alter rocks; uplift and erosion expose nappes, as in the Alps' Penninic nappes.

These occur in zones like the Appalachians or Caledonides. Recent seismic studies up to 2025 reveal active thrusting in the Himalayas, linking nappes to earthquake risks.
Nappes indicate intense deformation, aiding in reconstructing paleogeography.

(d) Explain the relationship between air masses and local winds.
Ans: Air masses are large bodies of air with uniform temperature, humidity, and stability, formed over source regions like oceans or continents. They influence weather patterns and are linked to local winds through thermal and pressure gradients.

Relationship:

• Formation of winds: Contrasting air masses create fronts; warm and cold air interactions generate pressure differences, driving winds. E.g., sea breezes occur when cooler maritime air moves inland to replace rising continental air.
• Monsoonal winds: Seasonal shifts in air masses, like moist equatorial air during Indian monsoons, reverse wind directions.
• Mountain and valley winds: Orographic effects modify air masses; anabatic (upslope) winds form as air heats over slopes, while katabatic (downslope) winds involve dense cold air descending.
• Jet streams and trade winds: Large-scale air mass movements influence persistent local winds.

With climate change altering air mass properties by 2025, local winds like intensified haboobs in deserts are becoming more erratic.

(e) What are the fundamental differences among ocean wave, ocean current and tide?
Ans: Ocean waves, currents, and tides are distinct marine phenomena driven by different forces.

• Ocean waves: Surface disturbances caused by wind friction, transferring energy across water without net water displacement. They are oscillatory, with height depending on wind speed, duration, and fetch. E.g., tsunamis from earthquakes differ from wind waves.
• Ocean currents: Large-scale, continuous flows of water influenced by wind, Coriolis effect, salinity, and temperature gradients (thermohaline circulation). They transport heat and nutrients globally, like the Gulf Stream warming Europe. Currents are horizontal and persistent.
• Tides: Periodic rise and fall of sea levels due to gravitational pulls of Moon and Sun, combined with Earth's rotation. They are predictable, with semi-diurnal or diurnal patterns, causing vertical water movement.

Fundamental differences: Waves are energy propagators, currents are mass transporters, tides are gravitational responses. Climate impacts by 2025, like stronger currents from melting ice, affect all.

Q2: (a) How does denudation chronology help in understanding the sequential development of landscapes and landforms? Elucidate.
Ans: Denudation chronology is the study of the long-term history of landscape evolution through processes of weathering, erosion, and deposition over geological time scales. It reconstructs the sequential development of landforms by analysing relict surfaces, erosional features, and stratigraphic evidence preserved in the present landscape.

It helps in understanding landscape development in the following ways:

1. Identification of polycyclic landscapes: Most landscapes are not the product of a single erosion cycle but multiple cycles interrupted by tectonic uplift or climatic changes. Denudation chronology identifies planation surfaces (peneplains, pediplains), river terraces, and knick points that represent remnants of older cycles.
2. Reconstruction of erosion cycles: Using concepts like Davis' cycle of erosion (youth, maturity, old age), Penck's slope replacement, and King's pediplanation, it establishes the sequence of base-level changes and corresponding landform development.
3. Correlation of surfaces across regions: Relict surfaces at similar altitudes are correlated to infer widespread erosion episodes, often linked to eustatic sea-level changes or tectonic stability.
4. Dating landscape evolution: By integrating evidence from marine terraces, laterites, duricrusts, and river longitudinal profiles, it provides a relative chronology of denudational events.

Examples include the Deccan Plateau with multiple pediplain levels, the Himalayan terraces indicating uplift phases, and the African landscape studied by L.C. King showing scarp retreat and pedimentation.

Thus, denudation chronology reveals that landscapes are dynamic records of past geomorphic processes, enabling a time-sequenced understanding of landform development beyond static description. It highlights the interplay of endogenic (tectonic) and exogenic (climatic, erosional) forces in shaping the Earth's surface over millions of years.

(b) What is deep-sea mining? What are the potential benefits and risks associated with it?
Ans: Deep-sea mining refers to the extraction of mineral deposits from the ocean floor at depths greater than 200 metres, primarily in international waters (the Area) or exclusive economic zones. Target resources include polymetallic nodules (rich in manganese, nickel, cobalt, copper), seafloor massive sulphides (copper, gold, zinc), and cobalt-rich ferromanganese crusts.

Potential benefits:

1. Supplies critical minerals essential for renewable energy technologies, electric vehicle batteries, and electronics, reducing dependence on land-based mining in politically unstable regions.
2. Offers large, high-grade deposits with potentially lower social impacts (no displacement of communities).
3. Supports the global energy transition by providing cobalt and nickel needed for green technologies.

Potential risks:

1. Environmental damage: Sediment plumes can smother benthic organisms, disrupt food chains, and affect mid-water ecosystems. Deep-sea biodiversity, much of it undiscovered, faces irreversible loss.
2. Noise and light pollution disturbing marine mammals and fragile habitats like hydrothermal vents.
3. Carbon storage disruption: Deep-sea sediments store significant carbon; disturbance could release it, worsening climate change.
4. Regulatory challenges: As of 2025, the International Seabed Authority (ISA) has issued exploration contracts but not yet finalised exploitation regulations. Some nations and NGOs continue to call for a moratorium due to insufficient scientific knowledge.

While deep-sea mining promises resource security, the ecological risks to largely unknown deep-ocean ecosystems demand precautionary approaches and robust environmental safeguards before commercial operations begin.

(c) Man and wildlife conflicts are ever increasing. Discuss its causes, consequences and remedies. 
Ans: Human-wildlife conflict (HWC) occurs when wildlife requirements overlap with human needs, resulting in negative impacts on both. In India and globally, such conflicts have intensified in recent decades.

Causes:

1. Habitat loss and fragmentation due to agriculture expansion, infrastructure, mining, and urbanisation, pushing animals into human settlements.
2. Growing human and wildlife populations increasing competition for space and resources.
3. Climate change altering animal migration and foraging patterns.
4. Crop raiding attraction: Animals like elephants and wild boar are drawn to nutritious crops.
5. Developmental activities encroaching on corridors (linear infrastructure disrupting elephant pathways).

Consequences:

1. Human losses: Deaths, injuries, and property/crop damage, leading to economic hardship and fear.
2. Wildlife losses: Retaliatory killings, poisoning, and poaching, threatening endangered species like tigers and elephants.
3. Social impacts: Reduced community support for conservation, perpetuating a negative cycle.

Remedies:

1. Habitat management: Secure wildlife corridors, restore degraded habitats, and create buffer zones.
2. Physical barriers: Solar-powered electric fencing, trenches, and bee-hive fences for elephants.
3. Compensation and insurance: Prompt, fair ex-gratia payments and crop insurance schemes (e.g., India's improved guidelines).
4. Community participation: Eco-development committees, eco-tourism benefits, and early-warning systems.
5. Scientific interventions: Use of chilli fences, motion-sensor lights, and population control where needed.
6. Policy measures like Project Elephant, Project Tiger, and integrated landscape planning.

Effective mitigation requires coordinated efforts between governments, NGOs, and local communities to ensure coexistence and long-term conservation success.

Q3: (a) Examine the formation of atmospheric tricellular circulation system. Describe with example its importance in making the Earth a living planet. 
Ans:

• The atmospheric tricellular circulation system is a global model that explains large-scale air movement in three distinct cells in each hemisphere: Hadley cell, Ferrel cell, and Polar cell. It forms due to uneven solar heating and Earth's rotation.
• At the equator, intense heating causes air to rise, creating low pressure (ITCZ). This warm air moves poleward aloft, cools, and descends around 30°N/S, forming high-pressure subtropical highs. The returning surface flow towards the equator, deflected by Coriolis force, creates trade winds - completing the Hadley cell.
• Between 30°-60°, the Ferrel cell (mid-latitude) is thermally indirect. Air rises at subpolar low (60°) and descends at subtropical high, driven largely by polar and tropical cells.
• At high latitudes, cold air sinks at the poles, flows equatorward at surface as polar easterlies, rises at 60° - forming the Polar cell.

This system is vital for making Earth a living planet as it redistributes heat from equator to poles, preventing extreme temperature contrasts - equator would be unbearably hot and poles freezing cold. It drives global wind patterns and precipitation, sustaining the water cycle.

For example, seasonal shift of Hadley cell and ITCZ causes the Indian monsoon, bringing rainfall essential for agriculture and supporting billions. It moderates climate, enables diverse ecosystems from rainforests to deserts, and supports biodiversity by facilitating nutrient cycling and oxygen distribution. Without this circulation, life would be confined to narrow equatorial zones, making Earth largely uninhabitable.

(b) What is the 'UN Decade on Ecosystem Restoration'? How does it balance ecological goals with emerging socio-economic needs like food security and development?
Ans:
The UN Decade on Ecosystem Restoration (2021-2030) is a global initiative proclaimed by the United Nations General Assembly in 2019 and launched in 2021, led by UNEP and FAO. It aims to prevent, halt, and reverse the degradation of ecosystems worldwide on a massive scale to achieve the Sustainable Development Goals (SDGs).

Its core objectives include restoring degraded lands, forests, wetlands, oceans, and urban areas to enhance biodiversity, combat climate change, and improve human well-being. As of 2025, progress reports highlight millions of hectares under restoration, with focus on agriculture and nutrition benefits.

The Decade balances ecological goals with socio-economic needs by promoting inclusive, sustainable restoration approaches. It integrates restoration with livelihoods:

• Restoring degraded farmlands through agroforestry and regenerative agriculture boosts soil health, increases crop yields, and ensures food security while sequestering carbon.
• Mangrove restoration protects coasts from erosion, supports fisheries (enhancing protein sources), and creates jobs.
• Watershed restoration improves water security for communities and agriculture.

It addresses SDGs like Zero Hunger (SDG-2), Clean Water (SDG-6), and Decent Work (SDG-8) by generating employment in restoration activities and supporting local economies. The approach avoids trade-offs by prioritizing community-led projects that deliver ecological benefits alongside poverty reduction and development. Thus, it views healthy ecosystems as foundations for sustainable socio-economic progress.

(c) "The Himalaya is still rising." Expand this statement and describe the processes involved in it with suitable sketches and examples. 
Ans:
The statement "The Himalaya is still rising" is true because the mountain range is geologically young and active, formed by ongoing continental-continental collision between the Indian Plate and Eurasian Plate. GPS measurements show uplift rates of 4-10 mm/year in parts, with Mount Everest growing ~1-2 mm annually.

Processes involved:

1. Plate convergence: Indian Plate moves northward at ~4-5 cm/year, colliding with Eurasian Plate since ~50 million years ago.
2. Crustal shortening and thickening: Unable to subduct fully due to buoyant continental crust, the plates compress, causing folding, thrusting, and uplift.
3. Faulting and thrusting: Major faults like Main Himalayan Thrust (MHT) and Main Boundary Thrust accommodate movement, leading to earthquakes.
4. Isostatic adjustment: Erosion removes material, causing rebound uplift.

Examples: Rapid uplift in Nanga Parbat (Pakistan) at ~7-10 mm/year; frequent earthquakes (e.g., 2015 Nepal) indicate active tectonics. The range has risen from sea level (Tethys sediments at Everest summit) to current heights, and continues due to persistent convergence.

Q4 (a) What are the ecological consequences of agricultural deforestation in the Amazon and Congo Basins, particularly concerning biodiversity and climate regulation? 
Ans:

• Agricultural deforestation in the Amazon and Congo Basins - driven by cattle ranching, soy plantations in the Amazon, and small-scale farming, charcoal production in the Congo - has severe ecological impacts, especially on biodiversity and climate regulation.
• Impact on BiodiversityThe Amazon holds about 10% of global biodiversity with millions of species, many endemic. The Congo Basin, the world's second-largest rainforest, supports unique wildlife like gorillas, forest elephants, and bonobos. Deforestation causes habitat fragmentation, leading to species extinction and reduced genetic diversity. In 2024-2025, despite a 34% cumulative decline in Amazon deforestation under Brazil's policies, illegal agriculture and fires continue to threaten endangered species. In the Congo, record-high deforestation in DRC (2024) from agriculture around mines accelerates biodiversity loss in this critical hotspot.
• Impact on Climate RegulationBoth basins act as major carbon sinks. Deforestation releases stored carbon, contributing to global warming. The Amazon risks reaching a tipping point, potentially turning into savanna, reducing regional rainfall via disrupted "flying rivers." This affects agriculture in South America. In the Congo, rising forest loss threatens rainfall in Central Africa and global cocoa supply. Recent data (2024) show tropical forests, including these basins, shifting toward net carbon emissions due to fires and degradation.
• At COP30 (2025) in Belém, Brazil highlighted progress in reducing Amazon deforestation, but weak global commitments allow continued agricultural expansion. Sustainable agriculture, zero-deforestation policies, and international funding are essential to protect these vital ecosystems.

(b) Examine the distribution and balance of energy in the Earth's atmosphere system. 
Ans:

• The Earth's atmosphere maintains a delicate energy balance through incoming solar radiation (insolation) and outgoing terrestrial radiation.
• The Sun emits short-wave radiation, with Earth receiving about 340 W/m² at the top of the atmosphere. Around 30% reflects back due to albedo (clouds, ice, surfaces), while 70% absorbs - 23% by the atmosphere (gases, dust) and 47% by the surface (land, oceans).
• The surface emits long-wave radiation upward. Greenhouse gases (CO₂, methane, water vapour) absorb much of this, re-emitting it downward and upward. This creates the greenhouse effect, keeping Earth's average temperature at 15°C instead of -18°C. Ultimately, the Earth radiates 340 W/m² back to space, balancing incoming energy.
• Latitudinal Distribution: Equatorial regions receive surplus energy (high insolation, low albedo), creating a heat surplus. Polar regions face deficit (low insolation, high albedo). This imbalance drives atmospheric and oceanic circulation - winds, hurricanes, ocean currents - transferring heat poleward to maintain global equilibrium.
• Human activities, especially greenhouse gas emissions, disrupt this balance by trapping more heat, leading to global warming. The energy budget thus regulates climate stability.

(c) Describe the process of formation of barrier islands and explain their significance. 
Ans:

• Barrier islands form as long, narrow, sandy landforms parallel to the coast, separated by lagoons or marshes.
• Process of FormationThey primarily develop on low-lying coasts with abundant sediment supply and gentle slopes. During the Holocene sea-level rise, longshore currents and waves transport sediments parallel to the shore. These deposits build offshore bars that gradually emerge as islands through wave action and wind-blown sand accumulation. Alternatively, they form by the breaking and submergence of coastal spits or by drowning of beach ridges during transgression. Vegetation (dunes grasses) later stabilises them. Examples include the US East Coast barrier islands.

Significance

• Coastal Protection: They act as natural buffers, absorbing wave energy and protecting mainland from storms, erosion, and sea-level rise.
• Ecological Value: Lagoons and marshes behind them serve as nurseries for fish, habitats for migratory birds, and biodiverse wetlands.
• Human Importance: They support tourism, fisheries, and settlements, but face vulnerability to hurricanes and rising seas.

In the context of climate change, barrier islands play a crucial role in coastal resilience but require conservation to prevent breaching or disappearance.