1.5 - Geography Notes 35

Elaborate Notes

Laterization

Laterization is a pedogenic (soil-forming) process that occurs intensely in hot and humid climates, characteristic of tropical and equatorial regions. The term was first used by Francis Buchanan-Hamilton in 1807 to describe a ferruginous, clay-rich soil material in southern India that hardens upon exposure to air.

• Process: The process is driven by intense and prolonged chemical weathering due to high temperatures and heavy rainfall. The abundant water percolating through the soil profile leads to a process known as leaching, where soluble minerals are washed away from the upper soil layers.
• Chemical Reactions: In these conditions, hydrolysis breaks down silicate minerals. Silica (SiO₂) and other base minerals like calcium, magnesium, and potassium are highly soluble and are leached downwards, often completely out of the soil profile.
• Accumulation: Less soluble compounds, primarily sesquioxides of iron (Fe₂O₃) and aluminium (Al₂O₃), are left behind and become concentrated in the upper layer, or solum. This accumulation is known as residual concentration.
• Resulting Soil: This process forms laterite soil (classified as Oxisols or Ultisols in the USDA Soil Taxonomy). The high concentration of iron oxides gives the soil a characteristic reddish-brown colour. When exposed to alternating wet and dry conditions, this layer can harden into a brick-like crust called a duricrust or ferricrete. The soil is typically deep, but has low natural fertility due to the loss of essential plant nutrients and organic matter. It is also slightly acidic because of the removal of alkaline base minerals.
• Examples: Laterite soils are widespread in the Amazon Basin, the Congo Basin, Southeast Asia, and in parts of India, such as the Western Ghats, Eastern Ghats, and parts of the Chota Nagpur Plateau.

Podzolization

Podzolization is a soil-forming process dominant in cool, moist climates, particularly in temperate and boreal regions characterized by coniferous forests (taiga). The term ‘podzol’ is Russian, meaning “under ash,” which refers to the distinct, light-coloured E-horizon that is a hallmark of these soils.

• Process: It begins with the slow decomposition of acidic litter from coniferous trees (like pine and spruce) and heaths. This decomposition produces a layer of acidic raw humus called mor.
• Chemical Reactions: As precipitation percolates through this acidic mor layer, it forms potent organic acids (fulvic and humic acids). This acidic solution initiates a process called chelation, where the organic acids bond with metallic ions like iron and aluminium, making them soluble and mobile.
• Translocation: This acidic leachate moves downward, stripping the upper soil layer (A and E horizons) of iron, aluminium, organic matter, and other minerals, a process known as eluviation. The only primary mineral that resists this acidic leaching is quartz (silica), which remains behind, creating a bleached, ashy-grey layer known as the E-horizon (albic horizon).
• Resulting Soil: The leached materials are then redeposited in the lower B-horizon, a process called illuviation, forming a dark, dense layer often cemented by iron/aluminium oxides and humus (spodic horizon). The resulting soil, Podzol (classified as Spodosols in USDA Taxonomy), is highly acidic, has distinct horizons, and is generally infertile for agriculture without significant amelioration like liming.
• Examples: Podzols are found extensively across Scandinavia, Russia, Canada, and in mountainous regions at higher altitudes with coniferous vegetation.

Calcification

Calcification is a pedogenic process that occurs in sub-humid to arid and semi-arid climates where potential evapotranspiration exceeds precipitation. It is particularly characteristic of grassland and steppe ecosystems.

• Process: In these environments, rainfall is insufficient to leach soluble minerals completely out of the soil profile. During dry periods, water from lower soil layers is drawn upwards towards the surface by capillary action.
• Chemical Reactions: This upward-moving water carries dissolved calcium bicarbonate (Ca(HCO₃)₂). As the water evaporates at or near the surface, the calcium bicarbonate precipitates as calcium carbonate (CaCO₃).
• Accumulation: This leads to the accumulation of calcium carbonate in a specific layer within the soil profile, typically the B-horizon or sometimes the C-horizon. This layer of carbonate accumulation is known as a calcic horizon, which can become cemented into a hardpan called caliche or kankar in India.
• Resulting Soil: The process results in soils rich in calcium and with a high base saturation, making them very fertile. The most famous soils formed through this process are the Chernozems (black earths), which are renowned for their agricultural productivity. These soils, studied extensively by the Russian scientist V.V. Dokuchaev in the late 19th century, are a type of Mollisol in the USDA system.
• Examples: This process is active in the Prairies of North America, the Pampas of South America, and the Steppes of Eurasia.

Salinization

Salinization is the process of accumulation of soluble salts, such as sodium chloride, magnesium and calcium sulfates, and bicarbonates, in the soil to an extent that it inhibits plant growth.

• Process: It is dominant in arid and semi-arid regions where low precipitation is coupled with high evaporation rates. Water containing dissolved salts is drawn to the surface by capillary action, and as the water evaporates, the salts are left behind as a white crust on the surface.
• Anthropogenic Causes: Salinization is also a significant issue in irrigated agriculture, particularly flood irrigation. Irrigation water, even with low salt content, can lead to a gradual build-up of salts over years. Poor drainage exacerbates the problem by causing the water table to rise, bringing dissolved salts closer to the root zone and the surface. This is a well-documented consequence of the Green Revolution in parts of Punjab and Haryana in India.
• Resulting Soil: The resulting soils are saline or sodic, with poor soil structure and low water infiltration. High salt concentrations create a high osmotic potential, making it difficult for plants to absorb water, leading to physiological drought. These soils are classified as Aridisols in the USDA system.

Gleisation

Gleisation is a soil-forming process associated with waterlogged, anaerobic (oxygen-deficient) conditions, common in poorly drained areas like swamps, bogs, and coastal plains.

• Process: The persistent saturation of soil with water eliminates oxygen, creating a reducing environment. In these anaerobic conditions, soil microbes use other elements instead of oxygen for respiration.
• Chemical Reactions: A key reaction is the reduction of ferric iron (Fe³⁺), which is insoluble and gives soils a red, brown, or yellow colour, to ferrous iron (Fe²⁺), which is soluble and mobile. Ferrous iron compounds impart a characteristic blueish-grey or greenish-grey colour to the soil. This subsoil layer is known as the gley horizon. The soil may exhibit a mottled pattern (mottling) if it experiences fluctuating water tables, with patches of red (oxidized) and grey (reduced) colours.
• Accumulation: The anaerobic conditions also slow down the decomposition of organic matter, leading to its accumulation in the upper layers, often forming a thick layer of peat or muck.
• Resulting Soil: The resulting gley soils (Histosols if rich in organic matter) are often acidic and nutrient-poor. They are common in tundra regions, deltas, and lagoons.

Distribution of Soils

Soils can be broadly classified based on the dominant pedogenic regime, which is largely influenced by the balance between precipitation and evaporation. This leads to two major categories: Pedocals and Pedalfers.

• Pedocal:

  • Derived from ‘ped’ (soil) and ‘cal’ (from calcium).
  • Characterized by the accumulation of calcium carbonate.
  • Forms in regions where evaporation exceeds precipitation, leading to a net upward movement of water and dissolved minerals through capillary action.
  • This category includes soils formed through calcification and salinization.
  • Types:
    • Chernozem soil: A highly fertile, black-coloured soil of temperate grasslands, rich in humus and carbonates.
    • Prairie soil: Similar to Chernozems but found in more humid grasslands, transitional between Pedocals and Pedalfers.
    • Chestnut soil: Found in drier steppe regions, lighter in colour and less fertile than Chernozems.
    • Desert soil (Aridisols): Characterized by very low organic matter and high concentration of salts.

• Pedalfer:

  • Derived from ‘ped’ (soil), ‘al’ (for aluminium), and ‘fer’ (for iron).
  • Characterized by the accumulation of iron and aluminium oxides.
  • Forms in humid regions where precipitation exceeds evaporation, leading to a net downward movement of water and leaching of soluble minerals.
  • This category includes soils formed through laterization and podzolization.
  • Types:
    • Laterite soil: Severely leached soils of the tropics, rich in iron and aluminium.
    • Red soil: Less leached than laterites, found in warm temperate and tropical regions.
    • Podzol soil: Acidic soils of cool, humid coniferous forests with a bleached E-horizon.

USDA Soil Taxonomy

The United States Department of Agriculture (USDA) developed a comprehensive soil classification system called Soil Taxonomy. It is a hierarchical system based on measurable soil properties (diagnostics horizons) rather than primarily on climatic or vegetative factors. The highest level of classification is the Soil Order.

USDA Soil Order	Key Characteristics / Common Name
Entisol	Recently formed soils with little to no profile development. Ex: Fresh Alluvium.
Inceptisol	Young soils with minimal horizon development. Ex: Old alluvial soils, volcanic soils.
Spodosol	Acidic forest soils with a subsurface accumulation of metal-humus complexes. Ex: Podzol soil.
Alfisol	Moderately leached soils with a subsurface clay accumulation, fertile. Ex: Leached Soil with Al and Fe.
Ultisol	Strongly leached, acidic forest soils with a subsurface clay accumulation. Ex: Leached Soil.
Oxisol	Highly weathered soils of tropical/subtropical regions, rich in Fe and Al oxides. Ex: Corresponds to Laterites.
Vertisol	Clay-rich soils that shrink and swell with changes in moisture. Ex: Black Soil / Regur.

• Histosol | Soils composed mainly of organic matter. Ex: Peaty Soil, Muck. | | Mollisol | Grassland soils with a thick, dark, fertile surface layer. Ex: Prairie Soil, Chernozem. | | Aridisol | Soils of arid regions with some subsurface horizon development. Ex: Desert Soil. |

Mapping

• Europe:

  • Seas: The Mediterranean Sea separates Europe from Africa. The Adriatic Sea is an arm of the Mediterranean separating the Italian and Balkan peninsulas. The Black Sea is an inland sea between Eastern Europe and Western Asia. The Caspian Sea is the world’s largest inland body of water, bordering both Europe and Asia.
  • Mountains: The Ural Mountains traditionally form the boundary between Europe and Asia. The Alps are the highest and most extensive mountain range system in south-central Europe. The Caucasus Mountains also lie at the intersection of Europe and Asia. Mt. Elbrus (5,642 m), located in the Caucasus range in Russia, is the highest peak in Europe.
  • Countries/Cities: Vatican City is the world’s smallest independent state, located within Rome, Italy. Istanbul, Turkey, is a transcontinental city straddling the Bosphorus strait, separating Europe and Asia. Rome is the capital of Italy.

• North America:

  • Seas/Bays: The Californian Bay (Gulf of California) separates the Baja California Peninsula from the Mexican mainland. The Gulf of Mexico is an ocean basin largely surrounded by North America. The Bering Sea separates the North American continent from Asia.
  • Mountains: The Rocky Mountains are a major mountain range in western North America. The Appalachian Mountains are a system of mountains in eastern North America. Mt. Denali (formerly Mt. McKinley, 6,190 m) in Alaska is the highest peak in North America.
  • Places: Death Valley, in California, is the lowest, driest, and hottest area in North America.

• Latin America: This term refers to the countries in the Americas where Romance languages (Spanish, Portuguese, French) are predominantly spoken. It encompasses most of the countries in the American continents except for the Anglophone countries of the USA and Canada, and Greenland.

• South America:

  • Places: The Drake Passage is the body of water between South America’s Cape Horn and the South Shetland Islands of Antarctica. The Valdes Peninsula is a peninsula on the Atlantic coast of Argentina known for its unique fauna. Angel Falls in Venezuela is the world’s tallest uninterrupted waterfall.
  • Mountains: The Andes Mountains are the longest continental mountain range in the world. Mt. Aconcagua (6,961 m) in Argentina is the highest peak outside of Asia. Ojos del Salado is a stratovolcano on the Argentina-Chile border, the world’s highest active volcano.
  • Rivers/Lakes: The Amazon River is the largest river by discharge volume in the world. The Orinoco River is one of the longest rivers in South America.

• Oceania:

  • Regions: A geographical region that includes Australasia, Melanesia, Micronesia, and Polynesia.
  • Island Groups:
    • Micronesia (“small islands”): Includes Kiribati, Marshall Islands, Caroline Islands, etc.
    • Melanesia (“black islands”): Includes New Guinea, Fiji, Solomon Islands, Vanuatu, etc.
    • Polynesia (“many islands”): A vast triangle including Hawaii (USA), New Zealand, Easter Island (Chile), Tonga, Samoa, etc.
  • Places: The Great Dividing Range is Australia’s most substantial mountain range. The Great Barrier Reef is the world’s largest coral reef system, off the coast of Queensland, Australia. Mt. Wilhelm is the highest peak in Papua New Guinea. The Southern Alps is a mountain range extending along much of the length of New Zealand’s South Island.

• Antarctica:

  • Governance: The Antarctic Treaty System, which came into force in 1961, establishes Antarctica as a zone of peace and scientific cooperation. It demilitarizes the continent and prohibits mineral extraction for commercial purposes.
  • Indian Base Stations: India is a signatory to the treaty and maintains active research stations.
    1. Dakshin Gangotri (1983): India’s first station, now buried under ice and used as a supply base.
    2. Maitri (1989): India’s second permanent station.
    3. Bharati (2012): India’s newest research station.

• India:

  • Neighbours:
    • Land Neighbours: Pakistan, Afghanistan, China, Nepal, Bhutan, Bangladesh, Myanmar. Afghanistan shares a small border (~106 km) with India in Pakistan-occupied Kashmir along the Wakhan Corridor.
    • Border Length Order: Bangladesh (4,096 km) > China (3,488 km) > Pakistan (3,323 km) > Nepal (1,751 km) > Myanmar (1,643 km) > Bhutan (699 km) > Afghanistan (106 km). Note: Figures may vary slightly across sources.
    • Maritime Neighbours: Countries with which India shares a maritime boundary include Bangladesh, Pakistan, Myanmar, Sri Lanka, Maldives, Indonesia, and Thailand.
  • Union Territories: As of recent reorganizations, India has 8 Union Territories: Andaman and Nicobar Islands, Chandigarh, Dadra and Nagar Haveli and Daman and Diu, NCT of Delhi, Jammu and Kashmir, Ladakh, Lakshadweep, and Puducherry.
  • Extreme Points:
    • Highest Peak: K2 (Godwin-Austen) at 8,611 m, located in Pakistan-occupied Kashmir (PoK). The highest peak on undisputed Indian territory is Kanchenjunga (8,586 m) in Sikkim.
    • Lowest Point: Kuttanad, a region in Kerala, lies about 2.2 meters below sea level.

Prelims Pointers

• Laterization: A soil-forming process in hot and wet equatorial regions leading to laterite soil.
• Leaching: The process where heavy rainfall washes away soluble minerals like silica.
• Residual Concentration: In laterization, insoluble iron and aluminium oxides accumulate at the surface.
• Laterite Soil: Characterized by high iron/aluminium content, reddish colour, and slight acidity.
• Podzolization: A soil-forming process in cool, temperate, and mountainous regions with coniferous forests.
• Mor Humus: Acidic raw humus formed from coniferous litter.
• Chelation: A process where organic acids make iron and aluminium soluble, facilitating their removal from the topsoil.
• Podzol Soil: Characterized by a bleached, ashy-grey E-horizon and a dark B-horizon; it is highly acidic.
• Calcification: Occurs where evaporation exceeds precipitation, common in temperate grasslands.
• Capillary Action: The upward movement of water in soil, which causes deposition of calcium carbonate in the top layer during calcification.
• Chernozem: Fertile “black earth” soil formed through calcification.
• Salinization: Accumulation of soluble salts (sodium, magnesium) in topsoil, common in arid/semi-arid regions and areas with flood irrigation.
• Gleisation: Occurs in water-logged, anaerobic conditions.
• Gley Horizon: A soil layer with a bluish-grey colour due to the chemical reduction of iron.
• Pedocal Soils: Formed where evaporation > precipitation (net upward water movement); rich in calcium. Examples: Chernozem, Prairie soil, Chestnut soil, Desert soil.
• Pedalfer Soils: Formed where precipitation > evaporation (net downward water movement); rich in aluminium and iron. Examples: Laterite soil, Podzol soil, Red soil.
• USDA Soil Orders (Examples from summary):
  1. Entisol: Fresh Alluvium
  2. Inceptisol: Old alluvial soil
  3. Spodosol: Podzol soil
  4. Oxisol: Weathered top layer rich in Al and Fe (Lateritic)
  5. Vertisol: Black Soil
  6. Histosol: Peaty Soil
  7. Mollisol: Prairie Soil
  8. Aridisol: Desert Soil
• Mt. Elbrus: Highest peak in Europe, located in the Caucasus Mountains.
• Mt. Denali: Highest peak in North America.
• Death Valley: Lowest point in North America.
• Angel Falls: World’s tallest uninterrupted waterfall, located in Venezuela.
• Mt. Aconcagua: Highest peak in South America and outside of Asia.
• Ojos del Salado: World’s highest active volcano, on the Chile-Argentina border.
• Antarctic Treaty: Signed in 1959, came into force in 1961, reserves Antarctica for peaceful scientific purposes.
• Indian Antarctic Stations:
  1. Dakshin Gangotri (1983)
  2. Maitri (1989)
  3. Bharati (2012)
• Wakhan Corridor: A narrow strip of territory in Afghanistan that borders India (in PoK).
• Order of India’s Land Border Length (longest to shortest): Bangladesh > China > Pakistan > Nepal > Myanmar > Bhutan > Afghanistan.
• India’s Highest Peak: K2 (8,611 m) in Pakistan-occupied Kashmir.
• Highest Peak in Undisputed Indian Territory: Kanchenjunga (8,586 m).
• India’s Lowest Point: Kuttanad in Kerala.

Mains Insights

Soil Processes and their Linkage to Agriculture and Environment (GS Paper I & III)

1. Laterization and Agricultural Challenges:

   • Cause-Effect: High rainfall leaches essential nutrients, making laterite soils infertile. The high concentration of iron and aluminium can also lead to phosphorus fixation, making it unavailable to plants.
   • Implications: This poses a significant challenge for agriculture in tropical regions. It necessitates heavy use of fertilizers, which can have downstream environmental impacts. It supports specific plantation crops like tea, coffee, and cashew, which are adapted to acidic and well-drained conditions.

2. Salinization as an Anthropogenic Disaster:

   • Link to Green Revolution: In India (GS-III), the practice of intensive flood irrigation in states like Punjab and Haryana, without adequate drainage, has led to widespread secondary salinization. This is a classic example of the negative externalities of a technological intervention aimed at food security.
   • Socio-economic Impact: Soil salinity reduces crop yields, threatens livelihoods, and can lead to farmer distress and abandonment of agricultural land, impacting national food security in the long run. Management requires integrated approaches like drip irrigation, proper drainage, and cultivation of salt-tolerant crops.

3. Podzolization and Forestry:

   • Ecological Niche: Podzols are naturally suited for coniferous forests. Their high acidity and low fertility make them unsuitable for conventional agriculture without costly interventions like liming to raise the pH.
   • Climate Change Perspective: The distribution of podzols is closely tied to the boreal climate zone. Climate change could alter the conditions for podzolization, potentially affecting the vast taiga ecosystem and its carbon sequestration capacity.

4. Calcification and the World’s Breadbaskets:

   • Positive Feedback Loop: The calcification process, combined with the decomposition of dense grassland root systems, creates Chernozems and Mollisols, the most fertile soils on Earth.
   • Geopolitical Significance: Regions with these soils (e.g., Ukrainian steppes, American prairies) are global “breadbaskets.” Their agricultural output is crucial for global food security, and any disruption (due to conflict, climate change, or land degradation) has worldwide ramifications.

Geopolitical and Strategic Dimensions of Mapping (GS Paper II)

1. India’s Neighborhood and Border Management:

   • Complex Borders: The varying lengths and terrains of India’s borders present unique security and management challenges. The long, porous border with Bangladesh is associated with illegal migration and smuggling, while the Line of Control (LoC) with Pakistan and the Line of Actual Control (LAC) with China are highly militarized and contentious.
   • Strategic Importance: The Wakhan Corridor’s proximity to India highlights its strategic location at the tri-junction of Central and South Asia. Effective and peaceful border management is central to India’s ‘Neighbourhood First’ policy and its internal security.

2. The Antarctic Treaty System as a Model for Global Governance:

   • Successful International Cooperation: The Antarctic Treaty is a landmark agreement that has successfully kept an entire continent free from military conflict and reserved for scientific inquiry for over 60 years.
   • Relevance for Today: It serves as a potential model for governing other global commons, such as outer space, the high seas, and cyberspace. India’s active presence with research stations like Maitri and Bharati solidifies its position as a consultative member and stakeholder in the continent’s future governance.

3. Strategic Chokepoints and Maritime Security:

   • Geopolitical Hotspots: Locations like the Drake Passage, though remote, are critical maritime routes. Understanding the geography of seas, straits, and passages is fundamental to analyzing global trade, naval strategy, and maritime security (e.g., India’s ‘SAGAR’ initiative).
   • Transcontinental Significance: Cities like Istanbul straddling continents have historically been, and remain, centers of geopolitical influence, controlling access and trade between regions.