Ans: C

Exp: 

Black soil covers most of the Deccan Plateau, which includes parts of Maharashtra, Madhya Pradesh, Gujarat, Andhra Pradesh and some parts of Tamil Nadu.  It covers around 15% of the total land area of the country. Chemically, the black soils are rich in lime, iron, magnesia and alumina. They also contain Potash. But they lack in phosphorus, nitrogen and organic matter.  Hence, option a is incorrect.

Laterite soils develop in areas with high temperatures and high rainfall. It accounts for approx 3.7% of the area of the country. This soil is the result of intense leaching due to tropical rains. These are acidic in nature and coarse and crumbly in texture. With rain, lime and silica are leached away, and soils rich in iron oxide and aluminium compounds are left behind.  These soils are poor in organic matter, nitrogen, phosphate and calcium, while iron oxide and potash are in excess. Hence, option b is incorrect.

Alluvial soils cover about 40 per cent of the total area of the country. They are depositional soils transported and deposited by rivers and streams. The alluvial soils vary in nature from sandy loam to clay. They are generally rich in potash but poor in phosphorus. The colour of the alluvial soils varies from light grey to ash grey. Its shades depend on the depth of the deposition, the texture of the materials, and the time taken for attaining maturity. Alluvial soils are intensively cultivated areas. Hence, option c is correct.

Arid soils range from red to brown in colour. They are generally sandy in structure and saline in nature. In some areas, the salt content is so high that common salt is obtained by evaporating the saline water. Due to the dry climate, high temperature and accelerated evaporation, they lack moisture and humus. It accounts for around 5% of the total land area of the country.  Hence, option d is incorrect.

Ans: A

Exp: 

Statement 1 is incorrect  : In the Upper and Middle Ganga plains, two different types of alluvial soils have developed, i.e.Khadar and Bhangar.  Khadar is the new alluvium (not Bhangar ) and is deposited by floods annually, which enriches the soil by depositing fine silts. 

Statement 2 is incorrect : Bhangar (Not Khadar) represents a system of older alluvium, deposited away from the flood plains. These areas are less fertile as they are less prone to flooding (which act as the primary source of nutrient enrichment for the soil).

Statement 3 is correct : Both Khadar and Bhangar soils contain calcareous concretions (Kankars) or impure calcium carbonate nodules. The Bhangar soil has more kankars than the Khadar soil. These soils are loamy and clayey in the lower and middle Ganga plain and the Brahmaputra valley. 

Ans: C

Exp: 

Option a is incorrect : Infiltration is the downward entry of water into the soil. The velocity at which water enters the soil is infiltration rate. Infiltration is an indicator of the soil’s ability to allow water movement into and through the soil profile. 

Option b is incorrect : Leaching, in geology, is the loss of soluble substances and colloids from the top layer of soil by percolating precipitation. It is the loss of water-soluble plant nutrients from the soil, due to rain and irrigation. 

Option c is correct : Capillarity refers to surface tension-driven phenomena appearing at fluid–fluid interfaces. In soil the water moves upwards through a tube against gravity; water moves upwards from the ground water table through soil pores or the spaces between soil particles. The height to which the water rises is dependent upon pore size.

Option d is incorrect : Percolation is the process by which water moves downward through the soil under gravitational forces. The rate of percolation depends on the water content and the hydraulic conductivity of the soil.

Ans: D

Exp:

Factors that influence soil formation are

• • Parent material: It can be any in-situ or on-site weathered rock debris (residual soils) or transported deposits (transported soils). Soil formation depends upon the texture (sizes of debris) and structure (disposition of individual grains/particles of debris) as well as the mineral and chemical composition of the rock debris/deposits.

• Topography: The influence of topography is felt through the amount of exposure of a surface covered by parent materials to sunlight and the amount of surface and sub-surface drainage over and through the parent materials.

• • Climate: The climatic elements involved in soil development are :  moisture in terms of its intensity, frequency and duration of precipitation – evaporation and humidity; and temperature in terms of seasonal and diurnal variations.
  • Biological Activity: The vegetative cover and organisms that occupy the parent materials from the beginning and also at later stages help in adding organic matter, moisture retention, nitrogen etc.

• Time: The time for which soil-forming processes operate, determines the maturity of soils and profile development.

Ans: D

Exp : 

Option a is incorrect : Lithification is the process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock. Essentially, lithification is a process of porosity destruction through compaction and cementation.

Option b is incorrect : Erosion is the process where rocks are broken down and transported by the natural forces such as wind or water. It is of two types: chemical and physical. 

• Chemical erosion occurs when a rock’s chemical composition changes. Ex: Limestone dissolves and gets eroded due to carbonation.  
• Physical erosion, the rock breaks down but its chemical composition remains the same. Ex: Landslide or bioerosion(when plants develop roots in rock and crack rocks).

Weathering is the mechanical and chemical hammer that breaks down and sculpts the rocks. Erosion transports the fragments away.

Option c is incorrect : Deposition is the laying down of sediment carried by wind, flowing water, the sea or ice. Sediment can be transported as pebbles, sand and mud, or as salts dissolved in water. Salts may later be deposited by organic activity (e.g. as sea shells) or by evaporation.

Option d is correct : Weathering is breaking down rocks, soil, and minerals, woods or even artificial materials into smaller pieces . Weathering takes place in situ(i.e. in the same place), with little or no movement. It can be of 2 types: physical weathering or chemical weathering : 

• Physical or mechanical weathering is breakdown of rock and soil by direct contact with atmospheric conditions such as heat, water, ice and pressure.
• Chemical weathering: involves breakdown of rocks due to chemicals –  biological or as present in atmosphere.