UGC NET Environmental Science Unit-IV: Environmental Geosciences Syllabus

What causes the Indian monsoon?

Differential heating of land and sea creating a low-pressure zone over the Indian subcontinent in summer, reversing the pressure gradient and drawing moisture-laden southwest winds; the seasonal reversal of wind direction defines the monsoon.

What is the El Niño phenomenon and its effect on the Indian monsoon?

Abnormal warming of the central/eastern equatorial Pacific Ocean that weakens the Walker circulation; it is generally associated with weak or deficient Indian monsoon rainfall and drought.

What is La Niña and its typical effect on the Indian monsoon?

Abnormal cooling of the central/eastern equatorial Pacific (the cold counterpart of El Niño), generally associated with a stronger-than-normal, good Indian monsoon.

What is a drought?

A prolonged period of abnormally deficient precipitation relative to the long-term average, leading to water shortage; types include meteorological, hydrological, agricultural, and socio-economic drought.

What is residence time in a natural cycle?

The average time a substance (e.g., a water or carbon molecule) spends in a reservoir, calculated as the reservoir's mass divided by the input or output flux rate (T = M/F).

What are geophysical fields?

Physical fields associated with the Earth that are measured in geophysics, principally the gravitational, magnetic (geomagnetic), electrical, and thermal (heat flow) fields, plus seismic wave fields.

What is weathering?

The in-situ physical disintegration and chemical decomposition of rocks and minerals at or near the Earth's surface by atmospheric, hydrologic, and biological agents, without significant transport.

Name the main chemical weathering reactions.

Hydrolysis (silicates to clays), oxidation (e.g., Fe2+ to Fe3+), hydration, dissolution (e.g., carbonates by carbonic acid), and carbonation.

How does carbonation weather limestone?

CO2 dissolves in water forming carbonic acid (H2CO3) which reacts with calcite: CaCO3 + H2CO3 -> Ca2+ + 2HCO3-, dissolving the rock (the basis of karst topography).

Distinguish erosion, transportation, and deposition.

Erosion is the loosening and removal of weathered material by agents (water, wind, ice); transportation is its movement; deposition (sedimentation) is its settling when the transporting agent loses energy.

What are soil-forming minerals?

Primary minerals inherited from parent rock (quartz, feldspars, micas, ferromagnesian minerals) and secondary minerals formed during weathering (clay minerals, Fe/Al oxides, carbonates).

What are the five factors of soil formation (CLORPT)?

Climate, Organisms, Relief (topography), Parent material, and Time (Jenny's factors: s = f(cl, o, r, p, t)).

What are the main soil-forming processes?

Additions, losses, translocations, and transformations within the profile; key processes include humification, eluviation/illuviation, leaching, podzolization, laterization, gleization, calcification, and salinization.

Name the three main groups of 1:1 and 2:1 clay minerals.

Kaolinite (1:1, non-expanding), illite (2:1, non-expanding/limited), and montmorillonite/smectite (2:1, expanding); along with vermiculite and chlorite.

How does a 1:1 clay mineral differ structurally from a 2:1 clay mineral?

A 1:1 mineral (kaolinite) has one silica tetrahedral sheet bonded to one alumina octahedral sheet per layer; a 2:1 mineral (smectite, illite) has one octahedral sheet sandwiched between two tetrahedral sheets.

Which clay mineral has the highest shrink-swell (expansion) capacity and why?

Montmorillonite/smectite, because its weakly bonded 2:1 layers allow water and cations to enter the interlayer space, causing strong swelling when wet and shrinkage when dry.

What are key soil physical properties?

Texture (sand/silt/clay proportions), structure, bulk density, porosity, water-holding capacity, color, consistency, and temperature.

What are key soil chemical properties?

Soil pH, cation exchange capacity (CEC), base saturation, salinity (EC), organic matter content, and nutrient availability.

What is cation exchange capacity (CEC)?

The total quantity of exchangeable cations a soil can adsorb and hold on negatively charged colloid surfaces, expressed in cmol(+)/kg (meq/100 g); it governs nutrient retention.

Rank kaolinite, illite, and montmorillonite by CEC.

Montmorillonite (high, ~80-150 cmol/kg) > illite (moderate, ~10-40) > kaolinite (low, ~3-15), reflecting their surface area and isomorphous substitution (humus is highest of all).

What is the mineralogical control on CEC?

CEC arises from permanent charge due to isomorphous substitution (in 2:1 clays) and pH-dependent charge on edge OH groups and organic matter; expanding 2:1 clays and humus have the highest CEC.

State Goldschmidt's geochemical classification of elements.

Lithophile (rock/silicate-loving, e.g., Si, Al, K, Ca), siderophile (iron-loving, e.g., Fe, Ni, Au, Pt), chalcophile (sulfur-loving, e.g., Cu, Zn, Pb, S), and atmophile (gas-forming, e.g., N, O, noble gases).

What are the most abundant elements in the Earth's continental crust by weight?

Oxygen (~46%) and silicon (~28%), followed by aluminium, iron, calcium, sodium, potassium, and magnesium.

What is the most abundant element in the bulk Earth (whole planet)?

Iron (~32%), followed by oxygen (~30%), silicon, and magnesium, because the dense Fe-rich core dominates the bulk composition.

What dissolved ions dominate the hydrosphere (seawater)?

Chloride (Cl-) and sodium (Na+) are dominant, along with sulfate, magnesium, calcium, and potassium; H and O make up the water itself.

What controls the partitioning of elements during surficial geologic processes?

Solubility, ionic potential (charge/radius), redox conditions (Eh), pH, and adsorption; soluble ions stay in solution while elements with high ionic potential form insoluble hydrolysates that concentrate in residues.

What is geochemical recycling of elements?

The continuous movement of elements among the crust, hydrosphere, atmosphere, and biosphere through weathering, erosion, sedimentation, subduction, volcanism, and uplift (biogeochemical cycling).

What is paleoclimate and name two proxies used to reconstruct it.

Paleoclimate is the climate of the geological past; proxies include ice cores (trapped gas and δ18O), ocean sediment/foraminifera oxygen-isotope ratios, tree rings, pollen, and corals.

How is water distributed on Earth among major reservoirs?

About 97% is saline ocean water; of the ~3% freshwater, most is locked in glaciers/ice caps (~69%), groundwater is ~30%, and surface water (lakes, rivers) is a small fraction (<1%).

State Darcy's law and define its terms.

Q = -K A (dh/dl): groundwater discharge Q equals hydraulic conductivity K times cross-sectional area A times the hydraulic gradient (dh/dl); the negative sign shows flow is from high to low head.

What is the validity limit of Darcy's law?

It is valid only for laminar (slow) flow, typically Reynolds number < 1-10; it breaks down for turbulent flow in coarse gravels/fractures and for very low gradients in dense clays.

What is hydraulic conductivity (K)?

A measure of an aquifer material's ability to transmit water under a hydraulic gradient (units m/day); it depends on both the medium's intrinsic permeability and the fluid's properties (density, viscosity).

What is the Ghyben-Herzberg relation?

In coastal aquifers, the depth of fresh-saltwater interface below sea level z ≈ 40 h, where h is the height of the freshwater table above sea level; i.e., for every 1 m of freshwater head, fresh water extends ~40 m below sea level.

What is land subsidence due to groundwater, and name an Indian example concern?

The gradual sinking of the land surface caused by compaction of aquifer sediments when excessive groundwater withdrawal reduces pore pressure; over-extraction in many Indian alluvial basins is a growing concern.

Name common effects of excessive groundwater use.

Declining water tables, land subsidence, drying of wells/springs, saltwater intrusion in coastal areas, deterioration of water quality, and increased pumping cost.

What are groundwater tracers used for?

Natural or artificial substances (dyes, isotopes like tritium/14C, salts) added to or measured in groundwater to determine flow direction, velocity, recharge age, and connectivity between aquifers.

What is the historical/conservation perspective on non-renewable resources?

Non-renewable resources (fossil fuels, minerals) form over geological timescales and are finite; conservation emphasizes efficient use, recycling, substitution by renewables, and equitable, sustainable exploitation to avoid depletion.

What environmental concerns arise from natural resource exploration and exploitation?

Habitat destruction, deforestation, soil erosion, water and air pollution, acid mine drainage, tailings/waste generation, land degradation, and displacement of communities.

List the major catastrophic geological hazards.

Floods, landslides, earthquakes, volcanism (volcanic eruptions), avalanches, tsunamis, and cloud bursts.

What is a tsunami and what commonly triggers it?

A series of long-wavelength ocean waves generated by sudden displacement of a large water volume, most often by submarine earthquakes, but also by undersea landslides or volcanic eruptions.

What is a cloud burst?

A sudden, very intense, localized rainfall event (conventionally >100 mm/hour) over a small area, often in mountainous terrain, that causes flash floods and landslides.

What is liquefaction in the context of earthquakes?

The process where saturated, loose granular soil temporarily loses strength and behaves like a liquid due to earthquake shaking, causing buildings to sink or tilt.

How are earthquake magnitude and intensity different?

Magnitude (Richter/moment scale) is an instrumental measure of the energy released at the source (single value); intensity (Mercalli scale) measures the observed effects/damage at a place and varies with distance.

Name common approaches to hazard prediction and mitigation.

Hazard mapping/zonation, early-warning systems, monitoring (seismic, weather, GPS), land-use planning/building codes, structural measures (dams, embankments), afforestation, public awareness, and emergency preparedness.

What are some major groundwater provinces/basins of India?

The Indo-Gangetic-Brahmaputra alluvial plains (most productive), the hard-rock Peninsular shield (Deccan basalts, crystalline rocks with limited fractured-zone storage), coastal sedimentary basins, and Cenozoic sedimentary tracts.

What is groundwater quality degradation and name common contaminants in India?

Deterioration of groundwater making it unfit for use; common Indian contaminants include fluoride, arsenic, nitrate, salinity, and iron, from geogenic sources and pollution.

How do tectonic and climatic controls jointly shape landforms?

Tectonics sets the elevation, rock type, and structural framework (uplift creating relief), while climate controls the dominant weathering/erosional processes (glacial, fluvial, aeolian, karst) that carve that relief into specific landform assemblages.