Explanation:

• Statement I is correct: The atmosphere consists of gases along with variable components like water vapour and dust.
• Statement II is correct: With increasing altitude, atmospheric composition changes—oxygen thins out significantly by ~120 km, and carbon dioxide and water vapour are mainly present below ~90 km.

Explanation:

• Statement 1: Correct
• Carbon dioxide allows incoming solar radiation to pass but absorbs outgoing terrestrial radiation.
• Statement 2: Correct
• By trapping heat near the Earth’s surface, carbon dioxide plays a key role in the greenhouse effect.
• Statement 3: Correct
• The increase in carbon dioxide concentration is mainly due to the burning of fossil fuels, leading to a rise in air temperature.

Explanation:

• Statement 1 is correct – The stratosphere is located above the troposphere, extending approximately from 13 km to 50 km.
• Statement 2 is correct – Temperature rises with height because ozone absorbs ultraviolet radiation.
• Statement 3 is correct – The ozone layer is present here, and the calm, stable conditions make it ideal for air travel.

Explanation:

• Statement 1 is correct – Aphelion is the farthest position (July).
• Statement 2 is incorrect – Aphelion occurs around 4th July, not January.
• Statement 3 is correct – Perihelion (3rd January) receives slightly more insolation.

Explanation :

• 1. Rotation of the Earth – Correct – Causes day and night, leading to daily variation in insolation.
• 2. Angle of Sun’s rays – Correct – Vertical rays concentrate energy over a smaller area, while oblique rays spread it, affecting intensity.
• 3. Length of the day – Correct – Longer daylight hours allow more insolation to be received.
• 4. Transparency of the atmosphere – Correct – Dust, clouds and water vapour absorb and scatter solar radiation, reducing insolation.
• 5. Configuration of land (Aspect) – Correct – Slopes facing the Sun receive more insolation than shaded slopes, though its influence is relatively less.

Explanation:

• Statement 1 is correct – Fresh snow has very high reflectivity (albedo range 0.80–0.95), reflecting most incoming sunlight.
• Statement 2 is correct – Forests have low albedo (0.06–0.20) because dense vegetation absorbs sunlight, whereas desert sand has moderately high albedo (0.30–0.45).
• Statement 3 is incorrect – Old or melting snow has lower albedo (0.40–0.70) than fresh snow due to impurities and melting.

Explanation:

• Planck’s Law explains how the energy and wavelength of radiation emitted by a body depend on its temperature. As temperature rises, the body emits more energy and the peak wavelength shifts toward shorter wavelengths, a principle fundamental to radiation physics and climate studies.

Explanation:

• Statement I is correct: Temperature inversion is the reversal of the normal lapse rate, where air near the ground becomes cooler than the air above.
• Statement II is correct: Clear skies, calm winds, and long winter nights favour inversion; in polar regions, inversion conditions prevail for most of the year.

Explanation:

• Pair I – Loo : Northern India and Pakistan – Loo is a hot, dry summer wind blowing over northern India and adjoining Pakistan.
• Pair II – Foehn : Windward side of the Alps – Foehn is a warm, dry downslope wind that blows on the leeward side of the Alps, not the windward side.
• Pair III – Chinook : Eastern slopes of the Rockies – Chinook winds descend on the eastern slopes of the Rocky Mountains and cause rapid warming.
• Pair IV – Harmattan : Northwest Africa – Harmattan is a hot, dry, dust-laden wind blowing from the Sahara across Northwest Africa.

Explanation:

• Statement 1 is correct – Tropical humid climates are found between the Tropic of Cancer and the Tropic of Capricorn, where the sun remains nearly overhead.
• Statement 2 is correct – Due to the influence of the Inter Tropical Convergence Zone (ITCZ), these regions experience high rainfall and a very small annual range of temperature.
• Statement 3 is correct – The tropical climatic group is classified into Af (Tropical wet), Am (Tropical monsoon), and Aw (Tropical wet and dry) climates.

Explanation:

• Statement I is correct: Tropical deciduous forests form the largest forest cover in India and are closely associated with the monsoon climate.
• Statement II is correct: Moist deciduous forests develop in areas with higher rainfall (100–200 cm) and are distributed in the regions mentioned above, with species such as teak, sal, and shisham.

Explanation:

• The Mediterranean Climate (Cs) occurs on the western coasts of continents between 30°–40° latitudes.
• Major regions include:
  • Areas around the Mediterranean Sea
  • Central California
  • Central Chile
  • Coastal regions of south-western and south-eastern Australia
• Seasonal pressure and wind systems govern this climate:
  • Subtropical high-pressure belt dominates in summer, causing hot and dry conditions
  • Westerly winds prevail in winter, bringing rainfall
• Climatic characteristics:
  • Summer temperature ≈ 25°C
  • Winter temperature below 10°C
  • Annual rainfall ranges between 35–90 cm

Why other options are incorrect:

• Tropical Wet Climate (Af) – Found near the equator with year-round rainfall.
• Steppe Climate (BS) – Semi-arid with low and irregular rainfall.
• Humid Subtropical Climate (Cfa) – Has rainfall throughout the year and hot, humid summers.

Explanation:

• Snowmelt feeds rivers and streams.
• Infiltration recharges groundwater.
• Springs are natural outlets of groundwater.

Explanation:

• Pair 1 : Correct: Atmospheric water returns via precipitation.
• Pair 2 : Incorrect: Oceans mainly undergo evaporation, not evapotranspiration.
• Pair 3: Correct: Infiltration leads to groundwater storage.

Explanation:

• Statement 1 – Correct
• Continental shelves may be as shallow as 30 metres.
• Statement 2 – Correct
  • It also mentions that in some regions shelves extend “as deep as 600 m.”
• Statement 3 – Incorrect
  • The depth of continental shelves varies significantly from place to place and is not uniform across oceans.

Continental Shelves

• Definition: Continental shelves are the shallow, gently sloping submerged extensions of continents from the coastline to the continental edge.
• Width:
  • Varies greatly from one ocean to another.
  • Average width: about 80 km.
  • Very narrow or absent along some active margins such as:
    • Coast of Chile
    • West coast of Sumatra
  • Widest shelf in the world:
    • Siberian Shelf (Arctic Ocean) – extends up to 1,500 km.
• Depth:
  • Generally shallow.
  • Ranges from about 30 m to 600 m.
• Sediments:
  • Covered with thick layers of sediments.
  • Sediments are brought by:
    • Rivers
    • Glaciers
    • Wind
    • Distributed by waves and ocean currents.
• Economic significance:
  • Long-term accumulation of sediments leads to the formation of fossil fuels.
  • Continental shelves are major zones for petroleum and natural gas reserves.

Explanation:

• Statement 1 is correct: Trenches are the deepest oceanic features and are steep-sided, narrow basins.
• Statement 2 is incorrect: Trenches are strongly associated with active volcanoes and earthquakes, making them crucial for plate tectonic studies.

Oceanic Deeps / Trenches

• Deepest parts of the oceans.
• Narrow, elongated and steep-sided basins.
• Depth: About 3–5 km deeper than the surrounding ocean floor.
• Occur:
  • At the base of continental slopes
  • Along island arcs
• Associated with:
  • Active volcanoes
  • Strong earthquakes
• Highly significant for the study of plate tectonics.
• Total explored trenches: 57
  • Pacific Ocean – 32
  • Atlantic Ocean – 19
  • Indian Ocean – 6

Explanation:

• Salinity is commonly expressed as parts per thousand (‰ or ppt).
• For example, average ocean salinity is about 35‰.

Explanation:

• Statement 1 is correct: A mid-oceanic ridge has two mountain chains separated by a large depression.
• Statement 2 is incorrect: Some ridge peaks rise above sea level—Iceland is a classic example.

Mid-Oceanic Ridges

• Long submarine mountain chains found in all major oceans.
• Composed of two parallel mountain chains separated by a central depression (rift valley).
• Mountain peaks may rise up to 2,500 m or more.
• Some peaks emerge above sea level.
• Example:
  • Iceland, part of the Mid-Atlantic Ridge.
• Formed due to divergent plate boundaries and magma upwelling.

Explanation:

• Statement 1 is correct: Seamounts are volcanic in origin and do not emerge above sea level.
• Statement 2 is correct: The Emperor Seamount lies in the Pacific Ocean as an extension of the Hawaiian Islands.

Explanation:

• Statement 1 – Correct
  • Humus is dark-coloured, amorphous and decomposes very slowly.
• Statement 2 – Correct
  • Being colloidal, humus stores nutrients efficiently.
• Statement 3 – Incorrect
  • Mineralisation releases inorganic nutrients; it does not accumulate humus.

Steps in the Process of Decomposition

1. Fragmentation
   • Breakdown of detritus into smaller particles.
   • Performed by detritivores (e.g., earthworms).
2. Leaching
   • Water-soluble inorganic nutrients are washed down into soil horizons.
   • Nutrients may get precipitated as unavailable salts.
3. Catabolism
   • Degradation of detritus by bacterial and fungal enzymes.
   • Converts complex organic compounds into simpler inorganic substances.
4. Humification
   • Formation of humus, a dark-coloured, amorphous substance.
   • Humus:
     • Highly resistant to microbial decomposition
     • Decomposes very slowly
     • Acts as a nutrient reservoir
     • Improves soil structure due to its colloidal nature
5. Mineralisation
   • Further breakdown of humus by microbes.
   • Leads to release of inorganic nutrients into the soil.

Explanation:

• Statement 1 – Correct
  • Decomposition converts complex organic matter into carbon dioxide, water and nutrients.
• Statement 2 – Correct
  • Detritus consists of dead plant remains, animal remains and faecal matter.
• Statement 3 – correct
  • Decomposition also involves mineralisation, which releases inorganic nutrients.

Decomposition

• Earthworm as farmer’s friend
  • Helps in breaking down complex organic matter.
  • Loosens the soil and improves soil aeration and fertility.
• Decomposition
  • Process by which complex organic matter is broken down into simple inorganic substances like:
    • Carbon dioxide (CO₂)
    • Water (H₂O)
    • Mineral nutrients
• Detritus
  • Raw material for decomposition.
  • Includes:
    • Dead plant parts (leaves, bark, flowers)
    • Dead animal remains
    • Faecal matter
• Decomposers
  • Mainly bacteria and fungi.
  • Convert organic matter into inorganic substances.

Explanation:

• Tides vary in their frequency, direction and movement from place to place and also from time to time. Tides may be grouped into various types based on their frequency of occurrence in one day or 24 hours or based on their height.

• Semi-diurnal tide: The most common tidal pattern, featuring two high tides and two low tides each day. The successive high or low tides are approximately of the same height. Hence, Statement 1 is incorrect.
• Diurnal tide: There is only one high tide and one low tide during each day. The successive high and low tides are approximately of the same height. Hence, Statement 2 is incorrect.
• Mixed tide: Tides having variations in height are known as mixed tides. These tides generally occur along the west coast of North America and on many islands of the Pacific Ocean. Hence, Statement 3 is correct.

Explanation:

The factors which affect the distribution of temperature of ocean water are :

(i) Latitude: the temperature of surface water decreases from the equator towards the poles because the amount of insolation decreases poleward.

(ii) Unequal distribution of land and water : The oceans in the northern hemisphere receive more heat due to their contact with larger extent of land than the oceans in the southern hemisphere.

(iii) Prevailing wind : the winds blowing from The land towards the oceans drive warm surface water away form the coast resulting in the upwelling of cold water from below. It results into the longitudinal variation in the temperature. Contrary to this, the onshore winds pile up warm water near the coast and this raises the temperature.

(iv) Ocean currents : warm ocean currents raise the temperature in cold areas while the cold currents decrease the temperature in warm ocean areas. Gulf stream (warm current) raises the temperature near the eastern coast of North America and the West Coast of Europe while the Labrador current (cold current) lowers the temperature near the north-east coast of North America.

• Longitudes are imaginary vertical lines that run from the North Pole to the South Pole. They are also called meridians and are used to measure distances east or west of the Prime Meridian. It is not related to distribution of insolation on earth. Hence, statement 2 is incorrect.

Explanation:

• Ocean currents are like river flow in oceans. They represent a regular volume of water in a definite path and direction.

The primary forces that influence the currents are :

(i) Heating by solar energy : This causes the water to expand. That is why, near the equator the ocean water is about 8 cm higher in level than in the middle latitudes. This causes a very slight gradient and water tends to flow down the slope.

(ii) Wind : Wind blowing on the surface of the ocean pushes the water to move. Friction between the wind and the water surface affects the movement of the water body in its course. Hence, Statement 1 is correct.

(iii) Gravity : Gravity tends to pull the water down the pile and create gradient variation. Hence, Statement 4 is correct.

(iv) Coriolis force : It causes the water to move to the right in the northern hemisphere and to the left in the southern hemisphere. These large accumulations of water and the flow around them are called Gyres. These produce large circular currents in all the ocean basins. Hence, Statement 2 is correct.

• Statement 3 is incorrect: The revolution of Earth around the Sun affects seasons but is not a primary force driving ocean currents.

Explanation:

• The water cycle, also known as the hydrological cycle, is a crucial process for maintaining Earth’s water balance. It describes the continuous movement of water within the atmosphere, oceans, and continents. Here’s how the process works in more detail:

1. Evaporation: Water from oceans, lakes, rivers, and other water bodies is heated by the sun and changes into water vapor, rising into the atmosphere. This is called evaporation.
2. Transpiration: Plants also release water vapor into the atmosphere through small pores on their leaves in a process called transpiration. This contributes to the overall moisture in the air.
3. Condensation: As the water vapor rises and cools in the atmosphere, it changes back into liquid form, forming tiny droplets that combine to create clouds. This process is called condensation.
4. Precipitation: When the water droplets in the clouds become heavy enough, they fall back to Earth as precipitation in the form of rain, snow, sleet, or hail.

• The water cycle is a vital natural process that ensures the circulation of water, supporting life on Earth and regulating climate patterns. It’s important to note that this cycle is continuous, with water constantly moving between its different states (gaseous, liquid, and solid).

Explanation:

• Warming and cooling of the Pacific Ocean is most important in terms of general atmospheric circulation. The warm water of the central Pacific Ocean slowly drifts towards the South American coast and replaces the cool Peruvian current. Such an appearance of warm water off the coast of Peru is known as the El Nino. Hence, statement 3 is correct.
• The El Nino event is closely associated with the pressure changes in the Central Pacific and Australia. This change in pressure condition over the Pacific is known as the southern oscillation.
• The combined phenomenon of southern oscillation and El Nino is known as ENSO.

• In the years when the ENSO is strong, large-scale variations in weather occur over the world. The arid west coast of South America receives heavy rainfall, drought occurs in Australia and sometimes in India and floods in China. This phenomenon is closely monitored and is used for long range forecasting in major parts of the world. Hence, statement 1 is correct and statement 2 is incorrect

Explanation:

• The air in motion is called wind. The wind blows from high pressure to low pressure. The wind at the surface experiences friction. In addition, rotation of the earth also affects the wind movement.
• The rotation of the earth about its axis affects the direction of the wind. This force is called the Coriolis force after the French physicist who described it in 1844. It deflects the wind to the right direction in the northern hemisphere and to the left in the southern hemisphere.

• The deflection is more when the wind velocity is high. Hence, Statement 1 is correct.
• The Coriolis force is directly proportional to the angle of latitude. It is maximum at the poles and is absent at the equator. Hence, Statement 2 is correct.
• The horizontal winds near the earth surface respond to the combined effect of three forces – the pressure gradient force, the frictional force and the Coriolis force. In addition, the gravitational force acts downward.
• The Coriolis force acts perpendicular to the pressure gradient force. The pressure gradient force is perpendicular to an isobar. The higher the pressure gradient force, the more is the velocity of the wind and the larger is the deflection in the direction of wind. As a result of these two forces operating perpendicular to each other, in the low-pressure areas the wind blows around it.
• At the equator, the Coriolis force is zero and the wind blows perpendicular to the isobars. The low pressure gets filled instead of getting intensified. That is the reason why tropical cyclones are not formed near the equator.

Explanation:

• Tropic of Cancer (23.5°N): On June 21, which is the Summer Solstice in the Northern Hemisphere, the Sun is directly overhead at the Tropic of Cancer. This results in the Northern Hemisphere experiencing the longest day of the year, with places north of the Tropic of Cancer (including the Arctic Circle) experiencing more than 12 hours of daylight.
• Arctic Circle (66.5°N): On June 21, the Arctic Circle experiences the Midnight Sun, where the Sun does not set at all, meaning it experiences 24 hours of daylight.

• Equator (0°): The Equator receives roughly 12 hours of daylight throughout the year, including on June 21, so it does not experience more than 12 hours of sunlight.
• Tropic of Capricorn (23.5°S): On June 21, the Tropic of Capricorn is tilted away from the Sun, and this is the Winter Solstice for the Southern Hemisphere, meaning it experiences the shortest day of the year. The daylight duration is less than 12 hours.
• Thus, Tropic of Cancer and Arctic Circle experience more than 12 hours of sunlight on June 21.

Explanation:

• The atmosphere consists of different layers with varying density and temperature. Density is highest near the surface of the earth and decreases with increasing altitude.

• The highest density of the atmosphere is found in the troposphere. This is because the air is compressed by the weight of the atmosphere above it. As a result, the air at the surface is much denser than at higher altitudes.
• The air density decreases in the stratosphere compared to the troposphere. The further you go up, the fewer air molecules there are.
• The density continues to decrease in the mesosphere. The air is very thin, and only a few gas molecules are present at this altitude.
• In the thermosphere, air density is very low. The atmosphere is so thin that gas molecules are widely scattered.
• The air in the exosphere is extremely sparse. It is so thin that individual molecules are far apart, and many particles escape into space.

Explanation:

• Water vapor is a variable gas in the atmosphere, and it plays a crucial role in weather patterns, climate, and the overall functioning of the Earth’s energy balance.
• Statement 1 is correct: Water vapor is not uniformly distributed in the atmosphere. Its concentration varies depending on location, altitude, and climate conditions. In tropical regions (warm and wet), water vapor can account for up to 4% of the air by volume, while in cold and dry regions (like deserts or polar areas), it can be less than 1%. This is because the ability of air to hold water vapor is highly temperature-dependent—warmer air can hold more moisture. Water vapor decreases with altitude because cooler temperatures in higher altitudes reduce the amount of moisture air can hold. In the upper layers of the atmosphere, especially the stratosphere, the concentration of water vapor becomes very low.
• Statement 2 is incorrect: Water vapor is fundamental in weather and climate because it contributes to the formation of clouds and precipitation. Water vapor condenses into tiny droplets or ice crystals when it cools, forming clouds, and if the water vapor condenses enough, it can fall as rain, snow, or other forms of precipitation. Water vapor also plays a significant role in stability and instability of the atmosphere. When the atmosphere is stable, warm air near the surface is less likely to rise. This can happen when there is little water vapor or if the air is cooler. Stable air tends to be associated with clear skies and calm weather. In contrast, if the air is moist and warmer, it tends to rise more easily, leading to convection and the formation of clouds and storms. The presence of water vapor makes the air more buoyant, increasing instability, which is essential for thunderstorms and other extreme weather events.
• Statement 3 is incorrect: The distribution of water vapor is also affected by geographic location. At the equator, where temperatures are warm and evaporation is high, there is more moisture in the air, resulting in higher concentrations of water vapor. As you move toward the poles, the temperature drops and evaporation decreases, leading to lower levels of water vapor in the atmosphere.
• Statement 4 is correct: Water vapor absorbs some of the incoming solar radiation, particularly in the form of infrared (IR) radiation. Although it is not as significant a factor as carbon dioxide, water vapor still plays a role in reducing the amount of solar energy that reaches the Earth’s surface. Water vapor is a major greenhouse gas, and it significantly contributes to Earth’s radiative balance. It absorbs parts of the energy radiated from the Earth’s surface (terrestrial radiation) and re-radiates it back toward the surface, helping to trap heat in the lower atmosphere. This process helps prevent excessive cooling and keeps the Earth’s surface warm. This is why water vapor is sometimes described as acting like a blanket for the Earth, maintaining a stable temperature. Without this blanket effect, the Earth’s surface temperature would fluctuate much more drastically, making it difficult for life to survive.