UPSC Geoscientist Archives

31. Which one of the following events has not been attributed to El Niño

Which one of the following events has not been attributed to El Niño during early 1980s?

The warmest winter in the Eastern US during the last 25 years

Drought in Southeast Africa, Australia, New Zealand and Southeast Asia

Prolific growth of coral reefs in the Pacific Ocean

Increased incidents of bubonic plague in Southwestern United States

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El Niño is associated with warming of the central and eastern tropical Pacific Ocean waters. This warming typically leads to coral bleaching, a stress response where corals expel their symbiotic algae (zooxanthellae), causing them to turn white and often die if the stress is prolonged. Therefore, prolific growth of coral reefs is not an effect attributed to El Niño; rather, coral bleaching and potential mortality are common consequences of the associated ocean warming. The early 1980s (specifically 1982-83) saw a significant El Niño event with widespread climate impacts.

– El Niño warms ocean surface waters in the Pacific.
– Ocean warming causes coral bleaching, not prolific growth.
– Droughts in certain regions (like Australia, parts of Africa, Southeast Asia) and altered temperature patterns are typical El Niño effects.

El Niño-Southern Oscillation (ENSO) is a major climate pattern involving variations in the temperature of the surface of the tropical eastern Pacific Ocean and in the air pressure over the tropical western Pacific. It has three phases: El Niño (warm phase), La Niña (cool phase), and Neutral. The 1982-83 El Niño event was particularly strong and well-documented for its global impacts.

32. Dew point temperature represents that

Dew point temperature represents that

thin layer of air near the ground surface has become cold enough to condensate

there is thorough mixing of air

evaporation has exceeded condensation

the night temperature is warm

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The dew point temperature is defined as the temperature to which air must be cooled at constant pressure and humidity for water vapor to condense into liquid water (dew). When the air near the ground surface cools down to this temperature, it becomes saturated, and any further cooling leads to condensation, forming dew.

– Dew point is the temperature of saturation for water vapor.
– Condensation occurs when air cools to or below the dew point.
– Dew forms when surface air cools to the dew point temperature.

Relative humidity is 100% at the dew point. The difference between the air temperature and the dew point indicates how close the air is to saturation. A smaller difference means higher relative humidity.

33. Which one of the following statements about North-facing slopes and So

Which one of the following statements about North-facing slopes and South-facing slopes in the Northern Hemisphere is not correct?

North-facing slopes are snow covered while South-facing slopes are bare.

North-facing slopes get less intense radiation as compared to South-facing slopes.

Snow on North-facing slopes is found at a lower altitude than South-facing slopes.

Tree line characteristics on North-facing slopes and South-facing slopes are similar.

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In the Northern Hemisphere, South-facing slopes receive more direct solar radiation than North-facing slopes. This difference in insolation leads to significant differences in temperature, soil moisture, snow cover duration, and ultimately, vegetation patterns and species distribution. The tree line, which is the upper limit of tree growth limited by cold temperatures and snow duration, is typically found at a lower altitude on colder, wetter North-facing slopes compared to warmer, drier South-facing slopes. Therefore, the tree line characteristics are generally *not* similar on North-facing and South-facing slopes.

– Solar radiation intensity (B) is higher on South-facing slopes in the Northern Hemisphere.
– Lower insolation on North-facing slopes leads to lower temperatures and longer-lasting snow cover (A), often resulting in snow being present at lower altitudes (C).
– These environmental differences (temperature, moisture, snow) drive differences in plant communities and ecological boundaries like the tree line.

This phenomenon of ecological differences based on aspect (the direction a slope faces) is well-studied and results in distinct microclimates and vegetation zones on opposite-facing slopes within the same mountain range or area. The effect is reversed in the Southern Hemisphere, where North-facing slopes receive more direct solar radiation.

34. Which one of the following is not correct in the context of daytime he

Which one of the following is not correct in the context of daytime heating experienced on the Earth?

The highest daytime temperatures usually occur several hours after the time of maximum solar input

Equilibrium between incoming and outgoing radiation occurs about an hour and a half after sunset

The extent of daily lag in maximum temperature varies

Presence of vegetation cover reduces the maximum temperature

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Equilibrium between incoming and outgoing radiation, leading to maximum temperature, occurs when the rate of energy gain equals the rate of energy loss. During the day, incoming solar radiation exceeds outgoing radiation. Maximum temperature is reached when the net radiation balance becomes zero or slightly negative, typically in the mid-afternoon, several hours *after* solar noon (maximum solar input). After sunset, there is no incoming solar radiation, and the Earth continues to lose radiation, so outgoing radiation significantly exceeds incoming (zero). Equilibrium (net radiation=0) does *not* occur after sunset; the surface cools.

– There is a lag between the time of maximum solar radiation input (solar noon) and the time of maximum daily temperature due to the heat capacity of the surface and atmosphere.
– Maximum temperature occurs when the net energy balance transitions from positive (energy gain) to negative (energy loss). This transition point usually happens a few hours after maximum solar input and *before* sunset.
– After sunset, the net radiation balance is negative, and the surface cools.

The duration of the temperature lag (C) is influenced by factors like wind speed (mixing), cloud cover (insulation), humidity (evaporative cooling, water vapour greenhouse effect), and the thermal properties of the surface material. Vegetation cover (D) promotes evapotranspiration, which consumes energy (latent heat), thus reducing the energy available for sensible heating and lowering maximum surface and air temperatures.

35. Which one of the following is not correct in the context of greenhouse

Which one of the following is not correct in the context of greenhouse effect?

Nitrogen and oxygen are poor absorbers of shortwave solar radiation

Clouds are poor absorbers of the Earth radiation

The most Earth radiation that escapes to space is in a narrow band from 8-13 micrometres

More than 70% of the atmospheric radiant energy is directed back to the surface

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Clouds are composed of water droplets or ice crystals and are very effective absorbers and emitters of longwave infrared radiation (Earth radiation). They significantly contribute to the greenhouse effect by absorbing outgoing radiation and re-emitting it back towards the surface. Therefore, the statement that clouds are poor absorbers of Earth radiation is incorrect.

– Nitrogen and oxygen (A) are diatomic molecules and are poor absorbers of both incoming solar (shortwave) and outgoing Earth (longwave) radiation, explaining why they are not greenhouse gases.
– The atmospheric window (C) is a range of wavelengths (roughly 8-13 µm) in the infrared spectrum where the atmosphere, particularly water vapour and CO2, is relatively transparent, allowing some Earth radiation to escape to space.
– A large proportion of atmospheric radiant energy, absorbed from the Earth’s surface, is indeed re-emitted downwards as back radiation (D), contributing significantly to surface warming via the greenhouse effect. While the exact percentage can vary, the concept that a large amount is directed back is correct.

Clouds have a complex effect on the Earth’s energy balance; they reflect incoming solar radiation (cooling effect) and absorb/emit outgoing infrared radiation (warming effect). The net effect depends on cloud type, altitude, and latitude. However, their role as strong absorbers and emitters of infrared radiation is well established.

36. The most significant ‘variable gases’ in the atmosphere are

The most significant ‘variable gases’ in the atmosphere are

oxygen and carbon dioxide

carbon dioxide and nitrogen

water vapour and carbon dioxide

water vapour and oxygen

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Variable gases in the atmosphere are those whose concentrations change significantly over time and space. Water vapour (H2O) is the most variable gas, with concentrations varying widely depending on temperature, location, and weather conditions. Carbon dioxide (CO2) is also a variable gas, with seasonal cycles and significant long-term increase due to human activities. Both are major greenhouse gases.

– Nitrogen (N2) and oxygen (O2) are the most abundant gases but are considered permanent or fixed gases because their global concentrations are relatively constant (around 78% N2 and 21% O2).
– Variable gases like water vapour, carbon dioxide, methane, and ozone exist in much smaller concentrations but play crucial roles in atmospheric processes, particularly climate and weather.

Water vapour is the most potent greenhouse gas, although its concentration is highly variable. Carbon dioxide is a less potent greenhouse gas molecule-for-molecule than some others (like methane) but its higher concentration and long atmospheric lifetime make it a primary driver of current climate change.

37. Which one of the following is not correct about marshes?

Which one of the following is not correct about marshes?

These transform mineral matter into organic matter

These function as physico-chemical sinks

These contribute to the beauty of the countryside

These are least productive natural environments

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Marshes are among the most biologically productive ecosystems on Earth. High nutrient input (often from surrounding land or water bodies) and abundant sunlight in shallow water fuel rapid plant growth. Therefore, the statement that they are the least productive natural environments is incorrect.

– Wetlands like marshes are known for their high primary productivity (conversion of mineral matter to organic matter by plants).
– They perform important ecological functions, including nutrient cycling, water purification (acting as sinks for pollutants and sediments), and providing habitat for diverse wildlife.
– Marshes contribute significantly to the aesthetic value of landscapes.

Other highly productive ecosystems include estuaries, coral reefs, and tropical rainforests. Less productive environments typically include deserts, open oceans, and polar regions.

38. Which one of the following is not an essential factor for the develo

Which one of the following is not an essential factor for the development of peat bog?

Presence of stagnant water

Presence of permeable soil

Presence of low temperature

Presence of acidic pH environment

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Peat bogs develop under specific conditions that inhibit the complete decomposition of organic matter. Essential factors include waterlogging (stagnant water creating anaerobic conditions), low temperature (slowing microbial activity), and acidic pH (further inhibiting decomposition). Permeable soil would allow water to drain away, preventing the crucial waterlogged conditions necessary for peat accumulation.

– Peat is partially decayed vegetation or organic matter that accumulates in wetland environments.
– Anaerobic conditions (lack of oxygen) caused by waterlogging are the primary reason for slow decomposition.
– Low temperatures and acidic conditions enhance the preservation of organic material.

Peat bogs are a type of wetland and significant carbon sinks. The lack of oxygen in the waterlogged conditions prevents aerobic bacteria from breaking down organic matter efficiently.

39. In a juvenile ecosystem, the zoocenoses are often

In a juvenile ecosystem, the zoocenoses are often

monophagous

polyphagous

oligophagous

carnivorous

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In a juvenile (early successional) ecosystem, the food webs are typically simpler and less specialized compared to mature ecosystems. Zoocenoses (animal communities) often include generalist species that can feed on a variety of food sources. Polyphagy, meaning feeding on multiple types of food, is characteristic of generalist consumers.

– Juvenile ecosystems are characterized by high growth rates and potentially fluctuating resource availability.
– Generalist feeding strategies (polyphagy) can be advantageous in such environments, providing resilience to changes in the abundance of specific food items.
– Mature ecosystems tend to have more complex food webs and a higher degree of specialization (monophagy, oligophagy) among consumers, as niches become more defined.

Monophagous organisms feed on only one type of food, and oligophagous organisms feed on a few types. These specialized strategies are more commonly associated with the stability and niche complexity of mature ecosystems. Carnivory refers to a trophic level (meat-eating) rather than the breadth of diet within that level.

40. The ultraviolet solar radiations are largely absorbed by

The ultraviolet solar radiations are largely absorbed by

carbon dioxide and nitrogen

oxygen and carbon dioxide

oxygen and ozone

nitrogen and ozone

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Ultraviolet (UV) solar radiation is primarily absorbed by ozone (O3) in the stratosphere, which forms the ozone layer. Oxygen (O2) also absorbs some high-energy UV radiation (UV-C), contributing to the formation of ozone.

– The ozone layer is crucial for life on Earth as it absorbs most of the harmful UV-B and UV-C radiation from the sun.
– Absorption of UV-C by oxygen molecules initiates the process of ozone formation (O2 + UV-C -> 2O; O + O2 -> O3).

Nitrogen and carbon dioxide are relatively transparent to ultraviolet radiation. Greenhouse gases like CO2 and water vapour are primarily involved in absorbing outgoing infrared radiation from the Earth’s surface, not incoming UV radiation.