Environmental Geosciences MCQ Quiz - Objective Question with Answer for Environmental Geosciences - Download Free PDF

The correct answer is: 1) A → D → B → C

Key Points

• Permanent Wilting Point (PWP):
  • The condition where the soil moisture is so low that plants cannot extract water and they start to wilt. It represents the lowest level of moisture a plant can use.
  • Typically occurs when soil moisture content is around 15-20% of the soil's total water holding capacity.
  • Plants cannot recover when they reach this stage, even if additional water is provided.
• Moisture Equivalent:
  • The amount of water held in soil against gravity after being centrifuged at a specified speed. It represents the soil's ability to retain moisture under certain conditions.
  • This is higher than the permanent wilting point but still does not indicate soil's full water holding capacity.
  • It provides a measure closer to soil moisture availability for plant use.
• Field Capacity (FC):
  • The amount of soil moisture or water content held in the soil after excess water has drained away and the rate of downward movement has decreased.
  • Occurs after the soil has been saturated and allowed to drain under gravity.
  • Represents the balance between soil moisture and air within the soil, optimal for plant growth.
• Saturation Capacity:
  • The point at which all the pores in the soil are filled with water, indicating the soil's maximum moisture content.
  • Any additional water beyond this point will lead to water logging or runoff, as the soil cannot hold any more water.
  • This condition is usually temporary in natural settings since water will eventually drain due to gravity.

​​​​​Additional Information

• Soil Moisture in Agriculture:
  • Understanding soil moisture conditions is vital for agricultural practices to ensure proper irrigation and optimal plant growth.
  • Excessive moisture (beyond field capacity) can lead to poor aeration and root diseases.
  • Insufficient moisture (below permanent wilting point) stresses plants, leading to reduced yield or plant death.
• Methods of Monitoring Soil Moisture:
  • Using tensiometers to measure soil water potential.
  • Deploying soil moisture sensors and data loggers for real-time monitoring.
  • Regular soil sampling and laboratory analysis.

The correct answer is Statement 1 is true, but Statement 2 is false.

Key Points

Statement I: Freshwater is less dense than saltwater, which causes it to float above saltwater in coastal aquifers, is true because,-

• Density Difference: Freshwater and saltwater have different densities, with freshwater having a lower density (approximately 1.00 g/cm³) compared to saltwater (approximately 1.025 g/cm³).
• Stratification: This difference in density causes stratification in coastal aquifers, where freshwater forms a lens above the denser saltwater.
• Buoyancy Effect: The lower density of freshwater leads to a buoyancy effect where it naturally tends to float on top of the denser saltwater.
• This phenomenon is critical in coastal hydrogeology and helps in understanding the behavior of freshwater lenses in coastal regions.
• Interface Zone: The zone where freshwater and saltwater meet in an aquifer is called the freshwater-saltwater interface or transition zone and is often characterized by a mixing of the two water types.

Statement II: The Ghyben-Herzberg relation is used to calculate the relative density of freshwater and saltwater, is false because,-

• The Ghyben-Herzberg relation is not used to calculate the densities of freshwater and saltwater but rather focuses on the depth of the freshwater-saltwater interface.
• The Ghyben-Herzberg principle describes a hydrostatic equilibrium where fresh groundwater floats above saline water in coastal aquifers.
• It provides a simple mathematical relationship to estimate the depth of the interface below sea level: h = 40*H, where h is the depth of the saltwater-freshwater interface below sea level, and H is the height of the water table above sea level.
• This relationship is based on the difference in density between freshwater and saltwater but does not directly calculate their densities.

Additional Information

• Coastal Aquifers: Coastal aquifers are significant sources of freshwater, especially in areas where surface water resources are limited.
• Saltwater Intrusion: Understanding the freshwater-saltwater interface is essential for managing saltwater intrusion, which can threaten freshwater supplies in coastal areas.
• Impacts of Over-extraction: Over-extraction of freshwater can cause a rise in the interface, leading to contamination of freshwater reserves with saltwater.
• The calculation and monitoring of the freshwater-saltwater boundary using the Ghyben-Herzberg principle help in sustainable groundwater management.

Concept: Chemical weathering refers to the breakdown of rocks and minerals through chemical reactions, usually involving water, oxygen, acids, and other chemicals present in the environment.

Common types of chemical weathering include:

• Hydration: Incorporation of water molecules into the mineral structure without decomposition.
• Hydrolysis: Breakdown of a substance when it reacts with water.
• Carbonation: Reaction with carbonic acid (H2CO3) formed from CO2 and water, particularly affecting carbonate minerals.
• Oxidation: Reaction with oxygen, often affecting iron-bearing minerals.

Explanation:

• Reaction: \(( \text{Al}_2\text{O}_3 + 3\text{H}_2\text{O} \rightarrow \text{Al}_2\text{O}_3 \cdot 3\text{H}_2\text{O} ) \)
  • Type: Hydration
  • Explanation: This reaction involves the addition of water molecules to aluminum oxide, forming hydrated aluminum oxide. Hydration does involve water and can occur in some weathering environments.
• Reaction: \(( 2\text{Fe}_2\text{O}_3 + 3\text{H}_2\text{O} \rightarrow 2\text{Fe}_2\text{O}_3 \cdot 3\text{H}_2\text{O} ) \)
  • Type: Hydration
  • Explanation: This reaction entails adding water to iron(III) oxide to form hydrated iron(III) oxide. Hydration is part of the broader weathering processes.
• Reaction: \( \text{CaCO}_3 + \text{H}_2\text{CO}_3 \rightarrow \text{Ca}^{2+} + 2\text{HCO}_3^{-}\)
  • Type: Carbonation
  • Explanation: Calcium carbonate reacts with carbonic acid, resulting in dissolved calcium ions and bicarbonate ions. This is a typical process of chemical weathering for calcareous rocks.
• Reaction: \( \text{FeO} + \text{O}_2 + \text{H}_2\text{O} \rightarrow \text{Fe(OH)}_3 \)
  • Type: Oxidation
  • Explanation: Iron(II) oxide reacts with oxygen and water to form iron(III) hydroxide. Oxidation is essential in the weathering of minerals containing ferrous iron.

While all the reactions can be related to processes in chemical weathering, the key distinction here is identifying which reaction is less representative of breaking down minerals through typical weathering processes. Hydration reactions (1 and 2) are less transformative compared to reactions involving carbonation and oxidation, which often alter the mineral structure significantly, leading to decomposition.

Therefore, the correct answer, based on detailed analysis, is:

\( \text{Al}_2\text{O}_3 + 3\text{H}_2\text{O} \rightarrow \text{Al}_2\text{O}_3 \cdot 3\text{H}_2\text{O} \)

This reaction is primarily a hydration reaction without significant breakdown of the mineral structure, making it the least likely to represent typical chemical weathering processes that involve more substantial chemical transformation.

The correct answer is 'chemical weathering.'

Key Points

• Chemical Weathering:
  • Chemical weathering involves the breakdown of minerals and rocks through chemical reactions, often involving water and atmospheric gases.
  • Hydrolysis is a common chemical weathering process where water reacts with minerals to form new minerals and dissolved ions.
  • In the case of feldspar, hydrolysis converts this mineral into clay minerals and soluble ions like potassium, sodium, or calcium, along with silica.

Additional Information

• Other Types of Weathering:
  • Physical Weathering: This refers to the physical breakdown of rocks into smaller pieces without changing their chemical composition, primarily through processes such as freeze-thaw cycles and abrasion.
  • Biological Weathering: This involves the effects of organisms such as plants and microbes in breaking down rocks, either through physical means like root growth or chemical means like the production of organic acids.
  • Mechanical Weathering: Another term for physical weathering, emphasizing the mechanical forces involved in breaking down rocks.

The correct answer is: 1.

Darcy’s law describes the flow of a fluid through a porous medium. It states that the discharge rate is proportional to the hydraulic gradient and the permeability of the medium. Darcy's law is fundamental in hydrogeology, soil science, and petroleum engineering. Its validity depends on the Reynolds number, which must be in the laminar flow range for Darcy's law to hold true.

Key Points

• Darcy's Law:
  • Expresses the relationship between the flow rate, hydraulic gradient, and permeability in porous media.
• Reynolds Number:
  • A dimensionless number used to predict the flow regime in fluid dynamics. It is defined as the ratio of inertial forces to viscous forces.
  • The formula is: \(( Re = \frac{\rho v d}{\mu} ) \), where:
    • \((\rho) \) = density of the fluid
    • v = velocity of the fluid
    • d = characteristic length (such as diameter of grains or pore spaces)
    • \((\mu) \) = dynamic viscosity of the fluid
• Laminar Flow:
  • Occurs when the Reynolds number is low (typically Re ≤ 1).
  • The fluid particles move in parallel layers with no disruption between the layers.
• Transitional and Turbulent Flow:
  • Transitional flow occurs for Reynolds numbers between 1 and roughly 2000. It is a mix of laminar and turbulent characteristics.
  • Turbulent flow occurs at Reynolds numbers Re > 2000. It is characterized by chaotic and irregular fluid motion.

Additional Information

• Applications of Darcy's Law:
  • Used in groundwater flow and solute transport modeling.
  • Essential for calculating the permeability of soils, rocks, and other porous materials.
  • Applied in petroleum engineering to estimate reservoir properties.
• Limitations of Darcy's Law:
  • Only valid for laminar flow conditions (Reynolds number ≤ 1).
  • Assumes that the flow is steady-state and the porous medium is homogenous and isotropic.
  • Not applicable for very high or very low permeability media where non-Darcian flow might occur.
• Modifications and Extensions:
  • For non-laminar flows, empirical adjustments are sometimes applied.
  • Extended Darcy's law accounts for non-Darcian flow behaviors, observed in fractured rocks and highly heterogeneous media.

The correct answer is  Mistral.

Important Points 

• A katabatic wind is a type of wind formed by cooling and sinking dense air. 
• This wind is typically found near large bodies of water and descends from higher elevations toward lower elevations.

The Mistral is a classic example of a katabatic wind, as it occurs in the Mediterranean region and is created by the cooling of air in the Massif Central mountains.

• It is a cold and dry wind that blows in Spain and France from North-west to the South-East direction, mostly during winter.
• Due to the presence of the Rhome River, these winds are channelized into the Rhome valley due to which they become extremely cold.
• As they pass through the narrow Rhome Valley, they turn into stormy northerly cold winds and their average velocity which is 55-65 km/hr may even reach 128km/hr.
• Such stormy cold northerly winds cause a sudden drop in temperature to below freezing point.

Key Points 

• The hot and dry wind
  • Chinook (Snow eaters) Hot, dry wind in the Rockies mountains.
  • Foehn Hot dry wind in the Alps.
  • Khamsin Hot, dry wind in Egypt.
  • Harmattan (Guinea Doctor) Hot, dry wind in West Africa.
• The cold and dry wind
  • Bora Cold, dry wind Blows from Hungary to North Italy.
  • Mistral Cold wind from The Alps and France.
  • Punas Cold dry wind from The western side of Andes Mountain.
  • Blizzard Cold wind from Tundra region.

• Chinook is a warm and dry wind that occurs in the western coastal regions of North America. It is created by the warming of air as it descends from high altitudes and is often associated with clear and sunny weather.

  Foehn is a warm and dry wind that occurs in the alpine regions of Europe. It is created by the warming of air as it descends from high altitudes and is often associated with clear and sunny weather.

  Santa Ana is a hot and dry wind that occurs in southern California and is associated with high-pressure systems. It is known for its strong gusts and low humidity and can contribute to the spread of wildfires in the region.

Additional Information   Katabatic winds 

Katabatic winds (from Greek katabatikos meaning ‘going down’) form when cold air above a plateau, mountain, glacier, or even a hill flows down a slope due to gravity. Katabatic winds are cool, dry, and can be strong. They are very common in the Antarctic and can achieve wind speeds of 190 mph.

Anabatic wind

Anabatic wind, also called upslope wind, local air current that blows up a hill or mountain slope facing the Sun. During the day, the Sun heats such a slope (and the air over it) faster than it does the adjacent atmosphere over a valley or a plain at the same altitude.

The correct answer is Low trophic level.

Important Points

Organisms with 'r-selected' growth patterns tend to occupy low trophic levels in their ecosystems.

• The concept of "r-selected" species and "K-selected" species comes from ecological theories related to reproductive strategies.
• "r-selected" species are characterized by high reproductive rates, small body sizes, early maturity, and the ability to colonize new environments quickly.
• They typically have a type III survivorship curve, where many offspring are produced with low parental investment, but many also die at an early stage.

These characteristics are often associated with organisms that occupy lower trophic levels in ecosystems. These species are often the primary producers or herbivores that form the base of the food chain. They reproduce rapidly to take advantage of available resources and are adapted to environments with fluctuating or unpredictable conditions.

In contrast, "K-selected" species have slower reproductive rates, larger body sizes, and higher levels of parental investment. They tend to occupy higher trophic levels and are often top predators or apex predators in the food chain.

Therefore, the correct answer is option 1) Low trophic level.

The correct answer is A - III, B - I, C - IV, D - II.  

Key Points

Therefore, the correct answer is A - III, B - I, C - IV, and D - II.

Additional Information

• Andisols are soils that have formed in volcanic ash or other volcanic ejecta. They differ from those of other orders in that they typically are dominated by glass and short-range-order colloidal weathering products such as allophane, imogolite and ferrihydrite.
• Gelisols are soils of very cold climates that contain permafrost within two meters of the surface. These soils are limited geographically to the high-latitude polar regions and localized areas at high mountain elevations.
• Histosols are soils that are composed mainly of organic materials. They contain at least 20-30% organic matter by weight and are more than 40 cm thick.
• Vertisols are clay-rich soils that shrink and swell with changes in moisture content. During dry periods, the soil volume shrinks and deep wide cracks form. The soil volume then expands as it wets up.

The correct answer is parallel to the strike of the fault plane.

Key Points

• A strike-slip fault, or a transform fault, is a fault in which movement is parallel to the strike of the fault plane.
• The opposite of a strike-slip fault is a dip-slip fault. 
• A transform fault can be either left-lateral or right-lateral.
• It is determined by selecting one block as a reference and then examining the movement of the other with the referenced block.
• For instance, a left-lateral strike-slip fault means the block opposite from which one is standing moves left.
• A right-lateral transform fault means the block opposite from which one is standing is moving right. 

Therefore, the correct answer is parallel to the strike of the fault plane.

The dating and study of annual rings of trees is called: Dendrochronology,

Key Points

• Dendrochronology is a process used to determine the order and timing (chronology) of events using the information in tree rings (dendro- refers to trees).
• Tree-ring dating is the study of growth rings in deciduous trees to identify absolute dates of wooden objects. 
• Tree rings are created by the tree as it grows in girth, and the width of a given tree ring is dependent on climate, so a stand of trees will all have a near-identical pattern of tree rings.
• The method was invented in the 1920s by astronomer Andrew Ellicott Douglass and archaeologist Clark Wissler. 
• Tree ring dating is also used to calibrate radiocarbon dates
• Dendrochronology is extremely precise: if the growth rings in a wooden object are preserved and can be tied into an existing chronology, researchers can determine the precise calendar year—and often season—the tree was cut down to make it.

Important Points 

Cross section of a tree illustrating the cambium layer. Lukaves / iStock / Getty Images

• Tree-ring dating works because a tree grows larger—not just in height but gains girth—in measurable rings each year in its lifetime.
• The rings are the cambium layer, a ring of cells that lies between the wood and bark and from which new bark and wood cells originate; each year a new cambium is created leaving the previous one in place.
• How large the cambium's cells grow each year, measured as the width of each ring, depends on temperature and moisture—how warm or cool, dry or wet each year's seasons were.

The correct answer is A - IV, B - II, C - III, D - I.

Key Points

Therefore, the correct answer is A - IV, B - II, C - III, and D - I.

Additional Information

• The Global Warming Potential (GWP) was developed to allow comparisons of the global warming impacts of different gases.
• Specifically, it is a measure of how much energy the emissions of 1 ton of a gas will absorb over a given period, relative to the emissions of 1 ton of carbon dioxide (CO₂).
• The larger the GWP, the more that a given gas warms the Earth compared to CO₂ over that period. 
• CO₂, by definition, has a GWP of 1 regardless of the period used, because it is the gas being used as the reference.
• Methane (CH₄) is estimated to have a GWP of 27-30 over 100 years. 
• Nitrous Oxide (N₂O) has a GWP 273 times that of CO₂ for a 100-year timescale.
• Chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF₆) are sometimes called high-GWP gases because, for a given amount of mass, they trap substantially more heat than CO_2. 

Answer 
Option 1) Occluded front

Key PointsAir Mass:

• Air mass is a volume of air defined by its temperature and water vapor content.
• The boundary between the two air masses is called the front.
• When warm air mass moves over cold air mass create a warm front and when cold air mass moves over warm air mass, that situation creates a cold front.

Occluded font:

• An occluded front is a front that is formed when a cold front overtakes a warm front.
• The cold front moves rapidly than the warm front.
• Ultimately, the cold front overtakes the warm front and completely displaces the warm air at the ground.

The correct answer is A, B and E only.

Key Points

• Basalts are common aphanitic igneous extrusive (volcanic) rocks.
• Basalts are composed of minute grains of plagioclase feldspar (generally labradorite), pyroxene, olivine, biotite, hornblende and <20% quartz. 
• Nepheline or leucite may associate or proxy the feldspar giving rise to verities with special names.
• The ferromagnesian minerals are mainly amphibole and rarely biotite.
• Basalts are usually dark grey to black. 

Therefore, the correct answer is A, B and E only.

The correct answer is Two plates move away from one another.

Key Points

• The mid-ocean ridge is the most extensive chain of mountains on Earth, stretching nearly 65,000 kilometres (40,390 miles) and with more than 90% of the mountain range lying underwater, in the deep ocean.
• The massive mid-ocean ridge system is a continuous range of underwater volcanoes that wraps around the globe like seams on a baseball, stretching nearly 65,000 kilometres (40,390 miles).
• The majority of the system is underwater, with an average water depth to the top of the ridge of 2,500 meters (8,200 feet).
• Mid-ocean ridges occur along divergent plate boundaries, where the new ocean floor is created as the Earth’s tectonic plates spread apart.
• A divergent boundary occurs when two tectonic plates move away from each other.
• As the plates separate, the molten rock rises to the seafloor, producing enormous volcanic eruptions of basalt.
• The speed of spreading affects the shape of a ridge – slower spreading rates result in steep, irregular topography while faster-spreading rates produce much wider profiles and more gentle slopes.

Therefore, the correct answer is two plates move away from one another.

Additional InformationA divergent boundary occurs when two tectonic plates move away from each other. Along these boundaries, earthquakes are common and magma (molten rock) rises from the Earth’s mantle to the surface, solidifying to create a new oceanic crust. The Mid-Atlantic Ridge is an example of divergent plate boundaries.

When two plates come together, it is known as a convergent boundary. The impact of the colliding plates can cause the edges of one or both plates to buckle up into mountain ranges or one of the plates may bend down into a deep seafloor trench. The Pacific Ring of Fire is an example of a convergent plate boundary.

Two plates sliding past each other form a transform plate boundary. One of the most famous transform plate boundaries occurs at the San Andreas fault zone, which extends underwater.

The correct answer is N2 and O2.

Key Points

• The atmosphere contains many gases, most in small amounts, including some pollutants and greenhouse gases. 
• The most abundant gas in the atmosphere is nitrogen, with oxygen second and argon, an inert gas the third most abundant gas in the atmosphere.
• The atmosphere is composed of a mix of several different gases in differing amounts. 
• The permanent gases whose percentages do not change from day to day are nitrogen, oxygen and argon. 
• Nitrogen accounts for 78% of the atmosphere, oxygen 21% and argon 0.9%. 
• Gases like carbon dioxide, nitrous oxides, methane, and ozone are trace gases that account for about a tenth of 1% of the atmosphere. 
• Water vapour is unique in that its concentration varies from 0-4% of the atmosphere depending on where you are and what time of the day it is.

Therefore, the correct answer is N2 and O2.