All questions of Geomorphology (Part 2) for Delhi Police Constable Exam

Explanation:
Not sedimentary rocks:
- Limestone: Limestone is a sedimentary rock formed from the remains of marine organisms such as coral and shells. It is composed mostly of calcium carbonate.
- Marble: Marble is a metamorphic rock formed from limestone that has undergone heat and pressure. It is composed of recrystallized carbonate minerals.
Therefore, limestone and marble are not sedimentary rocks, unlike sandstone and slate.

Formation Location:
- Alluvial fans are formed in the higher reaches of the river, while deltas form at lower reaches.

Composition of Load:
- Alluvial fans are made of much coarser load compared to deltas.

Stratification:
- Alluvial fans do not show clear stratification of river load during deposition, whereas deltas exhibit clear stratification.

Therefore, the correct answer is option 'D' as all the given points highlight the key differences between alluvial fans and deltas.

The correct answer is option 'A' (1 only).


- Mesas and buttes are table-like land masses found in desert regions.
- They are characterized by their very resistant horizontal top layers and steep slopes.
- These landforms are formed due to the differential erosion of sedimentary rock layers.
- The hard and resistant top layer protects the softer layers underneath from erosion.
- Over time, the softer layers erode away, leaving behind the resistant top layer, which forms a flat-topped mesa or butte.
- The steep slopes of mesas and buttes are often referred to as "scarps" and can be several hundred meters high.
- These landforms are commonly found in arid regions, including deserts.


- Zeugen are not isolated residual round hills found in the desert.
- Zeugen are actually elongated ridges or hills that are formed as a result of erosion.
- They are typically found in areas where there are horizontal layers of rock with alternating hard and soft layers.
- The soft layers erode more quickly, leaving behind the hard layers, which form the elongated ridges or hills.
- Zeugen are not exclusive to desert regions and can be found in various landscapes.

In conclusion, statement 1 is correct as mesas and buttes are table-like land masses with very resistant horizontal top layers and steep slopes. However, statement 2 is incorrect as zeugen are not isolated residual round hills found in the desert.

Weathering of rocks:
- Weathering is the process by which rocks are broken down into smaller pieces or undergo chemical changes due to exposure to various environmental factors such as wind, water, and temperature changes.
- As rocks undergo weathering, the minerals present in them are released and become available for other processes to act upon.
- This weathering process can be physical, such as the freezing and thawing of water in cracks, or chemical, such as the reaction of rock minerals with water or acids.
- The weathering of rocks plays a significant role in the enrichment of minerals in rocks because it breaks down the rock into smaller particles, exposing more surface area for chemical reactions to occur.

Erosional and depositional action of rivers:
- Rivers play a crucial role in the transportation and deposition of sediments.
- As rivers flow, they erode the land, carrying sediments such as rocks, minerals, and soil particles.
- These sediments are transported downstream and eventually deposited when the river's velocity decreases, such as in river bends or at the mouth of the river.
- During this process, minerals that were weathered from rocks in the upstream areas are carried by the river and deposited in new locations.
- The erosional and depositional action of rivers helps in redistributing and concentrating minerals, thereby contributing to the enrichment of minerals in rocks.

Both (a) and (b):
- Both weathering of rocks and the erosional and depositional action of rivers contribute to the enrichment of minerals in rocks.
- Weathering breaks down rocks, releasing minerals and making them available for other processes.
- Rivers then transport these minerals and deposit them in new locations, contributing to the enrichment of minerals in rocks.
- The combined action of weathering and rivers helps in the concentration and redistribution of minerals, ultimately leading to the enrichment of minerals in rocks.

Therefore, the correct answer is option 'C' - Both (a) and (b).

Sedimentary rocks make up about three-quarters of the rocks at the Earth’s surface.

• Sedimentary rocks preserve a record of the environments that existed when they formed. By looking at sedimentary rocks of different ages, scientists can figure out how climate and environments have changed through Earth’s history. Fossils of ancient living things are preserved in sedimentary rocks too.
• Quartz, K-feldspar and muscovite are some of the important minerals found there.

Explanation:
The correct answer is option 'D' - None of the above.

Let's analyze each statement one by one:

Statement 1:
A river drains the water collected from a specific area, which is called its 'catchment area'.

This statement is correct. A river collects water from a specific area, which is known as its catchment area. The catchment area is the area of land where the rainwater or snowmelt flows into the river and its tributaries.

Statement 2:
An area drained by a river and its tributaries is called a drainage basin.

This statement is correct. A drainage basin refers to the area of land that is drained by a river and its tributaries. It includes all the land where the water flows into the river system.

Statement 3:
The boundary line separating one drainage basin from the other is known as the watershed.

This statement is incorrect. The boundary line separating one drainage basin from the other is known as the watershed, not the catchment area. The watershed is the dividing line between two drainage basins, where the water flows in different directions.

Statement 4:
Watersheds are small in area while the basins cover larger areas.

This statement is incorrect. Watersheds are not necessarily small in area compared to basins. The size of a watershed or a drainage basin can vary greatly depending on various factors such as the size of the river and the topography of the land. Some watersheds can be large, covering a vast area, while others can be relatively small.

In conclusion, statement 3 is incorrect while the other statements are correct. Hence, the correct answer is option 'D' - None of the above.

Sedimentary rocks can be directly formed from which of the following:

1. Magma
2. Igneous rocks
3. Metamorphic rocks

The correct answer is option 'B' which is 2 and 3 only.

Explanation:
Sedimentary rocks are formed from the accumulation of sediments or organic matter that have been deposited in layers over time. These sediments can come from a variety of sources such as weathering and erosion of other rocks, as well as the remains of plants and animals.

Sedimentary rocks can be directly formed from two types of rocks:

1. Igneous rocks: These rocks are formed from the cooling and solidification of magma or lava. When these rocks are weathered and eroded, they can break down into sediments which can then be deposited and compacted to form sedimentary rocks.

2. Metamorphic rocks: These rocks are formed from the alteration of pre-existing rocks due to heat and pressure. When these rocks are weathered and eroded, they can break down into sediments which can then be deposited and compacted to form sedimentary rocks.

However, sedimentary rocks cannot be directly formed from magma as it cools and solidifies to form igneous rocks, nor from metamorphic rocks as they are already altered from pre-existing rocks.

Therefore, the correct answer is option 'B' which is 2 and 3 only.

Understanding Seaweeds
Seaweeds are fascinating organisms that play a crucial role in marine ecosystems. Let's analyze the given statements to determine their accuracy.
Statement 1: Seaweeds are plant-like organisms that generally live attached to rock or other hard substrata in coastal areas.
- This statement is correct.
- Seaweeds, also known as macroalgae, are indeed plant-like organisms.
- They primarily inhabit coastal areas, where they attach themselves to rocks or hard substrates.
- Their growth forms contribute significantly to marine biodiversity, providing habitats and food for various marine organisms.
Statement 2: All seaweeds are edible, though some are more nutritional and palatable than others, and some can cause stomach upset.
- This statement is incorrect.
- While many seaweeds are edible and consumed in various cuisines around the world, not all species are safe for human consumption.
- Some seaweeds can be toxic or indigestible, leading to stomach upset or other health issues.
- Therefore, it is essential to identify seaweed species properly before consumption.
Conclusion
Given the analysis above, the correct answer is option C: "1 only."
- Statement 1 is true, while Statement 2 is false due to the presence of non-edible and potentially harmful seaweed species.
- This distinction highlights the importance of understanding marine flora for both ecological and culinary purposes.

They are formed due to fluvial action.

Stream capture can also cause due to

Type of dune: Seif

A seif dune is a long, narrow sand dune or chain of dunes that is generally oriented in a direction parallel to the prevailing wind or a direction resulting from two or more winds blowing at acute angles to each other.

Characteristics of a Seif dune:
- Orientation: Parallel to the prevailing wind direction or a direction resulting from two or more winds blowing at acute angles to each other.
- Shape: Long and narrow with a gentle slope on the windward side and a steep slope on the leeward side.
- Size: Can be several meters to several kilometers long and up to 150 meters high.
- Formation: Results from the movement of sand grains by wind.

Other types of dunes:
- Barchan dune: Crescent-shaped and formed by winds blowing predominantly from one direction.
- Loess: A type of sediment formed from wind-blown dust and silt.
- Erg: Large area covered with sand dunes.

This question belongs to the UPSC category, which is the Union Public Service Commission in India.

Sediment maturity refers to the length of time that the sediment has been in the sedimentary cycle. Texturally mature sediment is sediment that is well rounded (as rounding increases with transport distance and time) and well sorted (as sorting gets better as larger clasts are left behind and smaller clasts are carried away). If the fragments are angular, it indicates that they have not been transported very far and the sediment is poorly sorted.

Explanation:

Metamorphic rocks are formed when existing rocks, either igneous or sedimentary, undergo a transformation due to intense heat and pressure. This process causes the minerals in the rocks to recrystallize, resulting in a new rock with different physical and chemical properties.

The correct conversions to metamorphic rocks are:

1. Clay to slate: Clay is a sedimentary rock composed mainly of fine-grained minerals. Under high pressure and temperature, the minerals in the clay recrystallize, forming a dense, fine-grained rock called slate. Slate is characterized by its ability to be easily split into thin, flat sheets.

2. Coal to graphite: Coal is a sedimentary rock formed from the remains of plant material. When subjected to high temperature and pressure, coal undergoes a metamorphic transformation and turns into graphite. Graphite is a crystalline form of carbon with a layered structure and is known for its lubricating properties and use in pencils.

3. Sandstone to quartzite: Sandstone is a sedimentary rock composed of sand-sized grains of mineral, rock, or organic material. Under intense heat and pressure, the sand grains in sandstone recrystallize and fuse together, forming a harder and more compact rock called quartzite. Quartzite is composed mainly of quartz and is known for its durability and resistance to weathering.

4. Shale to schist: Shale is a sedimentary rock composed of fine particles of clay minerals. When subjected to high temperature and pressure, shale undergoes metamorphism and transforms into a metamorphic rock called schist. Schist is characterized by its foliated texture, with minerals aligned in layers or bands.

Therefore, the correct conversions to metamorphic rocks are 1, 2, 3, and 4. Thus, option 'D' - "All of the above" is the correct answer.

The major characteristics of the Archaean rock system can be summarized as follows:

a) Formed before the appearance of life in the geologic sequence:
The Archaean rock system refers to the oldest rock system on Earth, which formed between 4 to 2.5 billion years ago. It predates the appearance of life on Earth, as the first evidence of life dates back to around 3.5 billion years ago. Therefore, the Archaean rock system was formed before the appearance of life in the geologic sequence.

b) Not the first metamorphic sedimentary rock:
While the Archaean rock system is known for its high-grade metamorphic rocks, it is not the first metamorphic sedimentary rock system. Metamorphic rocks are formed from pre-existing rocks under conditions of high temperature and pressure. The Archaean rock system is primarily composed of igneous rocks, which were formed through volcanic activity.

c) Not the host of major coal deposits of India:
The major coal deposits of India are primarily found in the Gondwana rock system, which formed during the Permian and Carboniferous periods, around 300 to 200 million years ago. The Archaean rock system, being much older, does not host the major coal deposits of India.

d) Largely igneous rocks:
The Archaean rock system is predominantly composed of igneous rocks. Igneous rocks are formed through the solidification and crystallization of molten magma or lava. The Archaean rock system is characterized by the presence of various types of igneous rocks, including granite, gneiss, and greenstone belts. These rocks provide valuable insights into the early history of Earth's formation and the processes that shaped its crust.

In conclusion, the major characteristic of the Archaean rock system is that it was formed before the appearance of life in the geologic sequence. This rock system is primarily composed of igneous rocks and is distinct from the later rock systems that host coal deposits and exhibit metamorphic sedimentary characteristics.

Himalayan region and its poor mineral resources

There are several factors that contribute to the Himalayan region being poor in mineral resources. However, the most significant reason is the complex rock structure in the region.

Complex rock structure

The Himalayan region is characterized by a complex geological history, resulting in the formation of diverse rock types and structures. The region is mainly composed of metamorphic and sedimentary rocks, which are less likely to contain significant mineral deposits compared to other types of rocks such as igneous rocks. Metamorphic rocks are formed through the transformation of pre-existing rocks under high pressure and temperature conditions, which often leads to the loss of mineral resources.

Unfavorable terrain and adverse climatic conditions

While the undulating terrain and adverse climatic conditions in the Himalayan region certainly pose challenges for mineral exploration and extraction, they are not the primary reasons for the region's poor mineral resources. These factors may make it difficult to access certain areas and conduct mining operations, but they do not directly impact the presence or absence of mineral resources in the region.

Crystalline rocks and mineral resources

The statement mentioned that the Himalayan region is made up of crystalline rocks, which do not hold mineral resources anywhere in India. This is incorrect. Crystalline rocks can indeed contain mineral resources, although their presence and abundance vary from region to region. Crystalline rocks, such as granite and gneiss, can host valuable minerals such as gold, silver, copper, and tin. However, in the case of the Himalayan region, the primary reason for the lack of mineral resources is the complex rock structure rather than the presence of crystalline rocks.

In conclusion, the Himalayan region's poor mineral resources can be attributed to its complex rock structure, which is dominated by metamorphic and sedimentary rocks. While other factors such as unfavorable terrain and adverse climatic conditions might pose challenges for mineral extraction, they are not the main reasons for the region's limited mineral resources.

Geos is a narrow inlet in a cliff while gloups are blow holes.

Vertical erosion is dominant in the upper courses of the river.

The correct answer is option 'D' - Deccan Traps.

Explanation:
The Deccan Traps is a large volcanic province located in west-central India. It is composed of multiple layers of solidified basalt lava flows. The rocks of the Deccan Traps were formed during the Late Cretaceous period, approximately 66 million years ago.

Formation of the Deccan Traps:
1. Geological Activity: The formation of the Deccan Traps can be attributed to intense volcanic activity that occurred during the breakup of the supercontinent Gondwana.
2. Massive Eruptions: The volcanic activity resulted in massive eruptions that released vast amounts of basaltic lava onto the surface.
3. Lava Flows: The lava flows spread over an area of approximately 500,000 square kilometers, covering the present-day states of Maharashtra, Madhya Pradesh, Gujarat, and Karnataka.
4. Layered Structure: Over time, the successive eruptions led to the formation of multiple layers of solidified lava flows, creating a distinctive layered structure.
5. Thickness and Extent: The Deccan Traps cover an immense thickness of up to 2,000 meters and are considered one of the largest volcanic provinces in the world.

Importance of the Deccan Traps:
1. Geological Significance: The Deccan Traps hold immense geological significance as they provide valuable insights into the Earth's history, climate changes, and mass extinctions.
2. Mass Extinction Event: The timing of the Deccan Traps' formation coincides with the mass extinction event that resulted in the extinction of the dinosaurs. It is believed that the volcanic activity and the release of gases and aerosols had a significant impact on the global climate, contributing to the extinction event.
3. Mineral Resources: The Deccan Traps also contain various mineral resources, including basalt, granite, and limestone, which are important for construction and industrial purposes.

In conclusion, the rocks of the Deccan Traps in India were formed the earliest among the given options. The intense volcanic activity during the Late Cretaceous period led to the deposition of multiple layers of solidified basalt lava flows, creating the distinctive geological formation known as the Deccan Traps.

Factors Aiding the Weathering of Rocks

Weathering refers to the process by which rocks are broken down into smaller fragments or transformed into different minerals through physical, chemical, and biological processes. Several factors contribute to the weathering of rocks. The correct answer, option 'D', states that all of the following factors aid in the weathering of rocks:

1. Intense heating during the day and rapid cooling at night:
- Temperature changes play a significant role in the weathering of rocks. When rocks are exposed to intense heating during the day, they expand. As a result, cracks and fractures develop within the rocks.
- At night, the rapid cooling causes the rocks to contract. This contraction further enhances the development of cracks and fractures. Over time, these cracks and fractures become pathways for water and other weathering agents to penetrate deeper into the rocks, accelerating the weathering process.

2. Pore pressure of water seeping into rocks:
- Water is one of the most important agents of weathering. When water seeps into rocks, it exerts pressure on the rock material, known as pore pressure.
- The pore pressure of water can weaken the rocks, especially if the water freezes and expands within the rock crevices. This process, known as frost wedging, causes the rocks to crack and break apart.

3. Thawing of rocks:
- Thawing refers to the process of melting frozen water within rocks. When water freezes within the rock crevices, it expands, exerting pressure on the surrounding rock material.
- During thawing, the ice melts, releasing the pressure within the rock. This repeated freezing and thawing cycle weakens the rocks, leading to the development of cracks and fractures.

In summary, all three factors mentioned in the given options contribute to the weathering of rocks. Intense heating and rapid cooling lead to thermal expansion and contraction, pore pressure of water seeping into rocks causes frost wedging, and the thawing process weakens the rocks. These processes eventually break down the rocks into smaller fragments, facilitating the further breakdown and transformation of the rocks through weathering processes.

Introduction:
Oxbow lakes are a common feature found in the upper courses of rivers. They are formed when a meandering river creates a loop or bend that eventually gets cut off from the mainstream due to erosion and deposition processes. Oxbow lakes are also known as bayous or cut-offs in the USA.

Explanation:
Let's analyze each statement given in the question to determine their correctness:

Statement 1: Oxbow lakes are formed when an almost circular meander is cut off from the mainstream.
This statement is correct. Oxbow lakes are formed when a river's meander loop becomes so pronounced that the river cuts through the narrow neck of the loop, creating a new straight channel. This process is known as "cutoff" or "abandonment." The loop, which is left isolated from the main river, becomes an oxbow lake.

Statement 2: Oxbow lakes are observed in the upper courses of a river.
This statement is correct. Oxbow lakes are typically found in the upper courses of rivers where the gradient is steep and the river is more prone to meandering. As the river flows through its course, it erodes the outer bank of a bend and deposits sediment on the inner bank, causing the bend to become more pronounced and eventually cutoff.

Statement 3: Oxbow lakes are also called Bayous or cut-offs in the USA.
This statement is correct. In the USA, oxbow lakes are commonly referred to as bayous or cut-offs. The term "bayou" is derived from the Choctaw word "bayuk," meaning a small river. These terms are often used interchangeably to describe the same landforms.

Conclusion:
In conclusion, both statements 1 and 3 are correct. Oxbow lakes are formed when a meander loop is cut off from the mainstream, and they are also known as bayous or cut-offs in the USA. However, statement 2 is incorrect as oxbow lakes are found in the upper courses of rivers, not exclusively in the upper courses. Therefore, the correct answer is option 'C' - 1 and 3 only.

Soil creep indicates slow movement while solifluction is fast movement.

Delta formation can have several consequences that can significantly impact the surrounding environment. These consequences include:

1. Change of river course:
When a river nears the sea and starts depositing its sediment load in the plains, the formation of a delta can cause a change in the course of the river. As the sediment accumulates at the river mouth, it can block the main channel and force the river to take a new path. This change in course can lead to the abandonment of the old channel and the formation of a new one. This process is known as avulsion.

2. Formation of several distributaries of the original river:
As the river deposits sediment at its mouth, it may create multiple channels or distributaries that branch out from the main river. These distributaries carry the sediment and water from the river to different areas, creating a network of channels that spread out across the delta. This branching pattern is often seen in large river deltas, such as the Mississippi Delta or the Ganges-Brahmaputra Delta.

3. Fertility of the local soil increases:
Deltaic soils are generally highly fertile due to the deposition of sediment carried by the river. The sediment deposited by the river contains minerals and nutrients that enrich the soil, making it suitable for agriculture. The constant flooding and deposition of sediment also help to replenish the soil with new nutrients, further enhancing its fertility. As a result, deltaic regions often support extensive agricultural activities and are considered highly productive.

In conclusion, the consequences of delta formation include a change in the river course, the formation of distributaries, and an increase in the fertility of the local soil. These consequences have both natural and human impacts on the environment, influencing river dynamics, landforms, and agricultural practices in deltaic regions.

Statement 1: Wind gaps in the course of a river do not allow the construction of upland roads and railways.

Explanation:
- Wind gaps are narrow passages or valleys in mountain ranges that are formed due to erosion by wind.
- These gaps are typically located in upland areas where rivers have cut through the mountain ranges.
- Due to their narrow and steep nature, wind gaps pose significant challenges for the construction of roads and railways.
- Constructing roads and railways in wind gaps would require extensive engineering efforts and may not be economically or technically feasible.
- The difficult topography, limited space, and high terrain make it challenging to create a stable and safe infrastructure in wind gaps.
- Therefore, it is correct to say that wind gaps in the course of a river do not allow the construction of upland roads and railways.

Statement 2: Deltas are less preferred sites than estuaries for the siting of large ports.

Explanation:
- Deltas are landforms formed at the mouth of a river where it meets a body of water, typically a sea or an ocean.
- Estuaries, on the other hand, are the areas where a river meets the sea and freshwater mixes with saltwater.
- Both deltas and estuaries are potential sites for the siting of large ports due to their proximity to the sea and availability of waterways for navigation.
- However, deltas have certain disadvantages compared to estuaries for port siting.
- Deltas are often characterized by shifting channels, sandbars, and sediment deposition, which can pose challenges for navigation and the maintenance of navigational channels.
- Deltas are also prone to frequent changes in their shape and size due to sedimentation and erosion, which can affect the long-term viability of port infrastructure.
- Estuaries, on the other hand, tend to have more stable and predictable water flows, making them more suitable for large port operations.
- Therefore, it is correct to say that deltas are less preferred sites than estuaries for the siting of large ports.

Conclusion:
- Both Statement 1 and Statement 2 are correct.
- Wind gaps in the course of a river indeed do not allow the construction of upland roads and railways due to their challenging topography.
- Deltas are less preferred sites than estuaries for the siting of large ports due to their dynamic nature and challenges associated with navigation and maintenance.

A) 1 and 2 only

Exfoliation refers to the peeling or shedding of rock layers due to the weathering process. It is a geological phenomenon that occurs in various environments, including deserts. Exfoliation occurs primarily as a result of mechanical weathering, which involves the physical breakdown of rocks without any chemical changes.

Mechanical Weathering:
Mechanical weathering is the process by which rocks are broken down into smaller fragments without any chemical alteration. It is primarily driven by physical forces such as temperature changes, pressure variations, and the action of water, wind, or ice. Exfoliation is one of the outcomes of mechanical weathering.

Process of Exfoliation:
Exfoliation occurs when rocks undergo expansion and contraction due to temperature fluctuations. During the day, rocks are exposed to high temperatures, causing them to expand. At night, the temperature drops, and the rocks cool down, leading to contraction. These repeated cycles of expansion and contraction result in stress being built up within the rocks.

As the stress accumulates, the outer layers of the rock start to detach from the underlying layers, leading to the formation of fractures or cracks. Over time, these cracks propagate parallel to the surface, causing the outer layers of the rock to peel or flake off. This process is similar to the peeling of an onion, where successive layers are shed.

Factors Affecting Exfoliation:
Several factors influence the rate and extent of exfoliation. These include:
1. Rock Type: Some rocks are more susceptible to exfoliation than others. For example, granite, a common rock found in many mountainous regions, is prone to exfoliation due to its mineral composition and structure.
2. Climate: Temperature variations play a crucial role in exfoliation. Regions with large diurnal temperature ranges, such as deserts and high-elevation areas, are more prone to exfoliation.
3. Jointing: The presence of pre-existing joints or fractures in the rocks can enhance the process of exfoliation as they provide pathways for the cracks to propagate.
4. Erosion: Exfoliation can be accelerated by erosion processes such as wind, water, or glaciers. These agents remove the overlying material, relieving the confining pressure on the rocks and promoting exfoliation.

Conclusion:
Exfoliation is a natural process that occurs due to mechanical weathering, specifically the repeated expansion and contraction of rocks caused by temperature fluctuations. It leads to the peeling or shedding of rock layers, resulting in the formation of characteristic rock formations such as domes, tors, and exfoliation sheets. While exfoliation can occur in various environments, including deserts, it is not synonymous with the carrying away of topsoil by wind or the cracking of rocks into small pieces.

Importance of Weathering

Weathering is a natural process that breaks down rocks and minerals on the Earth's surface. It plays a crucial role in shaping our environment and has several important implications for us. The correct answer is option 'D' as all the given statements are true.

1. Formation of Soil
Weathering aids in the formation of soil by eroding rocks and hard surfaces. Over time, the mechanical and chemical processes of weathering break down rocks into smaller particles, creating a layer of loose material known as regolith. This regolith, along with organic matter, forms the basis for the development of soil. Soil is essential for agriculture as it provides nutrients and water retention capacity necessary for plant growth.

2. Enrichment of Valuable Minerals
Weathering also helps in the enrichment of valuable minerals on Earth. Through chemical weathering, certain minerals can be dissolved and transported by water, creating new deposits in different locations. This process is called leaching. Valuable minerals such as gold, silver, copper, and uranium can be concentrated and accumulated in specific areas, making their extraction commercially viable. Weathering thus contributes to the availability of important resources that are essential for various industries.

3. Shaping and Denuding Landforms
One of the most visible impacts of weathering is the shaping and denuding of large landforms on Earth. Mechanical weathering processes like frost action, abrasion, and exfoliation contribute to the physical breakdown of rocks and the formation of diverse landforms. These include mountains, canyons, caves, valleys, and cliffs. Chemical weathering, on the other hand, alters the composition of rocks and minerals, leading to the formation of unique geological formations like stalactites and stalagmites in caves. The continuous process of weathering, along with erosion and deposition, helps sculpt the Earth's surface and create the diverse landscapes we see today.

Conclusion
Weathering is an important geological process that has significant implications for our lives. It aids in the formation of soil, enriches valuable minerals, and shapes large landforms. Understanding weathering processes is crucial for sustainable land management, resource extraction, and environmental conservation.

Upper course river features include steep-sided V-shaped valleys, interlocking spurs, rapids, waterfalls and gorges. Middle course river features include wider, shallower valleys, meanders, and oxbow lakes.

Lagoons and backwaters are important natural features that can serve various purposes. However, there are certain limitations to their use. Among the given options, irrigation of paddy crops is the only use that cannot be fulfilled by lagoons and backwaters. Let's discuss each option in detail to understand why.

1. Fishing:
Lagoons and backwaters are often abundant in aquatic life, making them ideal locations for fishing activities. These water bodies provide a suitable habitat for various fish species, making them attractive to fishermen. The calm and shallow waters of lagoons and backwaters support the growth and reproduction of fish, making it a popular fishing ground. Therefore, fishing is a common and feasible use of lagoons and backwaters.

2. Irrigation of paddy crops:
Paddy crops require a constant supply of water for their growth and development. While lagoons and backwaters can store water, they may not be suitable for irrigation purposes. Unlike rivers or canals, lagoons and backwaters may not have a consistent flow of water. The water levels in these water bodies can fluctuate significantly depending on rainfall and tidal movements. Therefore, it may not be reliable or efficient to rely on lagoons and backwaters for irrigation of paddy crops.

3. Navigation:
Lagoons and backwaters can serve as important waterways for navigation. These water bodies often provide a safe and navigable route for boats and ships, especially in coastal areas. They can act as natural harbors or channels, facilitating transportation and trade. Navigating through lagoons and backwaters can offer several advantages, such as avoiding rough seas or congestion in ports. Therefore, navigation is a feasible use of lagoons and backwaters.

In conclusion, fishing and navigation are viable uses of lagoons and backwaters, while irrigation of paddy crops is not. The fluctuating water levels and inconsistency of flow in lagoons and backwaters make them unsuitable for reliable irrigation purposes.

Explanation:

In this question, we are given three statements about lagoons and we need to choose the correct answer using the given options.

Statement 1: Lagoon is a fresh-water lake.
Statement 2: Lagoon is separated from the sea by sandbars and spits.
Statement 3: Lagoon is considered similar to some of the estuaries.

To determine the correct answer, let's analyze each statement.

Statement 1: Lagoon is a fresh-water lake.
A lagoon is not necessarily a fresh-water lake. It can be either fresh or saltwater, depending on its location and connection to the sea. Therefore, this statement is incorrect.

Statement 2: Lagoon is separated from the sea by sandbars and spits.
This statement is true. A lagoon is a shallow body of water separated from the sea by sandbars, spits, or barrier islands. These natural formations act as a barrier, creating a calm and sheltered environment within the lagoon.

Statement 3: Lagoon is considered similar to some of the estuaries.
This statement is also true. Lagoons and estuaries share some similarities. Both are partially enclosed bodies of water connected to the sea. However, there are some differences as well. Lagoons are typically separated from the sea by sandbars or spits, while estuaries are formed at the mouths of rivers and are influenced by freshwater inflow. Therefore, while some lagoons may be similar to estuaries, it is not universally true for all lagoons.

Based on the analysis above, we can conclude that the correct answer is option 'B' - 2 and 3 only. Statement 1 is incorrect as lagoons can be either fresh or saltwater. Statement 2 is true as lagoons are separated from the sea by sandbars and spits. Statement 3 is also true to some extent, as lagoons can share similarities with estuaries, but it is not universally applicable to all lagoons.

The correct answer is option 'A' which states that the correct statements are 1 and 2 only. Let's understand why option 'A' is correct by analyzing each statement:

1. The tributaries will join the main valley obliquely as insequent streams:
When a river passes through an area where rocks are composed of homogenous beds of uniform resistance to corrosion, it means that the rocks are equally resistant to erosion by the flowing water. In such a scenario, the river will not erode the rocks more in one direction than in another. As a result, the tributaries that join the main valley will do so obliquely, meaning at an angle, rather than perpendicularly. This is because the river will not have a preferred direction of flow due to the uniform resistance to corrosion of the rocks.

2. The evolving drainage pattern will be tree-like in appearance:
In a region where rocks are composed of homogenous beds of uniform resistance to corrosion, the river will erode the rocks uniformly in all directions. As the river erodes the rocks, it will form a network of tributaries that spread out in a pattern resembling the branches of a tree. This is known as a dendritic drainage pattern. The main river acts as the trunk, and the tributaries act as the branches that progressively get smaller as they extend away from the main river. This pattern is formed due to the uniform resistance to corrosion of the rocks, which does not favor the formation of any specific pattern.

Based on the above explanations, it can be concluded that options 1 and 2 are correct. Option 3, which states that it will not form a catchment area, is incorrect because regardless of the resistance to corrosion of the rocks, a river will always form a catchment area. A catchment area is the region from which a river and its tributaries collect water drainage. Hence, option 'A' is the correct answer.

Explanation:

Statement a: Depressions are formed when the wind blows away the sands. In the depressions where underground water reaches the surface, an oasis is formed.

This statement is correct. Depressions in deserts, known as basins, are formed when the wind blows away the sands. In some of these depressions, underground water reaches the surface, creating an oasis. The presence of water allows vegetation to grow, making it a suitable habitat for various plant and animal species.

Statement b: Oases are never larger than a few square kilometers.

This statement is incorrect. Oases can vary in size, and there are some oases that are larger than a few square kilometers. While many oases may indeed be small, there are also large oases that cover significant areas. For example, the Al-Hasa oasis in Saudi Arabia is one of the largest oases in the world, covering an area of over 1,000 square kilometers.

Statement c: Political or military control of an oasis has in many cases meant control of trade on a particular route.

This statement is correct. Oases have historically played an important role in trade routes, especially in arid regions where water is scarce. Controlling an oasis meant controlling access to water and resources, giving political or military control over trade routes passing through the oasis. This allowed those in control to exert influence over trade and secure economic advantages.

Statement d: The most important plant in an oasis is the date palm.

This statement is correct. The date palm is indeed one of the most important plants in an oasis. It is a highly valued and versatile plant that provides various resources and sustenance. Date palms provide shade, food in the form of dates, and materials for construction and handicrafts. They also contribute to the overall stability and biodiversity of the oasis ecosystem.

Conclusion:

The incorrect statement is option 'B' - Oases are never larger than a few square kilometers. Oases can vary in size, and there are some oases that cover significant areas. The other statements are correct, highlighting the formation of oases, the importance of controlling oases for trade routes, and the significance of the date palm in oasis ecosystems.

Depositional features are landforms created by the deposition of sediment carried by rivers, glaciers, wind, or waves. In the case of depositional features near a river mouth, there are three options given: ox-bow lakes, braided channels, and flat valleys. Let's explore each of these features in detail to understand why the correct answer is option 'D' - all of the above.

1. Ox-bow lakes:
- Ox-bow lakes are U-shaped bodies of water that form when a meandering river takes a new, shorter path, leaving behind a curved lake.
- As a river meanders, it erodes the outer bank and deposits sediment on the inner bank, causing the meander loop to grow larger over time.
- Eventually, the river cuts through the narrow neck of the meander, leaving behind an abandoned loop that becomes an ox-bow lake.
- Ox-bow lakes are commonly found near the downstream end of a river, close to its mouth, where the river's velocity decreases and it has a lower energy level.
- The deposition of sediment near the river mouth can contribute to the formation of ox-bow lakes.

2. Braided channels:
- Braided channels are characterized by a network of interconnected, shallow and wide channels that frequently split and rejoin.
- They form when a river carries a significant amount of sediment, which is deposited in bars and islands within the channel, causing it to divide into multiple smaller channels.
- The sediment deposition near the river mouth can lead to the creation of braided channels, especially in areas with a high sediment load and low gradient.
- Braided channels are common near river mouths as the river's energy decreases, and sediment is deposited, resulting in a complex network of channels.

3. Flat valleys:
- Flat valleys, also known as alluvial plains or floodplains, are broad, flat areas adjacent to rivers that are formed by the deposition of sediment over time.
- As a river approaches its mouth, its velocity decreases, and it loses its ability to carry sediment, causing the sediment to be deposited along its banks and floodplain.
- The deposition of sediment near the river mouth contributes to the formation of flat valleys, which are characterized by fertile soil and are often used for agriculture.

In conclusion, all three depositional features - ox-bow lakes, braided channels, and flat valleys - can be made near the river mouth. Ox-bow lakes form when a meander loop is cut off, braided channels form when a river deposits sediment and divides into smaller channels, and flat valleys form as sediment is deposited along the river's banks and floodplain.

Explanation:

Rejuvenation of a river:
Rejuvenation of a river refers to the process in which a river resumes its youthful characteristics after a period of erosion and deposition. It is a dynamic process that occurs due to changes in the landscape and various factors such as tectonic activity, changes in climate, and sea level changes.

Statement 1: A fall in sea level rejuvenates a river:
When the sea level falls, the base level of a river decreases. As a result, the river's gradient steepens, and it starts to erode its bed and banks more actively. This increased erosion leads to the removal of sediments and the formation of new channels. The river becomes rejuvenated as it adjusts to the new base level and resumes its youthful characteristics.

Statement 2: Submergence of land rejuvenates a river:
When land gets submerged, the base level of a river rises. This results in a decrease in the river's gradient and a reduction in its erosive power. The river may become sluggish and start depositing sediments instead of actively eroding. Therefore, the submergence of land does not rejuvenate a river but rather leads to the creation of a floodplain or delta.

Conclusion:
Based on the explanations above, it can be concluded that statement 1 is correct, while statement 2 is incorrect. Therefore, the correct answer is option 'A' - 1 only.

Lagoons are often called estuaries, sounds, bays or even lakes.

• Lagoons sheltered by sandbars or barrier islands are called coastal lagoons. Coastal lagoons form along coastal plains - flat or gently sloping landscapes.
• The size and depth of coastal lagoons often depend on sea level. When the sea level is low, coastal lagoons are swampy wetlands. When the sea level is high, they can look like coastal lakes or bays.

Reg - It is a stony desert composed of extensive sheets of angular pebbles and gravels. Erg - It is a sandy desert having vast deposits of dunes.

Levees are natural or man-made embankments that are formed along the banks of rivers or streams in floodplains. These embankments are typically made up of sediments and deposits that have been accumulated over time. Among the given options, the correct answer is option 'A', which states that levees are formed when the river flows normally in a bed that rises by the accumulation of deposits. Let's discuss this in detail:

Formation of Levees:
Levees are formed through a natural process known as avulsion. Avulsion occurs when a river or stream changes its course and deposits sediments along the banks due to the decrease in flow velocity. This deposition of sediments leads to the gradual build-up of the riverbed, causing it to rise above the surrounding floodplain.

The Role of Deposition:
Deposition is a key factor in the formation of levees. When a river flows normally, it carries sediments and deposits along with it. As the river reaches the floodplain, the flow velocity decreases, and the sediments start to settle. The larger and heavier particles, such as sand and gravel, are deposited near the river banks, while the smaller particles, such as silt and clay, settle further away.

Accumulation of Deposits:
Over time, as the river continues to deposit sediments during flood events, the deposited materials gradually build up, creating a natural embankment along the riverbanks. This accumulation of deposits forms the levees, which act as barriers to contain the river within its channel during normal flow conditions.

Advantages of Levees:
Levees play a crucial role in flood management. They help to confine the river within its channel, preventing it from overflowing onto the floodplain during regular flow events. By containing the river within its banks, levees protect the surrounding areas from flooding and minimize the risk to human life and property.

Conclusion:
In conclusion, levees are formed in a floodplain when a river flows normally in a bed that rises due to the accumulation of deposits. Deposition of sediments along the riverbanks gradually builds up over time, creating natural embankments that act as barriers to contain the river within its channel. Levees play a vital role in flood management by confining the river and protecting the surrounding areas from flooding.

Formation of Ox-Bow Lakes

Ox-bow lakes are formed due to the meandering tendency of the river. The process involves the following steps:

1. The river flows in a zigzag manner due to the uneven terrain and other factors.

2. The water flow is faster on the outer side of the curve, resulting in erosion of the soil/rock on the banks.

3. The sediment load of the river gets deposited on the inner side of the curve, resulting in the formation of a sandbar.

4. Over time, the sandbar grows and separates the river from the abandoned meander loop.

5. The river continues to flow in a straighter path, leaving behind a crescent-shaped water body, which is the ox-bow lake.

Thus, the formation of ox-bow lakes is a result of the meandering tendency of the river and the potential of the soil/rock to get eroded.

Responsibility of the Given Factors

1. Meandering Tendency of the River: This factor plays a crucial role in the formation of ox-bow lakes, as it determines the path of the river and the formation of curves.

2. Potential of the Soil/Rock to Get Eroded: This factor is equally important, as it determines the rate of erosion of the banks, which leads to the formation of sandbars and eventually, ox-bow lakes.

3. Sediment Load of the River: Although sediment load is important in the formation of sandbars, it is not directly responsible for the formation of ox-bow lakes. Therefore, option 'B' is incorrect.

Conclusion

In conclusion, the correct answer is option 'C', as both the meandering tendency of the river and the potential of the soil/rock to get eroded are responsible for the formation of ox-bow lakes.

Loess is fine loam, rich in lime, very coherent and extremely porous. Water sinks in readily so that the surface is always dry. Streams cut deep valleys through the thick mantle of soft loess and badland topography may develop. It is so soft that roads constructed through a loess region soon sink and their walls rise steeply. The most extensive deposit of loess is found in north-west China in the loess plateau of the Hwang-Ho basin.

Magma cools slowly as it rises towards Earth’s surface. It can take thousands to millions of years to become solid when it is trapped inside Earth. As the magma cools, solid rocks form (igneous). These rocks arc mixtures of minerals. Granite is a common rock that forms when magma cools.

Gneiss usually forms by regional metamorphism at convergent plate boundaries. It is a high-grade metamorphic rock in which mineral grains recrystallised under intense heat and pressure associated with mountain building and volcanic activity.