All questions of Geomorphology for UPSC CSE Exam

Marble and slate are metamorphic rocks.

Explanation:

Pole fleeing force is a term used to describe the outward-directed force associated with the spinning of the Earth. This force is also known as centrifugal force. It is the force that causes objects at or near the Earth's equator to experience a slight outward push. This force is due to the rotation of the Earth on its axis.

The centrifugal force is a result of the Earth's rotation, which causes the equator to bulge outwards slightly and the poles to flatten slightly. It is important to note that the pole fleeing force is not responsible for the bulging at the Earth's poles, which is primarily caused by the Earth's rotation and the gravitational pull of the Sun and Moon.

The pole fleeing force is an important factor to consider when studying the Earth's rotation. It influences the Earth's shape, the distribution of mass within the Earth, and the motion of the Earth's oceans and atmosphere.

Conclusion:

In summary, the pole fleeing force is the outward-directed force associated with the spinning of the Earth. It is not responsible for the bulging at the Earth's poles but is an important factor to consider when studying the Earth's rotation.

The question is asking about the incorrect statement but here both statement are correct so the option (D) is correct.

Explanation:

Volcanoes and earthquakes are natural phenomena that occur due to the movement of tectonic plates. These plates make up the Earth's crust and are constantly shifting and colliding with each other. The majority of volcanoes and earthquakes in the world are located at plate margins.

Plate Margins:

Plate margins are the boundaries where two tectonic plates meet. There are three main types of plate boundaries:

1. Divergent Boundaries: This is where two plates move away from each other. This movement creates a gap between the two plates which magma rises up to fill, creating new crust. This is where most of the world's volcanoes are located.

2. Convergent Boundaries: This is where two plates move towards each other. This movement can cause one plate to be forced under the other, creating a subduction zone. This can cause earthquakes and volcanic eruptions.

3. Transform Boundaries: This is where two plates slide past each other horizontally. This can cause earthquakes but rarely causes volcanic eruptions.

Conclusion:

In conclusion, the majority of volcanoes and earthquakes in the world are located at plate margins. The movement of tectonic plates at these boundaries causes geological activity such as volcanic eruptions and earthquakes. Understanding plate tectonics and plate boundaries is important for predicting and mitigating the risks associated with these natural phenomena.

Oldest Rocks in the World

The oldest rocks in the world are found in Western Australia.

Evidence

- The rocks in Western Australia are known as the Jack Hills group and have been dated to be 4.4 billion years old.
- These rocks were formed during the Hadean Eon, which lasted from the formation of the Earth around 4.6 billion years ago to the beginning of the Archean Eon around 4 billion years ago.
- The rocks contain tiny zircon crystals which have been used to determine their age.
- The zircon crystals have been found to be up to 4.4 billion years old, making them the oldest known rocks in the world.

Importance

- The discovery of these rocks in Western Australia has important implications for our understanding of the early Earth.
- It suggests that the planet was able to cool and solidify much faster than previously thought.
- It also suggests that conditions on the early Earth were more hospitable for life than previously thought, as life is believed to have emerged around 3.5 billion years ago.

Conclusion

In conclusion, the oldest rocks in the world are found in Western Australia and are known as the Jack Hills group. These rocks have been dated to be 4.4 billion years old and contain tiny zircon crystals which have been used to determine their age. The discovery of these rocks has important implications for our understanding of the early Earth and the emergence of life.

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.

Overview:
River capture is a geomorphological process in which a stream or river drainage system is diverted from its own bed and flows instead down the bed of a neighboring stream. It is also known as river beheading and can occur due to tectonic Earth movements or erosion.

Explanation:
The given statements are as follows:

Statement 1: It is a geomorphological phenomenon occurring when a stream or river drainage system or watershed is diverted from its own bed and flows instead down the bed of a neighboring stream.

This statement is correct. River capture is a natural process where water from one river or stream is diverted to flow into another river or stream. This can happen due to various factors such as changes in the landscape, erosion, or tectonic activities. When a river captures another, it usually occurs at a point where the two river systems are close to each other and the water can easily flow from one to another.

Statement 2: It is also called river beheading.

This statement is correct. River capture is also known as river beheading because one river captures the drainage of another river, leading to the diversion of water flow.

Statement 3: Apart from tectonic Earth movements, erosion also results in river capture.

This statement is correct. River capture can occur due to both tectonic Earth movements and erosion. Tectonic movements, such as the uplift of land or the creation of a new fault line, can alter the landscape and cause changes in the drainage patterns of rivers. Erosion, on the other hand, can occur due to the wearing away of the land by the force of the flowing water, leading to changes in the river courses and potential river capture.

Conclusion:
In conclusion, all the given statements are correct. River capture is a geomorphological phenomenon that can occur due to tectonic Earth movements or erosion. It involves the diversion of a river or stream from its own bed to flow down the bed of a neighboring stream.

Sandstone is a sedimentary rock formed by sedimentation of sand grains.

Salient Features of Fold Mountains

Fold mountains are formed by the folding of the Earth's crust. They are characterized by certain salient features, which are discussed below.

1. Conical Peaks:
Fold mountains are most likely to have conical peaks due to the volcanic activity associated with them. The magma below the surface rises and solidifies to form a cone-shaped structure.

2. Vertical Displacement:
Fold mountains are created when large areas of the Earth's crust are broken and displaced vertically, leading to the formation of fold structures.

3. Associated Volcanism:
Fold mountains are often associated with volcanism, either from the mountain core or its vicinity. This is due to the movement of tectonic plates, which leads to the formation of magma chambers and volcanic eruptions.

Correct Option
None of the above statements is correct as the first statement is incorrect. Fold mountains are most likely to have conical peaks due to the associated volcanic activity.

Explanation:

Alpine mountain building phase is the recent phase to which the Himalayan mountains belong to. The Ural Mountains were not formed during the Alpine orogeny (mountain building phase).

Therefore, the correct answer is option 'A' - 1 only.

- Alpine Mountain Building Phase
The Alpine mountain building phase is the most recent phase and began about 40 million years ago. This phase is ongoing and still forming mountains today in areas such as the Himalayas, the Alps, and the Andes.

- Himalayan Mountains
The Himalayan Mountains are a range of fold mountains located in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. They were formed during the ongoing Alpine mountain building phase.

- Ural Mountains
The Ural Mountains are a range of fold mountains located in western Russia, separating Europe and Asia. They were formed during the Variscan orogeny, which occurred about 300 million years ago, and not during the Alpine mountain building phase.

Therefore, statement 1 is correct, and statement 2 is incorrect.

Zeugen - Horizontal rock system of alternate hard and soft rocks in desert. Inselbergs are isolated round hills in 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).

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.

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.

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.

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.

Difference between Extrusive and Intrusive Rocks

Introduction
Extrusive and intrusive rocks are two types of igneous rocks that differ in their formation, texture, and the duration of their formation. Understanding these differences is important in the study of geology and helps in identifying and classifying various rock formations.

Formation
1. Extrusive Rocks: Extrusive rocks are formed from magma, which is molten rock that reaches the Earth's surface through volcanic activity. When magma erupts from a volcano, it cools rapidly and solidifies to form extrusive rocks. Examples of extrusive rocks include basalt, obsidian, and pumice.

2. Intrusive Rocks: Intrusive rocks, on the other hand, are formed from lava, which is magma that has reached the Earth's surface. Instead of erupting, lava flows out of the volcano and cools slowly beneath the surface. This slow cooling allows for the formation of large mineral crystals, resulting in coarse-grained textures. Examples of intrusive rocks include granite, gabbro, and diorite.

Texture
1. Extrusive Rocks: Extrusive rocks have a fine-grained texture due to their rapid cooling. As the magma cools quickly at the surface, there is insufficient time for large mineral crystals to form. Instead, small crystals or even glassy structures are observed in extrusive rocks.

2. Intrusive Rocks: Intrusive rocks have a coarse-grained texture because of their slow cooling process. As the magma cools slowly beneath the surface, there is ample time for large mineral crystals to develop. These crystals are often visible to the naked eye and contribute to the coarse-grained appearance of intrusive rocks.

Duration of Formation
1. Extrusive Rocks: Extrusive rocks are formed relatively quickly, as the magma reaches the surface and cools rapidly. This process typically takes place over a short duration of time, such as days or weeks.

2. Intrusive Rocks: In contrast, the formation of intrusive rocks occurs over a much longer duration of time. The slow cooling of lava beneath the surface can take thousands or even millions of years, allowing for the growth of large mineral crystals.

Conclusion
In summary, extrusive and intrusive rocks differ in their formation, texture, and the duration of their formation. Extrusive rocks are formed from magma, have a fine-grained texture, and are formed relatively quickly. In contrast, intrusive rocks are formed from lava, have a coarse-grained texture, and are formed over a longer duration of time. Understanding these differences is essential in the study of igneous rocks and helps in identifying and classifying various geological formations.

Geos and gloups are the landforms formed by the action of waves.

Waves are a powerful force of nature that constantly shape the Earth's coastlines. They are primarily formed by the wind blowing across the surface of the ocean, which creates ripples that eventually develop into waves. As waves approach the shore, they undergo various processes that lead to the formation of landforms such as geos and gloups.

Formation of Geos:
- Geos are narrow, steep-sided inlets or clefts in coastal cliffs. They are formed through the process of wave erosion.
- When waves approach the coastline, their energy is concentrated on headlands or areas of more resistant rock.
- The power of the waves, combined with the presence of joints or faults in the rock, causes the cliffs to be eroded and weakened over time.
- As the waves continue to crash against the cliffs, they exploit these weaknesses and create narrow, deep indentations known as geos.
- The erosion process is typically more pronounced during stormy weather or high tides when the waves are stronger.

Formation of Gloups:
- Gloups are circular or oval-shaped depressions in coastal cliffs that are also formed through wave erosion.
- Similar to geos, gloups are created by the relentless action of waves against the cliffs.
- However, the formation of gloups is influenced by the presence of caves or softer layers of rock within the cliffs.
- As the waves batter the cliffs, they gradually erode these weaker areas, creating cavities or caves.
- Over time, the roofs of these caves may collapse, resulting in the formation of depressions known as gloups.
- Gloups are often found near the base of the cliffs and can vary in size and depth.

Conclusion:
In conclusion, geos and gloups are landforms that are formed by the action of waves. Through the process of wave erosion, waves shape the coastal cliffs, exploiting weaknesses in the rock to create these distinctive features. Understanding the formation of geos and gloups is important in studying coastal processes and the evolution of coastlines.

Continental Drift Theory

The correct answer is option C, Continental Drift Theory. This theory, proposed by Alfred Wegener in the early 20th century, suggests that the continents were once joined together in a single supercontinent called Pangaea and have since drifted apart.

Key Points:

1. Belt of Ancient Rocks:
The belt of ancient rocks from the Brazil coast that matches those from western Africa is evidence of the existence of a supercontinent. The similarities in the rock formations indicate that these regions were once connected.

2. Matching Ancient Rocks:
The age and composition of the rocks found along the Brazil coast and western Africa are similar, suggesting a common geological history. This similarity supports the idea that these two continents were once part of the same landmass.

3. Earliest Marine Deposits:
The presence of Jurassic age marine deposits along the coastlines of South America and Africa further supports the Continental Drift Theory. The discovery of similar fossils and sedimentary layers in both regions indicates that they were once adjacent and shared the same marine environment.

4. Pangaea:
According to the Continental Drift Theory, approximately 200 million years ago, all the continents were connected as one supercontinent called Pangaea. Over time, Pangaea began to break apart, and the continents we know today gradually drifted to their current positions.

5. Plate Tectonics:
The movement of the continents is explained by the theory of plate tectonics, which states that the Earth's lithosphere is divided into several large plates that float on the semi-fluid asthenosphere below. These plates move and interact with each other, causing various geological phenomena such as earthquakes, volcanic activity, and the drifting of continents.

Conclusion:

The presence of matching ancient rocks and Jurassic age marine deposits between the Brazil coast and western Africa provides strong evidence for the Continental Drift Theory. This theory explains how the continents have moved over millions of years and helps us understand the geological history and formation of the Earth's landmasses.

All are correct.

• The catchments of large rivers are called river basins while those of small rivulets and rills are often referred to as watersheds.
• There is, however, a slight difference between a river basin and a watershed. Watersheds are small in area while the basins cover larger areas.
• River basins and watersheds are marked by unity. What happens in one part of the basin or watershed directly affects the other parts and the unit as a whole.
• That is why they are accepted as the most appropriate micro-, meso- or macro-planning regions. Every tributary too has a watershed. Sum of watersheds gives rise to river basin.

Answer:

Rocks That Make Up the Crust of Earth

The crust of the Earth is made up of various types of rocks, but some of them make up for large portions of it. These rocks are:

1. Granitic rocks
2. Basaltic rocks

Explanation:

Granitic rocks are igneous rocks that are light-colored and have a coarse-grained texture. They are formed from the slow cooling of magma beneath the Earth's surface. They are found in the continental crust and make up a large portion of it.

Basaltic rocks, on the other hand, are dark-colored igneous rocks that have a fine-grained texture. They are formed from the rapid cooling of lava on the Earth's surface. They are found in the oceanic crust and make up a significant portion of it.

Pumice rocks and obsidian rocks are also types of igneous rocks, but they do not make up large portions of the Earth's crust. Pumice rocks are formed from the rapid cooling of lava that is rich in gas bubbles, while obsidian rocks are formed from the rapid cooling of lava that is rich in silica.

Conclusion:

Therefore, the correct answer to this question is option 'B' - 1 and 2 only, as granitic rocks and basaltic rocks make up for large portions of the Earth's crust.

Overview of Seismic Waves
Seismic waves are generated by geological events such as earthquakes and are classified into different types based on their properties. The two main types discussed here are Primary (P) waves and Secondary (S) waves.
P Waves (Primary Waves)
- P waves are indeed the fastest seismic waves.
- They can travel through solids, liquids, and gases.
- Due to their speed, they are the first to be detected by seismic stations after an earthquake occurs.
S Waves (Secondary Waves)
- S waves are slower than P waves and arrive at seismic stations after them.
- They can only travel through solid materials and do not propagate through liquids or gases.
- This property is crucial in understanding the Earth's interior, as the behavior of S waves indicates the presence of liquid layers, such as the outer core.
Correctness of the Statements
1. Statement (a): P wave or primary wave is the fastest kind of seismic wave and, consequently, the first to ‘arrive’ at a seismic station.
- This statement is correct.
2. Statement (b): S wave or secondary wave can only move through solid rock, not through any liquid medium.
- This statement is also correct.
Conclusion
Both statements about P waves and S waves are accurate, confirming that the correct answer is option 'C', as both statements 1 and 2 are true. Understanding these waves provides insight into the internal structure of the Earth and the mechanisms behind seismic events.

Answer:

Factors responsible for changes on Earth's surface:

There are several factors responsible for bringing changes on the surface of the Earth. Some of the major factors are discussed below:

1. Tectonic forces:

Tectonic forces include processes like plate tectonics, earthquakes, volcanic eruptions, and mountain building. These forces are responsible for the creation of new landforms and the destruction of existing ones. Plate tectonics is the key process that drives the movement of the Earth's crust.

2. Gravitational force:

The gravitational force of the Earth is responsible for many changes on its surface. It causes erosion, weathering, and mass wasting. Erosion is the process by which the surface of the Earth is worn away by the action of water, wind, or ice. Weathering is the breakdown of rocks into smaller pieces due to the action of weather. Mass wasting is the downhill movement of soil and rock under the influence of gravity.

3. Electromagnetic radiation:

Electromagnetic radiation from the sun is responsible for many changes on the Earth's surface. It causes weather patterns, ocean currents, and the growth of plants. The sun's energy is also responsible for the water cycle, which is the process by which water evaporates from the surface of the Earth and is later returned as precipitation.

Correct answer:

All of the above (1, 2, and 3) are responsible for bringing changes on the surface of the Earth.

The Mid-Ocean Ridge system forms the most extensive chain of mountains on Earth, with more than 90% of the mountain range lying in the deep ocean - with a total length of about 60,000 km. Mid-ocean ridges are geologically important because they occur along divergent plate boundaries, where the new ocean floor is created as the Earth’s tectonic plates spread apart. As the plates separate, some molten rock rises to the seafloor, producing enormous volcanic eruptions of basalt, and building the longest chain of volcanoes in the world. Because most of these eruptions occur deep under the water, they often go unnoticed.

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 correct answer is option 'D' - All of the above.

Explanation:
The action of endogenic forces, which include processes like volcanic activity, faulting, and folding, is not uniform. This non-uniformity leads to an uneven and varied crustal surface. This can be attributed to several factors, including variation in crustal thickness, variation in geothermal gradients, and volcanism in the lithosphere.

1. Variation in crustal thickness:
The crust of the Earth is not uniform in thickness. It varies from place to place, with some regions having thicker crust and others having thinner crust. This variation in crustal thickness can be attributed to different geological processes, such as the collision of tectonic plates, the formation of mountain ranges, and the presence of deep-seated faults. The variation in crustal thickness results in an uneven crustal surface.

2. Variation in geothermal gradients:
Geothermal gradient refers to the rate at which temperature increases with depth in the Earth's interior. The geothermal gradient is not constant throughout the Earth's crust. It varies from region to region due to factors like heat flow from the mantle, presence of thermal anomalies, and local geologic conditions. This variation in geothermal gradients can lead to variations in the physical properties of rocks, such as their strength and viscosity, which in turn influence the action of endogenic forces and contribute to an uneven crustal surface.

3. Volcanism in the lithosphere:
Volcanism refers to the eruption of molten rock (magma) onto the Earth's surface. Volcanic activity is a common manifestation of endogenic forces and is associated with the movement of tectonic plates and the formation of volcanic landforms, such as volcanoes, lava flows, and volcanic ash deposits. Volcanism occurs in certain regions where there are active volcanic systems, such as the Ring of Fire in the Pacific Ocean. The presence of volcanism leads to localized uplift and subsidence of the Earth's crust, resulting in an uneven surface.

In conclusion, the action of endogenic forces is not uniform, and factors such as variation in crustal thickness, variation in geothermal gradients, and volcanism in the lithosphere contribute to the uneven and varied crustal surface. Therefore, the correct answer is option 'D' - All of the above.

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:

Statement 1: Estuaries are more favorable than deltas for the siting of large ports.
- Estuaries are coastal areas where rivers meet the sea and freshwater mixes with saltwater. They typically have deep channels and provide natural shelter from storms and high waves.
- Deltas, on the other hand, are formed at the mouths of rivers where sediment is deposited and can create shallow and shifting channels.
- Estuaries are more favorable for the siting of large ports because their deeper channels allow for larger ships to navigate and dock. They also provide natural protection from strong waves and storms, making it easier for ships to enter and exit the port.

Statement 2: In the outwash plains, eskers and kames have been excavated to provide sands and gravels for highway and building construction.
- Outwash plains are formed by the deposition of sediment carried by meltwater streams from glaciers. They typically consist of sand and gravel deposits.
- Eskers are long, winding ridges of sediment deposited by meltwater streams within or underneath glaciers.
- Kames are small mounds of sediment deposited by meltwater streams on the surface of glaciers.
- In some cases, eskers and kames found in outwash plains are excavated to provide sands and gravels for highway and building construction. These sediments can be used as construction materials due to their composition and availability in outwash plains.

Statement 3: Limestone vegetation in tropical regions is luxuriant because of the heavy rainfall all the year round.
- Limestone vegetation refers to plant life that grows on limestone rock formations. Limestone is a sedimentary rock formed from the accumulation of marine organisms over time.
- In tropical regions, where there is heavy rainfall throughout the year, limestone vegetation tends to be luxuriant.
- The heavy rainfall provides ample moisture for plant growth, and the limestone rock formations often have crevices and fissures that can retain water, creating favorable conditions for plant growth.
- Additionally, limestone is a rich source of essential minerals and nutrients for plants, which further contributes to the luxuriant growth of vegetation in tropical regions.

Conclusion:
- Based on the explanations above, it can be concluded that all three statements are correct.
- Estuaries are indeed more favorable than deltas for the siting of large ports, eskers and kames in outwash plains are excavated for construction materials, and limestone vegetation in tropical regions is luxuriant due to heavy rainfall.

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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.

Fold mountains are formed due to compressive action of forces in the Earth's crust. These are driven by magmatic convection.

Properties of Lava:

Basic Lava:
- Basic lavas are the hottest lavas and are highly fluid.
- These lavas have low viscosity and can flow easily.
- They have a low gas content and therefore, do not cause explosive volcanoes.
- Basic lava is also called as mafic lava.

Acid Lava:
- Acid lavas are highly viscous and cause less explosive volcanoes.
- These lavas have a high gas content and therefore, tend to be explosive.
- Acid lava is also called as felsic lava.

Correct Answer:
- Statement 1 is correct as basic lavas are hot and highly fluid.
- Statement 4 is correct as acid lava is also called felsic lava.
- Therefore, option 'A' is the correct answer.

Incorrect statements:
- Statement 2 is incorrect as basic lava does not cause explosive volcanoes.
- Statement 3 is incorrect as acid lavas are highly viscous and tend to be explosive.

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.

A river delta is a landform that occurs at the mouth of a river. It has very fertile soil as well as a large amount of vegetation. River slows down when it approaches the end point and starts depositing the silt which leads to formation of distributaries.

A) 1 and 2 only