Geomorphology

Concept: The Big Bang Theory is the most widely accepted scientific explanation for the origin of the universe. According to this theory, the universe began approximately 13.8 billion years ago from an extremely hot and dense point called a singularity. At this moment, a massive expansion occurred, causing space, time, matter, and energy to come into existence. This expansion is known as the Big Bang. Over billions of years, this expanding universe cooled down, allowing the formation of particles, atoms, stars, galaxies, and planetary systems. The theory was first proposed by the Belgian astronomer and physicist Georges Lemaître in 1927 and later supported by several observational evidences such as cosmic microwave background radiation and the expansion of galaxies.
Step 1: Understanding what the Big Bang explains.
The Big Bang Theory explains the:

• Origin of space and time
• Formation of matter and energy
• Expansion of the universe

It does not describe the formation of only a single planet, star, or galaxy, but rather the beginning of the entire universe.
Step 2: Key evidence supporting the Big Bang Theory.
Scientists support the Big Bang Theory using several observations:

• Expansion of the Universe: Discovered by Edwin Hubble, showing that galaxies are moving away from each other.
• Cosmic Microwave Background Radiation (CMB): The faint radiation left over from the early stages of the universe.
• Abundance of Light Elements: The predicted amounts of hydrogen and helium formed shortly after the Big Bang match observations.

Step 3: Evaluating the given options.

• Earth: Formed about 4.5 billion years ago, long after the Big Bang.
• Solar System: Formed from a collapsing cloud of gas and dust.
• Universe: The Big Bang Theory explains the origin of the entire universe.
• Milky Way Galaxy: One of billions of galaxies formed after the universe began.

Therefore, the correct answer is:

Concept: Coal is a fossil fuel formed from the remains of plants that lived millions of years ago. Over long geological periods, these plant remains were buried under layers of sediments and subjected to high pressure and temperature. This process gradually converted the plant material into different types of coal. The transformation of plant material into coal is known as coalification. During coalification, the carbon content increases, while moisture and volatile substances decrease. As a result, coal types are classified based on their carbon percentage and calorific value. The major types of coal in increasing order of carbon content are:

• Peat
• Lignite
• Bituminous
• Anthracite

Each successive stage contains a higher percentage of carbon and produces more heat when burned.
Step 1: Understanding the stages of coal formation.
Coal formation occurs in stages as pressure and temperature increase over time:

• Peat: This is the earliest stage of coal formation. It contains the lowest carbon content and a high amount of moisture. Peat is partially decayed plant material.
• Lignite: Also called \textit{brown coal}. It contains more carbon than peat but still has relatively high moisture content.
• Bituminous Coal: This is the most widely used type of coal. It has higher carbon content and greater heating value than lignite.
• Anthracite: This is the highest quality coal with the maximum carbon content and the highest calorific value. It burns with a clean, smokeless flame.

Step 2: Arranging coal types in increasing carbon content.
From lowest to highest carbon percentage: Thus, the correct sequence is:
Step 3: Checking the given options.
Among the given options, option (B) correctly represents the increasing order of carbon content in coal types.

Concept: The Continental Drift Theory is an important theory in physical geography and geology that explains the movement of continents over geological time. It was first proposed in 1912 by the German meteorologist and geophysicist Alfred Wegener. According to this theory, the continents were once joined together to form a single large landmass known as Pangaea. Over millions of years, this supercontinent gradually broke apart and the individual continents slowly drifted to their present positions on the Earth's surface. Wegener presented this idea to explain the similarities in coastlines, fossils, and rock formations found on continents that are now separated by oceans.
Step 1: Understanding the Continental Drift Theory.
The theory states that:

• All continents were once part of a single supercontinent called Pangaea.
• Around 200 million years ago, Pangaea began to break apart.
• The fragments slowly drifted across the Earth's surface and formed the modern continents.

This gradual movement of continents is referred to as continental drift.
Step 2: Evidence provided by Wegener.
Alfred Wegener supported his theory with several types of evidence:

• Jigsaw Fit of Continents: The coastlines of continents such as South America and Africa appear to fit together like puzzle pieces.
• Fossil Evidence: Identical fossils of plants and animals have been discovered on continents that are now widely separated by oceans.
• Rock and Mountain Evidence: Similar rock structures and mountain ranges are found across different continents.
• Paleoclimatic Evidence: Evidence of ancient climates, such as glacial deposits in present-day tropical regions, supports the idea that continents were once located in different positions.

Step 3: Identifying the scientist who proposed the theory.
Among the given options:

• Isaac Newton was a physicist known for the laws of motion and gravitation.
• Charles Darwin proposed the theory of evolution by natural selection.
• Alexander von Humboldt was a geographer known for his contributions to biogeography.
• Alfred Wegener proposed the Continental Drift Theory in 1912.

Therefore, the correct answer is:

Concept: Glaciers are large masses of ice that move slowly over land due to gravity. As they move, they erode the underlying rocks through processes such as plucking and abrasion. These erosional processes carve distinctive landforms on the Earth's surface. Major erosional landforms formed by glaciers include:

• U-shaped valleys
• Cirques
• Arêtes
• Horns

Among these, the U-shaped valley is the most common and characteristic feature produced by glacial erosion. Glaciers widen and deepen pre-existing river valleys. Rivers usually create V-shaped valleys, but when glaciers pass through these valleys, their immense weight and slow movement reshape them into broad, flat-bottomed valleys with steep sides, forming a U-shaped cross-section. Thus, a U-shaped valley clearly indicates that the landform was shaped by glacial erosion.
Step 1: Understanding glacial erosion.
When glaciers move downhill, they erode rock surfaces by:

• Plucking: Ice freezes into rock cracks and pulls pieces of rock away.
• Abrasion: Rocks embedded in the glacier scrape and grind the valley floor and sides.

These processes significantly reshape the landscape.
Step 2: Identifying the landform produced by glaciers.
Due to intense erosion, glaciers convert narrow V-shaped river valleys into wide U-shaped valleys. These valleys have:

• A flat or gently rounded valley floor
• Steep valley sides
• A broad U-shaped cross section

Hence, the landform produced by glacial erosion is a U-shaped valley.
Step 3: Eliminating incorrect options.

• Delta: Formed by deposition of sediments by rivers at their mouths.
• Sand Dune: Formed by the depositional work of wind in desert regions.
• Flood Plain: Created by river deposition during floods.

None of these landforms are formed by glacial erosion.

Concept: The interior of the Earth is divided into several layers based on their composition and physical properties. The three major layers of the Earth are:

• Crust
• Mantle
• Core

Between these layers, there exist boundaries known as discontinuities, where the properties of seismic waves change abruptly. These discontinuities help scientists understand the structure of the Earth's interior. One of the most important boundaries is the Mohorovičić Discontinuity, commonly called the Moho. It marks the boundary between the Earth's crust and the mantle.
Step 1: Understanding the Mohorovičić Discontinuity.
The Mohorovičić Discontinuity was discovered in 1909 by the Croatian seismologist Andrija Mohorovičić. He observed that seismic waves from earthquakes suddenly increased in speed at a certain depth inside the Earth. This change in velocity indicated that the waves had entered a different layer of the Earth with different physical properties.
Step 2: Location of the Moho boundary.
The Moho lies at different depths depending on the region:

• About 5–10 km below the oceanic crust
• About 30–50 km below the continental crust

At this boundary, seismic waves travel faster because mantle rocks are denser and more rigid than crustal rocks.
Step 3: Evaluating the options.

• Crust and Mantle: Separated by the Mohorovičić Discontinuity. (Correct)
• Mantle and Outer Core: Separated by the Gutenberg Discontinuity.
• Outer Core and Inner Core: Separated by the Lehmann Discontinuity.
• Lithosphere and Asthenosphere: Separated by a mechanical boundary within the upper mantle, not the Moho.

Thus, the Mohorovičić Discontinuity separates the: