Consider the following statements : 1. Coal is a sedimentary rock. 2. Basalt is an igneous rock. Which of the statements given above is/are correct?

1. Composition of the Earth's Crust (basic)

The Earth's crust is the outermost, solid shell of our planet. Think of it as the thin, brittle skin of an apple. While it is the layer we live on, it actually makes up less than 1% of the Earth’s total mass and volume Physical Geography by PMF IAS, Earths Interior, p.52. The crust is not a uniform layer; it varies significantly in thickness and chemical composition depending on whether you are standing on a continent or at the bottom of the ocean.

Broadly, geographers divide the crust into two distinct types based on their mineral content and density:

Feature	Continental Crust	Oceanic Crust
Main Minerals	Silica and Alumina (Sial)	Silica and Magnesium/Iron (Sima)
Average Thickness	Thicker (approx. 30–70 km)	Thinner (approx. 5 km)
Density	Lower (approx. 2.7 g/cm³)	Higher (approx. 3.0 g/cm³)
Rock Type	Granitic/Felsic (Lighter)	Basaltic/Mafic (Denser)

The Continental Crust is much thicker under major mountain systems like the Himalayas, where it can reach depths of over 70 km Geography Class XI (NCERT 2025 ed.), Interior of the Earth, p.22. Because it is composed of lighter elements like Aluminum and Potassium, it is quite buoyant and "floats" higher on the denser mantle below Environment and Ecology by Majid Hussain, Natural Hazards and Disaster Management, p.27. In contrast, the Oceanic Crust is thin and composed of heavy silicates like iron and magnesium, making it much denser and prone to sinking below continental plates during tectonic collisions.

Sources: Certificate Physical and Human Geography, GC Leong, Chapter 2: The Earth's Crust, p.17; Physical Geography by PMF IAS, Earths Interior, p.52-53; FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Interior of the Earth, p.22; Environment and Ecology, Majid Hussain, Natural Hazards and Disaster Management, p.27

2. The Rock Cycle: Transformation of Matter (basic)

Imagine the Earth's crust not as a static floor, but as a massive recycling plant. The Rock Cycle is the continuous process through which old rocks are transformed into new ones, ensuring that the matter making up our planet is constantly repurposed. It all begins with Magma. When this molten material cools and solidifies, it forms Igneous Rocks, often called 'Primary Rocks' because all other rock types eventually derive from them Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.174. For example, Basalt is a common igneous rock that forms when lava cools rapidly on the surface; it is typically dark and dense due to its high iron and magnesium content Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.170.

As these primary rocks are exposed to the elements, they undergo weathering and erosion. The resulting fragments (sediments) are transported and deposited in layers. Over millions of years, the weight of overlying layers compresses these fragments into Sedimentary Rocks. Interestingly, this isn't just limited to mineral fragments; organic matter, like ancient plants in a swamp, can be compressed to form Coal, which is classified as an organic sedimentary rock. When any rock type—be it igneous or sedimentary—is subjected to intense Pressure, Volume, and Temperature (PVT) changes without melting, it undergoes 'metamorphism' or a 'change of form' Fundamentals of Physical Geography NCERT, Geomorphic Processes, p.38. This results in Metamorphic Rocks, where minerals may even align in layers called foliation Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.173.

The cycle completes its loop through subduction. Tectonic plates carry crustal rocks (igneous, sedimentary, or metamorphic) deep into the Earth's mantle, where they melt back into molten magma due to extreme heat Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.174. This magma eventually rises to create new igneous rocks, starting the journey all over again. Understanding these transitions is crucial because the type of rock determines everything from soil fertility to the locations of oil and mineral reserves Certificate Physical and Human Geography GC Leong, The Earth's Crust, p.25.

Process	Transformation	Resulting Rock Type
Cooling/Solidification	Magma → Rock	Igneous (e.g., Basalt)
Weathering & Lithification	Any Rock → Fragments → Rock	Sedimentary (e.g., Coal)
Heat & Pressure (PVT)	Solid Rock → Recrystallization	Metamorphic (e.g., Marble)
Melting	Rock → Magma	Return to Cycle Start

Sources: Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.174; Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.170; Fundamentals of Physical Geography NCERT, Geomorphic Processes, p.38; Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.173; Certificate Physical and Human Geography GC Leong, The Earth's Crust, p.25

3. Igneous Rocks: Magmatic Origins (intermediate)

Welcome back! Now that we understand the building blocks of minerals, let’s look at the very first type of rock that appears in the rock cycle: Igneous Rocks. Often called "Primary Rocks," they are the ancestors of all other rocks on Earth. They form directly from the cooling and solidification of molten rock, which exists either as magma (below the surface) or lava (above the surface) Physical Geography by PMF IAS, Chapter 13, p.169.

The most critical factor determining an igneous rock's appearance is where it cools. This is because the location dictates the rate of cooling. If magma stays trapped deep underground, it cools very slowly over thousands of years. This slow pace gives mineral crystals enough time to grow large and visible to the naked eye. These are called Intrusive or Plutonic rocks, with Granite being the most famous example Physical Geography by PMF IAS, Chapter 13, p.169. Conversely, if the molten rock erupts as lava, it hits the cool air or water and solidifies almost instantly. This rapid cooling prevents large crystals from forming, resulting in a fine-grained or even glassy texture. These are Extrusive or Volcanic rocks, such as Basalt FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Chapter 3, p.24.

Beyond where they cool, we also classify these rocks by their chemistry. Basic rocks (like Basalt) contain a high percentage of metallic oxides like Iron and Magnesium. This makes them characteristically dense and dark in color. In India, the vast Deccan Traps are a prime example of basaltic origin Physical Geography by PMF IAS, Chapter 13, p.170. On the other hand, Acidic rocks (like Granite) have high silica content and are generally lighter in weight and color. One thing all igneous rocks share? Because they form under extreme heat, they are unfossiliferous—meaning you will never find a fossil inside a genuine igneous rock Physical Geography by PMF IAS, Chapter 13, p.169.

Feature	Intrusive (Plutonic)	Extrusive (Volcanic)
Cooling Speed	Slow (Deep Underground)	Rapid (On Surface)
Grain Size	Large, coarse grains	Small, fine grains
Key Example	Granite	Basalt

Sources: Physical Geography by PMF IAS, Chapter 13: Types of Rocks & Rock Cycle, p.169-170; FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Chapter 3: Interior of the Earth, p.24

4. Plate Tectonics and Rock Distribution (exam-level)

To understand why the Earth’s surface looks the way it does, we must view it as a massive, slow-motion recycling system. Plate Tectonics is the engine that drives the distribution of rocks, determining where new crust is born and where old rocks are transformed or destroyed. This process primarily happens at plate boundaries, where the interaction of the lithosphere and asthenosphere creates distinct geological environments.

At Divergent Boundaries (like the Mid-Oceanic Ridges), the Earth is literally pulling itself apart. As plates move away from each other, basaltic magma rises from the mantle to fill the gap. This magma is low in silica and less viscous, allowing it to flow easily and create the vast, dark plains of the oceanic crust Physical Geography by PMF IAS, Volcanism, p.153. This "seafloor spreading" creates a primary igneous rock layer that covers nearly 70% of the Earth's surface Physical Geography by PMF IAS, Divergent Boundary, p.129. We see similar basaltic activity in continental rifts, such as the Great Rift Valley of East Africa Environment and Ecology by Majid Hussain, Natural Hazards and Disaster Management, p.12.

Conversely, Convergent Boundaries are zones of destruction and transformation. When a dense oceanic plate subducts (sinks) beneath a continental plate, it carries water-saturated sediments deep into the asthenosphere. Under the intense heat and pressure of the subduction zone, these rocks undergo metamorphism, changing their mineral structure without fully melting Physical Geography by PMF IAS, Convergent Boundary, p.116. If they sink deep enough, they melt to form magma that rises to create volcanic mountain ranges (like the Andes) or island arcs (like the Philippines). Over millions of years, this process of volcanism and accretion transforms thin oceanic crust into the thicker, more complex continental crust Physical Geography by PMF IAS, Convergent Boundary, p.113.

Boundary Type	Primary Rock Process	Resulting Rock/Feature
Divergent	Decompression melting of the mantle	Basaltic Igneous Rocks (Oceanic Crust)
Convergent	Subduction, high pressure, and melting	Metamorphic rocks & Volcanic arcs
Hot Spots	Mantle plumes upwelling	Localized volcanic basalt (e.g., Hawaii)

Sources: Physical Geography by PMF IAS, Volcanism, p.153; Physical Geography by PMF IAS, Divergent Boundary, p.129; Environment and Ecology by Majid Hussain, Natural Hazards and Disaster Management, p.12; Physical Geography by PMF IAS, Convergent Boundary, p.116; Physical Geography by PMF IAS, Convergent Boundary, p.113

5. Metamorphic Rocks and Processes (intermediate)

Metamorphic rocks are the "shape-shifters" of the geological world. The term itself comes from the Greek words meta (change) and morph (form). Unlike igneous rocks that solidify from magma or sedimentary rocks that form from deposits, metamorphic rocks are created when existing rocks are subjected to intense heat and pressure. This process causes the minerals to recrystallize and reorganize without the rock actually melting into magma. If it melts, it becomes igneous; if it stays solid but changes its internal structure, it is metamorphism Certificate Physical and Human Geography, GC Leong, The Earth's Crust, p.19.

There are two primary drivers of this transformation. First is Thermal (Contact) Metamorphism, where rocks come into contact with hot, rising magma. This "cooking" effect alters the mineral composition. For instance, the very peak of Mount Everest consists of metamorphosed limestone, changed by magmatic intrusions Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.173. Second is Dynamic (Regional) Metamorphism, which occurs during massive earth movements like mountain building (orogeny). Here, intense pressure and friction at great depths squeeze the rocks, often creating a layered or "foliated" appearance.

The beauty of metamorphism lies in the specific pairings of parent rocks and their transformed versions. Because the original character is altered, the resulting rock is often much harder and more resistant to weathering than its predecessor. For example, soft clay becomes hard slate, and common sandstone turns into the extremely durable quartzite.

Original Parent Rock	Metamorphic Result
Limestone (Sedimentary)	Marble
Sandstone (Sedimentary)	Quartzite
Granite (Igneous)	Gneiss
Shale/Clay (Sedimentary)	Slate / Schist
Coal (Organic Sedimentary)	Graphite / Diamond

Sources: Certificate Physical and Human Geography, GC Leong, The Earth's Crust, p.19; Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.173

6. Sedimentary Rocks: Formation and Types (intermediate)

While Igneous rocks are born from the fiery depths of the Earth, Sedimentary rocks are the product of the surface world—shaped by water, wind, ice, and life itself. These rocks are formed through a process called lithification, which literally means "turning into stone." This happens when sediments (loose particles like sand, mud, or pebbles) are deposited in layers and, over millions of years, are compressed by the weight of overlying materials and cemented together by minerals like silica or calcium carbonate Physical Geography by PMF IAS, Chapter 13, p.171.

Sedimentary rocks are the Earth's primary storytellers. Because they form at the surface, they often trap the remains of plants and animals, making them fossiliferous. They are also characterized by stratification—distinct horizontal layers or "strata" that reflect different periods of deposition Certificate Physical and Human Geography, GC Leong, Chapter 2, p.18. Interestingly, while they cover about 75% of the Earth's land surface, they only make up about 5% of the total volume of the crust because they exist primarily as a thin veneer over the crystalline basement of igneous and metamorphic rocks.

We classify these rocks based on how the sediments were formed and gathered:

Type	Formation Process	Examples
Mechanically Formed	Physical accumulation of rock fragments (detritus) moved by wind, water, or ice.	Sandstone (sand), Shale (clay), Loess (wind-blown), Tillite (ice-deposited).
Organically Formed	Accumulation of remains from living organisms like corals, shells, or vegetative matter.	Coal (compacted plants), Chalk/Limestone (shells), Geyserite.
Chemically Formed	Direct precipitation of minerals from a solution (like evaporating seawater).	Halite (Rock Salt), Potash, Gypsum.

Sources: Physical Geography by PMF IAS, Chapter 13: Types of Rocks & Rock Cycle, p.171-172; Certificate Physical and Human Geography, GC Leong, Chapter 2: The Earth's Crust, p.18-19

7. Specific Case Studies: Coal and Basalt (exam-level)

To truly master the world of petrology, we must look at specific 'celebrity' rocks that define our landscape and economy. Coal and Basalt are perfect case studies because they represent two completely different life cycles: one born from ancient life (organic) and the other from the fiery interior of the Earth (igneous). 1. Coal: The Organic Sedimentary Rock
Coal is classified as an organically formed sedimentary rock, specifically a carbonaceous rock. Unlike rocks formed from sand or pebbles, coal begins in ancient swamps and forests. When vast amounts of vegetative matter are buried under layers of sediment, they are protected from complete decay. Over millions of years, the weight of overlying layers exerts immense pressure and heat, squeezing out moisture and gases to leave behind concentrated carbon Certificate Physical and Human Geography, Chapter 2, p.19. This transformation follows a progression of increasing carbon content: Peat → Lignite → Bituminous → Anthracite. Bituminous coal, for instance, contains 60% to 80% carbon and often still contains traces of the original vegetation Geography of India by Majid Husain, Energy Resources, p.1. 2. Basalt: The Volcanic Igneous Rock
In contrast, Basalt is a primary igneous rock of the extrusive or volcanic variety. It forms when molten lava reaches the Earth's surface and cools rapidly. Because it cools so quickly in the open air or water, large crystals don't have time to grow, resulting in a fine-grained texture. Basalt is typically dark-colored and dense, being rich in iron and magnesium. In India, the most famous occurrence is the Deccan Traps, a massive flood basalt province covering much of the Maharashtra plateau, where individual lava flows can range from 5 to 29 meters thick FUNDAMENTALS OF PHYSICAL GEOGRAPHY NCERT Class XI, Interior of the Earth, p.24 Geography of India by Majid Husain, Geological Structure, p.20.

Feature	Coal	Basalt
Rock Type	Organically formed Sedimentary	Extrusive Igneous (Volcanic)
Source Material	Vegetative matter (swamps/forests)	Molten Lava
Key Characteristic	Carbon-rich; stores energy	Fine-grained; rich in Iron/Magnesium
Indian Example	Gondwana Coalfields (Damodar Valley)	Deccan Plateau (Maharashtra)

Sources: Certificate Physical and Human Geography, GC Leong, Chapter 2: The Earth's Crust, p.19; Geography of India, Majid Husain, Energy Resources, p.1; FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT), Chapter 3: Interior of the Earth, p.24; Geography of India, Majid Husain, Geological Structure and formation of India, p.20

8. Solving the Original PYQ (exam-level)

This question tests your ability to apply the fundamental classification of rocks to specific, real-world examples. You’ve just learned that rocks are categorized by their origin: igneous from cooling magma, sedimentary from the lithification of deposits, and metamorphic from intense heat and pressure. In Statement 1, we identify coal. Recalling its formation, it originates from the accumulation of organic vegetative matter in swampy environments that is compressed over eons—this is the hallmark of an organically formed sedimentary rock. As noted in Certificate Physical and Human Geography, GC Leong, this process of layering and organic accumulation confirms its sedimentary nature.

Moving to Statement 2, we analyze basalt. During your study of volcanism, you learned that when lava reaches the Earth's surface and cools rapidly, it forms extrusive igneous rocks (or volcanic rocks). Basalt is the most common example of this, characterized by its dense, fine-grained texture. By verifying both facts, you can confidently eliminate options (A) and (B). The logical progression leads us directly to the correct answer: (C) Both 1 and 2, as both statements accurately link the specific rock to its geological category as detailed in Physical Geography by PMF IAS.

A common UPSC trap in rock-related questions is the confusion between a rock's origin and its metamorphic state. For instance, while high-grade coal like Anthracite has metamorphic properties, coal is fundamentally classified by its sedimentary accumulation. UPSC also frequently swaps examples—pairing an igneous rock with a metamorphic description—to test if your conceptual "building blocks" are firm. To avoid these traps, always look for the primary formation process mentioned in the statement; if it aligns with the rock's basic definition, you are on the right track.