Match List I with List II and select the correct answer using the codes given below the lists

(Rock/Mineral ) | (Example)
A. Sedimentary | 1. Granite Rock
B. Igneous Rock | 2. Quartz
C. Metamorphic | 3. Shale Rock
D. Mineral | 4. Basalt
| 5. Gneiss

1. Introduction to the Rock Cycle (basic)

The Earth's crust is never static; it is a dynamic system where rocks are constantly being created, transformed, and destroyed. This continuous process is known as the Rock Cycle. At its heart, the cycle explains how the three main types of rocks—Igneous, Sedimentary, and Metamorphic—are interrelated. Igneous rocks are often called 'primary rocks' because they are the first to form from the cooling of molten magma or lava Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.174. Depending on where they cool, they can be intrusive (cooling slowly underground, like Granite) or extrusive (cooling quickly on the surface, like Basalt) Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.169.

Once these primary rocks are exposed to the elements, the process of weathering and erosion breaks them down into fragments. These sediments are transported and deposited in layers, eventually undergoing lithification (turning to stone) to become Sedimentary rocks, such as Shale. However, the journey doesn't end there. If any rock type is subjected to intense heat and pressure (without melting), its mineral structure changes, creating Metamorphic rocks like Gneiss Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.174. It is also important to distinguish between a rock and a mineral: while a rock is an aggregate of different substances, a mineral like Quartz is a specific chemical compound with a distinct crystal structure.

The cycle is completed through a process called subduction. Tectonic movements can carry crustal rocks deep into the Earth's mantle, where they melt back into magma due to extreme internal heat. This magma then rises to form new igneous rocks, beginning the cycle once more Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.174. This constant recycling ensures that the Earth's surface is always being renewed over millions of years.

Sources: Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.174; Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.169

2. Igneous Rocks: Formation and Types (intermediate)

Igneous rocks, often called primary rocks, are the starting point of the rock cycle. They form when molten rock—either magma (below the surface) or lava (above the surface)—cools and solidifies Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.169. Because they originate from extreme heat, they are unfossiliferous (contain no fossils) and typically have a crystalline structure.

The most critical factor in their physical appearance is the rate of cooling. When magma stays deep within the Earth's crust, it cools very slowly, allowing large, well-defined crystals to grow over thousands of years. These are called Plutonic (Intrusive) rocks, with Granite being the most prominent example GC Leong, The Earth's Crust, p.18. Conversely, when lava erupts onto the surface, it encounters cooler air or water and solidifies rapidly. This prevents large crystals from forming, resulting in fine-grained or even glassy Volcanic (Extrusive) rocks like Basalt NCERT Geography Class XI, Interior of the Earth, p.24.

Geologists also classify these rocks based on their chemical composition. Acidic rocks (like Granite) have a high silica content and are generally lighter in color and density. Basic rocks (like Basalt) contain a higher proportion of metallic oxides, specifically Iron and Magnesium, making them denser and darker in color Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.170. For instance, the Deccan Traps in India are of basaltic origin, formed by massive lava flows that cooled at the surface.

Feature	Intrusive (Plutonic)	Extrusive (Volcanic)
Cooling Rate	Slow (Deep underground)	Rapid (On the surface)
Grain Size	Large, coarse crystals	Small, fine grains
Examples	Granite, Gabbro, Diorite	Basalt, Andesite, Rhyolite

Sources: Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.169-170; Certificate Physical and Human Geography, GC Leong, The Earth's Crust, p.18; FUNDAMENTALS OF PHYSICAL GEOGRAPHY, NCERT Class XI, Interior of the Earth, p.24

3. Sedimentary Rocks: Layering and Lithification (intermediate)

To understand Sedimentary Rocks, we must first look at their name, which comes from the Latin word sedimentum, meaning 'settling.' Unlike igneous rocks that crystalize from hot magma, sedimentary rocks are the Earth's ultimate recyclers. They form through lithification—a two-step process of consolidation and compaction. First, fragments of older rocks, minerals, or organic matter are deposited by agents like water, wind, or ice. As these layers pile up, the weight of the overlying material squeezes the lower layers (compaction), and minerals like silica or calcite act as a natural glue to bind them into solid rock (cementation) Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.171. Because this deposition happens over time, these rocks are characterized by stratification or layering, making them the primary record-keepers of Earth’s geological history. While sedimentary rocks cover a massive 75 percent of the Earth's surface, they are surprisingly thin, making up only about 5 percent of the total crustal volume Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.171. We classify them based on how those sediments were gathered:

Category	Formation Process	Examples
Mechanically Formed	Accumulation of fragments from other rocks.	Sandstone, Shale, Loess, Conglomerate
Organically Formed	Derived from remains of living organisms (corals, shells, vegetation).	Coal, Limestone, Chalk, Peat
Chemically Formed	Precipitated from mineral-rich solutions.	Gypsum, Rock Salt (Halite), Potash

Interestingly, the same starting material can lead to different rocks. For instance, sand grains (often quartz fragments) lead to Sandstone, while finer particles like clay and silt result in Shale Certificate Physical and Human Geography, The Earth's Crust, p.19. Organically formed rocks like coal are unique because they trap carbon from ancient swamps and forests under intense pressure, serving as a vital energy reservoir today Certificate Physical and Human Geography, The Earth's Crust, p.19.

Sources: Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.171; Certificate Physical and Human Geography, The Earth's Crust, p.19

4. Metamorphic Rocks: Heat and Pressure (intermediate)

In the grand cycle of our Earth, rocks are not static; they are constantly evolving. Metamorphism (from the Greek meta meaning change and morphe meaning form) is the process by which existing rocks—whether igneous or sedimentary—are transformed into new types of rocks. This transformation happens in the solid state, meaning the rock doesn't melt into magma, but its internal structure and mineral chemistry are completely overhauled. The two primary drivers of this change are Intense Heat and Great Pressure Certificate Physical and Human Geography, The Earth's Crust, p.19.

Heat acts as a catalyst for chemical reactions. When rocks are pushed deep into the crust or come into contact with rising magma (known as thermal metamorphism), the high temperature causes minerals to re-crystallize. For instance, the peak of Mount Everest is actually composed of metamorphosed limestone, transformed by the heat of magmatic intrusions Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.173. On the other hand, Pressure (often called dynamic metamorphism) typically occurs during mountain-building processes where tectonic plates collide. This pressure can flatten minerals into layers, a process that gives some metamorphic rocks a banded appearance.

The beauty of metamorphism lies in the specific "parent-to-daughter" relationships. Depending on the intensity of the heat and pressure, a simple sedimentary rock can become something far harder and more durable. Here is a quick reference for these transformations:

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

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

5. The Chemistry of Minerals (exam-level)

To master the earth's composition for the UPSC, we must distinguish between rocks and minerals. Think of a rock as a complex mixture (like a granite countertop) and a mineral as a specific ingredient (like the crystals within it). A mineral is a homogenous, naturally occurring substance with a definable internal structure and chemical composition, whereas a rock is usually an aggregate of several minerals NCERT, Contemporary India II, p.106. For instance, while Quartz (SiO₂) is a pure mineral, Granite is a rock made of quartz, feldspar, and mica.

The chemical "personality" of a mineral—its crystal form, luster, and hardness—is dictated by the physical and chemical conditions at the time of its formation. A key chemical differentiator in geology is the Silica (SiO₂) content. Rocks are often classified based on this chemistry:

Chemical Category	Characteristics	Examples
Acidic	High silica (up to 80%), lower density, lighter color.	Granite, Quartz, Feldspar
Basic	Low silica, rich in Iron and Magnesium, higher density, darker color.	Basalt, Gabbro

Minerals are also grouped by their abundance and utility. For example, Feldspar is the most common mineral group, making up nearly half of the Earth's crust PMF IAS, Types of Rocks & Rock Cycle, p.175. These minerals then organize into the three rock families we study: Igneous (from magma cooling), Sedimentary (from lithified debris like Shale), and Metamorphic (from intense heat/pressure transformation like Gneiss).

Sources: NCERT, Contemporary India II, Minerals and Energy Resources, p.106; PMF IAS, Physical Geography, Types of Rocks & Rock Cycle, p.170, 175

6. Volcanic Landforms and Magma Composition (intermediate)

To understand the majestic architecture of our planet, we must first look at the "chemistry of the kitchen" deep beneath the surface. The shape and explosiveness of a volcano are primarily dictated by Magma Composition, specifically the concentration of Silica (SiO₂). Think of silica as the "thickener" in the magma; the more silica there is, the more the magma resists flowing, a property we call viscosity.

Magma typically falls into two broad categories that create very different landscapes:

• Basaltic Lava: This is the "runny" variety. It is low in silica but rich in Iron and Magnesium, which gives it a dark color. Because it is highly fluid, it travels long distances at speeds of 10 to 30 miles per hour before solidifying Physical Geography by PMF IAS, Volcanism, p.140. This results in broad, low-profile Shield Volcanoes or massive Flood Basalt plateaus.
• Andesitic/Acidic Lava: This is the "sticky" variety. High in silica and light in color, it is extremely viscous and has a high melting point. It solidifies quickly, often plugging the volcanic vent and causing pressure to build up until it explodes violently Physical Geography by PMF IAS, Volcanism, p.139. This creates steep-sided, layered Composite Volcanoes (Stratovolcanoes).

While some magma reaches the surface (extrusive), much of it cools underground to form Intrusive Landforms. If the magma forces its way horizontally between layers of sedimentary rock, it forms a Sill. If it cuts vertically across these layers like a wall, it is called a Dyke Certificate Physical and Human Geography, Volcanism and Earthquakes, p.27. On a much larger scale, massive dome-shaped intrusions deep in the crust are known as Batholiths or Laccoliths, which often form the core of mountain ranges once the overlying rock erodes away Physical Geography by PMF IAS, Volcanism, p.154.

Feature	Basaltic (Basic) Lava	Andesitic (Acidic) Lava
Silica Content	Low (Fluid)	High (Viscous)
Eruption Style	Quiet, effusive	Explosive, violent
Landform	Shield Volcano, Plateau	Composite Volcano, Lava Dome

Sources: Physical Geography by PMF IAS, Volcanism, p.139-140; Physical Geography by PMF IAS, Volcanism, p.148; Physical Geography by PMF IAS, Volcanism, p.154; Certificate Physical and Human Geography, Volcanism and Earthquakes, p.27

7. Weathering and Soil Formation (intermediate)

Weathering is the fundamental process of rock breakdown in-situ (in place), serving as the first step toward soil formation. Unlike erosion, which involves the transport of material, weathering is a static process where rocks disintegrate or decompose due to exposure to the atmosphere and water. This process is broadly categorized into Physical (Mechanical) and Chemical weathering, each dominating under different climatic conditions. For instance, while dry climates favor physical breakdown, warm and wet climates act as a catalyst for rapid chemical decomposition GC Leong, Weathering, Mass Movement and Groundwater, p.37.

Physical weathering involves the mechanical disintegration of rocks into smaller fragments without changing their chemical composition. In arid regions, thermal expansion and contraction play a major role. Rocks composed of diverse minerals react differently to heat; dark-colored minerals absorb more heat and expand more than light-colored ones, leading to granular disintegration PMF IAS, Geomorphic Movements, p.84. Another striking phenomenon is exfoliation (or onion-peeling), where the outer layers of rock flake off in sheets due to pressure release (unloading) or temperature fluctuations, often resulting in smooth, rounded exfoliation domes NCERT Class XI, Geomorphic Processes, p.41.

Chemical weathering, on the other hand, is the slow decomposition of rock minerals through chemical reactions. Water and air (oxygen and carbon dioxide) are the primary agents here. A classic example is Oxidation: when iron-rich minerals in a rock come into contact with oxygen and moisture, they transform into iron oxide (rust), represented as Fe₂O₃. This brownish crust crumbles easily, weakening the rock's overall structure and making it susceptible to further erosion GC Leong, Weathering, Mass Movement and Groundwater, p.37. Other processes like carbonation (reaction with CO₂) and hydration work in tandem to dissolve or loosen mineral bonds, eventually turning solid rock into regolith—the loose material that eventually becomes soil.

Feature	Physical Weathering	Chemical Weathering
Primary Agent	Temperature change, frost, pressure	Water, oxygen, organic acids
Ideal Climate	Dry/Arid or Cold (High Altitudes)	Hot and Humid (Tropics)
Result	Rock breaks into smaller pieces	Rock decomposes into new substances
Examples	Exfoliation, Frost Wedging	Oxidation, Carbonation, Solution

Sources: Certificate Physical and Human Geography, GC Leong, Weathering, Mass Movement and Groundwater, p.36-37; Physical Geography by PMF IAS, Geomorphic Movements, p.84, 90; NCERT Class XI, Fundamentals of Physical Geography, Geomorphic Processes, p.41

8. Classification Matrix: Matching Rocks to Examples (exam-level)

To master geology for the UPSC, you must first understand the fundamental hierarchy of the Earth's crust: minerals are the building blocks, and rocks are the structures built from them. While a mineral like Quartz (SiO₂) has a specific chemical composition and crystalline structure, a rock is an aggregate of one or more minerals. Understanding this distinction is the first step in correctly classifying geological specimens.

Rocks are classified into three primary families based on their mode of formation:

• Igneous Rocks: Formed from the cooling of molten magma or lava. Basalt is a prime example of an extrusive igneous rock (cooled quickly on the surface), while Granite is an intrusive one (cooled slowly underground).
• Sedimentary Rocks: Formed through the accumulation and lithification of sediments over time. These are unique because they often occur in layers and contain fossils Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.172. Shale, formed from the compaction of silt and clay, is one of the most common sedimentary rocks.
• Metamorphic Rocks: These are "changed" rocks. Under intense heat or pressure, pre-existing igneous or sedimentary rocks transform into new forms without melting. For instance, Granite can metamorphose into Gneiss, a high-grade rock characterized by distinct banding Geography of India, Geological Structure and formation of India, p.5.

The transformation process is specific. As noted in standard references, the application of pressure and heat determines the final metamorphic product. For example, while pressure turns Granite into Gneiss, heat alone can turn Sandstone into Quartzite or Limestone into Marble Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.174.

Rock Category	Common Example	Key Characteristic
Igneous	Basalt, Granite	Crystalline, no fossils, formed from cooling melt.
Sedimentary	Shale, Sandstone	Layered (stratified), often contains fossils Physical Geography by PMF IAS, p.172.
Metamorphic	Gneiss, Schist, Slate	Recrystallized due to heat/pressure Physical Geography by PMF IAS, p.174.
Mineral	Quartz, Feldspar	Specific chemical compound (e.g., SiO₂).

Sources: Physical Geography by PMF IAS, Types of Rocks & Rock Cycle, p.172, 174; Geography of India by Majid Husain, Geological Structure and formation of India, p.5

9. Solving the Original PYQ (exam-level)

Now that you have mastered the Rock Cycle and the chemical composition of the Earth's crust, this question serves as the perfect synthesis of those concepts. It tests your ability to distinguish between genetic classifications (how a rock forms) and mineralogical definitions. To solve this, you must apply the building blocks of lithification, volcanic cooling, and pressure-induced transformation to identify specific geological specimens.

As a coach, I recommend starting with the most distinct category: D. Mineral. Unlike rocks, which are aggregates, a mineral has a definite chemical composition; thus, 2. Quartz is the only fit. Next, look for A. Sedimentary rocks, characterized by layers—here, 3. Shale (formed from clay) is the clear choice. For C. Metamorphic, recall that 5. Gneiss is the classic example of high-grade foliation. This leaves B. Igneous to be matched with 4. Basalt. By following this elimination logic, you arrive at Correct Answer (B).

UPSC often includes "distractors" to test your precision. In this case, 1. Granite is also an igneous rock, which might tempt you to choose Option C. However, if you assigned Granite to Igneous in that sequence, the remaining matches for Sedimentary and Metamorphic would fall apart. The trap lies in the over-representation of igneous examples; you must find the one unique arrangement where every piece of the puzzle fits perfectly. For a deeper review of these classifications, refer to NCERT Class 11: Fundamentals of Physical Geography.