Study Approach

Start with the big picture: Understand that the entire chapter is explaining how the Earth is continuously changing due to forces operating both inside and outside the planet. The flow of the chapter moves from Plate Tectonics and Continental Drift to Earthquakes, Volcanoes, Geomorphic Processes, Weathering, Mass Movement, and finally the formation of major landforms. If you study in this sequence, you will remember the chapter as one connected process instead of isolated topics.

Think of the chapter as a chain:

Plate Movements → Earthquakes & Volcanoes → Mountain Building → Geomorphic Processes → Weathering & Erosion → Landform Development

Divide the chapter into six study blocks:

• Continental Drift Theory and Plate Tectonics.
• Earthquakes and Seismic Activity.
• Tsunami and Disaster Management.
• Volcanoes and Volcanic Landforms.
• Geomorphic Processes (Endogenic and Exogenic).
• Weathering, Mass Movement, Erosion, and Transportation.

Study one block completely before moving to the next because every topic is conceptually linked with the previous one.

How to Read Each Block

1. Continental Drift and Plate Tectonics

Study this topic as a logical progression rather than separate theories: Pangaea → Continental Drift (Wegener) → Seafloor Spreading (Harry Hess) → Plate Tectonic Theory. Focus on understanding how the breakup of Pangaea led to the movement of continents and how later theories provided the mechanism for this movement. Pay special attention to Wegener’s evidences, seafloor spreading, and the three plate boundaries (divergent, convergent, and transform) along with the landforms they create. A small comparison table of plate boundaries and their associated features should be revised regularly for quick recall in both Prelims and Mains.

2. Earthquakes

Study earthquakes through the sequence Stress Accumulation → Rock Fracture → Energy Release → Seismic Waves, as this helps in understanding both causes and impacts. Focus on the concepts of Focus, Epicentre, P-waves, S-waves, Surface Waves, and Shadow Zones, and understand how they reveal Earth’s internal structure. Link Indian seismic zones and major earthquakes to plate movements, fault lines, and tectonic activity, especially in the Himalayas, Andaman-Nicobar region, and Peninsular India. This conceptual approach makes both Prelims facts and Mains explanations easier to remember.

3. Tsunami

Study tsunamis immediately after earthquakes because most major tsunamis originate from undersea seismic activity. Understand the sequence Underwater Earthquake → Seafloor Displacement → Wave Generation → Coastal Impact rather than memorizing facts. Focus on the causes, wave characteristics, coastal behaviour of tsunami waves, and India’s preparedness mechanisms such as INCOIS, ITEWC, and the DART system. During revision, add recent tsunami and earthquake-related current affairs examples to strengthen both Prelims and Mains preparation.

4. Volcanoes

Study volcanoes as another manifestation of plate movement and tectonic activity. Focus on understanding the structure of a volcano, types of volcanoes, active–dormant–extinct classification, volcanic landforms, and their benefits and hazards. Learn these concepts through simple labelled diagrams rather than lengthy notes, as diagrams greatly improve retention and answer presentation. Pay special attention to Barren Island, Narcondam Island, and the Deccan Traps, as they are frequently asked in both Prelims and Mains examinations.

5. Geomorphic Processes

Study geomorphic processes through the interaction of Endogenic and Exogenic forces. Remember the basic principle: Endogenic forces build and uplift landforms, while Exogenic forces weather, erode, and modify them over time. If this construction-versus-destruction framework is clear, topics such as mountain building, volcanism, weathering, erosion, and landform evolution become much easier to understand and remember.

6. Weathering, Mass Movement and Erosion

Prepare these topics through comparative study rather than isolated reading. Make short tables comparing Weathering vs Erosion, Soil Creep vs Solifluction, Earthflow vs Mudflow, and Abrasion vs Attrition, focusing on differences in process, agents, and outcomes. Such comparisons improve conceptual clarity, help in quick revision, and are particularly useful for solving statement-based and matching-type Prelims questions.

Diagram-Based Preparation

This chapter is highly visual, so diagrams should be an integral part of your preparation. Regularly practice simple sketches of plate boundaries, continental drift, seafloor spreading, earthquakes, shadow zones, volcanoes, fold mountains, horst–graben, rift valleys, and tsunami generation. Focus on clear labels rather than artistic presentation, and aim to draw each diagram within 30–40 seconds. Well-labelled diagrams improve conceptual understanding, aid quick revision, and significantly enhance the quality of Geography answers in the examination.

MCQ Practice Strategy

For Prelims, this chapter is frequently tested through conceptual, statement-based, and map-based questions, so practice should focus on understanding rather than rote learning. Solve MCQs on the causes of earthquakes, volcanism, plate movements, geomorphic processes, and landform formation, while paying special attention to statement-based questions, which are common in UPSC and PCS examinations. Also practice match-the-following questions related to volcanoes, plates, landforms, and geological processes.

Along with MCQs, regularly practice map-based locations such as:

• Ring of Fire
• Mid-Atlantic Ridge
• Andes and Rockies
• Himalayas
• Mariana Trench
• Barren Island

Consistent map practice improves conceptual clarity, geographical visualization, and accuracy in the examination.

Answer-Writing Method

For Mains, follow a simple and consistent structure for most Geography questions. Begin with a 2–3 line introduction defining the concept, followed by the main body explaining the process or mechanism using clear headings, subheadings, and wherever possible, a small labelled diagram. Add an analytical dimension by discussing significance, impacts, challenges, limitations, or mitigation measures, and conclude with a future-oriented, sustainable development, or disaster-management perspective.

A useful approach is:

• Introduction – Definition or context.
• Main Body – Process, causes, features, or explanation.
• Analysis – Significance, impacts, challenges, or solutions.
• Conclusion – Way forward or broader relevance.

For example, an earthquake answer can be written as Causes → Diagram → Impacts → Mitigation → Conclusion, while a volcano answer can follow Formation → Types → Benefits & Hazards → Conclusion. This format works effectively for most Geography Mains questions.

Revision strategy

• This chapter requires multiple revisions because it combines conceptual understanding with factual information. In the first revision (within 24 hours), focus only on understanding the concepts and revisiting important diagrams and flowcharts.
• During the second revision (within a week), condense each topic into 5–7 key bullet points and practice recalling diagrams from memory.
• In the third revision (within a month), solve PYQs, attempt MCQs, and practice answer writing.
• Finally, prepare a one-page master revision sheet covering plate boundaries, earthquake and volcano facts, major landforms, and important examples, which can serve as your last-minute revision resource before the examination.

Exam focus

From the Prelims perspective, focus on conceptual facts and frequently asked areas such as:

• Seismic waves and shadow zones
• Tsunami characteristics and warning systems
• Volcano types and volcanic landforms
• Plate boundaries and associated landforms
• Important geographical locations and current affairs related to earthquakes and volcanoes

From the Mains perspective, concentrate on cause-and-effect relationships, diagrams, Indian examples, human impacts, and disaster management measures. Try to link Geography topics with Disaster Management, Environment, Climate Change, and Sustainable Development. The most effective strategy is to combine concepts, diagrams, examples, and PYQs, as this helps in handling both analytical Mains questions and factual Prelims questions with confidence.

 INTERNAL FORCES

Distribution of Oceans and Continents

Continental Drift Theory (Alfred Wegener, 1912)

• Alfred Wegener proposed the Continental Drift Theory in 1912.
• Initially, all landmasses formed a single supercontinent called Pangaea, surrounded by a vast ocean called Panthalassa.
• Around 200 million years ago (MYA), Pangaea split into:
  • Laurasia (North): North America, Greenland, Eurasia.
  • Gondwanaland (South): South America, Africa, Antarctica, Australia, and India.
• Tethys Sea separated Laurasia and Gondwanaland.

Evidence for Continental Drift

• Jigsaw Fit: Coastlines of South America and Africa closely match.
• Rock Correlation: Similar-aged rock formations occur on opposite sides of the Atlantic Ocean.
• Glacial Tillite: Identical glacial deposits found in India, Africa, Antarctica, Australia, and Madagascar.
• Fossil Evidence: Fossils of Mesosaurus and Cynognathus found on widely separated continents.
• Placer Deposits: Gold deposits of Brazil correspond with source rocks in West Africa.
• Polar Wandering: Apparent movement of poles explained by continental movement.

Forces Proposed by Wegener

• Polar Fleeing Force: Rotation of Earth pushes continents toward the equator.
• Tidal Force: Gravitational pull of the Moon and Sun causes continental movement.

Limitations of Continental Drift Theory

• Failed to explain the exact mechanism of continental movement.
• Polar fleeing and tidal forces were inadequate.
• Could not explain movement in all directions.
• Timing and initiation of continental drift remained unclear.

Convection Current Theory (Arthur Holmes)

• Proposed that radioactive decay inside the mantle generates heat.
• Heat creates convection currents in the mantle.
• Rising currents form mid-oceanic ridges.
• Descending currents form trenches and subduction zones.
• Provided the mechanism missing in Wegener’s theory.

Seafloor Spreading Theory (Harry Hess)

• New oceanic crust is continuously created at mid-oceanic ridges.
• Older oceanic crust is destroyed at subduction zones.
• Ocean floor spreads away from the ridge on both sides.

Evidence of Seafloor Spreading

• Oceanic crust is younger than continental crust (generally less than 200 MYA).
• Symmetrical magnetic stripes occur on either side of ridges.
• Sediment thickness increases away from ridges.
• Shallow earthquakes occur near ridges, deeper ones near trenches.

Plate Tectonic Theory (McKenzie & Parker, 1967; Morgan, 1968)

• Earth’s lithosphere is divided into rigid plates floating over the semi-molten asthenosphere.
• Plate movement is driven by mantle convection currents.
• Explains earthquakes, volcanoes, mountain building, and continental movement.

Plate Boundaries and Associated Features

Convergent Boundary Types

Earthquakes

• An earthquake is the sudden release of energy inside the Earth that generates seismic waves.
• The focus (hypocenter) is the actual point of origin of an earthquake inside the Earth.
• The epicenter is the point on the Earth’s surface directly above the focus.
• Seismic waves spread in all directions from the focus.
• Foreshocks occur before the main earthquake, while aftershocks occur after the main shock.
• Shallow-focus earthquakes (0–70 km) are generally the most destructive because they occur close to the Earth’s surface.
• Intermediate-focus earthquakes occur between 70–300 km depth.
• Deep-focus earthquakes occur between 300–700 km depth and are usually associated with subduction zones.
• Shallow earthquakes account for nearly 70–85% of total seismic energy released globally.

Measurement and Recording

• A Seismograph records earthquake waves.
• The record produced by a seismograph is called a Seismogram.
• The Richter Scale measures earthquake magnitude (energy released).
• The Richter Scale is logarithmic; an increase of one unit represents about 31 times more energy release.
• The Moment Magnitude Scale (Mw) is preferred for earthquakes greater than magnitude 8.
• The Mercalli Scale measures earthquake intensity and damage on a scale of I to XII.
• Isoseismal lines connect places experiencing equal earthquake intensity.
• The Meizoseismal area is the region experiencing maximum damage.

Seismic Waves

• Seismic waves help scientists understand the Earth’s internal structure.
• The velocity of seismic waves generally increases with increasing density of the medium.

P-Waves

• P-waves are the fastest seismic waves and arrive first at seismic stations.
• P-waves are longitudinal (compressional) waves.
• P-waves can travel through solids, liquids, and gases.
• P-wave velocity is highest in solids and lowest in gases.

S-Waves

• S-waves arrive after P-waves.
• S-waves are transverse waves.
• S-waves travel only through solids.
• The inability of S-waves to travel through liquids provides evidence for the liquid outer core.

Surface Waves

• Surface waves are generated when body waves reach the Earth’s surface.
• Surface waves are the most destructive seismic waves.
• Love waves cause horizontal ground movement.
• Rayleigh waves produce rolling motion similar to ocean waves.
• Order of arrival: P-Waves → S-Waves → Love Waves → Rayleigh Waves.

Shadow Zone

• Shadow zones are regions where seismic waves are not detected.
• S-waves are absent beyond approximately 105° from the epicenter due to the liquid outer core.
• P-waves undergo refraction while passing through the liquid outer core.
• Between approximately 105° and 145° from the epicenter, a shadow zone exists for both P and S waves.
• Beyond 145°, only P-waves are recorded.

Earth’s Interior

• Seismic wave behavior provides evidence for the layered structure of the Earth.
• The Moho Discontinuity marks the boundary between the crust and mantle.
• Shadow zones helped establish the existence of the liquid outer core and solid inner core.

Important Himalayan Faults

• Main Central Thrust (MCT) lies between the Greater Himalayas and Lesser Himalayas.
• Main Boundary Thrust (MBT) lies between the Lesser Himalayas and Shiwalik ranges.
• Main Frontal Thrust (MFT)/Himalayan Frontal Fault (HFF) is the southernmost Himalayan fault system.

Peninsular Earthquakes

• Peninsular India is relatively stable but not free from earthquakes.
• Ancient fault lines are responsible for most earthquakes in Peninsular India.
• The 1967 Koyna earthquake, 1993 Latur earthquake, and 1997 Jabalpur earthquake are important examples.

Andaman and Nicobar Region

• The Andaman-Nicobar region lies in an active subduction zone.
• The region is highly vulnerable to earthquakes and tsunamis.
• Seafloor displacement during earthquakes can generate tsunamis.

Seismic Zones of India

• Earlier seismic zoning classified India into Zones II, III, IV, and V.
• Zone II represented low seismic risk.
• Zone V represented very high seismic risk.
• The revised seismic map proposes Zone VI as the highest seismic hazard category.
• The entire Himalayan belt has been placed under Zone VI in the revised classification.
• Border areas between two seismic zones are assigned to the higher-risk category.

Global Seismic Belts

• The Circum-Pacific Belt (Ring of Fire) accounts for about 81% of the world’s major earthquakes.
• About 75% of the world’s active volcanoes are located along the Ring of Fire.
• The Alpine-Himalayan Belt accounts for nearly 17% of major earthquakes.
• The Himalayas form a part of the Alpine-Himalayan Belt.
• The Mid-Atlantic Ridge is a divergent plate boundary where new oceanic crust is formed.
• Iceland is located on the Mid-Atlantic Ridge and experiences both earthquakes and volcanism.

Tsunami: Causes, Properties, and Impact

• The term Tsunami is derived from Japanese words: “Tsu” (harbour) + “Nami” (wave).
• Tsunamis are series of large sea waves generated by sudden displacement of ocean water.
• The most common cause of tsunamis is undersea earthquakes, particularly in subduction zones.
• Tsunamis can also be triggered by underwater landslides, submarine volcanic eruptions, and rarely by meteorite impacts.
• The 1960 Chile Earthquake (M 9.5) generated the strongest recorded tsunami.
• The 2004 Indian Ocean Tsunami was caused by the Sumatra–Andaman megathrust earthquake.

Characteristics of Tsunami Waves

• Tsunami waves possess very long wavelengths, often extending hundreds of kilometres.
• In deep oceans, tsunami waves have low wave height (amplitude) and are therefore difficult to detect.
• Tsunami waves carry enormous kinetic energy.
• In the open ocean, tsunami waves can travel at 500–800 km/h.
• Unlike ordinary sea waves, tsunami energy extends throughout the entire water column.
• As tsunami waves enter shallow coastal waters:
  • Velocity decreases.
  • Wavelength decreases.
  • Wave height increases.
  • Energy becomes concentrated near the coast.
• The first tsunami wave is not necessarily the most destructive.
• Successive waves are often larger and more destructive.
• Sudden withdrawal (receding) of seawater from the coast is an important natural warning sign of an approaching tsunami.

Tsunami Vulnerability in India

• India’s eastern coast is more vulnerable to tsunamis than the western coast.
• The Andaman & Nicobar Islands are highly vulnerable due to active subduction zones.
• Important tsunami-prone locations include: Puri, Kakinada, Chennai, Rameswaram and Andaman & Nicobar Islands

Tsunami Early Warning System (TEWS)

• Tsunamis cannot be predicted accurately; only early detection and warning are possible.
• A tsunami warning system consists of:
  • Detection network.
  • Communication and warning dissemination network.
• India’s tsunami warning mechanism is managed by the Indian Tsunami Early Warning Centre (ITEWC) which is located at INCOIS, Hyderabad.
• ITEWC monitors seismic activity and ocean conditions in real time.
• India provides tsunami warning services to 25 Indian Ocean countries under UNESCO’s IOC framework.
• The DART (Deep-ocean Assessment and Reporting of Tsunamis) system is among the world’s most advanced tsunami detection systems.
• INCOIS was established in 1999 under the Ministry of Earth Sciences.
• INCOIS uses GNSS and Strong Motion Accelerometers in the Andaman & Nicobar Islands for rapid earthquake assessment.

Volcanoes

• A volcano is an opening or vent in the Earth’s crust through which lava, ash, and gases are expelled.
• Volcanism refers to the movement of magma from the asthenosphere towards the Earth’s surface.
• Volcanic eruptions help release the Earth’s internal heat and pressure.
• Materials emitted during eruptions include lava, ash, volcanic bombs, pyroclastic materials, and gases.
• Major volcanic gases include water vapour, carbon dioxide, sulphur compounds, nitrogen compounds, chlorine, hydrogen, and argon.
• Olympus Mons (Mars) is the largest known volcano in the Solar System.
• Mauna Kea (Hawaii) is the tallest volcano on Earth when measured from its oceanic base.

Parts of a Volcano

• The Magma Chamber stores magma and volcanic gases beneath the surface.
• The Conduit is the pipe-like channel through which magma rises.
• The Vent is the opening through which volcanic materials escape.
• The Crater is the depression surrounding the vent.
• Volcanic slopes are formed by repeated deposition of lava and pyroclastic materials.

Classification of Volcanoes

·         Based on Frequency of Eruption

• • Active volcanoes erupt frequently or show signs of activity.
    • Examples: Mount Etna, Mount Stromboli, Kilauea, Mount St. Helens.
  • Dormant volcanoes have not erupted recently but may erupt again.
    • Examples: Mount Fuji, Mount Kilimanjaro.
  • Extinct volcanoes show no signs of future volcanic activity.
  • Examples: Mount Thielsen and Mount Balikabok.

·         Based on Nature of Lava

• • Andesitic volcanoes produce highly viscous, silica-rich lava and explosive eruptions.
  • Basaltic volcanoes produce fluid lava and generally non-explosive eruptions.

Volcanic Landforms

A. Extrusive Landforms (Formed on the Earth’s Surface)

B. Intrusive Landforms (Formed Below the Earth’s Surface)

Hot Springs and Geysers

• Hot springs form when groundwater is heated by geothermal energy and rises to the surface.
• Geysers periodically eject hot water and steam due to pressure build-up.
• Old Faithful (Yellowstone, USA) is the world’s most famous geyser.
• Important hot springs in India include Tattapani and Manikaran.

Hotspots and Mantle Plumes

• Hotspot volcanism occurs away from plate boundaries.
• Hotspots are produced by mantle plumes rising from deep within the mantle.
• Mantle plumes are columns of hot, buoyant material.
• The plume remains stationary while tectonic plates move over it.
• This creates chains of volcanoes over time.
• The Hawaiian Islands are the classic example of hotspot volcanism.
• Hotspot activity beneath oceans may create seamounts.

Volcanoes in India

• Barren Island is the only active volcano in India.
• It is located in the Andaman and Nicobar Islands.
• Narcondam Island contains an extinct volcano.
• There are no active volcanoes in the Himalayan region or Peninsular India.
• The Deccan Traps represent one of the largest flood basalt provinces in the world.

Important Volcanic Terms

• Pyroclastic Flow: Fast-moving mixture of hot gases, ash, and volcanic fragments.
• Lahar: Volcanic mudflow formed when volcanic ash mixes with water.
• Volcanic Forcing: Cooling of climate due to volcanic aerosols blocking sunlight.

Geomorphic Processes

• Geomorphic processes are physical and chemical processes that shape and modify the Earth’s surface.
• Earth’s surface is continuously modified by the interaction of endogenic and exogenic
• Endogenic forces originate from the Earth’s interior.
• Exogenic forces originate from the atmosphere and operate on the Earth’s surface.
• Endogenic forces are constructive (land-building), while exogenic forces are degradational (land-wearing).

Endogenic Processes

• Endogenic processes derive energy from Earth’s internal heat, radioactivity, tidal friction, and primordial heat.
• Endogenic processes are classified into sudden movements and diastrophic movements.
• Volcanism and earthquakes are examples of sudden endogenic movements.
• Diastrophism refers to slow crustal deformation that forms large-scale landforms.

Epeirogenic Movements

• Epeirogenic movements are broad vertical movements of the Earth’s crust.
• They are also known as radial movements.
• Upliftment results in the emergence of land.
• Subsidence results in the submergence of land.
• Coastal uplift may create emergent coasts.
• Coastal subsidence may produce drowned landforms.

Orogenic Movements

• Orogenic movements are mountain-building processes.
• They are caused by horizontal tectonic forces.
• Compressional forces create fold mountains.
• Tensional forces create faults, rift valleys, and block mountains.

Fold Mountains

• Fold mountains form due to compressional forces at convergent plate boundaries.
• Folds consist of two limbs connected by a hinge region.
• Examples: Himalayas, Alps, Andes, Rockies and Atlas Mountains.

Important Fold Terms

• Anticline is an upward arch-shaped fold.
• Syncline is a downward trough-shaped fold.
• Symmetrical folds have equal limbs.
• Asymmetrical folds have unequal limbs.
• Isoclinal folds have nearly parallel limbs.
• Recumbent folds have horizontal axial planes.
• Overturned folds have one limb tilted beyond vertical.
• Plunging folds have inclined fold axes.

Characteristics of Fold Mountains

• Fold mountains are generally young and tectonically active.
• They possess high peaks and steep slopes.
• Most fold mountains occur along convergent plate boundaries.

Faulting and Block Mountains

• Faulting occurs when rocks fracture due to tectonic stress.
• A fault is a fracture along which displacement has occurred.
• Example: Great African Rift Valley, Rhine Rift Valley

Types of Faults

• Normal Fault develops due to tensional forces.
• Reverse (Thrust) Fault develops due to compressional forces.
• Strike-Slip Fault involves horizontal displacement.

Great Rift Valley

• The Great Rift Valley extends from Southwest Asia to Mozambique.
• The East African Rift is an active continental rift system.
• It is gradually separating the African continent.
• Continued rifting may eventually create a new ocean basin.

Exogenic Processes

• Exogenic processes operate at or near the Earth’s surface.
• They derive energy mainly from solar radiation.
• Major geomorphic agents include running water, glaciers, wind, waves, and groundwater.
• Exogenic processes include weathering, erosion, transportation, and deposition.

Denudation

• Denudation is the combined action of weathering, erosion, transportation, and mass wasting.
• It lowers relief and modifies landscapes.
• Temperature and precipitation strongly influence denudation.

Weathering

• Weathering is the in-situ breakdown and decomposition of rocks.
• Unlike erosion, weathering does not involve transportation.
• Weathering is essential for soil formation.

Chemical Weathering

• Chemical weathering involves decomposition of rocks through chemical reactions.
• It is most active in hot and humid climates.

Important Processes

• Hydration: Addition of water molecules to minerals causing expansion.
• Chelation: Organic acids remove metallic ions from rocks.

Mechanical (Physical) Weathering

• Mechanical weathering involves physical disintegration without chemical change.

Important Processes

• Unloading: Release of pressure due to removal of overlying rocks.
• Exfoliation: Peeling of outer rock layers due to temperature variations.
• Granular Disintegration: Separation of individual mineral grains.
• Frost Wedging: Expansion of freezing water in rock cracks.
• Block Separation: Breaking of rocks along joints.
• Shattering: Breaking into angular fragments.
• Salt Weathering (Haloclasty): Expansion of salt crystals causing rock disintegration.

Biological Weathering

• Biological weathering is caused by living organisms.
• Plant roots break rocks by exerting pressure.
• Burrowing animals expose rocks to weathering.
• Fungi, bacteria, and human activities accelerate weathering.

Important Landforms Produced by Weathering

• Peneplain: Nearly level surface formed after prolonged erosion and weathering.
• Tor: Isolated rocky outcrop formed due to differential weathering.
• Exfoliation Dome: Dome-shaped feature formed by repeated exfoliation.

Mass Movement (Mass Wasting)

• Mass movement is the downslope movement of rock, soil, or debris under the direct influence of gravity.
• Unlike erosion, mass movement does not require geomorphic agents such as rivers, glaciers, wind, or waves.
• Gravity is the primary driving force behind all mass movements.

Factors Promoting Mass Movement

• Increase in slope gradient.
• Heavy rainfall causing saturation and lubrication of slope materials.
• Earthquakes and volcanic activity.
• Removal of vegetation due to deforestation or overgrazing.
• Undercutting or removal of slope support.

Slow Mass Movements

Rapid Mass Movements

Landslides

• Landslides are rapid downslope movements of rock, debris, or soil.
• Accumulated material at the foot of a slope forms a talus.

Types of Landslides

Erosion

• Erosion is the detachment, removal, and transportation of weathered materials by geomorphic agents.
• Major agents of erosion are running water, glaciers, wind, and sea waves.
• Processes of Erosion:
  • Abrasion (Corrasion): Wearing away of rocks due to rubbing by debris.
    • Vertical Corrasion: Erosion acting downward.
    • Lateral Corrasion: Erosion acting sideways.
  • Attrition: Collision between transported materials, breaking them into smaller pieces.
  • Corrosion: Chemical action of water on soluble rocks.
  • Hydraulic Action: Erosion caused by fast-moving water.
  • Plucking: Glaciers drag and break rock fragments during movement.
  • Deflation: Wind blowing away loose sand and abrading rock surfaces.

Transportation

Transportation is the movement of eroded material via geomorphic agents. Methods include:

1. Traction: Rolling of large rocks along the riverbed.
2. Saltation: Bouncing and jumping of rock fragments along the bed.
3. Suspension: Small particles like silt and mud are held in the flow of water.
4. Solution: Dissolved rock particles are carried by water.

Prelims Questions

Q.1) Which one of the following is the highest volcanic mountain in the world?

1. a) Mount Pinatubo
2. b) Mount Kilimanjaro
3. c) Mount Tall
4. d) Mount Cotopaxi

U.P.P.C.S. (Pre) 2015

Q.2) Match List – I with List – II and select the correct answer using the codes given below the lists :

List – I                                     List – II

(Volcanic Mountains)           (Country)

1. Mount Rainier 1. Italy
2. Mount Etna 2. Mexico
3. Mount Paricutin 3. Philippines
4. Mount Apo 4. U.S.A.

Codes:

A B C D

1. a) 4 2 1 3
2. b) 4 1 2 3
3. c) 2 1 4 3
4. d) 4 3 2 1

U.P.P.C.S. (Pre) 2021

Q.3) The North-Western Region of the Indian Sub-continent is susceptible to earthquake activity because of –

1. a) Volcanic activity
2. b) plate tectonic activity
3. c) coral formation activity
4. d) All of the above

U.P.P.C.S. (Mains) 2005

Q.4) Arrange in chronological order :

1. Patpara formation
2. Khetaunhi formation
3. Baghor formation
4. Sihawal formation

Codes:

1. a) 1, 4, 2, 3
2. b) 4, 1, 3, 2
3. c) 1, 2, 3, 4
4. d) 4, 3, 2, 1

U.P. P.C.S. (Mains) 2017

Q.5) Place the following mountain ranges of the world in the descending order of their lengths and fi nd the correct option from the given code –

(i) Andes

(ii) Great Dividing Range

(iii) The Himalaya

(iv) The Rocky

Code :

1. a) (i) (iii) (iv) (ii)
2. b) (i) (iv) (iii) (ii)
3. c) (iv) (i) (ii) (iii)
4. d) (iv) (iii) (i) (ii)

U.P.P.C.S. (Spl) (Pre) 2008

Mains Questions

Q.1) How are volcanoes, earthquakes, and tsunamis interrelated? Shed light on all the potential causes of volcanic eruptions.

Q.2) Discuss the causes of volcanic eruptions and describe the landforms created by the deposition of their lava.