Explanation:

• Statement 1 – Correct: Youthful rivers form shallow V-shaped valleys.
• Statement 2 – Correct: Floodplains are absent or poorly developed.
• Statement 3 – Incorrect: Stream divides are broad and flat in the youth stage.

Stages of Landscape Development by Running Water

1. Youth Stage

• Streams are few and poorly integrated.
• Flow over original land slopes.
• Valleys are shallow and V-shaped.
• Floodplains are absent or very narrow.
• Stream divides are broad and flat.
• Presence of marshes, swamps and lakes.
• Meanders may form on upland surfaces.
• Waterfalls and rapids are common due to hard rock exposure.

2. Mature Stage

• Streams are numerous and well integrated.
• Valleys remain V-shaped but deeper.
• Trunk streams develop wider floodplains.
• Meanders occur within valley confines.
• Inter-stream areas become sharp and narrow.
• Marshes and swamps of youth stage disappear.
• Waterfalls and rapids vanish.

3. Old Stage

• Only few small tributaries remain.
• Streams have gentle gradients.
• Rivers meander freely over broad floodplains.
• Features like natural levees and oxbow lakes develop.
• Divides become broad and flat.
• Presence of lakes, swamps and marshes.
• Landscape lies at or near sea level.

Explanation:

• When river load is not removed by strong waves or currents, it accumulates at the mouth, forming a delta that gradually extends seaward.

Explanation:

• Statement 1 – Correct: Old rivers have gentle slopes and extensive floodplains.
• Statement 2 – Correct: Meanders, oxbow lakes and levees are typical features.
• Statement 3 – Incorrect: Lateral erosion dominates; vertical erosion is minimal.

Explanation:

• Statement 1 is correct: Sinkholes are circular to funnel-shaped depressions typical of limestone/karst regions.
• Statement 2 is incorrect: Sinkholes may form by solution action (solution sinks) or by collapse of cave roofs (collapse sinks). Solution sinks are more common.

Karst Features: Pools, Sinkholes, Lapies, Limestone Pavements and Caves

• Small to medium-sized, round to sub-rounded shallow depressions formed on limestone surfaces by solution are called swallow holes.
• Sinkholes are very common in limestone or karst regions.
• A sinkhole is usually circular at the top and funnel-shaped at the bottom.
• Sinkholes vary greatly in size, ranging from a few square metres to a hectare in area.
• Their depth ranges from less than half a metre to 30 metres or more.
• Solution sinks are formed purely by the chemical dissolution of limestone.
• Collapse sinks form when the roof of an underground cave or void collapses.
• The term doline is often used for collapse sinkholes.
• Solution sinks are more common than collapse sinks.
• Many sinkholes get covered with soil and appear as shallow water pools.
• Such pools are dangerous as people may sink suddenly, similar to quicksand.
• Surface runoff often disappears into swallow holes and sinkholes.
• Water flows underground as streams and re-emerges at a distance through cave openings.
• When sinkholes and dolines merge due to slumping or roof collapse, they form elongated depressions called uvalas or valley sinks.
• Continuous solution activity eats away most of the limestone surface.
• This produces an extremely irregular surface with grooves, ridges and pits known as lapies.
• Lapies develop mainly due to differential solution along joints and fractures.
• Extensive lapie fields may gradually evolve into smoother limestone pavements.

Explanation:

1. Stalactites – Hang from the roof of caves, usually broader at the base and tapering downward – Correct
2. Stalagmites – Rise from the floor of caves, formed by dripping water from stalactites- Correct.
3. Pillars (Columns) – Form when stalactites and stalagmites fuse together– Correct

Stalactites, Stalagmites and Pillars

• Stalactites hang from the roofs of limestone caves like icicles.
• They are generally broader at the top and taper towards the free lower end.
• Stalactites occur in different shapes and diameters due to variations in dripping water and mineral deposition.
• Stalagmites rise upward from the cave floor.
• They are formed by dripping water falling from the cave roof or from the tip of a stalactite just above.
• Continuous deposition of calcium carbonate causes stalagmites to grow vertically.
• Stalagmites may appear as columns, discs, smooth rounded bulges, or crater-like depressions.
• Over time, stalactites growing downward and stalagmites growing upward may meet.
• When both fuse together, they form solid pillars or columns.
• Pillars vary in thickness depending on the rate and duration of mineral deposition.

Explanation:

• Terminal moraine – Correct; deposited at the end (toe) of the glacier.
• Lateral moraine – Correct; runs parallel to valley sides.
• Medial moraine – Correct; occurs in the centre, flanked by lateral moraines.
• Ground moraine – Incorrect; it forms an irregular sheet of till, not sharp ridges.

Moraines, Eskers, Outwash Plains and Drumlins

Moraines

• Moraines are long ridges of debris composed of glacial till.
• Terminal moraines are ridges of debris deposited at the end (toe) of a glacier.
• Lateral moraines form along the sides of glaciers, parallel to glacial valleys.
• Lateral moraines may join terminal moraines, forming a horseshoe-shaped ridge.
• Multiple lateral moraines may exist on either side of a glacial valley.
• These moraines partly or fully originate due to glacio-fluvial waters pushing debris to glacier margins.
• Ground moraines are irregular sheets of till left behind on valley floors by retreating glaciers.
• Ground moraines vary greatly in thickness and surface relief.
• Medial moraines occur at the centre of a glacial valley between two lateral moraines.
• Medial moraines are usually less distinct and sometimes merge with ground moraines.

Explanation:

• Statement 1 – Correct: P-waves are primary waves and the fastest.
• Statement 2 – Correct: P-waves can travel through all states of matter.
• Statement 3 – Incorrect: S-waves travel only through solids, not liquids.

Types of Seismic Waves

Body Waves

• Body waves travel through the interior of the Earth.
• There are two types of body waves: P-waves and S-waves.

P-Waves (Primary Waves)

• P-waves are the fastest seismic waves.
• They are the first to arrive at the Earth’s surface.
• Hence, they are called Primary waves.
• Their motion is similar to sound waves (compressional waves).
• They can travel through solids, liquids, and gases.

S-Waves (Secondary Waves)

• S-waves arrive at the surface after P-waves, with some time lag.
• Hence, they are called Secondary waves.
• They can travel only through solid materials.
• They cannot pass through liquids or gases.
• This property helped scientists understand the internal structure of the Earth, especially the liquid nature of the outer core.

Wave Behaviour

• Reflection: Causes seismic waves to rebound after striking a surface.
• Refraction: Causes seismic waves to change direction while passing through different materials.
• Changes in wave direction are studied using seismograph records.

Explanation:

• Esker – Correct; formed by streams flowing beneath glacier ice, leaving sinuous ridges.
• Outwash plain – Correct; made of sand, gravel, silt and clay deposited by meltwater.
• Drumlin (shape & orientation) – Correct; elongated ridges aligned with ice movement.

Eskers

• During summer melting, glacial meltwater flows on the surface, along margins, or beneath the glacier.
• Subglacial meltwater streams flow through ice-walled channels beneath the glacier.
• These streams carry coarse materials such as boulders, blocks, gravel and sand.
• When the ice melts, deposited materials appear as long, winding ridges called eskers.
• Eskers are sinuous and indicate the former course of subglacial streams.

Outwash Plains

• Outwash plains form beyond the limits of glaciers or at the foot of glacial mountains.
• They consist of glacio-fluvial deposits laid down by meltwater streams.
• Materials include gravel, sand, silt and clay.
• Broad flat alluvial fans often merge to form extensive outwash plains.
• Outwash plains are flatter and coarser near the glacier and finer away from it.

Drumlins

• Drumlins are smooth, oval-shaped, ridge-like landforms made mainly of glacial till.
• They also contain some gravel and sand.
• The long axis of a drumlin runs parallel to the direction of glacier movement.
• Drumlins may be up to 1 km long and about 30 m high.
• The end facing the glacier is called the stoss end, which is steeper and blunter.
• The opposite end is the tail, which is gentler and tapered.
• Drumlins form due to dumping and moulding of debris beneath heavily loaded moving ice.
• They are useful indicators of the direction of glacier movement.

Explanation:

• Barchans are crescent-shaped dunes formed under constant and moderate wind conditions.
• Their horns or wings point away from the wind direction (downwind).
• They develop where the surface is uniform and vegetation is absent.

Explanation:

• Statement 1 – Correct: Surface waves arrive after body waves.
• Statement 2 – Correct: They cause maximum damage to structures.
• Statement 3 – Incorrect: Core structure is inferred mainly using P and S-waves, not surface waves.

Surface Waves

• Surface waves travel along the Earth’s surface.
• They are the last waves recorded on a seismograph.
• These waves are the most destructive.
• They cause displacement of rocks and lead to the collapse of buildings and structures.Top of Form

Explanation:

• Batholith – Correct. Large granitic mass formed deep in the crust.
• Lacolith – Correct. Dome-shaped intrusion with a flat base and feeder conduit.
• Lapolith – Correct. Saucer-shaped body, concave upward.
• Phacolith – Incorrect. This description fits batholith, not phacolith.
  Phacoliths are wavy intrusions in folded regions.

Batholiths

• Very large bodies of intrusive igneous rocks formed by cooling of magma deep inside the Earth’s crust.
• They develop as huge dome-shaped masses.
• Appear on the surface only after denudation removes the overlying rocks.
• Cover extensive areas and may extend to several kilometres in depth.
• Usually composed of granite.
• Represent the solidified magma chambers.

Laccoliths

• Dome-shaped intrusive bodies with a flat base.
• Form when magma intrudes between rock layers and is fed by a pipe-like conduit from below.
• Resemble volcanic domes, but are formed beneath the surface.
• Act as a localised source of magma for surface eruptions.
• Karnataka Plateau has many granite domal hills, which are exposed laccoliths or batholiths after erosion.

Lapolith

• Formed when magma spreads laterally along weak planes and solidifies in a saucer-shaped body.
• The structure is concave upwards (towards the sky).
• Occurs due to horizontal movement of lava instead of vertical ascent.

Phacolith

• Wavy-shaped intrusive igneous bodies.
• Found at:
  • The base of synclines, or
  • The top of anticlines in folded regions.
• Connected to magma chambers below through conduits.
• Often associated with batholiths at depth.

Explanation:

• Statement 1 – Correct: Radiometric dating shows matching ancient rocks.
• Statement 2 – Incorrect: Jurassic deposits suggest oceans did not exist before Jurassic.
• Statement 3 – Correct: Tillite is a glacial sedimentary rock.

Evidence in Support of the Continental Drift Theory

1. Matching of Continents (Jig-Saw Fit)

• The eastern coast of South America and the western coast of Africa show a remarkable geometric fit.
• This fit becomes almost perfect when continental margins are matched along the 1,000-fathom (≈1,800 m) line, rather than present shorelines.
• In 1964, Bullard used computer techniques to demonstrate this near-perfect Atlantic fit, strongly supporting continental drift.

2. Rocks of the Same Age Across Oceans

• Radiometric dating shows rock belts of identical age on continents now separated by oceans.
• 2,000-million-year-old rocks on the Brazilian coast closely resemble those of Western Africa.
• The oldest marine deposits along the coasts of South America and Africa are of Jurassic age, indicating:
  • The Atlantic Ocean did not exist before the Jurassic period.
  • Continents were once joined and separated later.

3. Tillite Deposits

• Tillite is a sedimentary rock formed from glacial deposits.
• Thick tillite layers are found at the base of the Gondwana sedimentary system in India.
• Similar tillite deposits occur in:
  • Africa
  • Madagascar
  • Falkland Islands
  • Antarctica
  • Australia
• This wide distribution indicates:
  • Extensive glaciation in the past
  • These southern landmasses were once part of a single supercontinent (Gondwanaland).
• Tillite provides strong evidence of palaeoclimate similarity and continental drift.

4. Placer Deposits

• Rich placer gold deposits are found along the Ghana coast, but no source rocks exist there.
• The source rocks of gold occur in the Brazilian Plateau.
• This suggests:
  • Ghana and Brazil were once adjacent
  • Gold was transported before the continents drifted apart.

5. Distribution of Fossils

• Identical fossils of land and freshwater species are found on continents now separated by oceans.
• Mesosaurus, a freshwater/brackish-water reptile:
  • Fossils found only in South Africa and Brazil
  • Could not have crossed a wide ocean → strong drift evidence.
• Lemur fossils found in:
  • India
  • Madagascar
  • Africa
• Led to the idea of a former continuous landmass (Lemuria concept).

Explanation

• Statement 1 – Correct – According to sea floor spreading, new oceanic crust is continuously formed at mid-oceanic ridges, making rocks near the ridge crest the youngest.
• Statement 2 – Correct – Rocks located equidistant from the ridge show symmetrical age and magnetic properties, providing strong evidence for sea floor spreading and geomagnetic reversals.
• Statement 3 – correct – Rock age increases as one move away from the ridge crest, which is a fundamental feature of sea floor spreading.

Explanation:

• Cocos Plate – Lies between Central America and the Pacific Plate
• Nazca Plate – Located between South America and the Pacific Plate
• Arabian Plate – Consists mainly of the Saudi Arabian landmass
• Philippine Plate – Incorrect. It lies between the Asiatic (Eurasian) and Pacific Plates, not African

Important Minor Plates

Explanation:

• The Indian Plate collides with the Eurasian Plate along its northern margin.
• This continent–continent convergence led to the formation and uplift of the Himalayas.

Explanation:

• Statement 1: Correct – Edwin Hubble provided observational evidence that galaxies are moving away from each other, leading to the idea of an expanding universe.
• Statement 2: Correct – According to the Big Bang Theory, the universe began from an extremely hot and dense state around 13.7 billion years ago and has been expanding ever since.
• Statement 3: Incorrect – Expansion of the universe does not mean that galaxies themselves are expanding. It refers to the increase in space between galaxies as the universe expands.

Explanation:

• A light year is a unit of distance, not time.
• It represents the distance that light travels in one year at a speed of about 300,000 km per second.
• Numerically, 1 light year ≈ 9.461 × 10¹² km.
• The distance between the Sun and the Earth is much smaller and is measured in astronomical units (AU), taking about 8.3 minutes for light to travel.

Explanation:

• Statement 1: Correct – Stars originate in cold molecular clouds were gas and dust clump together and collapse under gravity, forming protostars.
• Statement 2: Correct – The main sequence phase is defined by stable nuclear fusion in which hydrogen nuclei fuse to form helium, releasing energy that balances gravity.
• Statement 3: Incorrect – Only massive stars end their lives as supernovae. Low-mass stars like the Sun evolve into red giants and finally shed their outer layers as planetary nebulae, leaving behind a white dwarf.

Explanation:

• Statement I is correct. – The Chandrasekhar limit (1.44 solar masses) determines that stars below this mass shed their outer layers and the core stabilises as a white dwarf supported by electron degeneracy pressure.
• Statement II is incorrect. – Stars with mass between 1.44 and 3 times the Sun become neutron stars after a supernova.
• If the stellar mass is greater than 3 solar masses, the remnant collapses further to form a black hole, not a neutron star.

Explanation:

• The Goldilocks (habitable) zone is the region around a star that is neither too hot nor too cold.
• In this zone, liquid water can persist on a planet’s surface, which is crucial because water is a fundamental requirement for life as we know it.
• Earth lies within the Sun’s habitable zone, which explains why its oceans have remained in liquid form for billions of years.

Explanation:

• Statement I is correct. – Most large galaxies host supermassive black holes at their centres, often with masses billions of times that of the Sun.
• Statement II is incorrect. – Superclusters are not gravitationally bound; they are large-scale arrangements of galaxy groups, clusters, voids, and filaments forming the cosmic web.

Explanation:

• Statement 1: Correct – The Milky Way is a spiral galaxy with a stellar disk extending more than 100,000 light-years.
• Statement 2: Correct – The Solar System takes roughly 240 million years to complete one orbit around the Milky Way, known as a galactic year.
• Statement 3: Incorrect – The Andromeda Galaxy is the largest member of the Local Group, not the Milky Way.

Explanation:

• Statement 1: Correct– The Sun is primarily made of hot gases, mainly hydrogen, with helium as the second major component.
• Statement 2: Correct– The photosphere is the visible, shining surface of the Sun from which sunlight is emitted.
• Statement 3: Incorrect– The core, not the corona, is the innermost and hottest part of the Sun where nuclear fusion occurs. The corona is the outermost layer.
• Statement 4: Correct– The corona is usually hidden by the bright photosphere and becomes visible only during a total solar eclipse.

Explanation:

• Sunspots are formed due to the Sun’s strong and tangled magnetic fields, which inhibit the upward flow of heat from the interior.
• As a result, these regions become cooler and darker than the surrounding photosphere.
• While the Sun’s surface temperature is around 10,000°F, sunspots are cooler, at about 6,000°F, making them appear dark.

Explanation:

• Statement 1: Correct– Gravitational forces within a nebula cause gas to concentrate into a core, surrounded by a rotating disc of gas and dust.
• Statement 2: Correct– As the gas cloud condenses, matter around the core forms small rounded objects known as planetesimals through cohesion.
• Statement 3: Correct– Through repeated collisions and gravitational attraction, numerous planetesimals accrete to form fewer, larger bodies called planets.

Statement I — Correct

• As given in the passage:
  • Nitrogen ≈ 78%
  • Oxygen ≈ 21%
  • Together they form about 99% of the atmosphere near Earth’s surface.
• Remaining gases (argon, carbon dioxide, neon, etc.) constitute only about 1%.

Hence, Statement I is correct.

Statement II — Correct

• The passage clearly states two protective roles of the atmosphere:
  • It shields Earth from harmful radiation coming from the Sun.
  • It burns up most meteoroids, which are then seen as meteors, preventing them from striking the surface as meteorites.

Hence, Statement II is correct.

Explanation:

• Pair 1 – Correct: Asteroids are belts of rocky and metallic bodies mainly found between Mars and Jupiter.
• Pair 2 – Incorrect: The tail of a comet always points away from the Sun, not towards it.
• Pair 3 – Correct: Meteors are small celestial bodies that burn up in Earth’s atmosphere and appear as shooting stars.

Explanation:

• Statement 1 – Correct – Temperature, pressure and density at different depths are estimated based on Earth’s thickness and physical laws, making them indirect sources.
• Statement 2 – Correct – Seismic waves provide crucial indirect evidence.
  • S-waves do not travel through liquids, indicating a liquid outer core.
  • Shadow zones and wave velocities reveal internal layering and discontinuities.
• Statement 3 – Correct – Variations in gravity across latitudes (gravity anomalies) indicate uneven mass distribution, helping infer internal structure.
• Statement 4 – Correct – Meteors have composition similar to Earth’s interior and thus act as an indirect clue to internal materials.

Explanation:

• Statements 1, 2 and 3 – Correct – These are direct geomorphological effects of earthquakes, affecting landforms through shaking, settlement, liquefaction, landslides and avalanches.
• Statement 4 – Correct – Structural collapse, fires and falling objects are immediate threats to life and property, especially in urban areas.
• Statement 5 – Correct – Tsunamis occur when an earthquake’s epicentre lies beneath oceanic waters and the magnitude is sufficiently high.
  • Tsunami waves are generated by seismic tremors, not by surface waves themselves.

Explanation:

• A solstice occurs when the Sun reaches its maximum northward or southward position relative to the Earth’s equator.
• On June 21, the Northern Hemisphere is tilted toward the Sun, resulting in the summer solstice there and the winter solstice in the Southern Hemisphere.
• On December 21, the situation is reversed: the Southern Hemisphere experiences its summer solstice, while the Northern Hemisphere has its winter solstice.
• Hence, seasons are opposite in the two hemispheres, making option (c) correct.