CDS Geography · Free notes
Earth's Structure and Landforms: CDS Geography
Earth's Structure, Landforms and Geological Time has 57 past-year questions in CDS General Knowledge, from 2016 (II) to 2026 (II), and 13 of them are HARD. It is asked more often now: 27 of the 57 come from 2023 or later, and 18 from the papers of 2025 and 2026. Despite the chapter's name, not one question has asked about geological time. CDS names a landform, a wave, a rock or a soil and asks what made it or what it is, often as a set of statements with one false line. The pages follow the NCERT order, from the inside of the Earth out to the surface, so each one builds on the last.
The handout has every subtopic, worked example, formula and trap with answers shown. The formula sheet is the chapter’s formulas and traps alone, on one page.
Subtopic notes
Interior, Plates and Earthquakes
11 PYQsThe layers of the Earth and what the crust is made of, the plates that carry the continents, and the earthquake waves that let us see inside.
Volcanoes, Rocks and Minerals
11 PYQsHow lava shapes a volcano, where the world's volcanoes stand, the three families of rock and the minerals they are built from.
Weathering, Mass Movement and Soils
13 PYQsHow rock breaks down where it stands, how loose material slides downhill, and the soil orders that form from what is left.
Landforms of Rivers, Ice, Wind and Sea
15 PYQsThe shapes that running water, glaciers, frost, wind, waves and groundwater carve and build, sorted by the agent that makes them.
Natural Hazards and Disasters
7 PYQsHow natural disasters are grouped, the kinds of drought, India's earthquake zones and what decides how much damage a quake does.
Formula & revision sheet
0 formulas · 18 reference tables · 33 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
0 formulas · 18 reference tables · 33 gotchas across all subtopics — the exam-eve cheat-sheet
Interior, Plates and Earthquakes
Reference tables (4)
Layers of the Earth and the elements of the crust6 rows
| Element in the crust | Share by weight | Rank |
|---|---|---|
| Oxygen | About 46.6% | 1st |
| Silicon | About 27.7% | 2nd |
| Aluminium | About 8.1% | 3rd |
| Iron | About 5.0% | 4th |
| Calcium | About 3.6% | 5th CDS 2025 (II): in ascending order the four ran calcium, aluminium, silicon, oxygen. |
| Sodium, potassium, magnesium | About 2 to 3% each | 6th to 8th |
Plates and the theories behind them10 rows
| Plate | Major or minor | Land on it |
|---|---|---|
| Pacific | Major | Most of the Pacific Ocean floor, Hawaii |
| North American | Major | North America, Greenland, Baffin Island CDS 2025 (II): Baffin Island is on the North American Plate. |
| South American | Major | South America |
| Eurasian | Major | Europe, most of Asia, the Andaman Islands |
| African | Major | Africa, Madagascar, Comoros |
| India-Australia-New Zealand | Major | India, Sri Lanka, Australia, New Zealand |
| Antarctic | Major | Antarctica and the ocean around it |
| Arabian | Minor | Mostly the Saudi Arabian landmassQ CDS 2020 (II): the Saudi Arabian plate was the one that is not a major plate. |
| Nazca and Cocos | Minor | Pacific floor off South and Central America |
| Theories | Not a plate | Planetesimal: Chamberlin. Thermal contraction: Jeffreys. Geosyncline: Kober. Sliding continents: DalyQ |
P-waves, S-waves and surface waves3 rows
| Wave | Kind of motion | Travels through | Arrives |
|---|---|---|---|
| P-wave | Longitudinal, like sound | Solids, liquids and gases | FirstQ |
| S-wave | Transverse, at right angles, makes crests and troughs | Solids only | SecondQ CDS 2024 (II): 'S-waves are less destructive to buildings' was the false statement. |
| Surface wave | Rolls along the surface | The crust near the surface | Last, most damaging |
Focus, epicentre and measuring earthquakes6 rows
| Term | What it means |
|---|---|
| Focus or hypocentre | Point inside the Earth where the quake startsQ |
| Epicentre | Point on the surface right above the focus |
| Richter scale | Magnitude: the energy releasedQ CDS 2025 (II): 'Richter is the intensity scale' was the false statement. |
| Mercalli scale | Intensity: the shaking and damage felt at a place |
| Collapse earthquake | Small, rare quake when an underground roof falls in |
| Where quakes cluster | Plate boundaries, mostly converging onesQ |
Watch out for (8)
- Aluminium, not iron, is the commonest metal in the crust→ Layers of the Earth and the elements of the crust
- The lithosphere is more than the crust→ Layers of the Earth and the elements of the crust
- The Arabian plate is minor→ Plates and the theories behind them
- Sri Lanka and the Andamans are on different plates→ Plates and the theories behind them
- P-waves cross liquids too→ P-waves, S-waves and surface waves
- S-waves are slower but more damaging than P-waves→ P-waves, S-waves and surface waves
- Richter is magnitude, not intensity→ Focus, epicentre and measuring earthquakes
- The epicentre is not always on land→ Focus, epicentre and measuring earthquakes
Volcanoes, Rocks and Minerals
Reference tables (4)
Kinds of volcano and cone5 rows
| Kind | Lava | Shape | Example |
|---|---|---|---|
| Shield volcano | Thin, runny basalt | Broad, gentle slopes | Mauna Loa, Hawaii |
| Acid lava cone | Viscous, silica-rich | High, steep slopes | Lava domes such as Lassen Peak, USAQ CDS 2026 (I): 'viscous lava travels long distances' was the false statement. |
| Composite cone (stratovolcano) | Lava and ash in layers | The highest cones | Fuji, Mayon, Vesuvius |
| Cinder cone | Mostly ash and cinders | Small, steep | Paricutin, Mexico |
| Volcanic Explosivity Index | Not a lava type | A scale for eruption strength | Used for any volcanoQ |
Where the volcanoes are7 rows
| Volcano or area | Country or region | Setting |
|---|---|---|
| Mount Merapi | Java, Indonesia | Subduction arc |
| Sakurajima | Kyushu, Japan | Subduction arc |
| Mount Vesuvius | Bay of Naples, Italy | Composite volcano |
| Mauna Loa | Hawaii, USA | Hot-spot shield volcano |
| Fuji and Mayon | Japan and the Philippines | Arc stratovolcanoesQ CDS 2024 (II): arc volcanoes lie at convergent boundaries, not divergent ones. |
| Himalayas | India, Nepal, Tibet | Continent-continent collision, no volcanoesQ |
| Iceland | North Atlantic | Mid-Atlantic Ridge, divergent |
Igneous, sedimentary and metamorphic rocks6 rows
| Family | How it forms | Examples |
|---|---|---|
| Igneous, intrusive | Magma cools slowly underground, coarse grains | Granite, gabbroQ CDS 2021 (I): granite was the igneous rock; marble, halite and shale were not. |
| Igneous, extrusive | Lava cools fast at the surface, fine grains | BasaltQ |
| Sedimentary, mechanical | Carried grains pressed together | Sandstone, conglomerate, shale, loess |
| Sedimentary, chemical | Precipitated from water | Geyserite, haliteQ CDS 2022 (II): geyserite was the one NOT formed mechanically. |
| Sedimentary, organic | Remains of plants and animals | Coal, chalk |
| Metamorphic | Older rock changed by heat or pressure | Marble, quartzite, slate, gneiss |
Rock-forming minerals6 rows
| Mineral | Main elements | Look and home | Use |
|---|---|---|---|
| Feldspar | Si, O, Na, K, Ca, Al | Light coloured; half the crust | Ceramics, glass |
| Quartz | Silica | White or colourless, hard | Radio and radar parts |
| Pyroxene | Ca, Al, Mg, Fe, silica | Green or black; in meteorites | A major rock mineral |
| Amphibole | Al, Ca, silica, Fe, Mg | Green or black | Asbestos |
| Mica | K, Al, Mg, Fe, silica | Thin sheets | Electrical instruments |
| Olivine | Mg, Fe, silica | Greenish crystal in basalt | Jewellery |
Watch out for (8)
- Viscous lava does not travel far→ Kinds of volcano and cone
- Largest and highest are different→ Kinds of volcano and cone
- Not every great range has volcanoes→ Where the volcanoes are
- Arc volcanoes are not at divergent edges→ Where the volcanoes are
- Deep cooling gives coarse grains, not fine→ Igneous, sedimentary and metamorphic rocks
- Lithification belongs to sedimentary rocks→ Igneous, sedimentary and metamorphic rocks
- Heat from magma is contact metamorphism→ Igneous, sedimentary and metamorphic rocks
- Pyroxene and olivine are both green→ Rock-forming minerals
Weathering, Mass Movement and Soils
Reference tables (4)
Physical weathering4 rows
| Process | What pushes the rock apart | Where it is strongest |
|---|---|---|
| Frost weathering | Water freezing in cracks | Cold regions with many freeze-thaw days |
| Thermal stress and shattering | Daily heating and cooling | Hot deserts |
| Exfoliation | Outer layers expanding and peeling | Crystalline rocks such as granite |
| Salt crystallisation | Salt crystals growing in pores | Porous sedimentary rocks, dry climatesQ CDS 2025 (I): both statements, most effective process and stronger on sedimentary rock, were correct. |
Chemical weathering5 rows
| Process | What happens | Example |
|---|---|---|
| Solution | Mineral dissolves in water | Rock salt |
| Carbonation | Carbonic acid dissolves calcium carbonate | Limestone caves |
| Hydration | Mineral takes up water and swells | Anhydrite to gypsum |
| Oxidation | Oxygen joins iron, like rusting | Red, crumbly iron-rich rock |
| Salt crystal growth | Physical pressure, no new mineral | Not chemical at allQ CDS 2024 (II): it was the odd one out among acid action, hydrolysis and oxidation. |
Mass movement and soil erosion5 rows
| Movement | Speed | Material |
|---|---|---|
| Creep | Very slow | Soil and loose rock |
| Solifluction | Slow | Water-soaked soil over frozen ground |
| Mudflow | Fast | Wet mud |
| Rockfall | Very fast | Rock falling free from a cliff |
| Gully erosion | Grows over years | Soft alluvial soilQ CDS 2019 (I): the Chambal valley was the one under intensive gully erosion. |
Soil orders and humus8 rows
| Order | Stand-out feature |
|---|---|
| Entisols | Youngest, no horizons |
| Inceptisols | Weakly developed horizonsQ |
| Histosols | Very high organic matter, peat and bogsQ CDS 2020 (I): the soil with very high organic matter was the histosol. |
| Oxisols | Very old, highly weathered, tropical |
| Vertisols | Clay-rich, basic, swell and crack |
| Mollisols | Dark, fertile grassland soilsQ CDS 2021 (II): inceptisols, entisols, vertisols and mollisols were named as orders of soil. |
| Gelisols | Permafrost within the soil |
| Humus | Dark, amorphous, colloidal store of nutrientsQ |
Watch out for (5)
- Salt crystal growth is physical, not chemical→ Physical weathering
- Hydration is not hydrolysis→ Chemical weathering
- The Chambal, not the Kosi or Damodar, is the gully river→ Mass movement and soil erosion
- Entisols and inceptisols are easy to swap→ Soil orders and humus
- Impoverished soil has lost nutrients→ Soil orders and humus
Landforms of Rivers, Ice, Wind and Sea
Reference tables (4)
Drainage patterns and kinds of stream8 rows
| Pattern or stream | What it looks like or follows |
|---|---|
| Dendritic | Leaf veins; uniform rock; the most common patternQ |
| Trellis | Parallel main streams, tributaries at right angles; folded rock |
| Radial | Outward from a dome or volcano |
| Centripetal | Inward from all sides into a lake or basinQ CDS 2021 (I): rivers draining from all directions into a lake make a centripetal pattern. |
| Consequent stream | The original slope of the land |
| Subsequent stream | Lines of weak rock structure |
| Resequent stream | Same direction as the consequent, at a lower level |
| Insequent stream | No apparent reason for its path |
River landforms and rejuvenation7 rows
| Landform | Made by | Stage or cause |
|---|---|---|
| Gorge and canyon | River cutting down | Youth |
| Meander and gooseneck | River swinging sideways | MaturityQ CDS 2024 (I): all three statements about meanders, goosenecks and entrenched meanders were correct. |
| Braided channel | River splitting around sand bars | Heavy load, gentle slope |
| Oxbow lake | A meander cut off | Old age |
| Incised meander | River cutting down along old loops | Rejuvenation after upliftQ CDS 2018 (I): incised meanders belong to rejuvenation, not to the mature stage. |
| River terrace | River cutting into its old floodplain | Rejuvenation |
| Wind gap | A river, later captured | River capture |
Glacial and periglacial landforms6 rows
| Landform | Agent | What it is |
|---|---|---|
| Cirque | Glacier | Armchair-shaped hollow at the valley headQ CDS 2020 (II): the cirque was the one that is not a fluvial landform. |
| Glacial trough | Glacier | U-shaped valley; flat parts come from later infillingQ |
| Fiord | Glacier, then the sea | Trough with its floor below sea level, flooded by the sea |
| Moraine | Glacier | Ridge of debris dropped by the ice |
| Esker | Glacial meltwater | Winding ridge of sand and gravel |
| Pingo | Frost (periglacial) | Ice-cored mound in permafrost |
Wind, coastal and limestone landforms7 rows
| Landform | Agent | What it is |
|---|---|---|
| Zeugen | Wind | Table of hard rock on a softer base |
| Dreikanter and demoiselle | Wind | Three-faced stone; rock pillar worn at the baseQ CDS 2016 (II): the wind gap was the one NOT related to wind erosion. |
| Inselberg | Weathering and wind in deserts | Lone residual hill |
| Bajada | Desert streams | Apron of joined alluvial fans |
| Stack | Sea waves | Rock pillar left standing off a cliff |
| Barrier island | Waves and currents | Narrow sand island along the shore, behind it a lagoon |
| Sinkhole | Groundwater dissolving limestone | The commonest karst hollowQ |
Watch out for (8)
- Radial goes out, centripetal comes in→ Drainage patterns and kinds of stream
- Resequent is not the same as obsequent→ Drainage patterns and kinds of stream
- Incised meanders mean rejuvenation→ River landforms and rejuvenation
- A wind gap is a river feature→ River landforms and rejuvenation
- Flat trough floors are filled in, not ground flat→ Glacial and periglacial landforms
- A cirque is glacial, not fluvial→ Glacial and periglacial landforms
- Barrier islands lie close to the shore→ Wind, coastal and limestone landforms
- Stalactites hang, stalagmites rise→ Wind, coastal and limestone landforms
Natural Hazards and Disasters
Reference tables (2)
Kinds of natural disaster4 rows
| Group | Examples |
|---|---|
| Atmospheric | Cyclone, drought, hailstorm, frost, heat waveQ CDS 2025 (II): the avalanche was the one that is NOT atmospheric. |
| Terrestrial | Earthquake, volcano, landslide, avalanche |
| Aquatic | Flood, storm surge, tsunami |
| Biological | Locust swarms, insect pests, epidemics |
Earthquake zones of India and damage4 rows
| Zone (2002 map) | Risk | Example places |
|---|---|---|
| Zone V | Very high | Pithoragarh and the Himalayan belt, North-East, Kachchh, Andaman Islands |
| Zone IV | High | Delhi, much of the Ganga plain near the Himalayas |
| Zone III | Moderate | Much of central and eastern India, including Bhubaneswar |
| Zone II | Low | Much of the Deccan plateau, including Hyderabad and Secunderabad |
Watch out for (4)
- Drought is atmospheric, avalanche is terrestrial→ Kinds of natural disaster
- Agricultural drought is the soil moisture drought→ Kinds of natural disaster
- Climate does not decide earthquake damage→ Earthquake zones of India and damage
- The Himalayan belt, not the plateau, is the danger zone→ Earthquake zones of India and damage
PYQ weightage by concept
18 concepts · 57 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
18 concepts · 57 PYQs — where the marks actually sit, so you know what to drill first
Interior, Plates and Earthquakes11 PYQs · 19%
| Concept | PYQs | Share |
|---|---|---|
| Focus, epicentre and measuring earthquakes | 4 | 7% |
| Plates and the theories behind them | 3 | 5% |
| P-waves, S-waves and surface waves | 3 | 5% |
| Layers of the Earth and the elements of the crust | 1 | 2% |
Volcanoes, Rocks and Minerals11 PYQs · 19%
| Concept | PYQs | Share |
|---|---|---|
| Igneous, sedimentary and metamorphic rocks | 4 | 7% |
| Kinds of volcano and cone | 3 | 5% |
| Where the volcanoes are | 3 | 5% |
| Rock-forming minerals | 1 | 2% |
Weathering, Mass Movement and Soils13 PYQs · 23%
| Concept | PYQs | Share |
|---|---|---|
| Soil orders and humus | 6 | 11% |
| Chemical weathering | 3 | 5% |
| Physical weathering | 2 | 4% |
| Mass movement and soil erosion | 2 | 4% |
Landforms of Rivers, Ice, Wind and Sea15 PYQs · 26%
| Concept | PYQs | Share |
|---|---|---|
| Wind, coastal and limestone landforms | 5 | 9% |
| Glacial and periglacial landforms | 4 | 7% |
| Drainage patterns and kinds of stream | 3 | 5% |
| River landforms and rejuvenation | 3 | 5% |
Natural Hazards and Disasters7 PYQs · 12%
| Concept | PYQs | Share |
|---|---|---|
| Kinds of natural disaster | 5 | 9% |
| Earthquake zones of India and damage | 2 | 4% |
Test yourself on Earth's Structure, Landforms and Geological Time
15 past CDS questions from this chapter, timed at 15 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.