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English · हिन्दी · తెలుగు · தமிழ் · മലയാളം · मराठी · ಕನ್ನಡ

Quick recap: the Earth, its motions and interior on one page

ಕನ್ನಡದಲ್ಲಿ ವಿವರಣೆ

The Earth: its place, motions and interior · Quick recap · Fact-checked on · how we check

Written with AI from the sources listed at the bottom of this page, then fact-checked by a separate AI.

All three parts condensed for quick revision: the solar system and the Earth's shape, rotation, revolution and seasons, latitude, longitude and time, IST and the Date Line, seismic waves and the shadow zone, the Earth's layers, and the three families of rock, with a one-table overview and eight mixed questions.

Each idea is explained first in Kannada (ಕನ್ನಡ), ending with the English and Hindi exam terms, followed by the same point in exam English. UPSC Prelims is in English or Hindi, so understand it in Kannada and revise it in English.

ಈ ಅಧ್ಯಾಯ ಭೂಮಿಯನ್ನು ಹೊರಗಿನಿಂದ ಒಳಗೆ ನೋಡುತ್ತದೆ — ಮನೆಯನ್ನು ಮೊದಲು ಹೊರಗಿನಿಂದ, ನಂತರ ಕೋಣೆಗಳು, ಕೊನೆಗೆ ಅಡಿಪಾಯ ನೋಡಿದಂತೆ. ಭಾಗ 1: ಸೌರವ್ಯೂಹದಲ್ಲಿ ಭೂಮಿ, ಅದರ ಆಕಾರ, ಎರಡು ಚಲನೆಗಳು. ಭಾಗ 2: ಅಕ್ಷಾಂಶ-ರೇಖಾಂಶಗಳ ಜಾಲ, ಸಮಯ, ಭಾರತೀಯ ಪ್ರಮಾಣಿತ ಸಮಯ, ದಿನಾಂಕ ರೇಖೆ. ಭಾಗ 3: ಭೂಮಿಯ ಒಳಪದರಗಳು, ಶಿಲೆಗಳು. (→ English: solar system · हिन्दी: सौर मंडल)

In exam EnglishThis chapter follows the Earth from the outside in. Part 1 places the planet in the solar system and explains its shape and its two motions, which give day and night and the seasons. Part 2 draws the grid of latitude and longitude and turns longitude into time, ending with Indian Standard Time and the International Date Line. Part 3 goes below the surface: how the interior is known, the layers that earthquake waves reveal, and the rocks of the crust. The figures in this recap are the ones Prelims tests most often.
The chapter at a glance
TopicMust-know factsCommon trap
SeasonsTilt 23½° (66½° with the orbital plane); solstices 21 June, 22 December; equinoxes 21 March, 23 SeptemberNearest the Sun in early January, so distance does not cause seasons
LatitudeTropics 23½°, polar circles 66½°; 1° ≈ 111 km; Tropic of Cancer crosses 8 statesOdisha, Bihar and Uttar Pradesh are not on the Tropic of Cancer
Longitude and time15° = 1 hour, 1° = 4 minutes; IST at 82°30′E = UTC + 5:30IST meridian passes near Mirzapur, not New Delhi
Date LineRoughly along 180°, bends around landWestward crossing adds a day; eastward repeats one
Seismic wavesP: all states; S: solids only; surface waves slowestS-wave shadow (beyond 105°) is larger than P-wave shadow (105°–145°)
LayersMoho (crust/mantle), Gutenberg about 2,900 km, Lehmann about 5,150 kmOuter core liquid, inner core solid
RocksIgneous, sedimentary, metamorphic; rock cycleFossils only in sedimentary; marble from limestone

ಸೂರ್ಯ ಮತ್ತು ಎಂಟು ಗ್ರಹಗಳು: ಒಳಗೆ ನಾಲ್ಕು ಸಣ್ಣ ಕಲ್ಲಿನ ಗ್ರಹಗಳು, ಹೊರಗೆ ನಾಲ್ಕು ದೈತ್ಯ ಅನಿಲ ಗ್ರಹಗಳು, ನಡುವೆ ಕ್ಷುದ್ರಗ್ರಹ ಪಟ್ಟಿ. 2006ರ ವ್ಯಾಖ್ಯೆಯಂತೆ ಪ್ಲೂಟೊ ತನ್ನ ಕಕ್ಷೆಯನ್ನು ಸ್ವಚ್ಛಗೊಳಿಸದ ಕಾರಣ ಕುಬ್ಜ ಗ್ರಹ — ತಂಡದಲ್ಲಿ ಪೂರ್ಣ ಸದಸ್ಯನಲ್ಲದ ಆಟಗಾರನಂತೆ. ಭೂಮಿ ಸಮಭಾಜಕದಲ್ಲಿ ಸ್ವಲ್ಪ ಉಬ್ಬಿದ ಗೋಳ (ಜಿಯಾಯ್ಡ್): ಸಮಭಾಜಕ ತ್ರಿಜ್ಯ ಸುಮಾರು 6,378 ಕಿ.ಮೀ., ಧ್ರುವ ತ್ರಿಜ್ಯ ಸುಮಾರು 6,357 ಕಿ.ಮೀ. ಸೂರ್ಯನಿಂದ ಸರಾಸರಿ ದೂರ ಸುಮಾರು 15 ಕೋಟಿ ಕಿ.ಮೀ. (→ English: dwarf planet, geoid · हिन्दी: बौना ग्रह, जियॉइड)

In exam EnglishThe solar system has the Sun and eight planets: four small rocky inner planets (Mercury, Venus, Earth and Mars) and four outer giants (Jupiter, Saturn, Uranus and Neptune), with the asteroid belt between Mars and Jupiter. Under the International Astronomical Union's definition of August 2006, Pluto is a dwarf planet, because it has not cleared its orbit of other bodies. The Earth is a geoid that bulges at the equator: its equatorial radius is about 6,378 km and its polar radius about 6,357 km. Its average distance from the Sun is about 150 million km.

ಭೂಮಿ ಪಶ್ಚಿಮದಿಂದ ಪೂರ್ವಕ್ಕೆ ತಿರುಗುತ್ತದೆ; ಸೂರ್ಯನ ಲೆಕ್ಕದಲ್ಲಿ ಒಂದು ಸುತ್ತು 24 ಗಂಟೆ, ನಕ್ಷತ್ರಗಳ ಲೆಕ್ಕದಲ್ಲಿ ಸುಮಾರು 23 ಗಂ. 56 ನಿ. ಸೂರ್ಯನ ಸುತ್ತ ಸುಮಾರು 365¼ ದಿನ — ಅದಕ್ಕೇ ಅಧಿಕ ವರ್ಷ. ಜನವರಿ ಆರಂಭದಲ್ಲಿ ಸೂರ್ಯನಿಗೆ ಹತ್ತಿರ, ಜುಲೈ ಆರಂಭದಲ್ಲಿ ದೂರ; ಅಂದರೆ ದೂರವಲ್ಲ, ಅಕ್ಷದ ಓರೆಯೇ ಋತುಗಳಿಗೆ ಕಾರಣ — ಓರೆಯಾಗಿ ಹಿಡಿದ ಟಾರ್ಚ್ ಬೆಳಕು ನೆಲದ ಮೇಲೆ ಹರಡುವಂತೆ. ಜೂನ್ ಅಯನ ಸಂಕ್ರಾಂತಿಯಲ್ಲಿ ಸೂರ್ಯ ಕರ್ಕಾಟಕ ವೃತ್ತದ ಮೇಲೆ, ಡಿಸೆಂಬರ್‌ನಲ್ಲಿ ಮಕರ ವೃತ್ತದ ಮೇಲೆ; ವಿಷುವತ್ ಸಂಕ್ರಾಂತಿಯ ದಿನಗಳಲ್ಲಿ ಸಮಭಾಜಕದ ಮೇಲೆ. (→ English: axial tilt, solstice, equinox · हिन्दी: अक्षीय झुकाव, अयनांत, विषुव)

In exam EnglishThe Earth rotates from west to east; one turn measured against the Sun is a solar day of 24 hours, a little longer than one turn measured against the stars, about 23 hours 56 minutes. It revolves round the Sun in about 365¼ days, so a leap year adds a day every fourth year, with century years counting only when divisible by 400. The Earth is nearest the Sun (perihelion) in early January and farthest (aphelion) in early July, so distance does not cause the seasons. The tilt of the axis does: about 23½° from the perpendicular, or 66½° with the orbital plane. At the June solstice (about 21 June) the overhead Sun reaches the Tropic of Cancer and at the December solstice (about 22 December) the Tropic of Capricorn; at each equinox (about 21 March and 23 September) it is over the equator.

ಅಕ್ಷಾಂಶ ಎಂದರೆ ಸಮಭಾಜಕ ವೃತ್ತದಿಂದ ಉತ್ತರ ಅಥವಾ ದಕ್ಷಿಣಕ್ಕೆ ಎಷ್ಟು ದೂರ (0°–90°) — ಮನೆಯ ಮೆಟ್ಟಿಲು ಎಣಿಸಿದಂತೆ. ಸುಮಾರು 23½°ರಲ್ಲಿ ಉಷ್ಣ ರೇಖೆಗಳು, 66½°ರಲ್ಲಿ ಧ್ರುವ ವೃತ್ತಗಳು; ಉಷ್ಣ, ಸಮಶೀತೋಷ್ಣ, ಶೀತ ವಲಯಗಳು. ಒಂದು ಡಿಗ್ರಿ ಸುಮಾರು 111 ಕಿ.ಮೀ. ಭಾರತ ಸುಮಾರು 8°4′ ಉ.ದಿಂದ 37°6′ ಉ.ವರೆಗೆ. ಕರ್ಕಾಟಕ ಸಂಕ್ರಾಂತಿ ವೃತ್ತ ಎಂಟು ರಾಜ್ಯಗಳ ಮೂಲಕ: ಗುಜರಾತ್, ರಾಜಸ್ಥಾನ, ಮಧ್ಯಪ್ರದೇಶ, ಛತ್ತೀಸ್‌ಗಢ, ಜಾರ್ಖಂಡ್, ಪಶ್ಚಿಮ ಬಂಗಾಳ, ತ್ರಿಪುರ, ಮಿಜೋರಾಂ. (→ English: latitude, Tropic of Cancer · हिन्दी: अक्षांश, कर्क रेखा)

In exam Englishlatitude measures distance north or south of the equator, from 0° to 90°. The tropics lie at about 23½° and the polar circles at about 66½°, dividing the globe into the torrid, temperate and frigid zones, and a degree of latitude is about 111 km everywhere. India's mainland stretches from about 8°4′N to 37°6′N. The Tropic of Cancer crosses eight states: Gujarat, Rajasthan, Madhya Pradesh, Chhattisgarh, Jharkhand, West Bengal, Tripura and Mizoram.

ರೇಖಾಂಶವನ್ನು ಗ್ರೀನ್‌ವಿಚ್‌ನಿಂದ (1884) ಪೂರ್ವ-ಪಶ್ಚಿಮ ಎಣಿಸುತ್ತೇವೆ. ಭೂಮಿ 24 ಗಂಟೆಯಲ್ಲಿ 360° ತಿರುಗುವುದರಿಂದ 15° = 1 ಗಂಟೆ, 1° = 4 ನಿಮಿಷ; ಪೂರ್ವದ ಊರುಗಳು ಸಮಯದಲ್ಲಿ ಮುಂದೆ. ಭಾರತೀಯ ಪ್ರಮಾಣಿತ ಸಮಯ 82°30′ ಪೂ. (ಮಿರ್ಜಾಪುರ ಬಳಿ) ಸ್ಥಳೀಯ ಸಮಯ = UTC + 5:30. ದೇಶ ಸುಮಾರು 30° ಹರಡಿರುವುದರಿಂದ ಪೂರ್ವದಲ್ಲಿ ಸೂರ್ಯೋದಯ ಪಶ್ಚಿಮಕ್ಕಿಂತ ಸುಮಾರು ಎರಡು ಗಂಟೆ ಮೊದಲು. ಅಂತರರಾಷ್ಟ್ರೀಯ ದಿನಾಂಕ ರೇಖೆ ಸುಮಾರು 180° ಉದ್ದಕ್ಕೂ, ನೆಲವನ್ನು ತಪ್ಪಿಸಿ ಬಾಗುತ್ತದೆ; ಪಶ್ಚಿಮಕ್ಕೆ ದಾಟಿದರೆ ಒಂದು ದಿನ ಮುಂದೆ, ಪೂರ್ವಕ್ಕೆ ದಾಟಿದರೆ ಅದೇ ದಿನ ಮತ್ತೆ — ಕ್ಯಾಲೆಂಡರ್ ಹಾಳೆ ತಿರುಗಿಸಿದಂತೆ. (→ English: longitude, Indian Standard Time, International Date Line · हिन्दी: देशांतर, भारतीय मानक समय, अंतर्राष्ट्रीय तिथि रेखा)

In exam Englishlongitude is counted east and west from the Prime Meridian at Greenwich, chosen by the International Meridian Conference in Washington in 1884. Because the Earth turns 360° in 24 hours, 15° of longitude equals one hour and 1° equals 4 minutes, and places to the east are ahead in time. Indian Standard Time is the local time of 82°30′E, which passes near Mirzapur, making it UTC + 5:30; the CSIR-National Physical Laboratory keeps it. India spans about 30° of longitude, so sunrise in the far east comes nearly two hours before the far west. The International Date Line runs roughly along 180° and bends around land; crossing it westward adds a day, while crossing it eastward repeats one.

ಭಾಗ 3 ಸಾಕ್ಷ್ಯಗಳಿಂದ ಆರಂಭ. ಗಣಿಗಳು, ಆಳದ ಕೊಳವೆಬಾವಿಗಳು (ಕೋಲಾ ಸುಮಾರು 12.2 ಕಿ.ಮೀ.), ಜ್ವಾಲಾಮುಖಿ ವಸ್ತು ನೇರ ಸಾಕ್ಷ್ಯಗಳು; ಉಷ್ಣತೆ, ಒತ್ತಡ, ಸಾಂದ್ರತೆ, ಉಲ್ಕೆಗಳು, ಗುರುತ್ವ, ಕಾಂತೀಯತೆ, ಎಲ್ಲಕ್ಕಿಂತ ಮುಖ್ಯವಾಗಿ ಭೂಕಂಪನ ಅಲೆಗಳು ಪರೋಕ್ಷ ಸಾಕ್ಷ್ಯಗಳು. P ಅಲೆಗಳು ವೇಗ, ಎಲ್ಲದರಲ್ಲೂ ಸಾಗುತ್ತವೆ; S ಅಲೆಗಳು ಘನದಲ್ಲಿ ಮಾತ್ರ; ಮೇಲ್ಮೈ ಅಲೆಗಳು ನಿಧಾನ, ಹೆಚ್ಚು ಹಾನಿ. 105°–145° ನಡುವೆ P ಬರುವುದಿಲ್ಲ, 105° ದಾಟಿ S ಬರುವುದೇ ಇಲ್ಲ — ಈ ನೆರಳು ವಲಯವೇ ಹೊರ ತಿರುಳು ದ್ರವ ಎಂದು ತೋರಿಸಿತು, ಗೋಡೆಯ ಹಿಂದಿನ ನೆರಳು ಗೋಡೆ ಇದೆ ಎಂದು ಹೇಳುವಂತೆ. (→ English: seismic waves, shadow zone · हिन्दी: भूकंपीय तरंगें, छाया क्षेत्र)

In exam EnglishPart 3 starts from evidence. Mines, deep drilling (the Kola borehole reached about 12.2 km) and volcanic material are direct sources; temperature, pressure and density, meteorites, gravity and magnetism, and above all seismic waves are indirect ones. P waves are the fastest and pass through solids, liquids and gases; S waves pass only through solids; surface waves are the slowest and most destructive. Direct P waves are missing between about 105° and 145° from the epicentre, and S waves everywhere beyond 105°; this shadow zone revealed a liquid outer core.

ಹೊರಪದರ ತೆಳು: ಖಂಡಗಳ ಕೆಳಗೆ 30–40 ಕಿ.ಮೀ. (ಹಿಮಾಲಯದ ಕೆಳಗೆ 70ರವರೆಗೆ), ಸಾಗರಗಳ ಕೆಳಗೆ 5–10 ಕಿ.ಮೀ.; ತಳದಲ್ಲಿ ಮೋಹೋ (1909). ಕವಚ ಸುಮಾರು 2,900 ಕಿ.ಮೀ.ವರೆಗೆ; ಅದರ ಮೇಲ್ಭಾಗದಲ್ಲಿ ಮೃದು ಅಸ್ತೆನೋಸ್ಫಿಯರ್, ಅದರ ಮೇಲೆ ಗಟ್ಟಿ ಶಿಲಾಗೋಳ (ಹೊರಪದರ + ಮೇಲಿನ ಕವಚ) ಫಲಕಗಳಾಗಿ ಒಡೆದಿದೆ — ಕಾವಲಿಯ ಮೇಲೆ ಮುರಿದ ದೋಸೆ ತುಂಡುಗಳಂತೆ. ತಿರುಳು ಕಬ್ಬಿಣ ಮತ್ತು ನಿಕ್ಕಲ್: ಹೊರಗಿನ ದ್ರವ ಭಾಗ ಕಾಂತಕ್ಷೇತ್ರ ಕೊಡುತ್ತದೆ, ಒಳಗಿನ ಘನ ಭಾಗ ಸುಮಾರು 5,150 ಕಿ.ಮೀ. ಆಚೆ. (→ English: lithosphere · हिन्दी: स्थलमंडल)

In exam EnglishThe crust is thin: continental crust, granitic and once called SIAL, is about 30–40 km thick and up to about 70 km under the Himalaya, while oceanic crust, basaltic and called SIMA, is about 5–10 km; the Moho, identified in 1909, marks its base. The mantle reaches about 2,900 km. Its weak, partly molten asthenosphere lies beneath the rigid lithosphere, the crust plus the uppermost mantle, which is broken into plates. The core, mainly iron and nickel, begins at the Gutenberg discontinuity; its liquid outer part generates the magnetic field, and its solid inner part lies beyond the Lehmann discontinuity at about 5,150 km.

ಹೊರಪದರದಲ್ಲಿ ತೂಕದ ಪ್ರಕಾರ ಆಮ್ಲಜನಕ ಹೆಚ್ಚು, ನಂತರ ಸಿಲಿಕಾನ್, ಅಲ್ಯೂಮಿನಿಯಂ, ಕಬ್ಬಿಣ; ಇಡೀ ಭೂಮಿಯಲ್ಲಿ ಮಾತ್ರ ಕಬ್ಬಿಣ ಮೊದಲು. ಅಗ್ನಿಶಿಲೆಗಳು: ಗ್ರಾನೈಟ್ (ಒಳಗೆ), ಬಸಾಲ್ಟ್ (ಹೊರಗೆ), ದಖ್ಖನ್ ಟ್ರ್ಯಾಪ್. ಸಂಚಿತ ಶಿಲೆಗಳು: ಪದರಗಳು, ಪಳೆಯುಳಿಕೆಗಳು, ಮರಳುಗಲ್ಲು, ಸುಣ್ಣದಕಲ್ಲು, ಕಲ್ಲಿದ್ದಲು. ರೂಪಾಂತರ ಶಿಲೆಗಳು: ಸುಣ್ಣದಕಲ್ಲು → ಅಮೃತಶಿಲೆ, ಮರಳುಗಲ್ಲು → ಕ್ವಾರ್ಟ್‌ಜೈಟ್, ಶೇಲ್ → ಸ್ಲೇಟ್, ಗ್ರಾನೈಟ್ → ನೀಸ್. ಈ ಮೂರನ್ನೂ ಶಿಲಾಚಕ್ರ ಜೋಡಿಸುತ್ತದೆ — ಮೇಲೆ ಸೂರ್ಯನ ಶಕ್ತಿ, ಒಳಗೆ ಭೂಮಿಯ ಶಾಖ ನಡೆಸುವ ದೊಡ್ಡ ಮರುಬಳಕೆ ಯಂತ್ರದಂತೆ. (→ English: rock cycle · हिन्दी: शैल चक्र)

In exam EnglishBy weight the crust is mostly oxygen, followed by silicon, aluminium and iron, while iron leads for the Earth as a whole. Igneous rocks form from cooling magma: granite is intrusive, basalt is extrusive, and the Deccan Traps are basalt. Sedimentary rocks are layered, hold fossils and include sandstone, shale, limestone and coal. Metamorphic rocks are changed by heat and pressure without melting: limestone becomes marble, sandstone quartzite, shale slate and granite gneiss. The rock cycle links all three families, driven by the Sun's energy at the surface and the Earth's heat within.

Exam traps

Recap

Practice questions

Q1. In which month is the Earth nearest to the Sun?

  1. Early January
  2. Late March
  3. Early July
  4. Late September
Show answer

Answer: A. Early January

Perihelion, the Earth's closest point to the Sun, falls in early January, during the northern winter. Early July is aphelion, the farthest point. Late March and late September are near the equinoxes, which are about the overhead Sun reaching the equator, not about distance.

Q2. Consider the following statements:
1. The Earth's axis is tilted about 23½° from the perpendicular to the plane of its orbit.
2. At the equinoxes, the noon Sun is overhead at the Tropic of Cancer.
Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2
Show answer

Answer: A. 1 only

Statement 1 is correct. Statement 2 is wrong: at the equinoxes the overhead Sun is at the equator; it reaches the Tropic of Cancer at the June solstice. So (b) and (c) are wrong because they accept statement 2, and (d) is wrong because statement 1 is correct.

Q3. When it is 12 noon at Greenwich (0°), what is the local time at a place on 45°E?

  1. 9:00 a.m.
  2. 3:00 p.m.
  3. 12:45 p.m.
  4. 3:45 p.m.
Show answer

Answer: B. 3:00 p.m.

The difference is 45°, and 45 × 4 minutes = 180 minutes = 3 hours. The place is east of Greenwich, so it is ahead: 12 noon + 3 hours = 3:00 p.m. 9:00 a.m. wrongly subtracts; 12:45 p.m. treats 45° as 45 minutes; 3:45 p.m. adds an extra 45 minutes.

Q4. The Tropic of Cancer does NOT pass through which one of the following states?

  1. Jharkhand
  2. Tripura
  3. Odisha
  4. Mizoram
Show answer

Answer: C. Odisha

The Tropic of Cancer crosses Gujarat, Rajasthan, Madhya Pradesh, Chhattisgarh, Jharkhand, West Bengal, Tripura and Mizoram. Jharkhand, Tripura and Mizoram are on that list; Odisha lies wholly south of the tropic.

Q5. Consider the following statements about the International Date Line:
1. It follows the 180° meridian exactly, without any bends.
2. A traveller crossing it westward moves the date forward by one day.
Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2
Show answer

Answer: B. 2 only

Statement 1 is wrong: the line runs roughly along 180° but bends around land and island groups so that no country is split between two dates. Statement 2 is correct. So (a) and (c) are wrong because they accept statement 1, and (d) is wrong because statement 2 is correct.

Q6. The shadow zone in which no direct P waves are recorded lies at an angular distance from the epicentre of about:

  1. 0° to 105°
  2. 105° to 145°
  3. 145° to 180°
  4. 35° to 105°
Show answer

Answer: B. 105° to 145°

Direct P waves are missing between about 105° and 145°. Up to 105° both P and S waves arrive directly, so 0°–105° and 35°–105° are wrong; beyond 145° P waves appear again, so 145°–180° is wrong.

Q7. Consider the following statements:
1. Iron is the most abundant element in the Earth's crust by weight.
2. Iron is the most abundant element in the Earth as a whole by mass.
Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2
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Answer: B. 2 only

Statement 1 is wrong: oxygen (about 46 percent) leads in the crust, with iron only fourth. Statement 2 is correct because the core is mostly iron. So (a) and (c) are wrong because they accept statement 1, and (d) is wrong because statement 2 is correct.

Q8. Which one of the following pairs of rock and rock family is correctly matched?

  1. Basalt : sedimentary
  2. Marble : metamorphic
  3. Shale : igneous
  4. Granite : metamorphic
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Answer: B. Marble : metamorphic

Marble is limestone changed by heat and pressure, so it is metamorphic. Basalt is extrusive igneous, not sedimentary; shale is sedimentary, not igneous; granite is intrusive igneous, not metamorphic (it turns into gneiss when metamorphosed).

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