Study this in the app →

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

Quick recap: geomorphology on one page

मराठीत स्पष्टीकरण

Geomorphology: plates, earthquakes, volcanoes and landforms · 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 four parts condensed for quick revision: drift, sea-floor spreading and plate tectonics, earthquakes, tsunamis and volcanoes, weathering, mass movement and rivers, and the landforms of glaciers, wind, groundwater and waves, with a one-table overview and eight mixed questions.

Each idea is explained first in Marathi (मराठी), 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 Marathi and revise it in English.

पृथ्वीचा पृष्ठभाग दोन विरोधी शक्ती घडवतात — एक विटा रचणारा गवंडी, दुसरा त्या झिजवणारा पाऊस. अंतर्जनित बले आतल्या उष्णतेने भूपट्ट हलवतात, पर्वत उचलतात, भूकंप, ज्वालामुखी आणतात. बहिर्जनित बले सूर्याची ऊर्जा व गुरुत्वाने त्यांना झिजवतात. भाग 1: भूपट्ट; भाग 2: भूकंप, ज्वालामुखी; भाग 3: विदारण, नद्या; भाग 4: बर्फ, वारा, भूजल, लाटा. (→ English: endogenic forces, exogenic forces · हिन्दी: अंतर्जात बल, बहिर्जात बल)

In exam EnglishThis chapter explains how the Earth's surface is shaped by two opposing sets of forces. endogenic forces, driven by the Earth's internal heat, build relief: they move plates, raise mountains, and cause earthquakes and volcanoes. exogenic forces, driven by the Sun's energy and gravity, wear that relief down through weathering, erosion and deposition. Part 1 covers drift and plate tectonics, Part 2 earthquakes, tsunamis and volcanoes, Part 3 weathering, mass movement and rivers, and Part 4 glaciers, wind, groundwater and waves.

1912 मध्ये वेगेनरने खंडवहन सांगितले — खंड एकेकाळी पँजियात जोडलेले होते, नंतर लॉरेशिया, गोंडवानालँड असे फुटले; भारत गोंडवानात. फाटलेल्या कागदाचे तुकडे जुळवावे तसे किनारे जुळणे, एकाच प्रकारचे खडक, जीवाश्म हे पुरावे; पण हलवणारी शक्ती सांगता आली नाही. होम्सने संवहन प्रवाह, हेसने सागरतळ विस्तार सांगितला — कटकांवर नवा तळ, खंदकांत नाश; म्हणून सागरतळ सुमारे 20 कोटी वर्षांपेक्षा जुना नाही. (→ English: continental drift, sea-floor spreading · हिन्दी: महाद्वीपीय विस्थापन, सागर नितल प्रसरण)

In exam EnglishIn 1912 Alfred Wegener put forward continental drift, arguing that the continents were once joined as Pangaea, with a single ocean, Panthalassa, around it; Pangaea broke into Laurasia and Gondwanaland, and India was part of Gondwanaland. His evidence included the fit of the Atlantic coasts, matching rocks and tillite, and fossils such as Mesosaurus and Glossopteris, but his proposed forces were too weak. Holmes suggested mantle convection in the 1930s, and Hess explained sea-floor spreading in the early 1960s, confirmed by symmetrical magnetic stripes: new crust forms at mid-ocean ridges and is destroyed at trenches, so no ocean floor is older than about 200 million years.

भूपट्ट विवर्तनिकीनुसार पृथ्वीचे वरचे कवच सात मोठ्या व अनेक लहान भूपट्टांत तुटून दरवर्षी काही सेंटीमीटर सरकते — फुटलेल्या अंड्याच्या कवचाच्या तुकड्यांसारखे. दूर जातात तिथे नवा तळ; जवळ येतात तिथे अधोगमन किंवा धडक; बाजूबाजूने घासतात तिथे काही बनत नाही, नष्ट होत नाही. सागर–खंड धडकले की अँडीजसारख्या ज्वालामुखी रांगा; खंड–खंड धडकले की ज्वालामुखी नसलेले वली पर्वत. भारत उत्तरेकडे सरकला, दख्खनचे पठार (ट्रॅप) बनले, आशियाशी धडकून हिमालय उठला — अजूनही उठतो आहे. (→ English: plate tectonics, subduction · हिन्दी: प्लेट विवर्तनिकी, अधोगमन)

In exam Englishplate tectonics, developed in the late 1960s, treats the lithosphere as seven major plates and many minor ones moving a few centimetres a year over the asthenosphere. Divergent (constructive) boundaries create crust at ridges and rifts; convergent (destructive) boundaries destroy it by subduction or crumple it in collisions; transform (conservative) boundaries such as the San Andreas Fault neither create nor destroy crust. Ocean-continent subduction builds volcanic ranges like the Andes, ocean-ocean subduction builds trenches and island arcs, and continent-continent collision builds fold mountains without active volcanoes. India drifted north from Gondwanaland over the Réunion hotspot, which produced the Deccan Traps, and its collision with Asia raised the Himalaya, which is still rising.

भूकंप म्हणजे खडकांत साठलेली ऊर्जा अचानक सुटणे — जास्त ताणलेली स्प्रिंग सोडल्यासारखे. आत सुरुवात होते ते केंद्र; त्याच्या अगदी वर जमिनीवर अपिकेंद्र. तीव्रतामान एकच आकडा (ऊर्जा); तीव्रता गावागावात बदलते (नुकसान). त्सुनामी खोल समुद्रात वेगाने, कमी उंचीने जाऊन किनाऱ्याजवळ मोठी होते; 2004 नंतर हैदराबादला इशारा केंद्र. भारतात क्षेत्रे II ते V. (→ English: earthquake, epicentre, tsunami · हिन्दी: भूकंप, अधिकेंद्र, सुनामी)

In exam EnglishAn earthquake is a sudden release of energy stored in rocks, usually by slip along a fault. The focus is where rupture begins and the epicentre is the point on the surface directly above it. Magnitude (Richter or moment magnitude) is a single logarithmic measure of energy; intensity (Modified Mercalli, I to XII) describes effects and varies from place to place. A tsunami is fast but low in deep water and grows tall only near the coast; after the 2004 Indian Ocean tsunami, India set up its warning centre at INCOIS, Hyderabad. Earthquakes cluster along the Circum-Pacific belt, the Alpine-Himalayan belt and the mid-ocean ridges, and India's seismic zones run from II to V under IS 1893 (Part 1): 2016.

ज्वालामुखी म्हणजे शिलारस लाव्हा, वायू, राख म्हणून बाहेर येण्याचे दार. पातळ लाव्हा — मध ओतल्यासारखा हळू वाहून ढालीचा आकार (हवाई); घट्ट लाव्हा — सोडा बाटली हलवून उघडल्यासारखा स्फोट (फुजी). दख्खनचे ट्रॅप भेगांतून पुरासारखा वाहिलेला लाव्हा. आतच थंड झाला तर बॅथोलिथ, सिल (थरांना समांतर), डाइक (थर आडवे कापत). अंदमान समुद्रातील बॅरन बेट आपला एकमेव जागृत ज्वालामुखी; नारकोंडम निद्रिस्त. (→ English: volcano, magma · हिन्दी: ज्वालामुखी, मैग्मा)

In exam EnglishA volcano is an opening through which magma reaches the surface as lava, gases and ash. Volcanoes form at subduction zones, at mid-ocean ridges and over hotspots. Shield volcanoes, built of fluid basalt, erupt gently, as in Hawaii; composite volcanoes, built of viscous, silica-rich lava, erupt explosively, as at Fuji; calderas form when a volcano's summit collapses; and flood basalts such as the Deccan Traps pour from fissures. Magma that cools below the surface forms intrusive bodies such as batholiths, laccoliths, lopoliths and phacoliths; sills spread out between rock layers, whereas dykes slice across them. Barren Island in the Andaman Sea is India's only active volcano, and Narcondam is dormant.

विदारण खडक जागीच फोडते — भौतिक, रासायनिक, जैविक; उष्ण-दमट भागात रासायनिक वेगाने. मग वस्तुमान हालचाल गुरुत्वाने तो खाली आणते — हळू सरकण्यापासून अचानक दरड कोसळण्यापर्यंत; हिमालय, पश्चिम घाटात जास्त. नदी वरच्या भागात 'V' दऱ्या, धबधबे कोरते; खाली आल्यावर सापासारखी वळणे घेत मैदाने बांधते. गाळ जास्त झाला तर त्रिभुज प्रदेश (गोदावरी, कृष्णा); भरती वाहून नेत असेल तर खाडी (नर्मदा, तापी). (→ English: weathering, mass movement, delta · हिन्दी: अपक्षय, वृहत् संचलन, डेल्टा)

In exam Englishweathering breaks rock down in place, physically (frost wedging, heating and cooling, exfoliation), chemically (carbonation, oxidation, hydrolysis) or biologically; chemical weathering is fastest in hot, wet climates. mass movement then carries loosened material downslope under gravity, from slow soil creep to sudden landslides, which are most frequent in the Himalaya and the Western Ghats. Rivers erode most in their steep upper course, cutting V-shaped valleys, gorges and waterfalls; in the gentler middle and lower course they swing into meanders, leave ox-bow lakes, and build floodplains, levees and alluvial fans. Where sediment outpaces the sea a river builds a delta, as the Godavari and Krishna do; where tides scour it away, as for the Narmada and Tapi, it ends in an estuary.

बाकी शक्तीही तोच नियम — जोर असेल तर झीज, कमी झाला की टाकणे. हिमनदी सर्क, हॉर्न, 'U' दऱ्या, फियॉर्ड कोरते आणि न चाळलेला हिमोढ टाकते; तिचे वितळलेले पाणी चाळलेली वाळू पसरवते. वाळवंटी वारा छत्रीसारखे खडक, बारखान टेकड्या बनवतो. चुनखडी विरघळवणारे पाणी कार्स्ट भूरूपे, गुहांत स्टॅलॅक्टाइट-स्टॅलॅग्माइट. लाटा कडे, स्टॅक कापतात आणि पुळणी, चिलिकासारखी खाजणे बांधतात. (→ English: glacier, moraine, karst topography · हिन्दी: हिमनद, हिमोढ़, कार्स्ट स्थलाकृति)

In exam EnglishThe other agents repeat the same pattern of erosion where energy is high and deposition where it falls. A glacier carves cirques, arêtes, horns, U-shaped and hanging valleys and fjords, and drops unsorted till as moraines and drumlins, while its meltwater leaves sorted eskers and outwash plains. Wind in deserts makes deflation hollows and mushroom rocks and piles sand into barchans and seif dunes, with fine silt settling far away as loess. In limestone, dissolving groundwater creates karst topography with sinkholes, uvalas and poljes, and caves decorated by stalactites and stalagmites. Waves cut cliffs, arches and stacks and build beaches, spits, bars and lagoons such as Chilika. The table below gathers the facts most often tested.
The chapter at a glance
TopicMust-know factsCommon trap
Drift and spreadingWegener 1912; Holmes 1930s (convection); Hess early 1960s (spreading)India was in Gondwanaland, not Laurasia
Plate boundariesDivergent = constructive; convergent = destructive; transform = conservativeHimalaya (collision) has no active volcanoes
EarthquakesFocus inside, epicentre above; magnitude one number, intensity variesNo Zone I in India; zones II to V
VolcanoesShield (fluid basalt, gentle); composite (viscous, explosive)Deccan Traps are flood basalt, not a shield volcano
RiversV-valleys and waterfalls upstream; meanders, ox-bows, deltas downstreamNarmada and Tapi form estuaries, not deltas
Ice, wind, karst, wavesMoraines unsorted; barchan horns downwind; stalactites hangFjord = drowned glacial valley; ria = drowned river valley

Exam traps

Recap

Practice questions

Q1. Who among the following explained the theory of sea-floor spreading in the early 1960s?

  1. Alfred Wegener
  2. Arthur Holmes
  3. Harry Hess
  4. Charles Richter
Show answer

Answer: C. Harry Hess

Harry Hess proposed sea-floor spreading in the early 1960s. Wegener proposed continental drift in 1912, Holmes suggested mantle convection currents in the 1930s, and Richter devised an earthquake magnitude scale.

Q2. Consider the following statements:
1. At transform plate boundaries, crust is neither created nor destroyed.
2. A continent-continent collision typically produces chains of active volcanoes.
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: transform boundaries are conservative. Statement 2 is wrong: collisions such as the one that built the Himalaya produce fold mountains without active volcanoes. So (b) and (c) accept the wrong statement and (d) rejects the correct one.

Q3. With reference to earthquakes, which one of the following statements is correct?

  1. The epicentre is the point inside the Earth where rupture begins.
  2. Intensity of an earthquake is the same at every place it is felt.
  3. A tsunami is low in deep water and grows tall near the coast.
  4. India's seismic zones range from I to V.
Show answer

Answer: C. A tsunami is low in deep water and grows tall near the coast.

Option (c) is correct. The point where rupture begins is the focus, not the epicentre; intensity varies from place to place; and India's zones run from II to V, with no Zone I.

Q4. Which one of the following is India's only active volcano?

  1. Narcondam
  2. Barren Island
  3. Deccan Traps
  4. Manikaran
Show answer

Answer: B. Barren Island

Barren Island in the Andaman Sea is India's only active volcano. Narcondam is dormant, the Deccan Traps are ancient flood basalts, and Manikaran is known for hot springs, not a volcano.

Q5. Which of the following rivers end in estuaries rather than deltas?
1. Narmada
2. Tapi
3. Godavari
Select the correct answer using the code given below:

  1. 1 and 2 only
  2. 2 and 3 only
  3. 1 and 3 only
  4. 1, 2 and 3
Show answer

Answer: A. 1 and 2 only

The west-flowing Narmada and Tapi end in estuaries. The Godavari builds a delta on the east coast, so every option including 3, namely (b), (c) and (d), is wrong.

Q6. Consider the following statements:
1. Weathering involves the transport of rock material away from its source.
2. Chemical weathering is fastest in hot and humid climates.
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: weathering happens in place, while transport is erosion. Statement 2 is correct. So (a) and (c) accept the wrong statement and (d) rejects the correct one.

Q7. Match List I (landform) with List II (agent):
List I
A. Esker
B. Barchan
C. Uvala
D. Tombolo
List II
1. Waves
2. Groundwater
3. Wind
4. Glacial meltwater
Select the correct answer using the code given below:

  1. A-4, B-3, C-2, D-1
  2. A-3, B-4, C-2, D-1
  3. A-4, B-3, C-1, D-2
  4. A-2, B-3, C-4, D-1
Show answer

Answer: A. A-4, B-3, C-2, D-1

Eskers are laid down by glacial meltwater, barchans by wind, uvalas by groundwater dissolving limestone, and tombolos by waves: A-4, B-3, C-2, D-1. Option (b) swaps the esker and barchan, (c) swaps the uvala and tombolo, and (d) gives the esker to groundwater and the uvala to meltwater.

Q8. When the sea floods a glaciated valley, producing a long, deep inlet with steep walls, the feature is called a:

  1. Ria
  2. Fjord
  3. Lagoon
  4. Estuary
Show answer

Answer: B. Fjord

A fjord is a glacial trough that the sea has flooded. A ria is a river valley flooded by the sea, a lagoon is water cut off behind a bar or spit, and an estuary is a river mouth widened and scoured by tides.

← Part 4All parts

Study this in the Upscore app to keep notes, save it for revision, track your practice scores and follow a plan to the exam date. It's free.

Study this in the app →

Sources