Karnataka 2nd PUC Question Paper 2025 Answer Key Geology

Government of Karnataka
Karnataka Secondary Education Examination Board

Question Paper
ANSWER KEY

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Government of Karnataka
Karnataka School Examination and Assessment Board
II PUC Exam - 1 MARCH - 2025
Subject: 37- Geology Scheme of Evaluation Max. Marks: 80

PART – A
I. Answer all the following questions (5 X 1 = 5)
1. During rock cycle, how can sedimentary rock become metamorphic rock?
(a) By pressure and temperature-------------------------------------------------------------------------1 mark
2) Choose the hypabyssal rock among the following:
(b) Dolerite--------------------------------------------------------------------------------------------------1 mark
3) • The rock consists of finest particles.
• Average grain size is less than 0.01 mm.
Based on the above information, identify the rock.
(c) Shale-----------------------------------------------------------------------------------------------------1 mark
4) The rock which is formed by dynamothermal metamorphism is
(a) Schist ----------------------------------------------------------------------------------------------------1 mark
5) Which of the following is the youngest era?
(d) Cenozoic------------------------------------------------------------------------------------------------1 mark

II. Fill in the blanks: (5x1=5)
(Dip, Sills, Transport-direction, Brunton compass, Fossils, Strike)
6) Sills are thin, tabular concordant bodies. -----------------------------------------------------------1 mark
7) Cross-bedding and ripple structures help us to know the Transport-direction of sediments. -1 mark
8) Dip is defined as the angle of inclination with horizontal bed. ----------------------------------1 mark
9) Brunton compass is used to measure attitude of beds. --------------------------------------------1 mark
10) Fossils are the remains or traces of organisms of geologic past. -------------------------------1 mark

III. 11) Match the following: (5×1=5)
A B
(a) Primary rock iii. Granite--------------------------------------------------------------1 mark
(b) Pegmatite iv. Gemstone-----------------------------------------------------------1 mark
(c) Limb i. Fold------------------------------------------------------------------1 mark
(d) Himalayan mountain ii. Cenozoic era--------------------------------------------------------1 mark
(e) Glossopteris. vi. Lower Gondwana--------------------------------------------------1 mark

IIPUC EXAM-1, MARCH 2025 KSEAB 01-KANNADA MODEL ANSWERS

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IV. Answer all the following questions: (5x1=5)
12) What are secondary rocks?
Ans) Sedimentary rocks or Define-----------------------------------------------------------------------1 mark
13) What is the composition of shale?
Ans) Clay minerals ----------------------------------------------------------------------------------------1 mark
14) Give any two examples for metamorphic rocks.
Ans) Schists, granulite, eclogite, slate, marble, quartzite, gneiss, charnockite (any two) -------1 mark
15) Define axis of a fold.
Ans) line of intersection of axial plane with bedding plane------------------------------------------1 mark
16) What is corallum?
Ans) Entire body of coral/calceola----------------------------------------------------------------------1 mark

PART - B
V. Answer any seven of the following questions: (7×2=14)
17) Define Texture.
Ans) • small scale features observed in microscope.
• shows mutual relation between mineral and glassy matter--------------------------------2 marks
18) What is Pahoehoe structure?
Ans) •Also called as ropy lava
• low viscosity and basic composition
• Appears like rope
• Igneous rock structure. (Any two points) ----------------------------------------2 marks
19) Write the uses of igneous rocks.
Ans) • Economically important
• Building material.
• Road construction.
• Decorative purposes. ----------------------------------------------------------------------------2 marks
20) How are sedimentary rocks formed?
Ans) Weathering, Transportation, Deposition, Lithification, Diagenesis-------------------------2 marks
21) Define the roundness in sedimentary rocks.
Ans) • Degree of angularity of grain.
• Rounding of edges of clast. --------------------------------------------------------------------2 marks
22) Define Hypozone. Give an example.
Ans) • it is zone of metamorphism
• Temperature (550°C-1200°c), great depth
• Hydrostatic stress.
• Plutonic metamorphism--------------------------------------------------------------------------1 mark
E.g. granulite, eclogite------------------------------------------------------------------------------1 mark

IIPUC EXAM-1, MARCH 2025 KSEAB 01-KANNADA MODEL ANSWERS

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23) What is Charnockite? Mention its texture.
Ans) • Charnockite is metamorphic rock---------------------------------------------------------------1 mark
• Granoblastic texture-------------------------------------------------------------------------------1 mark
24) Define Outlier.
Ans) • Younger rock surrounded by older rock
• Erosion of older overlying rocks. -------------------------------------------------------------2 marks
25) Occurrence and distribution of Archaean rocks. Explain.
Ans) • Two third of peninsula
• Best developed in South India
• Rajasthan, Madhya Pradesh, Eastern parts of India
• Extra peninsular India along Himalayas. -----------------------------------------------------2 marks
26) Define track and trails.
Ans) • Formed over soft mud and sandy bottom.
• impressions of movement.
• Pseudo fossil--------------------------------------------------------------------------------------2 marks
27) What is mummification? Give an example.
Ans) • entire body is preserved in cold region. --------------------------------------------------------1 mark
E.g.: woolly mammoth------------------------------------------------------------------------------------1 mark
28) Define Carbonization.
Ans) • Material of plant / animal becomes Carbonized
• Undergo decomposition, loosing oxygen and nitrogen with increase in carbon---------2 marks
VI. Answer any seven of the following questions: (7 x 3 = 21)
29) Explain volcanic igneous rocks. Give an example.
Ans) Explanation-----------------------------------------------------------------------------------------2 marks
• Rocks formed on the surface
• Rapid cooling.
• Eruptive condition.
• fine grained or glassy nature.
E.g.: Rhyolite, Dacite, Trachyte, Andesite, Phonolite, Basalt, Pumice-----------------------1 mark
30) Explain aphanitic grain size of igneous rocks.
Ans) Explanation-----------------------------------------------------------------------------------------3 marks
• Refers to grains size of crystal.
• grains cannot be identified by eyes.
• microcrystalline - observed under microscope.
• cryptocrystalline- not observed under microscope.
• glassy- no traces of crystal

IIPUC EXAM-1, MARCH 2025 KSEAB 01-KANNADA MODEL ANSWERS

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31) Explain dynamothermal metamorphism. Give an example.
Ans) Explanation-----------------------------------------------------------------------------------------2 marks
• Type of metamorphism.
• Combined action of pressure, temperature and fluids
• Large scale changes in structures and chemical constituent of pre-existing rock
E.g.: Himalayas. ----------------------------------------------------------------------------------1 mark

32) With a neat labelled diagram, explain symmetrical fold.
Ans) Diagram-----------------------------------------------------------------------------------------------1 mark

Explanation------------------------------------------------------------------------------------------------2 marks
• Axial plane is vertical.
• bisect fold equally.
• Same dip on either side.

33) With a neat labelled diagram, explain the types of dips.
Ans) Diagram-----------------------------------------------------------------------------------------------1 mark

Explanation------------------------------------------------------------------------------------------------2 marks
• True dip - Perpendicular to strike
• Apparent dip - other than true dip

34) Write a note on the importance of geologic structures.
Ans) Explanation-----------------------------------------------------------------------------------------3 marks
• Economic, Petroleum, mining, environmental geology.
• Natural disaster, dam, road cut, tunnel.
• Potential groundwater.
• Seepage, sewage.

35) List the non-metallic deposits of Archaeans.
Ans) Explanation-----------------------------------------------------------------------------------------3 marks
• Mica - Bihar
• Kyanite - Singhbhum
• Sillimanite - Assam, Rajasthan
• Magnesite - Selam, Mysore
• Marble, Granite, Basalt, Slate

IIPUC EXAM-1, MARCH 2025 KSEAB 01-KANNADA MODEL ANSWERS

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36) Explain the law of order of superposition.
Ans) Explanation-----------------------------------------------------------------------------------------3 marks
• Undisturbed sequence
• Bottom sequence is older
• Overlying sequence is younger.
• Beds deposit horizontally.
• Establishing natural sequence

37) Write a note on thorax.
Ans) Explanation-----------------------------------------------------------------------------------------3 marks
• Part of trilobite.
• Consists of segments.
• Median and lateral parts.
• Lateral part known as pleurae.
• Curved downward or backward
• Fulcrum
• Termination of pleurae produced into spine
38) Define the following.
(a) Spire
(b) Peristome
(c) Suture.
Ans) Define------------------------------------------------------------------------------------------------3 marks
a. Spire - All whorls except the last.
b. Peristome - margin of aperture.
c. Suture - line between two contiguous whorls.

VII. Answer any five of the following questions: (5 x 5 = 25)
39) With a neat labelled diagram, explain porphyritic texture.
Ans) Diagram---------------------------------------------------------------------------------------------2 marks

Explanation------------------------------------------------------------------------------------------------3 marks
• Exhibit in igneous rocks.
• larger grain embedded in ground mass.
• larger grain called phenocrysts.
• E.g.: Diorite porphyry
IIPUC EXAM-1, MARCH 2025 KSEAB 01-KANNADA MODEL ANSWERS

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40) Discuss the physical properties of dolerite.
Ans) Explanation-----------------------------------------------------------------------------------------5 marks
• Hypabyassal igneous rock
• Dark colour (mafic)
• Compact and medium specific gravity
• Mineral pyroxene-plagioclase
• Mineral grains are fine to medium
• occurs as dyke.

41) Classify sedimentary rocks based on grain size.
Ans) Explanation-----------------------------------------------------------------------------------------5 marks
• Rudaceous - consist chiefly of gravel, pebbles, cobbles or boulders
• > 2 mm size.
• e.g., conglomerate and breccia.
• Arenaceous - sand grade materials
• 0.1 to 2 mm size.
• e.g., sandstones, grits, arkose, greywacke.
• Argillaceous - consist finest particles of rock,
• < 0.01 mm
• e.g., Shale.

42) With a neat labelled diagram, explain granulose structure.
Ans) Diagram---------------------------------------------------------------------------------------------2 marks

Explanation------------------------------------------------------------------------------------------------3 marks
• Metamorphic structure.
• Granular character
• Equidimensional and interlocking
• Foliation absent
• Granulite
• example: marble & quartzite

IIPUC EXAM-1, MARCH 2025 KSEAB 01-KANNADA MODEL ANSWERS

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43) Explain the types of joints.
Ans) Explanation-----------------------------------------------------------------------------------------5 marks
• Dip joint: run parallel to the dip of country rocks.
• Strike joint: run parallel to the strike of the country rocks.
• Oblique joint: runs oblique or diagonal to the strike of a bed.
• Bedding joint: oriented parallel to the bedding planes.
• Columnar joint: produced due to the tension set up during the cooling of magma,
- especially in basalts and rhyolites.
- hexagonal and polygonal shapes.

44) With a neat labelled diagram, explain the formation of fault.
Ans) Diagram---------------------------------------------------------------------------------------------2 marks

Explanation------------------------------------------------------------------------------------------------3 marks
• opposite walls along fracture/rupture move past each other
• differential movement parallel to the surface of fracture
• Relative displacement

45) Describe the geology of Karnataka.
Ans) Explanation-----------------------------------------------------------------------------------------5 marks
• Part of Indian shield
• Coastal strip of 5000 km of Tertiary and Quaternary Sediments.
• 31.250 sq.km Deccan basalt
• Archean and proterozoic rock
• Dharwar Craton
- Greenstone - granite belt
- Gneisses and granulites.
- Meta-volcanic sedimentary rock.
- Peninsular gneiss
- epicratonic basin or intracratonic sedimentary

IIPUC EXAM-1, MARCH 2025 KSEAB 01-KANNADA MODEL ANSWERS

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46) With a neat labelled diagram, explain Terebratula.
Ans) Diagram---------------------------------------------------------------------------------------------2 marks

Explanation------------------------------------------------------------------------------------------------3 marks
• bivalved, equilateral and inequivalved.
• Valves are plano-convex.
• Prominent umbo with pedicle opening.
• Hinge line is short and curved
• Composed of CaCO3
• Cretaceous age.

47) With a neat labelled diagram, explain Paradoxide.
Ans) Diagram---------------------------------------------------------------------------------------------2 marks

Explanation------------------------------------------------------------------------------------------------3 marks
• body is large, elongated & posteriorly narrow.
• head by shield is semi-circular.
• long genal spine
• broad glabella
• Arched eyes
• long thorax with 10-20 segments.
• chitinous material
• middle cambrian.

IIPUC EXAM-1, MARCH 2025 KSEAB 01-KANNADA MODEL ANSWERS

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