Fossils of ancient plants and animals are found mainly in which type of rock?
- A.Igneous rocks
- B.Sedimentary rocks
- C.Metamorphic rocks
- D.Plutonic rocks
Correct answer
Explanation
The correct answer is B, sedimentary rocks. They are built up layer by layer as sediment settles over the remains of living things and hardens gently, so shells, bones and plant matter survive as fossils. The same layered basins hold coal and petroleum, which makes this family the most valuable one economically.
Option A, igneous rocks, form from molten magma or lava at temperatures that destroy every trace of organic material. Option C, metamorphic rocks, may begin as fossil-bearing sedimentary rock, but the heat and pressure of metamorphism deform and erase the fossils. Option D, plutonic rocks, is only another name for intrusive igneous rocks such as granite, so it fails for the same reason as option A. Remember that layering, or stratification, and fossils always point to the sedimentary family.
Read the full article: Structure of the Earth and Rocks: Layers, Waves and Types
Practice Questions
View allThe boundary that separates the crust from the mantle is known as the
- A.Conrad discontinuity
- B.Mohorovicic discontinuity
- C.Gutenberg discontinuity
- D.Lehmann discontinuity
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Named after the Croatian seismologist who noticed that earthquake waves suddenly speed up at a certain depth, it marks the base of the crust and the top of the mantle, and is commonly shortened to the Moho.
Read the full explanation →Which of the following seismic waves cannot travel through liquids?
- A.Primary or P waves
- B.Secondary or S waves
- C.Surface or L waves
- D.All three types
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They are transverse waves, in which particles vibrate at right angles to the direction of travel, and such motion cannot be sustained in a fluid, so S waves die out at the outer core.
Read the full explanation →Marble is a metamorphic rock formed from which of the following parent rocks?
- A.Sandstone
- B.Shale
- C.Limestone
- D.Granite
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Limestone is a sedimentary rock made largely of calcium carbonate, and when heat and pressure recrystallise it without melting it, the result is marble, the stone used in the Taj Mahal and in the Dilwara temples.
Read the full explanation →The Deccan Trap of peninsular India is composed mainly of which rock?
- A.Granite
- B.Basalt
- C.Limestone
- D.Gneiss
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The Deccan Trap was formed by vast fissure eruptions in which lava spread over the surface and cooled quickly, giving a fine-grained extrusive igneous rock, basalt.
Read the full explanation →Which element is the most abundant in the Earth crust by weight?
- A.Silicon
- B.Aluminium
- C.Oxygen
- D.Iron
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Almost half the weight of the crust, about 46.6 per cent, is oxygen, because it is locked into the silicate minerals of which nearly all crustal rocks are made rather than existing as free gas.
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