Which one of the following 'discontinuities' separates the Earth's crust from the mantle?
- A.Gutenberg
- B.Mohorovicic
- C.Conrad
- D.Repetti
Correct answer
Explanation
The correct answer is B, Mohorovicic. The Mohorovicic discontinuity, or Moho, is the boundary between the crust and the mantle, where seismic waves suddenly speed up.
The Moho was identified in 1909 by the Croatian seismologist Andrija Mohorovicic, who noticed that earthquake waves travel faster below a certain depth. It lies about 30-35 km deep on average under the continents, deeper under high mountains, and only about 5-10 km below the ocean floor. The rocks below it, in the mantle, are denser than those of the crust.
A is wrong because the Gutenberg discontinuity, about 2,900 km deep, separates the mantle from the outer core.
C is wrong because the Conrad discontinuity lies within the continental crust, between its upper granitic (sial) and lower basaltic (sima) layers.
D is wrong because the Repetti discontinuity separates the upper mantle from the lower mantle.
Exam tip: Conrad (within crust) → Moho (crust-mantle) → Repetti (upper-lower mantle) → Gutenberg (mantle-core) → Lehmann (outer-inner core).
Practice Questions
View allWhich one of the following is applicable to collision-coalescence process of precipitation?
- A.Clouds which do not extend beyond the freezing level
- B.Clouds which extend beyond the freezing level
- C.All types of clouds
- D.Cirrocumulus cloud
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Collision-coalescence is the way rain forms in warm clouds, whose tops stay below the level where water freezes. In such clouds all droplets are liquid.
Read the full explanation →Identify the type of drainage pattern on the basis of the given characteristics :
1. It represents the most common pattern of streams and their tributaries
2. It occurs in areas of uniform rock type and regular slope
3. A map, or aerial photograph, shows a pattern like the veins on a leaf— smaller streams join the main stream at an acute angle
Select the correct answer.
- A.Dendritic
- B.Radial
- C.Trellis
- D.Centripetal
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A pattern that looks like the branches of a tree or the veins of a leaf, formed on uniform rock with a regular slope, is dendritic.
Read the full explanation →The Research Design and Standards Organization is the R&D wing of which one of the following organizations ?
- A.Bhabha Atomic Research Centre
- B.Indian Space Research Organization
- C.Indian Railways
- D.Defence Research and Development Organization
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The Research Design and Standards Organisation (RDSO) is the sole research and development wing of the Ministry of Railways. RDSO is headquartered at Lucknow.
Read the full explanation →Which one of the following Indian States has recorded negative growth population as per Census 2011?
- A.Manipur
- B.Mizoram
- C.Tripura
- D.Nagaland
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Nagaland was the only Indian state whose population fell between 2001 and 2011; its decadal growth rate in Census 2011 was about −0.6 per cent.
Read the full explanation →Piecing together the puzzle of geologic time to create and analyze historical maps of the Earth is known as
- A.paleoclimatology
- B.paleogeomorphology
- C.paleolithology
- D.paleogeography
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Paleogeography is the study of the Earth's geography in the geological past, and its main product is a set of maps showing where continents, oceans, mountains and shorelines lay at different times.
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