Question:

Passage:

The theory of plate tectonics describes the motions of the lithosphere, the comparatively rigid outer layer of the Earth that includes all the crust and part of the underlying mantle. The lithosphere is divided into a few dozen plates of various sizes and shapes; in general the plates are in motion with respect to one another. A mid-ocean ridge is a boundary between plates where new lithospheric material is injected from below. As the plates diverge from a mid-ocean ridge they slide on a more yielding layer at the base of the lithosphere.

Since the size of the Earth is essentially constant, new lithosphere can be created at the mid-ocean ridges only if an equal amount of lithospheric material is consumed elsewhere. The site of this destruction is another kind of plate boundary: a subduction zone. There one plate dives under the edge of another and is reincorporated into the mantle. Both kinds of plate boundary are associated with fault systems, earthquakes and volcanism, but the kinds of geologic activity observed at the two boundaries are quite different.

The idea of sea-floor spreading actually preceded the theory of plate tectonics. In its original version, in the early 1960s, it described the creation and destruction of the ocean floor, but it did not specify rigid lithospheric plates. The hypothesis was substantiated soon afterward by the discovery that periodic reversals of the Earth's magnetic field are recorded in the oceanic crust. As magma rises under the mid-ocean ridge, ferromagnetic minerals in the magma become magnetized in the direction of the geomagnetic field. When the magma cooks and solidifies, the direction and the polarity of the field are preserved in the magnetized volcanic rock. Reversals of the field give rise to a series of magnetic stripes running parallel to the axis of the rift. The oceanic crust thus serves as a magnetic tape recording of the history of the geomagnetic field that can be dated independently. The width of the stripes indicates the rate of the sea-floor spreading.

Question:
According to the passage, which of the following statements about the lithosphere is least likely to be true?

Show Hint

Check the passage's own definition sentence against each option; one option introduces material never mentioned in the text.
Updated On: Jul 20, 2026
  • It is a relatively inflexible layer of the Earth
  • It includes the crust and some of the mantle of the Earth
  • It is made up entirely of volcanic ash
  • It is divided into plates of various shapes and sizes
  • Lithosphere is connected to the solid part of the earth consisting of crust and the outer mantle
Show Solution
collegedunia
Verified By Collegedunia

The Correct Option is C

Solution and Explanation

The passage defines the lithosphere as "the comparatively rigid outer layer of the Earth that includes all the crust and part of the underlying mantle," and separately states it "is divided into a few dozen plates of various sizes and shapes." Nowhere does the passage say or imply that the lithosphere is made of volcanic ash; ash is not mentioned in the text at all. So option (c) is the statement least supported, and it is the answer.

Option (a) matches "comparatively rigid," which is another way of saying inflexible. Option (b) matches "includes all the crust and part of the underlying mantle" almost word for word. Option (d) matches "divided into a few dozen plates of various sizes and shapes" exactly. Option (e) is simply a rephrasing of the same crust-plus-outer-mantle definition given in the passage, so it is also well supported. Only (c) introduces a claim the passage never makes.
Was this answer helpful?
0
0

Top IBSAT Verbal Ability & Reading Comprehension (VARC) Questions

View More Questions

Top IBSAT Plate tectonics Questions

View More Questions