Question

What is the core theme of the passage?

• A. Magnetic field reversal
• B. The formation of magma
• C. The location of mid-ocean ridges
• D. Plate tectonic theory
• A. Subduction zone
• B. Lithosphere
• C. Fault systems
• D. Geomagnetic field
• A. They move in relationship to one another
• B. They have unchanging borders
• C. They are located far beneath the lithosphere
• D. They have the same shape
• A. It is a relatively inflexible layer of the Earth
• B. It includes the crust and some of the mantle of the Earth
• C. It is made up entirely of volcanic ash
• D. It is divided into plates of various shapes and sizes
• A. It analyses the association of plate boundaries
• B. It indicates the amount of magma present in earth's crust
• C. It clarifies formation of new lithosphere
• D. It supports the hypothesis of sea-floor spreading
• A. Date of a volcanic eruption
• B. Speed of sea-floor spreading
• C. Width of oceanic crust
• D. Future behavior of the geomagnetic field
• A. Magma rises from earth's crust
• B. Polarity of magnetic field is maintained
• C. Tectonic plates are incorporated into the mantle
• D. An equal amount of lithospheric material is consumed elsewhere
• A. Tectonic plates
• B. Oceanic crust
• C. Ferromagnetic minerals
• D. Geomagnetic field

Answer 1

The Correct Option is D

This question asks for the central idea that ties the whole passage together, not just one detail from it.

1. Magnetic field reversal: This is only discussed in the third paragraph as evidence that supports sea floor spreading. It is a supporting detail, not the main theme.
2. The formation of magma: Magma is mentioned only in passing, in the sentence about ferromagnetic minerals becoming magnetized. It is never the focus of the passage.
3. The location of mid-ocean ridges: Mid-ocean ridges are mentioned several times as one part of the process, but their location is never actually discussed. This detail alone cannot summarize the passage.
4. Plate tectonic theory: The very first sentence introduces this theory, and every paragraph after that, lithosphere motion, subduction zones, sea floor spreading, magnetic evidence, builds the case for it. This is the thread that runs through the whole passage.

The passage opens by defining plate tectonic theory and then spends the rest of its length explaining how the lithosphere moves, how it is destroyed at subduction zones, and how sea floor spreading and magnetic stripe evidence back up the theory. So the core theme is plate tectonic theory, option (d).

Let's summarize:

• Every other option names a small detail used somewhere in the passage to support the main idea.
• Only "plate tectonic theory" covers what all three paragraphs are actually building toward.

The correct answer is plate tectonic theory.

Answer 2

The question asks which item is actually created at mid-ocean ridges, based on what the passage states directly.

1. Subduction zone: The passage says the subduction zone is where lithosphere is destroyed, not created. This is the opposite of what the question asks.
2. Lithosphere: The passage states, "A mid-ocean ridge is a boundary between plates where new lithospheric material is injected from below," and later adds that "new lithosphere can be created at the mid-ocean ridges." This directly answers the question.
3. Fault systems: Fault systems are said to be associated with both kinds of plate boundary, but they are not described as being created at mid-ocean ridges specifically.
4. Geomagnetic field: The geomagnetic field already exists and gets recorded in the rock; it is not something that mid-ocean ridges create.

Since the passage explicitly says new lithospheric material is injected and new lithosphere is created at mid-ocean ridges, the correct option is (b) Lithosphere.

Let's summarize:

• Mid-ocean ridges are the site of creation; subduction zones are the site of destruction.
• Only lithosphere is named directly as something created there.

The correct answer is Lithosphere.

Answer 3

This question checks which statement about tectonic plates the passage actually supports.

1. They move in relationship to one another: The passage states, "in general the plates are in motion with respect to one another." This matches the option word for word in meaning.
2. They have unchanging borders: The passage describes plates diverging at mid-ocean ridges and colliding at subduction zones, which means their borders are active, not unchanging.
3. They are located far beneath the lithosphere: This is backwards. The plates are pieces of the lithosphere itself, not something located beneath it.
4. They have the same shape: The passage says the lithosphere "is divided into a few dozen plates of various sizes and shapes," which directly contradicts this option.

Only the first option is backed by the passage, so the correct answer is (a) They move in relationship to one another.

Let's summarize:

• The passage confirms plate motion, not fixed borders or identical shapes.
• Plates are part of the lithosphere, not below it.

The correct answer is that tectonic plates move in relationship to one another.

Answer 4

This question wants the statement about the lithosphere that the passage does NOT support, since it asks for what is least likely to be true.

1. It is a relatively inflexible layer of the Earth: The passage calls the lithosphere "the comparatively rigid outer layer of the Earth," which matches inflexible. This is supported.
2. It includes the crust and some of the mantle of the Earth: The passage says the lithosphere "includes all the crust and part of the underlying mantle." This is supported.
3. It is made up entirely of volcanic ash: The passage never mentions volcanic ash at all. It describes the lithosphere as crust plus part of the mantle, made of rigid rock, not ash. This statement has no support and conflicts with the description given.
4. It is divided into plates of various shapes and sizes: The passage says the lithosphere "is divided into a few dozen plates of various sizes and shapes." This is supported.

Since three options are directly confirmed by the passage and one, volcanic ash, is never mentioned and conflicts with the crust and mantle description, the least likely to be true is (c).

Let's summarize:

• Rigidity, crust plus mantle, and division into plates are all stated facts.
• "Made up entirely of volcanic ash" is an unsupported and inaccurate claim.

The correct answer is that the lithosphere is made up entirely of volcanic ash.

Answer 5

This question asks what the periodic reversal of the Earth's magnetic field tells us, according to the author.

1. It analyses the association of plate boundaries: The passage discusses plate boundary types, mid-ocean ridge and subduction zone, separately from the magnetic reversal discussion. Magnetic reversal is not linked to comparing boundary types.
2. It indicates the amount of magma present in earth's crust: Magma is mentioned as the source of the magnetized rock, but the reversal itself is never said to measure magma quantity.
3. It clarifies formation of new lithosphere: Lithosphere formation is explained earlier in the passage through the mid-ocean ridge discussion, not through the magnetic reversal evidence.
4. It supports the hypothesis of sea-floor spreading: The passage says, "The hypothesis was substantiated soon afterward by the discovery that periodic reversals of the Earth's magnetic field are recorded in the oceanic crust." This directly states that the reversal evidence backs up sea floor spreading.

Since the passage explicitly links the magnetic reversal discovery to substantiating, meaning supporting, the sea floor spreading hypothesis, the correct answer is (d).

Let's summarize:

• "Substantiated" in the passage means the same as "supports" in the option.
• The other options describe things the passage discusses elsewhere, not what the reversal itself proves.

The correct answer is that it supports the hypothesis of sea-floor spreading.

Answer 6

This question is answered by the very last sentence of the passage, which directly explains what stripe width tells us.

1. Date of a volcanic eruption: The passage says the oceanic crust can be "dated independently," but it links dating to the crust as a whole record, not specifically to the width of individual stripes.
2. Speed of sea-floor spreading: The passage states plainly, "The width of the stripes indicates the rate of the sea-floor spreading." Rate and speed mean the same thing here, so this matches exactly.
3. Width of oceanic crust: This confuses the width of the magnetic stripes with the width of the crust itself; the passage never equates the two.
4. Future behavior of the geomagnetic field: The stripes record past reversals, not future behavior, so this cannot be right.

Since the passage's closing line directly ties stripe width to the rate of sea floor spreading, the correct answer is (b).

Let's summarize:

• "Rate of the sea-floor spreading" and "speed of sea-floor spreading" are the same idea.
• None of the other options are ever connected to stripe width in the text.

The correct answer is speed of sea-floor spreading.

Answer 7

The question asks for the specific condition, stated in the passage, that must hold for new lithosphere to form at mid-ocean ridges.

1. Magma rises from earth's crust: Magma rising is mentioned later, in the sea floor spreading paragraph, but it is not the condition tied to lithosphere creation in this sentence.
2. Polarity of magnetic field is maintained: Magnetic polarity is discussed only in connection with the magnetic stripe evidence, not with the size or balance of the Earth.
3. Tectonic plates are incorporated into the mantle: This describes what happens at a subduction zone to the plate that dives under another, not the condition for new lithosphere to be created at a ridge.
4. An equal amount of lithospheric material is consumed elsewhere: The passage states directly, "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." This is an exact restatement of the passage's own condition.

Because the Earth's size stays the same, creation at ridges must be balanced by destruction somewhere else, which the passage names directly. So the correct option is the one stating that an equal amount of lithospheric material is consumed elsewhere.

Let's summarize:

• The passage uses an "only if" condition, which is a strong signal to look for matching wording elsewhere in the same sentence.
• The correct option repeats that condition almost word for word.

The correct answer is that an equal amount of lithospheric material is consumed elsewhere.

Answer 8

This question is answered almost word for word by a sentence near the end of the passage.

1. Tectonic plates: Plates are the larger structures that move and collide; they are never described as recording magnetic history.
2. Oceanic crust: The passage states, "The oceanic crust thus serves as a magnetic tape recording of the history of the geomagnetic field that can be dated independently." This is an exact match for the question.
3. Ferromagnetic minerals: These minerals are what get magnetized within the rock, but the passage identifies the oceanic crust as a whole, not the minerals alone, as the magnetic tape.
4. Geomagnetic field: The geomagnetic field is the thing being recorded, not the recording medium itself, so this cannot be the answer.

Since the passage names the oceanic crust directly as the magnetic tape recording, the correct answer is (b).

Let's summarize:

• The recording medium is the oceanic crust; the geomagnetic field is what is being recorded.
• Ferromagnetic minerals are part of the crust's rock, not the recording surface named by the author.

The correct answer is oceanic crust.