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655-705 (Hard)|   Assumption|         
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When volcanic lava solidifies, it becomes uniformly magnetized in the 27 Sep 2019, 04:19
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65% (hard)

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63% (02:15) correct 37% (02:22) wrong based on 865 sessions

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When volcanic lava solidifies, it becomes uniformly magnetized in the direction in which the Earth’s magnetic field points. There are significant differences in the direction of magnetization among solidified lava flows from different volcanoes that erupted at different times over the past several million years. Therefore, it must be that the direction of the Earth’s magnetic field has changed over time. Since lava flows differing by thousands of years in age often have very similar directions of magnetization, the change in the direction of the Earth’s magnetic field must take place very gradually over hundreds of thousands of years.

The argument that the direction of the Earth’s magnetic field has changed over time requires the assumption that


(A) only lava can be used to measure the direction of the Earth’s magnetic field as it existed in the distant past

(B) a single volcano can produce lava of differing consistencies during different eruptions

(C) not all solidified lava has changed the direction of its magnetization unpredictably

(D) there are fewer volcanic eruptions now than there were millions of years ago

(E) as lava flows down the side of a volcano, it picks up magnetized rocks
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C
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When volcanic lava solidifies, it becomes uniformly magnetized in the 27 Sep 2019, 04:48
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Bunuel
When volcanic lava solidifies, it becomes uniformly magnetized in the direction in which the Earth’s magnetic field points. There are significant differences in the direction of magnetization among solidified lava flows from different volcanoes that erupted at different times over the past several million years. Therefore, it must be that the direction of the Earth’s magnetic field has changed over time. Since lava flows differing by thousands of years in age often have very similar directions of magnetization, the change in the direction of the Earth’s magnetic field must take place very gradually over hundreds of thousands of years.

The argument that the direction of the Earth’s magnetic field has changed over time requires the assumption that


(A) only lava can be used to measure the direction of the Earth’s magnetic field as it existed in the distant past

(B) a single volcano can produce lava of differing consistencies during different eruptions

(C) not all solidified lava has changed the direction of its magnetization unpredictably

(D) there are fewer volcanic eruptions now than there were millions of years ago

(E) as lava flows down the side of a volcano, it picks up magnetized rocks
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Same stem, Weaken question: https://gmatclub.com/forum/when-volcani ... 06627.html
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When volcanic lava solidifies, it becomes uniformly magnetized in the 21 Oct 2019, 09:55
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chetan2u - please provide explanation
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When volcanic lava solidifies, it becomes uniformly magnetized in the 24 Oct 2019, 06:43
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The main conclusion of the Argument - The Earth's magnetic field has changed over time.

The Author relies on 2 facts to make this Suggestion.

Line 1 - General fact = Solidified Lava gets magnetized to the direction of the Magnetic Field.

Line 2 - Another Fact = Solidified Lava from different time periods point to different directions.

To make the claim that the Earth's Magnetic Field has changed, the Author has considered that the change in directions must be due to the Earth's Magnetic Field only. In this case, it happens to be a change in direction.
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When volcanic lava solidifies, it becomes uniformly magnetized in the 24 Oct 2019, 06:50
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C...strengthen the statement

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When volcanic lava solidifies, it becomes uniformly magnetized in the 22 Aug 2023, 11:01
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The argument is based on the observation that solidified lava flows from different volcanoes, which erupted at different times over millions of years, have significant differences in the direction of magnetization. This observation leads to the conclusion that the direction of the Earth's magnetic field has changed over time and that this change must occur gradually over hundreds of thousands of years.

The assumption underlying this argument is that the magnetization of lava flows accurately reflects the direction of the Earth's magnetic field at the time of their solidification. If this assumption were not true, then the argument's conclusion about changes in the Earth's magnetic field based on differences in lava magnetization would be called into question.

Among the given options:

(A) This option introduces the idea of using lava to measure the Earth's magnetic field, but it doesn't address the assumption that the magnetization of lava accurately reflects the Earth's magnetic field. It's not directly relevant to the argument.

(B) This option discusses the consistency of lava produced by a single volcano, which is not relevant to the assumption regarding whether lava magnetization accurately reflects the Earth's magnetic field.

(C) This option is directly relevant to the assumption because it suggests that not all solidified lava changes its magnetization unpredictably, which is necessary for the argument's conclusion to hold. If all lava changed its magnetization unpredictably, then the argument's basis for inferring changes in the Earth's magnetic field would be undermined.

(D) This option discusses the frequency of volcanic eruptions, which is not directly related to the assumption about the accuracy of lava magnetization.

(E) This option introduces the idea of lava flows picking up magnetized rocks, but it doesn't address the assumption about the accuracy of lava magnetization in reflecting the Earth's magnetic field.

The correct answer is (C) because it addresses the critical assumption that not all solidified lava changes the direction of its magnetization unpredictably, which is necessary for the argument's conclusion to hold.
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When volcanic lava solidifies, it becomes uniformly magnetized in the 20 Feb 2026, 00:16
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