Reading ComprehensionDifficulty: Hard

PT106 S4 P2 Q12 Explanation

Volcanoes

A free, expert breakdown of this official LSAT Reading Comprehension question.

TopicsInferenceScience

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Passage

Long after the lava has cooled, the effects of a major volcanic eruption may linger on. In the atmosphere a veil of fine dust and sulfuric acid droplets can spread around the globe and persist for years. Researchers have generally thought that this veil can block enough sunlight to have a chilling United States and southeastern Canada were hit by snowstorms in June and frosts in August.

The volcano-climate connection seems plausible, but, say scientists Clifford Mass and Davit Portman, it is not as strong as previously believed. Mass and Portman analyzed global temperature data for the years before and after nine volcanic eruptions, from Krakatau in 1883 to El Chichón in 1982. In the process they tried to the volcano happens to erupt just as an El Niño-induced warm period is beginning to fade.

Once El Niño effects had been subtracted from the data, the actual effects of the eruptions came through more clearly. Contrary to what earlier studies had suggested, Mass and Portman found that minor eruptions have no discernible effect on temperature. And major, dust-spitting explosions, such as Krakatau or El Chichón, cause a half a degree centigrade or less-a correspondingly smaller drop in the opposite hemisphere.

Other researchers, however, have argued that even a small temperature drop could result in a significant regional fluctuation in climate if its effects were amplified by climatic feedback loops. For example, a small temperature drop in the northeastern U.S. and southeastern Canada in early spring might delay the melting of snow, and of feedbacks a small temperature drop could be blown up into a year without a summer.

What this question is testing

Inference

Your task

Find what must be true based on what the passage or stimulus states.

Common trap

Answers that are plausible or likely but not actually guaranteed by the text.

Winning move

Keep only the choice the statements fully support — eliminate anything that requires an extra assumption.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
12.

The information in the passage provides the LEAST support for which one of

Answer choices

  1. Supported16% picked this

    Major volcanic eruptions have a discernible effect on

    The end of the 3rd paragraph says that "major, dust-spitting explosions, cause a smaller drop than expected -- only half a degree centigrade or less (in the hemisphere where they occur)." While that is slight and smaller than expected, it is still discernible. We know that because the previous sentence specifies that minor eruptions have no discernible effect on temperature, so this statement about major eruptions is meant as a contrast.

  2. Supported3% picked this

    The effect of major volcanic eruptions on global temperature is smaller than

    The same sentence we used to support (A) helps us support this. At the end of the 3rd paragraph it says that "major, dust-spitting explosions, cause a smaller drop than expected -- only half a degree centigrade or less (in the hemisphere where they occur)."

  3. Correct66% picked this

    Major volcanic eruptions have no discernible effect on

    Why this is right

    This is more or less contradicted by the end of the 3rd paragraph and by the 4th paragraph. We're told that major eruptions cause the hemisphere they occur in to cool by about 0.5º Celsius. If something is having a discernible effect on the whole hemisphere, then it seemingly has to have a discernible effect on regions within that hemisphere. Something could affect a region without affecting the whole hemisphere, but it doesn't seem possible for the converse to be true. Additionally, the final paragraph is telling us that the effects on regional temperatures might be more than just discernible; they might be as dramatic as "a year without a summer"! That mild cooling effect on the hemisphere can be amplified via feedback loops into huge effects on individual regions.

    Skill tested: Inference · how this choice captures the passage's function is the move to repeat next time.

  4. Supported3% picked this

    Minor volcanic eruptions have no discernible effect on temperature in the hemisphere in

    The 2nd sentence of the 3rd paragraph supports this: Minor eruptions have no discernible effect on temperature If something has no discernible effect on temperature at all, then clearly it has no discernible effect on its hemisphere.

  5. Supported12% picked this

    Minor volcanic eruptions have no discernible effect on temperature in the hemisphere opposite the hemisphere

    The 2nd sentence of the 3rd paragraph supports this: Minor eruptions have no discernible effect on temperature If something has no discernible effect on temperature at all, then clearly it has no discernible effect on the other half of the globe.

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