Reading Comprehension

PT106 · S4 · P2 · Q12 Volcanoes

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Long after the lava has cooled, the effects of a major volcanic eruption may linger on.

Topic

The lingering climate effects of major volcanic eruptions and how they influence global and regional temperatures.

Framework

Present Debate

Main Point

While volcanic eruptions are thought to cool Earth's climate, recent research suggests the cooling effect is smaller and more complicated than previously believed, with global impacts being minor but potential for larger regional effects due to feedback loops. (The “most valuable sentence” encapsulating the main point appears in P3: )

P1: Common Belief about Volcanic Eruptions

After a big volcano erupts, the dust and acid it throws into the air can cool the planet by blocking sunlight—some even blame Tambora’s 1815 eruption for an entire summer without warm weather in 1816.

P2: New Findings Challenge Conventional Wisdom

Scientists Mass and Portman say this connection isn’t quite as strong as we think. By analyzing global temperatures around nine eruptions—while accounting for El Niño’s effects—they find the supposed volcanic cooling can be tricky to pin down.

P3: Refining the Evidence—What Eruptions Really Do

Once they filtered out El Niño, they saw that smaller eruptions don’t noticeably affect temperatures, and even huge eruptions only slightly cool the hemisphere—much less than earlier studies had claimed.

12.

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

  1. Major volcanic eruptions have a

    Supported

    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.

    16% picked this

  2. The effect of major volcanic

    Supported

    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% picked this

  3. Correct

    Major volcanic eruptions have no

    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.

    67% picked this

  4. Minor volcanic eruptions have no

    Supported

    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.

    2% picked this

  5. Minor volcanic eruptions have no

    Supported

    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.

    12% picked this

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