In 1883, the Indonesian island Krakatoa, home to a massive volcano, se

Question

In 1883, the Indonesian island Krakatoa, home to a massive volcano, seemingly disappeared overnight as an eruption rent the entire island apart, catapulting rock and debris into the atmosphere. For the next years, as ash circled the entire globe, the average world temperature dropped by several degrees Fahrenheit. Therefore, an eruption of similar power in terms of the amount of debris ejected into the atmosphere will likely cause the average temperature around the world to drop by several degrees.

Which of the following, if true, best challenges the main claim of the argument?

A. The eruption of the Indonesian island of Tambora was even larger than that of Krakatoa, yet the average world temperature did not drop as much as it did following the eruption of Krakatoa.

B. In 1883, the ocean-atmospheric phenomenon La Nina occurred, an event that is always followed by a drop of several degrees in the world’s average temperature.

C. Due to the effects of climate change, the average world temperature has been steadily increasing over the last few decades.

D. According to sophisticated computer analysis, the eruption of Mt. Toba between 69,000 and 77,000 years ago, one of the most powerful ever, may have hastened an ice age.

E. No volcanic eruption in the 20th century was close to the magnitude of the Krakatoa eruption, yet average world temperatures dropped between 1950 and 1960.

kungfury42 · Answer

(A) Perfect! If another island eruption of a greater magnitude did not cause as much drop in the temperatures worldwide, it certainly challenges the main contention of the argument.

(B) La Nina could've played a role alongwith the eruption of Krakatoa in the temperature drop worldwide, but just the fact that La Nina happened doesn't undermine the main contention of the argument that a massive volcanic eruption can cause drop in temperatures.

(C) Irrelevant.

(D) If one of the most powerful eruptions hastened the ice age it strengthens the argument that massive volcanic eruptions can lead to drop in temperatures.

(E) We haven't said that the volcanic eruptions are the only way temperatures can drop.

Posted from my mobile device

NHUANH · Answer

This is a common Cause- Effect scenario in CR. Let's put this question in a simple story:
"One event happened, and, as consequence, something happened. => Conclusion: If similar event happen, then similar sequence will occur"
To undermine this argument, we can look for following alternative answer:
1. Something else cause both events
2. The consequence is cause by different event
3. Both event and "consequence" are not actually related.
---------------------
A. This is a trap: the author plays with words and trick test takers with the phrase "did not drop as much as". Under time constraint, test takers may read that phrase as "it did not drop". And they think that "The consequence is cause by different event". But they are wrong because "did not drop as much as" means the cause and effect happened but in a lesser degree. So, the cause-and-effect still exists. It does not invalidate the argument.

B. this is the correct answer. This option implies that another event (La Nina) may be the cause of the decrease in temperature.

C,D, and E are just outright wrong.

Hope this helps

Bunuel · Answer

Magoosh Official Explanation:

The argument assumes that one event caused another event. In this case, the volcano eruption, and the subsequent debris pushed into the atmosphere, led to a drop in global temps. The correct answer will provide another cause to the drop in global temperatures.

Only (B) does so.  Note, (B) is not saying that the volcano did not cause any drop in temperature, but it attacks the part of the conclusion that states that a volcanic eruption of equal intensity will cause the same drop in temperature. If La Nina was responsible for compounding the drop in temperature, then a similar eruption, without the attendant La Nina, would not necessarily result in the same drop.

(A) is really tempting. The reason it is not the answer is it does not address the conclusion as directly as (B). Though Tambora was a larger eruption, the conclusion states, "in terms of the amount of debris ejected into the atmosphere". We do not know if Tambora ejected more debris into the atmosphere than did Krakatoa.

(C) states that temperatures worldwide have been increasing. That does not mean that a massive eruption could not lead to a drop in world temperatures.

(D) is a general fact that does not relate to the argument.

(E) is wrong because the drop in temperatures is not related to any eruption. Thus, (E) is irrelevant.

naveengmat15 · Answer

The argument assumes that one event caused another event. In this case, the volcano eruption, and the subsequent debris pushed into the atmosphere, led to a drop in global temps. The correct answer will provide another cause to the drop in global temperatures.

Only (B) does so. Note, (B) is not saying that the volcano did not cause any drop in temperature, but it attacks the part of the conclusion that states that a volcanic eruption of equal intensity will cause the same drop in temperature. If La Nina was responsible for compounding the drop in temperature, then a similar eruption, without the attendant La Nina, would not necessarily result in the same drop.

(A) is really tempting. The reason it is not the answer is it does not address the conclusion as directly as (B). Though Tambora was a larger eruption, the conclusion states, "in terms of the amount of debris ejected into the atmosphere". We do not know if Tambora ejected more debris into the atmosphere than did Krakatoa.

(C) states that temperatures worldwide have been increasing. That does not mean that a massive eruption could not lead to a drop in world temperatures.

(D) is a general fact that does not relate to the argument.

(E) is wrong because the drop in temperatures is not related to any eruption. Thus, (E) is irrelevant.

Posted from my mobile device

rito54 · Answer

Hello! I don't understand why E is incorrect. Looking at the stamenet it means, that even without eruption the temperature is still dropping? Could someone kindly clarify? Thank you!!

DmitryFarberMPrep · Answer

rito54

But E is talking about the 20th century, not 1883. The fact that temperatures dropped more recently doesn't tell us anything about whether volcanic eruptions similar to Krakatoa's would cause a large drop in temperature.

In 1883, the Indonesian island Krakatoa, home to a massive volcano, se

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Critical Reasoning (CR) Questions

In 1883, the Indonesian island Krakatoa, home to a massive volcano, se

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards