#9 - Must Be True, Author's Perspective

[jared.xu]

I would like to know why the correct answer is D. It is true that line 32 tells us that Krakatau and El Chichon are "major, dust-spitting explosions," but how can we infer from this line that "minor" eruption introduces "a relatively small amount of debris into the atmosphere"? Is it "relatively" as compared to the major ones? I chose answer B, which I thought was safer than answer D. Do we not know for certain that "minor" eruption has less of an effect on global temperature than either Krakatau or El Chichon since even those two cause a smaller drop than expected, "only half a degree centigrade or less"? I thought that this was a must be true question, and B was "must be true." Is it because of the question words "most accurately characterizes" that makes answer D better? Thank you.

[Steve Stein]

You are correct--answer choice (D) can be chosen based on the author's point in the third paragraph. The authors tells us that minor eruptions have almost no effect on temperature, while major, dust-spitting explosions cause a smaller-than-expected temperature drop. The implication is that the minor eruptions, by contrast, are not "dust-spitting."

[jared.xu]

Thank you so much for the confirmation. But I would like to know how we would know to eliminate B. As you said, "The authors tells us that minor eruptions have almost no effect on temperature." Is it not much safer to choose B? It makes reference to climate via the words "effect on global temperature," and implies that the feedback loop would not be applicable in "minor" eruptions, and probably applicable in "major" eruptions. I would really like to know because as things are now, I am quite certain I would fall for an answer like B again, given a similar question. It just appears so much safer, and definitely true. Thank you.

[Steve Stein]

The author provides that neither minor eruptions nor major eruptions have much of an effect on temperature. In order to figure out what is meant by "minor" we can look for contrast provided by the author between minor and major eruptions. "Minor eruptions have no discernable effect on temperature, whereas major dust spitting eruptions have little effect." Dust-spitting seems to be the point of contrast provided. Let me know if that makes sense--thanks!

[tug59567]

I didn't see the inverse relationship between "dust splitting" and "relatively small amount of debris". It seems to me that one concern a quality (dust splitting) and the other a quantity (amount of debris). My logic was that you could theoretically split one particle of dust and therefore dust-splitting refers to the force of an explosion, not necessarily just the size. Thus I was lost when picking an answer that matched my prephrase that a minor eruption meant "an eruption that has no discernable effect on temperature"

Was I thinking to deep in this question? Where did I go wrong?

Thank you so much

[Adam Tyson]

Where you went wrong on this, tug59567, was in a simple mis-reading of one word in the passage. The passage doesn't talk about volcanoes that SPLIT dust (cutting it into smaller parts). It's talking about volcanoes that SPIT dust (sending dust out of the volcano and up into the atmosphere). Dust and debris are being used synonymously, and so a volcano that spits dust into the air is one that introduces debris, while a minor volcano that does not spit dust is one that emits relatively little debris.

One letter makes all the difference, so read carefully!