#9 - Very powerful volcanic eruptions send large amounts of

[est15]

I can see why D is right, but I'm having trouble understanding why B is incorrect. I thought about it this way: if abnormal weather in China didn't last for a full year or longer, then we know that it wasn't caused by a powerful volcanic eruption, so it couldn't have been Mount Etna. So if the abnormal weather did last for a full year or longer, it would support the possibility that it was caused by a powerful eruption such as Mount Etna.

[Emily Haney-Caron]

Hi est15,

I understand your reasoning for B, but I think you're reading too much into the year timeframe. We know that cold temperatures exist for a year or more, but we don't know whether that would be just right by the eruption site or whether even far away places that were impacted would be impacted for a full year. Therefore, B is much less relevant than D to the stimulus. Does that make sense?

[est15]

Hi Emily,

Yes, that makes sense. In the future, I'll try to keep the answer more within the scope of the argument.

Thanks!

[Alexis]

Hi, could you clarify again why D is correct? I chose C, be cause I thought even though the eruption is "powerful" at Mt. Etna, it was not necessarily "very powerful". So if there was no temp drop in Sicily due to the eruption, then there was no way that if the dust travelled, it could be powerful enough to make the temp drop in China. Also, for D, again I thought yes ok so maybe there are volcanic eruptions. But again, are they powerful enough to cause a temp drop? If not, then it doesn't matter. Any help would be much appreciated!

[Jonathan Evans]

Hi, Alexis!

This question is tricky because the conclusion does something kinda funny: it takes away part of the cause-effect gap between the premises and the conclusion and restricts the conclusion to a narrower question of causality.

Allow me to explain. The big question you might be asking yourself after reading this stimulus is, "Did Mount Etna cause the temperature drops at all? Maybe there was some other cause."

The conclusion acknowledges this possibility by starting off, "If these phenomena [the temperature drops] were caused by volcanic ash, then..."

In other words, when we are considering the validity of this conclusion, we are taking it for granted, for the purpose of the argument, that the temperature drops were caused by volcanic ash. Now we have a narrower question to deal with: we have to determine whether the volcanic ash causing the temperature drops came from Mount Etna. Even if we grant that the temperature drops come from volcanic ash, at the moment we do not know whether the volcanic ash causing the temperature drops came from Mount Etna.

This is where answer choice D came it. It brought up the possibility that another eruption closer to China occurred. If such an eruption had occurred, then it would be less likely that Etna's volcanic ash needed to travel all the way around the world. If no such eruption occurred, then it would be more likely that Etna's volcanic ash was responsible for the temperature drops.

The problem with answer choice C is that it disregards the fact that for the purposes of the conclusion, we are already granting that volcanic ash caused colder temperatures in China. Regardless of the temperatures in Sicily, we will not know whether the volcanic ash causing the colder temperatures in China came from Mount Etna or not.

Good question. Does this make sense?

[Adam Tyson]

I'll add to Jonathan's excellent explanation by anticipating a concern. If the temp in Sicily didn't drop, you might be thinking that Mt Etna didn't produce enough ash/wasn't powerful enough to be the cause of any such decline in temp, and if it did drop you might be thinking that it could have been powerful enough to be the cause. But there is a problem with both sides of that evaluation, and that is that the stimulus never gave us any information about where the temperature would drop. If the ash cloud moves with the wind and gets carried away from the site of the eruption, then perhaps it would be powerful enough to cause a drop in temperature somewhere downwind from the site of the eruption, with no impact at the eruption site. That is, normal temperatures in Sicily tell us nothing about whether Mt Etna could have cause a temperature drop somewhere else. Likewise, a drop in temperature in Sicily would tell us nothing about whether Mt Etna could have caused a similar temperature drop in China. Maybe it could do both, but then again maybe it could only do one? It would have to be a mighty big ash cloud to cause both places to drop in temperature, right?

[Alexis]

I think those explanations really help. Thanks!

[ashpine17]

what is wrong with C? is it a premise booster?

Is D right because if the answer is yes, then it's less likely that the ash from the volcanic explosion from S affected China?