#16 - Scientist: An orbiting spacecraft detected a

[Administrator]

Please post your questions below!

[par453]

I picked D because I thought it would go against the argument and show that volcanic activity could have caused the sulfur dioxide spike on Venus since there was a similar pattern for volcanic activity on Earth. Why is D wrong and A correct?

[Brook Miscoski]

Par,

The stimulus concludes that since we haven't identified active volcanoes on Venus, that's not where the S02 spikes are from.

I quickly eliminated B,C, and E because they have no clear relevance to the stimulus.

I immediately picked A not out of any judgment against D but rather because A is about conditions on Venus which are a clearer way of weakening an observation about Venus. D is about conditions on Earth, so inferences about Venus don't immediately follow. I would pick A every single time on those grounds and not worry about it further.

You can eliminate D for other reasons. (D) says that "traces" are detectable, but the stimulus is trying to explain a "spike." (D) is about an effect that lingers for years, but the stimulus is trying to explain a "short term" phenomenon. Those are other strong grounds for eliminating (D).

[stu(dying)]

Another reason for eliminating D is that if it is difficult for an instrument to detect volcanic eruptions on Venus, then how do we know for certain then that it wasn't volcanic activity that caused a spike in sulfur dioxide on Venus?

This undermines the conclusion the Scientist made, which was that we cannot conclude that volcanic activity caused the spike because no active volcanoes have been identified.

[Jeremy Press]

Hi stu(dying),

Yes, I think you've identified another great reason answer choice D is not a weaken answer, whereas answer choice A is! The most significant premise supporting the conclusion that this sulfur dioxide spike on Venus should not be understood to have come from a volcano is that "[n]o active volcanoes have been identified on Venus." Answer choice A attacks that premise directly, by clarifying that we would be unlikely to detect an active volcano (thus the lack of detection of such a volcano is not good evidence that there are no such volcanos on Venus). Answer choice D, as Brook helpfully notes, speaks to conditions on Earth, not Venus, and thus cannot be assumed to be directly relevant to either the premises of the argument or its conclusion.

Great work on this question!

Jeremy

[teddykim100]

However doesn’t this force us to assume the premise about active volcanoes is NOT true? Which makes us break the rule to assume all premises are true.

By saying it is hard to accurately detect data in Venus’ current conditions, doesn’t that straight up contradict the first premise, and now we cannot even consider it true anymore?

[Adam Tyson]

You may have misunderstood that premise, teddykim100. The author never said that there are no active volcanos on Venus, but only that none have been identified. That leaves open the possibility that they exist but have escaped our notice! That's not denying the premise, but accepting it and then providing an explanation that undermines the reasoning based on it.

[teddykim100]

Hi Adam,

when I think about what you said in my "real-life" terms, it makes perfect sense. However, I am used to spotting the weakness in these arguments by identifying a gap between premise and conclusion, rather than directly weakening a premise's or conclusion's statements themselves.

Therefore I think I still struggle in seeing how we are accepting the premise here, because to me it seems as if we are trying to weaken it and go after it.

[willwants170]

I saw answer choice D as strengthen, because a "spike" is describing something right now. Answer choice D would then support the "spike" as coming from a volcano years ago, not a current active volcano, therefore strengthening, not weakening the argument. Obviously, there's also a lot of things wrong in D such as "traces", but would my train of thought be correct? I'm worried it's not correct because the conclusion didn't explicitly say "current volcanic activity" but it seemed implied.

[Dana D]

Hey Will,

The stimulus here specifically says that spikes in sulfur dioxide are the indicator for volcanoes and it adds the clarification of 'short-term.'

Answer choice (D), in contrast, says there are traces of sulfur dioxide from past eruptions. If (D) were true, all it tells us is that there is probably also trace sulfur dioxide in Venus's atmosphere, since there were signs of past volcanic activity there. We still don't know what to make of the short-term spike in sulfur dioxide. Also, the reasoning the scientist uses for why we shouldn't look at volcanoes as the cause of the spike is that no active volcanoes have been identified on Venus, and planetary atmospheres undergo cyclical variations in composition. Therefore, if we wanted to strengthen this argument, we would need to explain why these two factors are sufficient for us to rule out volcanoes.