Q17 - Climatologists believe they know why

[maryadkins]

Tricky!

(C) doesn't present an alternative cause for the ICE AGE. I agree it's kind of hard to see how it strengthens at first, but it definitely doesn't weaken b/c it just says the temp drops a tad after a volcano erupts. Once we're down to it and (D), however, we have to see that (C) provides a link between dust and temperature: those two things are now correlated in a different context, too, which boosts the hypothesis. (D) using the term "dust" but doesn't provide any correlation between dust and the temperature of the earth, and remember, we're trying to support a claim about dust causing ice ages.

[haeeunjee]

There are multiple postings above that already talk about why (C) is wrong.

I just wanted to comment on a previous post from way back, but also use it as an example to posit a greater point about this type of question:

An example to illustrate :

Scientists hypothesize that the decline in the native salmon population of Alaska is due to an increase in ethanoliantacob-VD4, a synthetic chemical byproduct of processing plants located north of the continental US. They base their hypothesis on data collected by the US government that show higher concentrations of chemicals in native salmon habitats throughout Alaska.

All of the following strengthen the scientists' claim EXCEPT:

(A) Ethanoltaco-AC4, similar in composition to ethanoliantacob-VD4, is known to be toxic to fish

(B) The agency that collected the data on chemical concentrations utilized standard procedures that have produced accurate results in the past

(C) The data collected by the US government shows that Ethanoltaco-AC4 is not one of the chemicals found in higher concentrations throughout Alaskan waters
(D) Some processing plants that produce ethanoliantacob-VD4 are located adjacent to native salmon habitats in Alaska

(E) Samples of tissue from dead native salmon in Alaska reveal high concentrations of ethanoliantacob-VD4

I think (A) requires a bit more analysis because while it does strengthen because it characterizes ethano-VD4 as a thing that can actually harm fish, it also presents ethano-AC4 as an alternative cause. Because the conclusion pointed to ethano-VD4 as the cause, this alternative cause can actually weaken the conclusion. So (A) seems more ambivalent. But LSAT writers, who get paid to NOT make ambivalent answer choices, will not have an answer choice like (A). They would probably fashion an answer choice like (A) to make it a clear weakener or strengthener or neutral. This tends to twist and turn the wording, and sometimes they turn out really funky.

Which is why on StrengthenX-causal questions, it is my suspicion that LSAT writers put in answer choices that either seem out of scope or MAY weaken as an alternative cause, to trip you up, but the answer choices actually serve to bridge a gap in the premise-conclusion by making the premises relevant for the conclusion. In this question, (C) plays that role. It seems to present an alt cause and therefore weaken, but is actually different enough in many considerations (cosmic dust vs. volcanic dust, ice ages might require more than just a few drops in average temperature, do volcanic eruptions happen every 800,000 years?, etc), so that this actually just strengthens an assumption: that it is possible for dust to reduce global temperature.

For another example, Google-search the LSAT question on seals and storing oxygen in their blood vessels or something. (Horse anatomy, of all things, is brought up in one of the answer choices that actually serve to strengthen the conclusion. We wouldn't say the anatomy of a horse is the alt cause of seals storing oxygen, and it does seem out of scope because they're two diff animals, but at the very least, now we are shown that it is possible for mammals to store oxygen in vessels, and that strengthens.) I have noticed this pattern on many StrengthenX questions.

[emily.odermatt]

I'm down to C versus D on this one, and still getting fooled.

I understand why D is right - the argument essentially is talking only about cosmic dust muting the sun, and says nothing about dust from the Earth's surface having temperature-muting powers. D specifically says that the dust it is talking about is "from Earth's surface." D is essentially a correct answer because it doesn't match the correct kind of dust. Like UVA versus UVB sunscreen, kinda.

My problem with still being fooled by C is the part AFTER assuming the strengthener part about correlating dust and temperature. Since the dust in C is neither identified as cosmic dust nor Earth-generated dust, like D's dust, we cannot assume the source of the dust. So, it would be a strengthener IF the source of the dust was cosmic dust, previously rolled through, and essentially being re-spewed into the atmosphere by the force of a volcanic eruption. Essentially that means the volcanos are helping to prolong the ice ages. Ideally, the answer would be worded, "spew large amounts of [COSMIC] dust [back] into Earth's atmosphere."

However, if it is Earth-sourced dust, then it is a weakener, because it is an alternate source of dropped temperatures, not from the roll-through of cosmic dust, but from the dust Earth self-creates and spreads up to its own atmosphere. Thinking about it that way, the scientist could be right about the process - i.e. dust in the atmosphere blocks the sun, chills the Earth - but wrong about the kind of dust that causes it - i.e. Earth's own dust is the right kind of blocker and the volcanoes erupting started the ice age. Since we don't know whether the "before eruptions" temperature on C is low enough that the drop talked about in C could set off an ice age, it is plausible to say a small change was the step off the cliff needed to set off an ice age. Ideally, the answer would be worded, "spew large amounts of [Earth's own/] dust [/for the first time] into Earth's atmosphere."

I guess the answer C could have been a whole lot clearer if, like D, they said what kind of dust the volcanoes blew up into the atmosphere.

Thoughts? This is go-number-two at the problem, by the way.

[LeonC641]

I'm down to C versus D on this one, and still getting fooled.

I understand why D is right - the argument essentially is talking only about cosmic dust muting the sun, and says nothing about dust from the Earth's surface having temperature-muting powers. D specifically says that the dust it is talking about is "from Earth's surface." D is essentially a correct answer because it doesn't match the correct kind of dust. Like UVA versus UVB sunscreen, kinda.

My problem with still being fooled by C is the part AFTER assuming the strengthener part about correlating dust and temperature. Since the dust in C is neither identified as cosmic dust nor Earth-generated dust, like D's dust, we cannot assume the source of the dust. So, it would be a strengthener IF the source of the dust was cosmic dust, previously rolled through, and essentially being re-spewed into the atmosphere by the force of a volcanic eruption. Essentially that means the volcanos are helping to prolong the ice ages. Ideally, the answer would be worded, "spew large amounts of [COSMIC] dust [back] into Earth's atmosphere."

However, if it is Earth-sourced dust, then it is a weakener, because it is an alternate source of dropped temperatures, not from the roll-through of cosmic dust, but from the dust Earth self-creates and spreads up to its own atmosphere. Thinking about it that way, the scientist could be right about the process - i.e. dust in the atmosphere blocks the sun, chills the Earth - but wrong about the kind of dust that causes it - i.e. Earth's own dust is the right kind of blocker and the volcanoes erupting started the ice age. Since we don't know whether the "before eruptions" temperature on C is low enough that the drop talked about in C could set off an ice age, it is plausible to say a small change was the step off the cliff needed to set off an ice age. Ideally, the answer would be worded, "spew large amounts of [Earth's own/] dust [/for the first time] into Earth's atmosphere."

I guess the answer C could have been a whole lot clearer if, like D, they said what kind of dust the volcanoes blew up into the atmosphere.

Thoughts? This is go-number-two at the problem, by the way.

Hi,
Thank you for the question. It helped me to understand LSAC's logic when designing the ACs.

For me, it's clear that both C and D use a type of additional dust (volcano dust & Earth surface dust), then the discrepancy lies in what each added element trigger.

In C, the volcano dust --> slightly temperature drop. So this confirms the scientise hypo.

But in D, we don't really know what effect does the Earth surface dust have? So D literally has no bearing. To say D has any effect, I think it's more of a stretch rather than what D really manifest.

[DPCTE4325]

This is a causal STR question.

Curious Fact: why has Earth undergone a regular sequence of ice ages beginning around 800,000 years ago?

Author’s Story: Climatologists surmise that orbit fluctuations causes Earth’s atmosphere to trap cosmic dust which causes dimming of the Sun thereby causing ice age.

Since this is a STR except, let’s eliminate answer choices that either

1) increase Author’s Plausability

Or

2) gets rid of an alternate explanation

A) Increases author’s plausability
B) increases author’s plausability
C) increases author’s plausability
E) increases Author’s plausability

D) this provides an ALTERNATE explanation. D states that it’s EARTH’s dust that enters the atmosphere, NOT the cosmic dust.

Thoughts Patrick?

[ohthatpatrick]

Nice!

I would just slightly tweak the Author's Story: "the Earth passes through particularly dense clouds of cosmic dust -> that dust enters the atmosphere -> that dims the Sunlight received by earth"

And for (D), I don't necessarily think we need to see it as an alternate explanation to see that it isn't doing anything to strengthen THIS explanation.

But I see what you're saying -- if we sometimes have a large bit of cosmic rock (i.e. meteorite / asteroid) plummet into Earth, which kicks up tons of Earth dust into the atmosphere, that WOULD be a different story for why we might have periodic ice ages.