Q6

[goriano]

I'd like some help on deciding between (B) and (D):

(B) says that the extended periods of colder temperatures occur on the earth's SURFACE, whereas the passage seems to be saying that the extended periods of colder temperatures occurs in the earth's ATMOSPHERE. Since this passage goes into detail with delineating the different components of the earth's layers, I figured this distinction would be relevant, but it turned out not to be?

(D) says "changes in circulation patterns" whereas the passage talks about "redistribution." If the water has been redistributed, why can't we say that the circulation patterns have changed from their normal course?

[ohthatpatrick]

Yeah, this is a classic "down to 2" dilemma.

Your reservation about (B), I think, is slightly off because the passage doesn't specify that the temperature change was in the atmosphere.

Rather, it says that "an extended period of and darkness" resulted from a cloud of dust being kicked up into the atmosphere.

The cause of the cold/darkness comes from the atmosphere, but that sentence doesn't localized the cold/darkness in the atmosphere; the passage is just saying a cloud of dust impedes incoming sunlight, so the Earth as a whole is cooler and darker than usual.

We know from all the causal language in lines 41-49 ("results from", "following this", "this increases", "causing" and "initating"), that the extended period of cold and darkness ultimately leads to the magnetic field switching over.

Meanwhile, for (D), there IS a crucial difference between "redistributing global seawater" and "changing the circulation pattern of the ocean".

A little outside knowledge helps to make this distinction easier: the world basically has a finite amount of water that alternates in proportion between frozen (at the polar ice caps) and liquid (in the oceans).

Throughout the year, ice caps grow when the earth is cooler and melt when it's warmer, decreasing and increasing the amount of ocean water. (An Ice Age refers to when polar ice caps grow super big).

The circulation pattern of the ocean, instead, refers to the overall currents within the ocean. For example, if you're going from eastern U.S. to Europe by boat, you don't go in a straight line. You follow a certain curved path that makes efficient use of the ocean's current. (I think it's related to the "jet stream", a global air current pattern).

I similarly labored over whether (D) was an okay match for what was said in the passage, but "redistributing" water refers to how much is allocated to the ocean / how much is allocated to the ice caps. "Circulation patterns" refers to how the ocean flows amongst itself.

The one potential crutch you could have leaned on to suspect that (D) was our answer (i.e., that (D) is NOT a good match for the passage), is that the phrase "perturbing the circulation pattern" was used in line 38, to refer to something else ... the heat-circulation pattern within the Earth's core.

When you see an answer choice is using a verbatim phrase from the passage, but grabbing it from the wrong area (based on what the question is asking about), you have yourself a trap answer.

Hope this helps. Let me know if questions remain.

[phoebster21]

To Ohthatpatrick:
You are seriously the best at explaining the RC questions.

I've read a few dozen of your responses now. I love how in a few of your explanations you even go as far as to explain "what would make this answer right" by adding in or taking away x,y,z. That helps tremendously!

Keep up the great work!

Super appreciated!

[tommywallach]

I'll let him know!