According to the passage, which of the following is true of the rock

Recent studies of sediment in the North Atlantic’s deep waters reveal possible cyclical patterns in the history of Earth’s climate. The rock fragments in these sediments are too large to have been transported there by ocean currents; they must have reached their present locations by traveling in large icebergs that floated long distances from their point of origin before melting. Geologist Gerard Bond noticed that some of the sediment grains were stained with iron oxide, evidence that they originated in locales where glaciers had overrun outcrops of red sandstone. Bond’s detailed analysis of deep-water sediment cores showed changes in the mix of sediment sources over time: the proportion of these red-stained grains fluctuated back and forth from lows of 5 percent to highs of about 17 percent, and these fluctuations occurred in a nearly regular 1,500-year cycle.

Bond hypothesized that the alternating cycles might be evidence of changes in ocean-water circulation and therefore in Earth’s climate. He knew that the sources of the red-stained grains were generally closer to the North Pole than were the places yielding a high proportion of “clean” grains. At certain times, apparently, more icebergs from the Arctic Ocean in the far north were traveling south well into the North Atlantic before melting and shedding their sediment.

Ocean waters are constantly moving, and water temperature is both a cause and an effect of this movement. As water cools, it becomes denser and sinks to the ocean’s bottom. During some periods, the bottom layer of the world’s oceans comes from cold, dense water sinking in the far North Atlantic. This causes the warm surface waters of the Gulf Stream to be pulled northward. Bond realized that during such periods, the influx of these warm surface waters into northern regions could cause a large proportion of the
icebergs that bear red grains to melt before traveling very far into the North Atlantic. But sometimes the ocean’s dynamic changes, and waters from the Gulf Stream do not travel northward in this way. During these periods, surface waters in the North Atlantic would generally be colder, permitting icebergs bearing red-stained grains to travel farther south in the North Atlantic before melting and depositing their sediment.

The onset of the so-called Little Ice Age (1300-1860), which followed the Medieval Warm Period of the eighth through tenth centuries, may represent the most recent time that the ocean’s dynamic changed in this way. If ongoing climate-history studies support Bond’s hypothesis of 1,500-year cycles, scientists may establish a major natural rhythm in Earth’s temperatures that could then be extrapolated into the future. Because the midpoint of the Medieval Warm Period was about A.D. 850, an extension of Bond’s cycles would place the midpoint of the next warm interval in the twenty-fourth century.

According to the passage, which of the following is true of the rock fragments contained in the sediments studied by Bond?

  1. The majority of them are composed of red sandstone.
  2. They must have reached their present location over 1,500 years ago.
  3. They were carried by icebergs to their present location.
  4. Most of them were carried to their present location during a warm period in Earth’s climatic history.
  5. They are unlikely to have been carried to their present location during the Little Ice Age.

An important thing to keep in mind about the Reading Comprehension section of the GRE as we use PowerPrep online to study is that it is just that—reading comprehension. In other words, as difficult as it may seem, and it can be pretty tricky, the test makers will always give us all the information we need in the passage to answer the question. For questions that come from monster passages, such as question 8 of the first Verbal section on practice test 1, the search can be difficult, but we still need to learn to find support for an answer from the passage.

Alright, there’s always one LONG passage on the GRE—fortunately only one, but it’s something we can’t really get around. Since the test will tell us that questions 8-11 (four whole questions) are based on this passage, it is worth our time to read the passage. We’ll need to read somewhat quickly—after all, four questions cannot possibly quiz us over every detail—but we need to be able to find information quickly. One way we can keep track of everything is to take very short notes on our scratch paper about each paragraph.

This question begins “according to the passage,” which is a hint that it is asking us about a specific detail in the passage. The only problem is that this passage is lousy with details! However, we can use keywords in the question to help us navigate. “Bond” would be a good thing to skim for since it’s a proper noun (one that is capitalized) BUT we see that Bond comes up in every paragraph. But not every paragraph talks about the “rock fragments contained in sediments.” In fact, rock fragments are described in the first paragraph (if we ever have trouble locating keywords in the question, we might also try using keywords in our answer choices to help).

In the first sentence, we learn that “sediments” could tell us something about cyclical patterns in Earth’s climatic history. The second sentence specifically mentions the fragments in these sediments—red alert! This sentence tells us that the fragments are too big to be transported by ocean currents; instead, they must have been transported by icebergs. The next sentence continues to describe the sediments themselves, but we have to be very specific: the question made the distinction that we were talking about “rock fragments,” so we want to stick to information about rock fragments.

So, what do we know about these fragments? They must have been transported by icebergs because they are too big for ocean currents to have done so. Let’s go ahead and see if our answers reflect any of this information.

  • The majority of them are composed of red sandstone.

Hmm. This does not match the information we discovered about the fragments specifically—red sandstone comes up later in the paragraph. Additionally, the information in this later part of the paragraph only says the “sediments” are “stained” with iron oxide from the red sandstone. Not that they are made up of red sandstone. We can eliminate A.

  • They must have reached their present location over 1,500 years ago.

Skimming the passage for what it says about 1500 years ago is easy since 1500 is in numerals, and it is in the same paragraph so we might want to double check. Apparently the percent of red-stained grains in sediments fluctuates every 1500 years, which doesn’t actually tell us WHEN the sediments Bond studied got to their current positions—in fact, it’s implied that the has samples from all different dates. We can eliminate B.

  • They were carried by icebergs to their present location.

Yes, C matches the information that was specifically about the rock fragments in these sediments, so we should keep C.

  • Most of them were carried to their present location during a warm period in Earth’s climatic history.

This answer uses information from later in the passage, but for specific detail questions we very very rarely need to venture more than a sentence or two away from our keywords. We can eliminate D since it doesn’t match any information we found in the first paragraph.

  • They are unlikely to have been carried to their present location during the Little Ice Age.

Same as answer D: the Little Ice Age isn’t mentioned until the end of the passage.

From this, we can see that a very important thing to keep in mind for specific detail questions is that we want to make sure we answer using information from the same part of the passage as our keywords. The test makers will often use information found elsewhere in order to try to trick us. C is the only answer that matches information found in the first couple of sentences, which is the only part of the passage that described the “rock fragments” the question refers to. C is correct.


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