The diagram shows, in three column groupings, various divisions of Ear

Question

https://gmatclub.com/blog/wp-content/uploads/2023/09/diagram.png

The diagram shows, in three column groupings, various divisions of Earth's geological history since its formation approximately 4,600 million years ago. In the leftmost column grouping, the Precambrian eon is subdivided into chronometric eons shown on the far left; but otherwise, in the rest of the graphic, each subsequent column to the right shows the subdivisions of the timeframes to its left. Each of the rightmost two column groupings is a magnification—with additional information—of a portion of the grouping directly to its left.

Fill each blank using the drop-down menu to create the most accurate statement on the basis of the information provided.

1. The Miocene epoch spans closest to of the era of which it is a part.

2. According to the diagram the beginning of the marks the onset of a new eon, era, and period in geological history.

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Fill each blank using the drop-down menu to create the most accurate statement on the basis of the information provided.

1. The Miocene epoch spans closest to  GRAPH_1_PLACEHOLDER  of the era of which it is a part.

2. According to the diagram the beginning of the  GRAPH_2_PLACEHOLDER  marks the onset of a new eon, era, and period in geological history.

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egmat · Accepted Answer

Hi Yatesri, I now understand your doubt. Let's pay attention to the question stem: "The diagram shows, in three column groupings, various divisions of Earth's geological history since its formation approximately 4,600 million years ago ." The diagram gives information from the time since 4600 years ago. Now, if I ask you, what is the information given for the year "4600 million", would you tell me the information for the current year or the beginning year (i.e. the year which happened 4600 million years ago)? It should be the beginning year because the language is phrased that way. You move from 4600 million years ago to present i.e. 0 years ago. Besides, there is also a cue inside the diagram: the eon directly below "Cambrian period" is pre-cambrian eon. It means that this period occured before Cambrian period. So, basically, you need to read the diagram downside-up if you want to read it chronologically. So, at the bottom, a time period (eon, era or period) starts and it ends at its top in the diagram. Hope this helps

Thanks, Chiranjeev

DhruvBadaya · Answer

The graph is meant to be read from bottom people. 0 years ago is the most recent, 10 years ago is less recent and so on. Keep that in mind.

KapTeacherEli · Answer

Ki karikris,

As is always the case with Graphics problems, we should read the text to help understand this image. Some questions can be answered without referencing the passage, but it's always easier to read first. And in this case, a single word--"magnification"--helps us understand the image. Those gray triangles marked off by dotted lines are telling us which part of the bar on the left is magnified by the bars moving right.

So, for the first question, the Miocene Epoch isn't in the same bar of the graph as any of the Eras. But looking at the magnification indicators, we can see that the entire rightmost graphic is expanded from the Cenozoic era. So, since the Miocene takes up about 25% of it's bar, it takes up about 25% of the Cenozoic Era of which it is part.

As for the second question, it asks for something about eons, eras, and periods--that puts us in graph 2. We're asking for the beginning of all three, which means we want a line straight across the graph. That's the Cambrian period, which starts the Phanerozoic Eon and the Paleozoic Era.

Good luck!

egmat · Answer

Hi,

Though I am not sure where your confusion lies but let me have a try.

Basically, if you look at the first figure from the left, you can see that there are only two eons: Precambrian and Phanerozoic.

Now, for anything to start with an eon, it has to start with either Precambrian eon or Phanerozoic eon.

However, there is no information about eras or periods at the beginning of Precambrian eon.

So, the only solution possible which can start with eon, era and period, will be the one starting with Phanerozoic eon.

Now that is the case with Cambrian period. For this, Phanerozoic eon starts, Paleozoic era starts and Cambrian period starts. Therefore, this is the correct answer.

In addition, you can see that the answer also could have been Phanerozoic eon. (same three times start in this case also).

Hope this helps

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Thanks,
Chiranjeev

e-GMAT has recently launched a full fledged course on IR encompassing 15+ hours of interactive audio visual content, 35 concepts, 120+ original questions, and 2 full length Mock Tests. Visit e-gmat.com for a free trial. Thanks, Chiranjeev

yatesri · Answer

Thank you for your response!

What is confusing for me is that the answer states that "According to the diagram the  beginning  of the Cambrian period marks the onset of a new eon, era, and period in geological history.

However, according to the expanded graph to the right, the beginning of the Cambrian period does not mark the onset, the  end  of the Cambrian period does.

This is also the beginning of the Precambrian Era; also an answer choice.

Doesn't the question wording prevent the Cambrian period from being a correct answer?

Thanks,
yatesri

Apt0810 · Answer

A) 25% per the third graph (Magnified version)

B) Cambrian period per the second graph ( Magnified version)

Posted from my mobile device

Sajjad1994 · Answer

Official Explanation

According to the rightmost column of the diagram, the Miocene epoch spans 17 million years, from about 6 million to 23 million years ago. The rightmost column also represents the entire Cenozoic era that appears in the middle column and spans 65 million years. Dividing 17 by 65 yields approximately 0.262, or 26.2%, which is closest to the menu option of 25%.

The correct answer is 25%.

The only place in the diagram that distinctly represents eons, eras, and periods together is in the middle column, and the only place in the middle column where there is a dividing line common to an eon, era, and period is at the beginning of the Cambrian period at about 550 million years ago.

The correct answer is Cambrian period.

pranskius · Answer

What was confusing to me is that zero is "the present" whereas 4600 is in the past. Is there a rule of thumb stating that generally historical graphs graphs count years up (up to BC I would assume)?

poojaarora1818 · Answer

ScottTargetTestPrep   JeffTargetTestPrep   MartyMurray    GMATNinja    Bismuth83  Could you pls explain the second part of the problem? Though I agree with the official explanation provided still it's not very clear.

Bismuth83 · Answer

We're interested in finding a point in time where a new eon, era, and period all start together.

The point must be at where a new eon starts. There are only two eons, however starting at the Precambrian doesn't work, since no information is given on the eras and periods that happening during that time. So, the point must be where the Phanerozoic eon starts.

This is time point can be called the beginning of the Phanerozoic eon, Paleozoic era, or Cambrian period. The Cambrian period is an answer choice.

I hope that helps explain the second part of the question!

poojaarora1818 · Answer

Thank you so much for the explanation. Now, it's very much clear to me and makes sense.

KarishmaB · Answer

Responding to a pm:

Recall how in pie charts, sometimes one portion is blown up and its segments are shown. This question does something like that twice. 
It starts from 4600 million years ago (as the text explains too) and that's the precambrian eon. The only other Eon is Phanerozoic (the blue part in the first section of the graph). 
In the second section, the blue part of Phanerozoic eon is blown up and its eras and periods are shown. In the third section, the Cenozoic era (the orange one - the most recent) is blown up and its periods and epochs are shown. 
So in a snapshot, last 4600 million years of Earth are divided into 2 Eons - Precambrian and Phanerozoic. The Phanerozoic eon is divided into 3 eras - Paleozoic, Mesozoic and Cenozoic. The Cenozoic era is divided into 2 periods and each period is divided into Epochs. Rest of the details we can worry about if we are tested on it. We just need to understand the graph first.

1. The Miocene epoch spans closest to ___ of the era of which it is a part.

Miocene epoch is a part of neogene period (about 80% of neogene and the rest is Pliocene epoch)) which is a part of Cenozoic era (neogene is about 30-40% of Cenozoic era and rest is Paleogene period)
So Miocene is 80% of 30% of Cenozoic era. There is only one option close to this i.e. 25%.

Select 25%

2. According to the diagram the beginning of the ____ marks the onset of a new eon, era, and period in geological history.

There are only 2 Eons - a new eon begins at 500 million years ago - Pherozoic. That is when Paleozoic era starts. The Paleozoic era starts with the Cambrian period. So the start of the Cambrian period marks the beginning of a new Eon, era and period.

Select Cambrian period

The diagram shows, in three column groupings, various divisions of Ear

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The diagram shows, in three column groupings, various divisions of Ear

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