Historical flooding events are documented through sediment layers found in river deltas. Research through geological surveys has established that delt...
GMAT Information and Ideas : (Ideas) Questions
Historical flooding events are documented through sediment layers found in river deltas. Research through geological surveys has established that delta areas containing thicker sediment accumulations also demonstrate signs of more numerous prehistoric flooding incidents. Research by James Chen and his team established that sediment thickness alone fails to explain the observed flood frequency patterns, as the sediment volume required to generate these patterns significantly surpasses the actual accumulation in these locations. The investigation demonstrated that mineral-rich particles—transported by flood waters and deposited in sediment layers—create a significantly clearer marker of flooding activity.
According to the text, what did Chen and colleagues discover about mineral-rich particles?
They gather mainly in locations with rare flooding occurrences.
They consist primarily of sedimentary accumulations.
They create a significantly clearer marker of flooding activity.
They are capable of limiting excessive sediment buildup in river deltas.
Step 1: Decode and Map the Passage
Create Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| Historical flooding events are documented through sediment layers found in river deltas. |
|
| Research through geological surveys has established that delta areas containing thicker sediment accumulations also demonstrate signs of more numerous prehistoric flooding incidents. |
|
| Research by James Chen and his team established that sediment thickness alone fails to explain the observed flood frequency patterns, as the sediment volume required to generate these patterns significantly surpasses the actual accumulation in these locations. |
|
| The investigation demonstrated that mineral-rich particles—transported by flood waters and deposited in sediment layers—create a significantly clearer marker of flooding activity. |
|
Provide Passage Architecture & Core Elements
Main Point: Research by Chen and his team discovered that mineral-rich particles provide a clearer marker of historical flooding activity than sediment thickness alone.
Argument Flow: The passage begins by explaining how flooding history is studied through sediment layers, then presents initial research showing thicker sediments correlate with more floods. However, Chen's research challenged this simple relationship, finding that sediment thickness alone could not explain flood patterns because the required volume exceeded actual accumulation. His investigation then revealed that mineral-rich particles transported by floods serve as a significantly clearer marker of flooding activity.
Step 2: Interpret the Question Precisely
This is a fill-in-the-blank question asking us to choose the best logical connector. The answer must create the right relationship between what comes before and after the blank.
Step 3: Prethink the Answer
- From our analysis, Chen's research specifically found that mineral-rich particles create a significantly clearer marker of flooding activity
- The key elements the correct answer must have are: It should relate to what Chen's investigation discovered about these particles
- It should capture that these particles serve as markers or indicators of flooding
- It should reflect that they're better/clearer than other methods like sediment thickness alone
They gather mainly in locations with rare flooding occurrences.
- Claims particles gather mainly where flooding is rare
- This directly contradicts the passage since mineral-rich particles are transported BY flood waters, so they would be found where flooding occurs, not where it's rare
They consist primarily of sedimentary accumulations.
- Says particles consist primarily of sedimentary accumulations
- The passage describes particles as being deposited IN sediment layers, not consisting OF sedimentary accumulations
They create a significantly clearer marker of flooding activity.
- States they create a significantly clearer marker of flooding activity
- This matches exactly what the passage says about mineral-rich particles creating a significantly clearer marker of flooding activity
They are capable of limiting excessive sediment buildup in river deltas.
- Claims particles can limit excessive sediment buildup
- The passage never mentions particles limiting or controlling sediment - it only discusses them as markers of flood activity