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Difficulty: MediumParagraph-Level Transitions

The following paragraphs are from an essay about Marie Tharp's mapping of the ocean floor. To make the essay flow most logically, in what order should the paragraphs be placed?

  1. 1For centuries, scientists and mariners assumed that the deep ocean floor was a vast, featureless abyss. Lacking the technology to explore these depths, researchers believed the seabed was a static plain of mud and rock, undisturbed by geological activity.
  2. 2In the mid-1950s, however, geologist Marie Tharp began analyzing sonar data collected from transatlantic research ships. Using these depth measurements, she painstakingly drafted detailed topographic profiles that revealed a massive, continuous mountain range slicing through the center of the Atlantic Ocean.
  3. 3This groundbreaking map did more than just chart the seabed; it also provided crucial physical evidence supporting the controversial theory of continental drift. By visualizing the deep rift valley running down the center of this underwater range, Tharp helped show that the Earth's crust was actively spreading.

Answer

The paragraphs should be placed in the order: first, the paragraph describing the historical assumption of a flat ocean floor; second, the paragraph introducing Marie Tharp's sonar analysis and creation of topographic profiles; and third, the paragraph explaining the impact of this groundbreaking map on continental drift theory.
The correct sequence begins with the paragraph establishing the historical belief that the seafloor was a featureless plain. The next paragraph transitionally shifts focus using 'however' to describe Marie Tharp's mid-1950s research and her creation of topographic profiles. The final paragraph logically follows by using 'This groundbreaking map' to refer back to Tharp's profiles and explain the map's role in supporting plate tectonics.

Step-by-Step Solution

1
Identify the introductory paragraph that establishes the context or baseline belief.
The paragraph starting with 'For centuries' describes the historical view that the ocean floor was a flat, featureless plain.
This establishes the status quo before any discoveries were made.
2
Look for transition words or phrases that signal a shift away from this status quo.
The paragraph starting with 'In the mid-1950s, however' uses the contrast transition 'however' to introduce Marie Tharp's research and the discovery of a mountain range, contradicting the flat seafloor theory.
The word 'however' directly connects to and refutes the idea of a featureless seabed established in the first paragraph.
3
Identify the paragraph that builds upon the details of the discovery.
The paragraph starting with 'This groundbreaking map' references the map created in the previous step ('topographic profiles') and explains its larger scientific implications.
The demonstrative adjective 'This' in 'This groundbreaking map' requires a prior mention of mapmaking, which occurs at the end of the second paragraph.

Key Concept

Paragraph-Level Transitions
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Topics

Paragraph-Level Transitions

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