Question

Difficulty: MediumDetermining Paragraph-Level Main Ideas

The following passage is adapted from an article on the history of science, focusing on the development of continental drift theory.

[Paragraph 1] (lines 1–10)
Alfred Wegener is best remembered today for his theory of continental drift, which he proposed in 1912. However, his formal training was in astronomy and meteorology. The geological establishment of the early twentieth century was highly specialized and resistant to outsiders, viewing Wegener’s lack of geological credentials with skepticism. Yet, it was precisely his meteorological background that allowed him to approach the Earth’s features with a fresh perspective, analyzing global climate patterns and fossil distributions to construct a unified theory of a shifting Earth.

[Paragraph 2] (lines 11–22)
Wegener's meteorological research in Greenland proved crucial to his thinking, though contemporary geologists dismissed these expeditions as irrelevant. By studying polar air currents and glacial movement, Wegener began to view the Earth's crust not as a rigid shell, but as a dynamic system subject to massive, slow-moving forces. He reasoned that if giant ice sheets could flow under the influence of gravity, entire continents might similarly migrate over geological time. This glaciological perspective provided the conceptual bridge that enabled him to visualize continental movement in a way that traditional geology could not.

Which of the following best expresses the main idea of Paragraph 2 (lines 11–22)?

  1. Wegener's observations of glacial movement in Greenland provided the conceptual model for how continents could shift over time.Answer
  2. B
    Wegener’s unconventional scientific background enabled him to challenge the skeptical and highly specialized geological establishment.
  3. C
    Glaciers and polar ice sheets flow slowly across the Earth's surface due to the pull of gravity.
  4. D
    Geologists eventually accepted Wegener's Greenland expeditions as foundational to the field of traditional geology.

Answer

Wegener's observations of glacial movement in Greenland provided the conceptual model for how continents could shift over time.
The correct answer accurately summarizes the main point of Paragraph 2, which argues that Wegener's observation of glacial flow in Greenland provided him with the necessary analogy to conceptualize how solid continents could move over time.

Step-by-Step Solution

1
Identify the target paragraph and locate the core focus.
Paragraph 2 focuses on Wegener's research in Greenland, studying glaciers and polar air currents.
To narrow down the scope of the paragraph's specific argument.
2
Determine how the author connects the Greenland research to Wegener's theory.
The author notes that Wegener compared the flow of ice sheets to the potential migration of continents, providing a conceptual bridge.
To find the paragraph's main point about the significance of this research.
3
Evaluate the options to find the one that paraphrases this connection without being too narrow or too broad.
The correct option correctly identifies the glacial research as the source of his conceptual model for continental movement.
To select the option that represents the primary purpose rather than a minor detail or a global passage theme.

Key Concept

Determining Paragraph-Level Main Ideas
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