PrepTest 156

Paragraph 1

• Paragraph note
  • Phenomenon, explanation, evidence it's wrong
• Views, minor Meta-Structures, and the author's attitude
  • Phenomenon - Ukhaa Tolgod has very well preserved fossils
  • Old Explanation - Big, sudden sandstorms buried animals
  • New Evidence - Geological formations - Sandstorm hypothesis wrong

Paragraph 2

• Paragraph note
  • New evidence/geological formations
• Views, minor Meta-Structures, and the author's attitude
  • 3 types of sandstone
    • Tilted layers, sorted by particle size = wind - Footprints, no fossils
    • Tilted layers, not sorted = wind - No fossils
    • No layers, pebbles = not wind - All the fossils

Paragraph 3

• Paragraph note
  • Explanation for third layer
• Views, minor Meta-Structures, and the author's attitude
  • Not wind, but water from heavy rains → sudden debris flow
  • New explanation - Sudden debris flow from rain, not wind

Paragraph 4

• Paragraph note
  • Cause of sandslides
• Views, minor Meta-Structures, and the author's attitude
  • Cause - Not well understood
  • Evidence - Clay plays a role, with dunes and vegetation also relevant
  • Implication - If sandslide explanation correct, then desert not sterile but had dunes/plants/rain

Main Point:

New evidence suggests sandslides caused by sudden, heavy rains — rather than sandstorms caused by wind — may have preserved Ukhaa Tolgod fossils.

Key Lines?

P1, S2 - Phenomenon
P1, S3 - Old Explanation
P1, S4 - Evidence suggests Old Explanation is wrong
P3, S3 - New Explanation
P4, S1 - Cause of New Explanation not fully understood
P4, S7 - Implication of New Explanation

Meta-Structure?

Old Explanation/New Explanation (or Phenomenon/Explanation): The passage opens with a description of an area with unexpectedly well-preserved fossils. While that doesn't necessarily establish a Meta-Structure, we know that Science passages often fall into the Phenomenon/Explanation Meta-Structure, and the "extraordinar[y]" nature of these fossils suggests that the passager might head in that direction. Paragraph 1, Sentence 3 (P1, S3) reinforces this prediction, as the author raises an explanation: the preservation was "due to" immense, sudden sandstorms. At this point, we might think that this is a Phenomenon/Explanation passage. But then the author goes in a different direction, claiming that evidence suggests the sandstorm explanation is wrong and a new explanation is warranted. The author eventually elaborates on this new explanation in paragraph 3: sandslides, rather than sandstorms, preserved the fossils.

The third paragraph's alternative explanation suggests that the author uses an Old Explanation/New Explanation Meta-Structure (though we could still consider it a Phenomenon/Explanation passage, only with this added wrinkle). In the former Meta-Structure, the author's preferred explanation is the main point; in the latter, it's the author's opinion on the new explanation. Here, the author is the one presenting the new explanation, though the author may not be 100% committed to it (note the noncommittal language in P3, S3 — "could have trapped"; and P4, S7 - "If the animals…"). So the main point is the new explanation, though we have to be careful not to oversell how committed the author is to that explanation.

Causality: Outside of the typically causal nature of a Phenomenon/Explanation passage (in which the explanation is generally causal, as it is here), the author spends a lot of time walking through the causal chain of events that may lead to a sandslide in P4. We probably don't want to get too bogged down with understanding and memorizing it as we read. Still, a prudent test taker would note that P4 is a cause-and-effect-focused paragraph to help answer any questions about P4 or the possible causes of a sandslide.

Comparison: the author spends P2 comparing the different types of sandstones and the evidence found at each site of Ukhaa Tolgod to build to her intermediate conclusion (the sandstorm hypothesis is probably mistaken). These comparisons could feature in a question, and they play into the role of P2, which very well could itself be a question (see "Last Thoughts?", below).

Last Thoughts?

Two things, both about the second paragraph ...

First, it's important to understand the role of that paragraph in the passage's overall organization. P2 and P1 are closely tied. P1 cites "geological formations" as new evidence that the sandstorm hypothesis (the Old Explanation) is probably wrong. The sandstone at the site, discussed in P2, are those "geological formations."

Second, it's important to understand how the author uses this evidence to undermine the old hypothesis. The author brings up three layers of sandstone and highlights similarities and differences between them. Crucially, it's only the third layer that contains fossils. The first layer explicitly doesn't contain fossils, and the second layer implicitly doesn't since "all the vertebrate skeletal fossils" are found in the third layer. Wind caused the first two layers, but wind couldn't have caused the third. Since the fossils are all in the third layer, wind/sandstorms cannot explain why the fossils are "extraordinarily well preserved." Ergo, something else must have preserved those fossils. Understanding this argument will likely play a role in answering at least a few questions!