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Question

Difficulty: MediumSequence of Events

Passage

Dr. Marcus Vance cleared away the limestone silt of the riverbed, tracing the overlapping tracks of a carnivorous theropod and a herbivorous sauropod. To the untrained eye, the theropod’s deep, sharp three-toed prints seemed to have been stamped into the mud after the heavy, circular depressions left by the sauropod. However, Vance knew the sequence was more complex. The sauropod had crossed the tidal flat during a period of high humidity, when the mud was malleable but firm. Three days later, a sudden flash flood deposited a thin layer of fine silt across the flat. It was through this fresh layer of silt that the theropod subsequently trampled, pressing the silt down into the open sauropod prints below. Weeks later, mineral-rich groundwater seeped into the tracks, beginning the slow process of petrification. Finally, millions of years later, modern river erosion uncovered the fossilized footprints, exposing the interlaced sequence of prehistoric steps.

Based on the passage, arrange the following events in chronological order, from the earliest to the latest.

  1. 1A herbivorous sauropod walks across the damp clay of the tidal flat.
  2. 2A flash flood deposits a thin layer of fine silt across the flat.
  3. 3A carnivorous theropod steps into the silt-covered depressions.
  4. 4Mineral-rich groundwater infiltrates the tracks and starts petrification.
  5. 5Modern river erosion uncovers the fossilized footprints.

Answer

The correct chronological sequence is: first, the sauropod walks across the damp clay; second, a flash flood deposits a layer of silt; third, the theropod steps into the silt-covered depressions; fourth, mineral-rich groundwater infiltrates the tracks; and finally, modern river erosion uncovers the footprints.
The correct order follows the chronological progression described in the text: the sauropod's crossing is described as the initial state, followed three days later by the flash flood depositing silt, which was then stepped in by the theropod, before groundwater seeped in weeks later, and finally, modern erosion exposed the tracks.

Step-by-Step Solution

1
Identify the earliest event in the chronological sequence.
The sauropod crossing the mud flat.
The author states that the sauropod crossed the tidal flat during a period of high humidity before the other events occurred.
2
Locate the second event by identifying what happened three days later.
The flash flood depositing silt.
The text explicitly says that three days after the sauropod crossed, a flash flood left a thin layer of fine silt.
3
Identify what occurred subsequently after the silt deposition.
The theropod walks across the silt.
The passage explains that the theropod subsequently trampled through this fresh silt layer.
4
Find the post-track geological processes.
Groundwater infiltration starting petrification.
The author notes that weeks later, groundwater seeped into the tracks to begin petrification.
5
Determine the final event in the timeline.
Modern river erosion uncovering the fossilized tracks.
The text states that finally, millions of years later, modern river erosion exposed the footprints.

Key Concept

Determining the chronological order of events from a non-linear narrative.
Estimated Time:1m 30s
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Topics

Sequence of Events

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