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Question

Difficulty: HardCause-and-Effect Relationships

Passage

During the late Miocene epoch, approximately 5.96 million years ago, the Mediterranean Sea underwent a dramatic transformation known as the Messinian Salinity Crisis. Tectonic uplift in the Gibraltar region, combined with a global drop in sea levels driven by Antarctic glaciation, restricted the inflow of Atlantic water through the Betic and Rifian corridors. Deprived of its primary water source, the Mediterranean Sea, which lies in an arid climate zone, experienced evaporation rates that far exceeded precipitation and river runoff. Consequently, the sea levels plummeted, leaving behind a desiccated basin covered with salt deposits up to three kilometers thick. This massive accumulation of salt withdrew roughly six percent of the oceans' salt content, which directly lowered the salinity of the remaining global oceans. As a result, the freezing point of water in high-latitude regions rose, facilitating the rapid expansion of sea ice around Antarctica and further accelerating global cooling. While tectonic isolation initiated this regional crisis, the resultant global oceanic changes subsequently reinforced the glacial processes that had partially driven the sea-level drop in the first place.

Based on the passage, the rapid expansion of sea ice around Antarctica was directly facilitated by which of the following environmental changes?

  1. A
    The tectonic uplift in the Gibraltar region that restricted Atlantic water inflow through the Betic and Rifian corridors.
  2. B
    The expansion of Antarctic sea ice, which withdrew six percent of the salt content from the global oceans.
  3. A decrease in the salinity of the global oceans, which raised the freezing point of water in high-latitude regions.Answer
  4. D
    An increase in precipitation and river runoff that lowered the evaporation rate in the Mediterranean basin.

Answer

A decrease in the salinity of the global oceans, which raised the freezing point of water in high-latitude regions.
The correct answer identifies the direct cause of the Antarctic sea ice expansion: a decrease in global ocean salinity, which raised the freezing point of high-latitude waters. This aligns with the passage's explanation that the removal of salt from the oceans directly lowered global ocean salinity, which consequently raised the freezing point of water in high-latitude regions, facilitating sea ice expansion.

Step-by-Step Solution

1
Identify the target effect in the passage: the rapid expansion of sea ice around Antarctica.
Locate the sentence: 'As a result, the freezing point of water in high-latitude regions rose, facilitating the rapid expansion of sea ice around Antarctica...'
This establishes the direct cause-and-effect link leading to the ice expansion.
2
Trace the cause of the rising freezing point of high-latitude water.
Locate the preceding sentence: 'This massive accumulation of salt withdrew roughly six percent of the oceans' salt content, which directly lowered the salinity of the remaining global oceans.'
This connects the lowered salinity of global oceans to the rising freezing point, which in turn facilitated the sea ice expansion.
3
Select the option that accurately describes this multi-step causal relationship.
The correct option states that the decrease in global ocean salinity raised the freezing point of water in high-latitude regions, thereby facilitating the ice expansion.
This option correctly captures the causal chain without reversing the relationship or introducing incorrect details.

Key Concept

Tracing multi-step cause-and-effect relationships and identifying direct vs. indirect causes in a reading passage.
Estimated Time:1m 30s
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Topics

Cause-and-Effect Relationships

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