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Difficulty: HardWeathering and Mass Wasting Processes

In an arid, high-altitude alpine environment experiencing diurnal freeze-thaw cycles and torrential seasonal rainfall, angular rock fragments disintegrate from steep granite cliffs and accumulate at the base. Subsequent heavy rainfall saturates these loose debris accumulations, causing them to flow rapidly down a narrow drainage channel. Which combination of physical weathering and mass wasting processes accurately accounts for this sequence of landscape evolution?

  1. Frost shattering followed by mudflowAnswer
  2. B
    Hydrolysis followed by soil creep
  3. C
    Metamorphic recrystallization followed by rock fall
  4. D
    Carbonation followed by solifluction

Answer

The initial mechanical disintegration of granite cliffs is caused by frost shattering (frost wedging), and the subsequent rapid downslope movement of saturated debris along a channel is a mudflow.
The correct response correctly identifies frost shattering as the mechanical weathering process driven by freeze-thaw cycles in high-altitude environments, and mudflow as the rapid movement of water-saturated debris down a defined channel.

Step-by-Step Solution

1
Analyze the primary weathering process described in the scenario.
In high-altitude areas with diurnal freeze-thaw temperature fluctuations around 0∘C0^\circ\text{C}, water trapped in rock joints expands by approximately 9%9\% upon freezing. This exerts internal stress, leading to frost shattering (gelifraction) that detaches angular fragments (scree/talus).
Identifying the specific mechanical weathering process operating under alpine freeze-thaw conditions.
2
Analyze the mass wasting mechanism operating on the accumulated debris.
When sudden torrential rainfall saturates the loose scree fragments, the material behaves as a high-density liquid and surges rapidly down confined channels as a mudflow (or debris flow).
Distinguishing rapid, channelized, water-saturated mass movement from slow or non-fluid slope movements.

Key Concept

Interaction of Frost Wedging and Rapid Channelized Mass Wasting
Estimated Time:2m 0s
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Topics

Weathering and Mass Wasting Processes

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