Arrange the following stages of alpine glacial landform evolution in sequential order from the initial pre-glacial hollow to the final alpine peak landform.
- 1Freeze-thaw weathering and localized snow accumulation deepen a shallow hillside depression into a nivation hollow.
- 2Rotational ice movement, plucking, and basal abrasion enlarge the depression into a steep-sided, bowl-shaped cirque.
- 3Back-to-back headward erosion of two adjacent cirques narrows the intervening rock wall into a sharp arête.
- 4Convergent headward erosion of three or more adjacent cirques isolates a steep, pointed pyramidal peak.
Answer
The correct sequence begins with the formation of a nivation hollow, followed by its enlargement into a bowl-shaped cirque, the sharpening of dividing rock walls into an arête by adjacent cirques, and culminates in the formation of a pyramidal peak by three or more converging cirques.
Alpine glacial landscapes evolve systematically from small localized hollows to complex high-relief landforms. Snow accumulates in hillside depressions where freeze-thaw weathering creates a nivation hollow. As ice thickens and begins rotational movement, plucking and abrasion transform the hollow into a deep, bowl-shaped cirque. When neighboring cirques erode headward towards each other, their dividing rock wall is carved into a narrow, sharp-edged arête. Finally, when three or more cirques erode into the same mountain block from different directions, their intersecting headwalls isolate a steep, horn-like pyramidal peak.
Step-by-Step Solution
Key Concept
Evolutionary sequence of erosional alpine glacial landforms from cirque development to pyramidal peak isolation.