In glaciated highland regions, frost action and glacial movement progressively transform mountain slopes into distinctive alpine landforms over time. Arrange the following geomorphic stages in the correct chronological order of their evolutionary sequence, from the initial process to the final landform.
- 1Perennial snow collects in a shallow mountain hollow, undergoing nivation and freeze-thaw breakdown of the underlying bedrock.
- 2Rotational ice movement and basal plucking deepen and enlarge the hollow into a steep-sided, armchair-shaped cirque.
- 3Headward erosion by glaciers in three or more adjacent cirques cuts back into the main mountain mass.
- 4Intersecting arêtes leave behind a sharp, isolated pyramidal peak at the mountain summit.
Answer
The correct sequence of glacial landform evolution is: (1) Snow accumulation and nivation in a mountain hollow, (2) Deepening into an armchair-shaped cirque by rotational ice flow and plucking, (3) Headward erosion of adjacent cirques into a central mountain mass, and (4) Isolation of a sharp pyramidal peak.
Alpine glacial landscape evolution begins with perennial snow accumulation and freeze-thaw nivation in mountain depressions. As ice builds up, rotational sliding and basal plucking deepen these hollows into armchair-shaped cirques. When three or more surrounding cirques erode headward into the same central mountain summit, the narrowing dividing ridges converge to leave a sharp, steep-sided pyramidal peak.
Step-by-Step Solution
Key Concept
Evolutionary sequence of alpine glacial erosional landforms from nivation hollows to pyramidal peaks.