Stack
Explanation
Coastal landforms are primarily shaped by the erosional and depositional actions of sea waves. On rocky coasts, high-energy waves erode headlands, creating a specific sequence of erosional features based on the rock structure and resistance.
Process of Formation:
- Sea Cave: The continuous action of waves on weak points (cracks or crevices) in a rocky headland widens them to form hollows known as sea caves.
- Sea Arch: When caves on opposite sides of a headland unite, or when a single cave is eroded all the way through the rock, a bridge-like structure called a sea arch is formed.
- Stack: Over time, the roof of the sea arch becomes unstable due to gravity and continued erosion from below. When the roof collapses, it leaves behind an isolated, vertical pillar of rock standing in the sea. This feature is called a stack (or sea stack).
- Stump: Further erosion of the stack reduces its height, eventually forming a stump.
Analysis of Other Options:
- Sea Cave Sea Cave: This is the precursor to an arch, formed before the arch is created.
- Cliff: A steep rock face along the coast, formed by the undercutting action of waves, but not specifically defined by the collapse of an arch.
- Beach: This is a depositional landform consisting of sand, gravel, or pebbles, not an erosional feature associated with headland collapse.
Key Takeaway:
The chronological sequence of erosional landforms on a headland is: Crack → Cave → Arch → Stack → Stump.