Back to Coastal and Oceanic Landform
- A stack is a vertical column or columns of rock.
- Isolated by erosion.
- formed by;
- There are Part of a headland is eroded by hydraulic action.
- Stacks form in horizontally-bedded sedimentary / volcanic rocks.
- Mostly limestone cliffs.
The formation process begins;
1.The sea attacks small cracks in a headland and opens them.
2.The cracks gradually get larger.
3. It turn into a small cave.
4. The cave wears through the headland, an arch forms.
5. Erosion causes the arch to collapse.
6. Leaving the pillar of hard rock.
7. Then it standing away from the coast - the stack.
8.Erosion cause the stack to collapse, leaving a stump.
9. This stump forms a small rock island.
- Some stacks last for a very long time .
example ; Balls Pyramid volcanic stack in Lord Howe Island, New South Wales, Australia.