A geological stack is a coastal landform, a large vertical column of rock in the sea.
Meoto Iwa (the wedded rocks), Mie Prefecture, Japan
Island Archway, Victoria, Australia
Arched Rock, California
At Faroe Islands
Tall Rock in Ponza Island, Italy
Flowerpot Island, Georgian Bay, Ontario
Twelve Apostles, Australia
Am Buachaille, Sutherland, Scotland
Old Man of Hoy, Scotland
Ball's Pyramid, Australia, is the tallest volcanic stack in the world.
Volcanic stack, part of the Motu islets near Easter Island, Chile
Painting by Claude Monet