Hou'ao

An Unmissable Natural Geological Classroom. The sea-eroded landforms in Hou'ao, Xiyin, are incredibly rich, featuring sea caves, sea arches, and sea stacks, making it one of the best places to observe such formations. Sea caves are formed when a headland jutting into the sea is gradually eroded by seawater along fractured joints or softer parts of the rock layers, creating a hollowed-out cliff face over time. If the erosion continues, and a sea cave is eroded through, it forms a sea arch. If the top of a sea arch collapses due to lack of support, or if the middle section of a headland collapses due to erosion, separating the front rock mass from the land, an isolated rock pillar in the sea—a sea stack—is formed.