Why is Ireland’s western coast more deeply indented than its eastern coast?

The western coast of Ireland is more deeply indented than the eastern coast primarily due to its unique geological structure and the presence of mountains that extend directly into the Atlantic Ocean. In the west and southwest, these coastal highlands—such as those found in Donegal, Mayo, Galway, and Kerry—thrust out into the sea, creating a rugged landscape separated by deep, wide-mouthed bays.1

Many of these prominent indentations, including Bantry Bay and Dingle Bay, are classified as drowned river valleys. By contrast, the eastern coast is characterized by a lack of such deep indentations, resulting in a much smoother coastline. The diversity of this scenery is further influenced by the country's complex geological history, which includes the effects of at least two major glaciations that shaped the Irish landscape.1