Fjords are found in locations where current or past glaciation extended below current sea level. A fjord is formed when a glacier retreats, after carving its typical U-shaped valley, and the sea fills the resulting valley floor. This forms a narrow, steep sided inlet (sometimes deeper than 1300 metres) connected to the sea. The terminal moraine pushed down the valley by the glacier is left underwater at the fjord’s entrance, causing the water at the neck of the fjord to be shallower than the main body of the fjord behind it.