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Dee Estuary
The Dee Estuary ((ウェールズ語:Aber Dyfrdwy)) is a large estuary by means of which the River Dee flows into Liverpool Bay. The estuary starts near Shotton after a five miles (8 km) 'canalised' section and the river soon swells to be several miles wide forming the boundary between the Wirral Peninsula in north-west England and Flintshire in north-east Wales.
==Geology==
The estuary is unusual in that comparatively little water occupies so large a basin. One theory is that larger rivers such as the Severn and/or Mersey once flowed into the Dee. The current view is that the estuary owes its origin to the passage of glacial ice southeastwards from the Irish Sea during successive ice ages, eroding a broad and shallow iceway through the relatively soft Triassic sandstones and Coal Measures mudstones which underlie the area. The inner parts of this channel were filled by glacially derived sands and gravels long ago and infilling by mud and silt has continued since. It is also thought that prior to the ice ages, the estuary received larger river flows as the upper Severn flowed into the Dee near Chirk. For a period, the Mersey may also have flowed into the Dee by means of a channel which it cut through the base of the Wirral Peninsula.〔(Proudman Oceanographic Laboratory - Dee Estuary )〕〔Davies et al 2004, Geology of the Country around Flint. memoir of the British Geological Survey, sheet 108 (E&W)〕
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