Firth of Tay
The Firth of Tay (Scottish Gaelic: Linne Tatha) is a firth in Scotland between the council areas of Fife, Perth and Kinross, the City of Dundee and Angus, into which Scotland's largest river in terms of flow, the River Tay empties. The firth has a maximum width of at Invergowrie.
Firth
A firth is generally the result of ice age glaciation and is very often associated with a large river, where erosion caused by the tidal effects of incoming sea water passing upriver has widened the riverbed into an estuary. Demarcation can be rather vague. The Firth of Clyde is sometimes thought to include the estuary as far upriver as Dumbarton, but the Ordnance Survey map shows the change from river to firth occurring off Port Glasgow, while locally the change is held to be at the Tail of the Bank where the river crosses a sandbar off Greenock at the junction to the Gare Loch, or even further west at Gourock point.