Geography of Scotland example at Aberdeen. Much of the Scottish coastline consists of a machair formation, a dune pasture land formed as sea levels subsided. The east coast has several significant estuaries and other nature reserves including the Ythan Estuary and Fowlsheugh, both of which have been designated as Important Bird Areas. Firths of Scotland include the Solway Firth, Firth of Clyde, and Firth of Lorne on the west coast, and the Cromarty Firth, Moray Firth, Firth of Tay, and Firth of Forth on the east coast. The Pentland Firth is not an inlet, but the strait that separates the Orkney Isles from
Firth "firth" (e.g. the Minch and Loch Torridon); instead, these are often called sea lochs. Before about 1850, the spelling "Frith" was more common. 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