A strait separating the Orkney Islands from the Scottish mainland, the Pentland Firth extends 14 miles (22.5 km) from Dunnet Head in the west to Duncansby Head in the east and has a maximum width of nearly 8 miles (13 km). It is noted for its rough passage and dangerous tidal races. The Pentland Skerries and the island of Stroma lie within the firth.