Its name means 'ox ford', from the myth of a girl turned into a heifer swimming across it
Io, fleeing Hera; the Greek is bous plus poros
Geography · Physical geography
The Bosporus
governed by the Montreux Convention of 1936
Strait dividing Europe from Asia at Istanbul — links the Black Sea to the Sea of Marmara
A strait about 31 kilometres long and at its narrowest only some 700 metres wide, running through Istanbul and joining the Black Sea to the Sea of Marmara and so, through the Dardanelles, to the Mediterranean. It is the boundary between Europe and Asia, the only sea route out of the Black Sea, and one of the busiest and most strategically fought-over waterways on Earth.
How to spot them
- ▸The strait through a city that stands on two continents, and the Black Sea's only outlet
- ▸Quiz clue: 'Montreux Convention', 'Golden Horn', 'Symplegades', 'Rumelihisari', 'Marmaray'
- ▸Its name means 'ox ford', from the myth of Io crossing it as a heifer
- ▸Do not confuse it with the Dardanelles, the second strait further south-west
Key facts
A 1936 convention signed in Switzerland still governs warship passage through it (1936)
The Montreux Convention, which restored Turkish control of the straits
In Greek myth the Argonauts had to row between clashing rocks at its Black Sea end
The Symplegades; Jason sent a dove through first
Mehmed II built a fortress on its European bank in 1452 to cut Constantinople off before his siege (1452)
Rumelihisari, facing the older Anadoluhisari
The first bridge across it opened in 1973 and was renamed in 2016 after those who died resisting a coup (1973)
Now the 15 July Martyrs Bridge; a third bridge, the Yavuz Sultan Selim, opened in 2016
A rail tunnel beneath it, opened in 2013, finally linked the European and Asian commuter networks (2013)
The Marmaray; the Eurasia road tunnel followed in 2016
An inlet on its European side, shaped like a horn, formed the harbour of Byzantium
The Golden Horn, closed in wartime by a great chain
It is barely 700 metres wide at its narrowest and about 31 kilometres long
The narrowest point is between the two fortresses
Quick-fire facts
- •Length about 31 km; width from roughly 700 m to 3,400 m
- •It connects the Black Sea to the Sea of Marmara; the Dardanelles then connect that to the Aegean
- •It forms part of the conventional boundary between Europe and Asia
- •The Montreux Convention of 1936 governs the passage of merchant and naval vessels
- •The Turkish name is Istanbul Bogazi, 'the Istanbul strait'
- •Three road bridges now cross it: the 15 July Martyrs Bridge (1973), the Fatih Sultan Mehmet (1988) and the Yavuz Sultan Selim (2016)
- •The Marmaray rail tunnel opened in 2013 and the Eurasia Tunnel for cars in 2016
- •A strong surface current runs from the Black Sea southwards, with a saltier counter-current beneath
- •Turkey has long promoted a parallel artificial waterway, Kanal Istanbul, to relieve traffic
Drill it — 8 cards
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Sources
- Encyclopaedia Britannica — Bosporus
- Republic of Turkiye Ministry of Foreign Affairs — The Turkish Straits and the Montreux Convention