It has long been thought – now apparently without evidence – that the muscular whirlpools that make the Sound of Corryvreckan the third most powerful set in the world, are caused by water thrust upwards by tidal movements against the sides of a steep pinnacle of rock projecting well upwards from the sea bed in the Sound.
A team of scientists, with Dr John Howe, from the Scottish Association of Marine Science [SAMS] are conducting an ongoing marine survey as part of the collaborative INIS Hydro project, with Ireland, Northern Ireland and Scotland.
INIS is seeing advanced hydrography surveying being undertaken in all three countries. SAMS, with collaboration from staff at the UK Hyrdrographic Office, is surveying the entire Firth of Lorne – and it was part of this work that took them into the Corryvreckan.
Lying between the isles of Jura and Scarbha and with an 8 knot tidal bore [the Sound of Islay is 9 knots and watching boats fly through is a compelling spectator sport], the SAMS team found two major facts of note.
There is no rock pinnacle but there is a steep-sided rock bluff projecting from a rock wall on Scarbha, on the north shore of the sound. This rock formation is causing the upheavals in the sound when the tides are running
The bed of the sound is scoured clean of mud and sand by the force of the twice daily tidal flows coming through it. Some of this material has been swept out of the tidal flow track to form sandy dunes beyond it, changing their shape and position with the tides.
The ‘pinnacle’ theory wasn’t wrong, simply a little misplaced – and solitary, where the actual cause of the maelstrom is attached to a rock wall and does not stand independently.
The next SAMS Open Day – always a major diary date for Argyll - is bound to display the images from the survey, resulting from the process used. This was a form of echo sounding using high resolution multi-beam technology.
When the tide is running, the Corryvreckan is not the place to be, but yachts can come through it safely at judicious point of the tide, by keeping to the Jura shore and by using the Bay of Pigs as a holding base.
People swim the sound – at slack water – for charity; and For Argyll has recently recorded [ here ] the successful efforts by a team supporting the important charity for Scottish war veterans – Houses for Heroes.