Secrets of Muddy Hollow

Rare and mysterious underwater 'volcanoes' off North Wales coast

- By ANDREW FORGRAVE Countryside and Tourism Editor

TWENTY years ago, marine biologists at Bangor University made a dramatic discovery off the Gwynedd coast.

In a seabed area known as Muddy Hollow, off the Llŷn Peninsula, they found a strange creature responsible for a series of "underwater volcanos".

The conical structures weren't large, less than 30cm high. However mud was known to spew from their funnel-shaped apertures, so having significant impacts on the surrounding marine environment.

The submerged mounds were created by creatures known as volcano worms. Among the most bizarre inhabitants of Britain's coastal waters, they can be more than 35cm long and are notoriously shy. Scientists describe them as "rare and mysterious".

Later assessments of the site concluded it should be designated a habitat of conservation importance by the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR). The seabed volcanoes are now key features of the Llŷn Peninsula and Sarnau Special Area of Conservation.