The mounds are about 1,000 metres (3,300 ft) below the surface of the North Atlantic ocean, approximately 100 nautical miles (190 km) north-west of Cape Wrath, the north-west tip of mainland Scotland.[2] There are hundreds of mounds in the field, which in total cover approximately 100 square kilometres (39 sq mi). Individual mounds are typically circular, up to 5 metres (16 ft) high and 100 metres (330 ft) wide. Most of the mounds are also distinguished by the presence of an additional feature referred to as a 'tail'.