A possible impact crater site is the feature known as St. Magnus Bay in the Shetland Islands.
A massive impact seems to be the cause for the peculiar shape of the bay.
It has a diameter of eleven kilometres and is about 165m deep, which is very deep for the coastal waters in the region. The crater is oval in shape because of the east-west geological compression that the area has suffered.
It is suggested that the crater was formed in the late Tertiary.
Ice age erosions have removing the rims and smoothed out the bottom of the crater.
In size the submarine St. Magnus Bay crater would rank among the dozen or so largest terrestrial impact features and is thus an important object for further study.
The volcanic rocks of the small island Papa Stour forms the southern rim of St, Magnus Bay.