Skomer Island
feature by Mike Davies
Skomer is an island off the coast of Pembrokeshire in south-western Wales. It is well known for its wildlife: a third of the world population of Manx Shearwaters nest on the island, the Atlantic Puffin colony is the largest in southern Britain, and the Skomer Vole (a subspecies of the Bank Vole) is unique to the island. It is also known for its stone circle, standing stone and remains of prehistoric houses.
Skomer is a National Nature Reserve, a Site of Special Scientific Interest and a Special Protection Area. Much of the island has also been designated an Ancient Monument.
It is surrounded by a Marine Nature Reserve and is managed by the Wildlife Trust of South and West Wales.
Skomer Puffin with her catch of sand eels
(photo Mike Davies)
Geology
The volcanic rocks of which Skomer is comprised date from the Silurian period around 440 million years ago. A series of basalts, rhyolites, felsites, keratophyres, mugearite and associated sedimentary rocks (quartzites etc.) are grouped together as the 'Skomer Volcanic Series'. The series which is up to 1000m thick also includes trachyte, dolerite and skomerite which is an altered andesite.
Basalt is the most common component of this sequence; some of it appears as pillow lava indicating that it was erupted under water. Other basalt flows show signs of contemporary sub-aerial weathering.
This same suite of rocks can also be traced eastwards on the mainland along the northern side of the Marloes peninsula and extends almost as far east as St Ishmael's.
The entire sequence on Skomer dips between 15° and 25° to the south-southeast. Is cut by several faults, notably those responsible for the erosion of the inlets of North Haven and South Haven.
A NW-SE aligned fault stretches between Bull Hole and South Haven, offsetting the strata on either side.
Skomer was cut off from the mainland by rising sea levels after the last Ice Age.
I was privileged to go there to film the Puffin. The following video is best viewed full screen
