Skomer Island, off the coast of Pembrokeshire is composed almost entirely of volcanic and related rocks. The volcanic rock is basic in nature with some rarer intermediate and silicic (formed from magma rich in silica) rocks. Mainly formed by magma coming to the surface (extrusion), a small number of the rocks are also pyroclastic in nature, formed by fluidized masses of rock fragments and gases from a volcano moving rapidly in response to gravity.
Skomer Island is of national geological importance as it provides excellent exposures of the youngest major volcanic episode in the southern part of the British area. The entire area stretches east-west for about 43 Km with Skomer forming only part of this major area of geology, representing a major volcanic field which developed in the southern part of the Welsh area during the early Silurian period (443.7 - 416 million years ago).
It is believed that the rocks on Skomer were formed by relatively thin uniform lava flows which were non-explosive in character. In some areas on the island there is also evidence of subaqueous eruptions forming pillow flows.
The best place to see the layers of rock that form the different eras of the geological development of the rocks in this area are on the coast line where the sea has eroded the rocks clearly exposing the distinctive bands from each era of volcanic activity. The oldest rocks exposed are on the north side of the island and the youngest on the south.
Terrain-wise, Skomer boasts some of the most breathtaking coastline features of the Pembrokeshire coast. Separated from the mainland by the often treacherous Jack Sound, the island has numerous sheltered bays, exposed headlands, towering offshore rocks and shaded inlets, all painted with the graduated colours of lichen.
Probably the most remarkable feature is The Wick, a coastal inlet with a sheer cliff face with numerous ledges forming ideal homes for nesting sea birds as they come in to roost during the spring and early summer months.
Many other birds also nest on the island itself including the bird that the island is most famous for, the Puffin.
The puffin is well known for its large, distinctive, brightly coloured beak. The bill is coloured only during the breeding season and the colourful outer parts are shed leaving a smaller duller beak during the rest of the year – however they only tend to come to land during the breeding season and are rarely observed in their duller appearance. Juvenile puffins also only have dark bills.
As well as flying in the air, this little bird’s wings are equally as at home under water where they appear to “fly”, diving distances of up to 70m (200 ft), where they also use their webbed feet as rudders beneath the water. The large bill is perfectly shaped to catch herring, sprats, zooplankton, sand eels and a number of other small fish. Feeding areas are often located 100 km (60 miles) offshore from the nest or more, though when provisioning young the birds venture out only half that distance.
They lay their eggs in shallow boroughs in the ground and for this reason they tend to only breed on coastal islands where there are few, if any land based predators. They appear completely oblivious to visitors, only becoming agitated if you stand between them and their burrow!
In the past, their population was greatly reduced by humans, hunting for their meat and eggs. They are now a protected species here on this island. On some islands, populations have been decimated due to accidental introduction of rats – Skomer is devoid of mammal predators as none have crossed from the mainland.
Despite their appearance, puffins are not penguins nor are they related to the Southern Hemisphere’s flightless birds. They have been given several nicknames over the years because of their appearance, including “clown of the ocean" and "sea parrot". Locally, they have also been dubbed the “Pembrokeshire Penguin”.
For this cache to be accepted, you will need to do 2 tasks:
First task (no longer compulsory)
- Photography – you will need to include 2 photographs as part of logging the find for this Earthcache – one photograph, with your GPSr in the picture with The Wick clearly visible behind you.
- At least one other photograph of some of the wildlife you discover.
Second task
Please send me the answer to the following question via my Geocaching contact point in order for this Earth Cache to be accepted.
Can you suggest why The Wick has such a steep cliff face in comparison to the surrounding geology?
Don't forget to click the box to include your email address so that I can respond!
Non-compliance of these requirements may result in your log being deleted.
Please note that there is a modest landing fee for visiting Skomer to aid the important wildlife preservation that goes on there. Although I thoroughly recommend visiting the island (especially between April & June where the wildlife and flowers are at their most diverse and spectacular), the cache's requirements can be fulfilled from a boat trip as well - and this is probably the best way to see the spectacular geology too. Attempting this cache from the mainland is however not acceptable.
Be aware that there is a strict daily limit of 250 visitors to the island due to the fragile nature of the flora and fauna, and during peak periods (when the puffins are in residence), even arriving a while before the first boat is due to sail may be far too late - Eclectic Penguin arrived 3 hours before the first scheduled departure and there were already about 50 people standing in line ahead of me...
Note: The triangulation pillar ("trig-point") on the island can also be logged as a cache find as part of the Yo Ole Survey Monuments virtual cache.
This Earthcache has been placed with the assistance, kind approval and ongoing oversight of the Wildlife Trust of South and West Wales (who own and manage Skomer and Skokholm).
