Sarn y Bwch, ( Welsh for 'buck's causeway'), is one of three parallel reefs extending beneath the sea into

Cardigan Bay Cardigan Bay () is a large inlet of the Irish Sea, indenting the west coast of Wales between Bardsey Island, Gwynedd in the north, and Strumble Head, Pembrokeshire at its southern end. It is the largest bay in Wales. Geography Cardigan Bay ha ...

from the west coast of

Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...

. The causeway, probably a

medial moraine A moraine is any accumulation of unconsolidated debris ( regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice s ...

, is made of glacial deposits left by receding ice sheets at the end of the last

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages, and g ...

. It is sometimes called ''Sarn y Bwlch'' ('the causeway of the pass'), but this form is later and less common than ''Sarn y Bwch''. Sarn y Bwch is the central one of the three, extending south-westwards from near

Tywyn Tywyn (; ), formerly spelled Towyn, is a town, community, and seaside resort on the Cardigan Bay coast of southern Gwynedd, Wales. It was previously in the historic county of Merionethshire. It is famous as the location of the Cadfan Stone, a ...

. To the north is the causeway of Sarn Badrig, whilst to the south is

Sarn Gynfelyn Sarn Gynfelyn (or Sarn Cynfelyn) is a shingle spit on the coast of Cardigan Bay, in the county of Ceredigion, Mid-Wales, in the United Kingdom. It is located at Wallog, a few kilometres north of Llangorwen, close to Clarach Bay, south of Bor ...

, which extends from near

Aberystwyth Aberystwyth (; ) is a University town, university and seaside town and a community (Wales), community in Ceredigion, Wales. It is the largest town in Ceredigion and from Aberaeron, the county's other administrative centre. In 2021, the popula ...

External links

Cantre'r Gwaelod (The Lowland Hundred)
Reefs of Gwynedd Cardigan Bay Reefs of the Atlantic Ocean {{Gwynedd-geo-stub