Morecambe Bay is a large estuary in northwest England, just to the south of the Lake District National Park. It is the largest expanse of intertidal mudflats and sand in the United Kingdom, covering a total area of 310 km2 (120 sq mi). In 1974, the second largest gas field in the UK was discovered 25 miles (40 km) west of Blackpool, with original reserves of over 7 trillion cubic feet (tcf) (200 billion cubic metres). At its peak, 15% of Britain's gas supply came from the bay but production is now in decline.
The rivers Leven, Kent, Keer, Lune, and Wyre drain into the Bay, with their various estuaries making a number of peninsulas within the bay. Much of the land around the bay is reclaimed, forming salt marshes used in agriculture. Morecambe Bay is also an important wildlife site, with abundant bird life and varied marine habitats, and there is a bird observatory at Walney Island. The bay has rich cockle beds, which have been fished by locals for generations.
There are seven main islands in the bay, all to the north; Walney, Barrow, Sheep, Piel, Chapel, Foulney and Roa. Walney is substantially larger than the others, with its southern tip marking the north-western corner of the Bay. Sheep, Piel, Chapel and Foulney Islands are tidal and can be walked to at low tide with appropriate care. Local guidance should be sought if walking to Chapel or Piel islands as fast tides and quicksand can be extremely dangerous. Roa Island is linked to the mainland by a causeway, while Barrow Island has been connected to the mainland as part of the docks system at Barrow-in-Furness.