Tidal island

Diagram of tidal island at low tide and high tide

St Michael's Mount, Cornwall, at high tide, c. 1900

Cramond Island, Scotland, at high tide: the causeway is submerged, but the anti-submarine pylons are still visible.

A tidal island is a piece of land that is connected to the mainland by a natural or man-made causeway that is exposed at low tide and submerged at high tide. Because of the mystique surrounding tidal islands many of them have been sites of religious worship, such as Mont Saint-Michel with its Benedictine Abbey. Tidal islands are also commonly the sites of fortresses because of their natural fortifications.

List of tidal islands

Asia

Europe

Channel Islands

Lihou in Guernsey, one of the Channel Islands

Denmark

Mandø Island – on Denmark's western coast
Knudshoved Island – north of Vordingborg on southern Zealand, Denmark

France

Mont Saint-Michel in Normandy

Germany/Denmark

The Halligen in the North Frisian Islands, Germany/Denmark
The Neuwerk in the Wadden Sea, Germany

Ireland

Coney Island near Rosses Point, County Sligo
Omey Island in Connemara, County Galway, Connacht
Inishkeel, County Galway, Connacht

Iceland

Grótta in Seltjarnarnes in Capital Region

Spain

Cortegada Island in Pontevedra coast, Galicia.
San Nikolas Island in Lekeitio, Bizkaia

United Kingdom

Rough Island opposite Rockcliffe, Dumfries & Galloway, Scotland

Worm's Head at the end of Gower, Wales

England

Asparagus Island, Mount's Bay, Cornwall
Burgh Island, Devon
Burrow Island, Portsmouth Harbour
Chapel Island, Cumbria
Chiswick Eyot in the River Thames in London
Gugh in the Isles of Scilly (joined to St Agnes at low tide)
Hilbre Island, Middle Eye and Little Eye in the River Dee estuary, between North Wales and the English Wirral, but administratively in England.
Horsey Island, Essex
Lindisfarne, Northumberland
Mersea Island, Essex (accessible to road traffic via the Strood)
Northey Island, Essex
Osea Island, Essex
Piel Island, Cumbria
Ray Island in Essex
Sheep Island, Cumbria (joined at low tide to Piel Island and to Walney Island)
St Mary's Island, North Tyneside
St Michael's Mount, Cornwall

Northern Ireland

Nendrum Monastery on Mahee Island, Strangford Lough

Scotland

Baleshare in the Outer Hebrides, joined to North Uist
Brough of Birsay in Orkney, joined to Orkney Mainland
Castle Stalker on Loch Laich in Argyll
Cramond Island in the Firth of Forth
Davaar Island near Campbeltown, off the Kintyre peninsula
Eilean Shona in Loch Moidart, Lochaber, Highland
Eilean Tioram, in Loch Moidart
Erraid off the Isle of Mull
Hestan Island near Rough Island in Auchencairn Bay
Islands of Fleet: Ardwall Isle and Barlocco Isle in Galloway
Isle Ristol, the innermost of the Summer Isles
Kili Holm in Orkney, joined to Egilsay
Oronsay in the Inner Hebrides, joined to Colonsay
Rough Island opposite Rockcliffe, Dumfries & Galloway
Vallay (Bhàlaigh), joined to North Uist, Outer Hebrides

Wales

Burry Holms off the Gower
Gateholm off the south west coast of Pembrokeshire
Ynys Llanddwyn off Anglesey
Mumbles Lighthouse located in Mumbles, near Swansea
St Catherine's Island in Pembrokeshire
Sully Island in the Vale of Glamorgan
Worm's Head at the end of the Gower
Ynys Gifftan in Gwynedd, north Wales
Ynys Lochtyn on the coast of Cardigan Bay

43 (unbridged) tidal islands can be walked to from the UK mainland.^[1]

North America

Canada

Micou's Island in St. Margarets Bay, Nova Scotia, Canada
Minister's Island in New Brunswick, Canada

United States

Bar Island in Maine, U.S.

Bar Island in Maine
Battery Point Light in California
Bumpkin Island in Massachusetts
Camano Island in Puget Sound of Washington State, since earth filled
Cana Island Lighthouse in Wisconsin
Charles Island, in Connecticut
Douglas Island in Alaska
High Island, New York
Long Point Island,^[2] Harpswell, Maine

Australasia

Australia

The Point Walter Sandbar in Perth, Western Australia has slowly formed into a tidal island and is only connected to the mainland in extreme low tides.
Penguin Island (Western Australia) in the Shoalwater Islands Marine Park
Former tidal island Bennelong Island in Sydney, Australia was developed into Bennelong Point and is now the location of the Sydney Opera House.

New Zealand

Rangitoto Island forms a backdrop to a wave-cut platform off Achilles Point, Auckland, New Zealand.

Matakana Island in Tauranga Harbour
Opahekeheke Island in the Kaipara Harbour
Puddingstone Island in Otago Harbour
Rabbit Island, Bells Island, and Bests Island in Tasman Bay
The Hauraki Gulf islands of Motutapu Island and Rangitoto Island are connected at low tide
The Okatakata Islands and Walker Island in Rangaunu Harbour

References

Wikimedia Commons has media related to Tidal islands.

↑ Peter Caton (2011). No Boat Required – Exploring Tidal Islands. ISBN 978-1848767-010.
↑ longpointisland.com

Coastal geography
Landforms	Anchialine pool Archipelago Atoll Avulsion Ayre Barrier island Bay Baymouth bar Bight Bodden Brackish marsh Cape Channel Cliff Coast Coastal plain Coastal waterfall Continental margin Continental shelf Coral reef Cove Dune cliff-top Estuary Firth Fjard Fjord Freshwater marsh Fundus Gat Geo Gulf Gut Headland Inlet Intertidal wetland Island Islet Isthmus Lagoon Machair Marine terrace Mega delta Mouth bar Mudflat Natural arch Peninsula Reef Regressive delta Ria River delta Salt marsh Shoal Shore Skerry Sound Spit Stack Strait Strand plain Submarine canyon Tidal island Tidal marsh Tide pool Tied island Tombolo Windwatt
Beaches	Beach cusps Beach evolution Coastal morphodynamics Beach ridge Beachrock Pocket beach Raised beach Recession Shell beach Shingle beach Storm beach Wash margin
Processes	Blowhole Cliffed coast Coastal biogeomorphology Coastal erosion Concordant coastline Current Cuspate foreland Discordant coastline Emergent coastline Feeder bluff Fetch Flat coast Graded shoreline Headlands and bays Ingression coast Large-scale coastal behaviour Longshore drift Marine regression Marine transgression Raised shoreline Rip current Rocky shore Sea cave Sea foam Shoal Steep coast Submergent coastline Surf break Surf zone Surge channel Swash Undertow Volcanic arc Wave-cut platform Wave shoaling Wind wave Wrack zone
Management	Accretion Coastal management Integrated coastal zone management Submersion
Related	Bulkhead line Grain size boulder clay cobble granule pebble sand shingle silt Intertidal zone Littoral zone Physical oceanography Region of freshwater influence
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