# Does a canal cutting across an isthmus make an island? **URL:** \ **Category:** Factual Questions\ **Created:** [February 17, 2022, 5:37pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682 "2022-02-17T17:37:36Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Johanna](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johanna/32/8318_2.png) [@Johanna](https://boards.straightdope.com/u/Johanna)\ **Post date:** [February 17, 2022, 5:37pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/1 "2022-02-17T17:37:36Z")
> **[File:Peloponnese relief map-blank.svg](https://en.wikipedia.org/wiki/File:Peloponnese_relief_map-blank.svg)** > > Original file ‎(SVG file, nominally 2,611 × 2,044 pixels, file size: 1.97 MB) > Own work ; > Blank map with shaded relief > Click on a date/time to view the file as it appeared at that time. Did the [Corinth Canal](https://en.wikipedia.org/wiki/Corinth_Canal) turn the Peloponnese into an island? Is there a clear yes-or-no answer to this, or is the definition of “island” a sliding scale of truth values? Wikipedia says “Indeed, the Peloponnese is rarely, if ever, referred to as an island.” ---
**Author:** ![Schnitte](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/schnitte/32/9033_2.png) [@Schnitte](https://boards.straightdope.com/u/Schnitte)\ **Post date:** [February 17, 2022, 5:41pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/2 "2022-02-17T17:41:16Z")
There’s no hard definition of an island, but typically, artificially dug stretches of water are considered not to count as water for the purposes of that definition. A similar example is that [Afro-Eurasia](https://en.wikipedia.org/wiki/Afro-Eurasia) is still, even after the completion of the Suez Canal, considered to be a contiguous landmass (by far the largest in the world). Much the same way artificially constructed dry connections are similarly disregarded - that’s why people still consider Britain to be an island even after the construction of the channel tunnel. ---
**Author:** ![Schnitte](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/schnitte/32/9033_2.png) [@Schnitte](https://boards.straightdope.com/u/Schnitte)\ **Post date:** [February 17, 2022, 5:44pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/3 "2022-02-17T17:44:48Z")
Speaking of hard definitions, the closest thing you’ll find is the definition in [UNCLOS](https://www.un.org/depts/los/convention_agreements/texts/unclos/unclos_e.pdf), the United Nations Convention on the Law of the Sea - an international treaty that codifies the legal regime of the seas. It includes the following provision: > Article 121 > Regime of islands > > 1. An island is a naturally formed area of land, surrounded by water, which is above water at high tide. > (…) This is also the reason why China’s attempts to expand its territorial waters and exclusive economic zones by means of building artificial islands are not internationally recognised. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [February 17, 2022, 6:04pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/4 "2022-02-17T18:04:13Z")
I doubt it. There’d be a helluva lot more island if it did. Cape Cod would be an island, cut off by the Cape Cod Canal The piece of Canada next to Niagara Falls would be an island, cut off by the Welland Canal The piece of Wisconsin with Egg Harbor and Sturgeon Bay would be an island, cut off by the Sturgeon Bay Ship Canal The Hamptons on Long Island would be on an even smaller island, cut off by the Shinnecock Canal An un-named blob of land near my home town of South River NJ would be an un-named island, cut off by the Washington Canal … and so on, and so on, and so on ---
**Author:** ![burpo\_the\_wonder\_mutt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/burpo_the_wonder_mutt/32/365_2.png) [@burpo\_the\_wonder\_mutt](https://boards.straightdope.com/u/burpo_the_wonder_mutt)\ **Post date:** [February 17, 2022, 6:16pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/5 "2022-02-17T18:16:58Z")
South America is an island? Say it ain’t so! ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [February 17, 2022, 7:05pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/6 "2022-02-17T19:05:42Z")
Saudi Arabia would say yes as it planned to cut off its neighbor Qatar from the mainland as a political statement by building a canal. ---
**Author:** ![Wrenching\_Spanners](https://avatars.discourse-cdn.com/v4/letter/w/ecb155/32.png) [@Wrenching\_Spanners](https://boards.straightdope.com/u/Wrenching_Spanners)\ **Post date:** [February 17, 2022, 7:42pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/7 "2022-02-17T19:42:22Z")
Although northwest Scotland is part of the island of Britain, and includes many smaller islands, the mainland region isn’t usually referred to as an island because of the Caledonian Canal. > **[Caledonian Canal](https://waterways.org.uk/waterways/discover-the-waterways/caledonian-canal#:~:text=The%20Caledonian%20Canal%20runs%20from,Inverness%20on%20the%20east%20coast.%23)** > > The Caledonian Canal runs from Corpach (just north of Fort William) on the west coast of Scotland, through the Great Glen, to Inverness on the east coast. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [February 17, 2022, 9:28pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/8 "2022-02-17T21:28:50Z")
Even Long Island isn’t considered an island, but [a peninsula](https://apnews.com/article/dec6c2d35be955657c5f332412c9871b), even though it’s separated from the mainland by water. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [February 18, 2022, 7:01am UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/9 "2022-02-18T07:01:08Z")
Maybe OP is thinking of a peninsula. Does a canal cutting across a peninsula make an island? If someone builds a canal connecting the San Francisco Bay at San Mateo with the Pacific Ocean at Half Moon Bay (roughly, the route of State Route 92 on [this Google Map](https://www.google.com/maps/place/Half+Moon+Bay,+CA/@37.5114909,-122.3558821,10z/data=!4m5!3m4!1s0x808f0ba50a19cb0b:0x5efd9cc835e79b54!8m2!3d37.4635519!4d-122.4285862)), would San Francisco become an island? ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [February 18, 2022, 7:27am UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/10 "2022-02-18T07:27:21Z")
> [@Senegoid](#): > > Maybe OP is thinking of a peninsula. Does a canal cutting across a peninsula make an island? No. Most of the examples given in the thread above are actually of peninsulas that have canals across them. The canals are usually at a narrow section, that is, an isthmus, because that’s the easiest place to dig them. ---
**Author:** ![PatrickLondon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/patricklondon/32/4422_2.png) [@PatrickLondon](https://boards.straightdope.com/u/PatrickLondon)\ **Post date:** [February 18, 2022, 12:01pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/11 "2022-02-18T12:01:54Z")
Whatever the legalities, or the principles of geographical taxonomy, there’s also a perceptual effect. I live on the Isle of Dogs (the bit of east London in a 'tear drop" curve). When there were dock entrances to the Thames on both sides, it could become an island while the entrances were open to ships; and over the years it came to feel like a separate community, and under-served by the powers that be - to the extent that about 50 years ago, some local activists did a “[Passport to Pimlico](https://en.wikipedia.org/wiki/Passport_to_Pimlico)” and ‘[declared independence](https://www.ianvisits.co.uk/articles/the-isle-of-dogs-declares-independence-from-the-uk-3243/)’. It’s common shorthand around here to refer to it as “the island”. ---
**Author:** ![3AxisCtrl](https://avatars.discourse-cdn.com/v4/letter/3/ecd19e/32.png) [@3AxisCtrl](https://boards.straightdope.com/u/3AxisCtrl)\ **Post date:** [February 18, 2022, 12:56pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/12 "2022-02-18T12:56:57Z")
> [@panache45](#): > > Even Long Island isn’t considered an island, but [a peninsula](https://apnews.com/article/dec6c2d35be955657c5f332412c9871b) … This SCOTUS ruling applies in matters of maritime law, but not universally. From [Wiki](https://en.wikipedia.org/wiki/Long_Island): > [@](#): > > In 1985, the [United States Supreme Court](https://en.wikipedia.org/wiki/United_States_Supreme_Court) ruled in _[United States v. Maine](https://en.wikipedia.org/wiki/United_States_v._Maine)_ that Long Island is integrally related to the mainland enough that [Long Island Sound](https://en.wikipedia.org/wiki/Long_Island_Sound) and the western part of [Block Island Sound](https://en.wikipedia.org/wiki/Block_Island_Sound) constitute a “juridicial bay” for the purpose of determining maritime state boundaries.[[44]](https://en.wikipedia.org/wiki/Long_Island#cite_note-45) In the popular media this has been often misinterpreted as a ruling that Long Island is legally not an island.[[45]](https://en.wikipedia.org/wiki/Long_Island#cite_note-46)[[46]](https://en.wikipedia.org/wiki/Long_Island#cite_note-47)[[47]](https://en.wikipedia.org/wiki/Long_Island#cite_note-48) The [United States Board on Geographic Names](https://en.wikipedia.org/wiki/United_States_Board_on_Geographic_Names) still considers Long Island an island, because it is surrounded by water.[[48]](https://en.wikipedia.org/wiki/Long_Island#cite_note-piniat20160220-49) ---
**Author:** ![Kent\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kent_clark/32/105_2.png) [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)\ **Post date:** [February 18, 2022, 4:33pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/13 "2022-02-18T16:33:41Z")
When the Chain of Rocks Canal was constructed in 1953, it sliced off an 8+ mile section of Illinois just north of St. Louis. That slice is divided by a slough which is only full during high water. Despite not technically being an island at all, this slice of land is officially two different islands, Choteau and Gabaret. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [February 18, 2022, 4:53pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/14 "2022-02-18T16:53:04Z")
We’ve got a few cases like that down on the south coast: Hayling Island is a legit island, probably once a connected headland, now joined only by a road bridge. Portsea Island (Portsmouth) is an island separated only by a fairly narrow canal Whale Island (connected to Portsea Island only by a road bridge The Isle of Portland is perhaps the most odd - it’s connected to the mainland by a narrow strip of natural dry land (Chesil Beach) What people call an island isn’t necessarily a very tight technical definition, I think. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [February 18, 2022, 5:19pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/15 "2022-02-18T17:19:31Z")
If a ship canal doesn’t make an island, what about the curious case of Manhattan? The Spuyten Deyvil Creek connected the Hudson and Harlem Rivers. But it had an odd bend in it that hurt shipping, so in the late 19th century the Harlem River Ship Canal replaced it with a straighter waterway. That had the effect of isolating Marble Hill, which is now physically part of The Bronx but politically still in Manhattan. So is the northern end of Manhattan a natural creek or an artificial canal? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 18, 2022, 5:55pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/16 "2022-02-18T17:55:21Z")
Heck, you can’t even go from Mexico to Canada without crossing some body of water or another. There’s at least one case of a lake right on the Great Divide, that drains (eventually) into both the Atlantic and the Pacific (though it’s only a trickle at the start). North America is still one continent. ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [February 18, 2022, 6:08pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/17 "2022-02-18T18:08:13Z")
Yeah, but the East River isn’t something man-made. In a geographic sense, Long Island is definitely an island. Manhattan’s separation from the mainland by the Harlem river seems like a much more technical definition of island to me. ---
**Author:** ![Johanna](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johanna/32/8318_2.png) [@Johanna](https://boards.straightdope.com/u/Johanna)\ **Post date:** [February 18, 2022, 10:17pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/18 "2022-02-18T22:17:45Z")
> [@Chronos](#): > > There’s at least one case of a lake right on the Great Divide, that drains (eventually) into both the Atlantic and the Pacific (though it’s only a trickle at the start). 😲 Name, coordinates, and topography, or it didn’t happen. ---
**Author:** ![Johanna](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johanna/32/8318_2.png) [@Johanna](https://boards.straightdope.com/u/Johanna)\ **Post date:** [February 18, 2022, 10:20pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/19 "2022-02-18T22:20:32Z")
Hell of a dick move that would be. Meanwhile, Qatar defiantly sticks up as a thumb signaling “Up yours” in rude sign language. So there! ---
**Author:** ![ThisOneGuy](https://avatars.discourse-cdn.com/v4/letter/t/c0e974/32.png) [@ThisOneGuy](https://boards.straightdope.com/u/ThisOneGuy)\ **Post date:** [February 18, 2022, 11:24pm UTC](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682/20 "2022-02-18T23:24:10Z")
> [@Johanna](#): > > Name, coordinates, and topography, or it didn’t happen. It’s not a very big lake: > **[Isa Lake](https://en.wikipedia.org/wiki/Isa_Lake)** > > Isa Lake is located in Yellowstone National Park, in the U.S. state of Wyoming. The lake straddles the continental divide at Craig Pass. Indigenous peoples have lived in the Yellowstone region for at least 11,000 years. In the 1800s, at the time of the first European exploration of the area, the region was home to several Indigenous Nations including the Nimíipuu, Absaroke, and Shoshone Nations. Hiram M. Chittenden became the first known European to sight the lake in 1891, while searching f Isa L... Other sources say it only drains to the west in the spring when the water level is high. And there is this other nearby creek: > **[Parting of the Waters](https://en.wikipedia.org/wiki/Parting_of_the_Waters)** > > Parting of the Waters is an unusual hydrologic site at Two Ocean Pass on the Great Divide, within the Teton Wilderness area of Wyoming's Bridger-Teton National Forest. Two Ocean Pass separates the headwaters of Pacific Creek, which flows west to the Pacific Ocean, and Atlantic Creek, which flows east to the Atlantic Ocean. At Parting of the Waters, at .mw-parser-output .geo-default,.mw-parser-output .geo-dms,.mw-parser-output .geo-dec{display:inline}.mw-parser-output .geo-nondefault,.mw-parser-o... [Next page](https://boards.straightdope.com/t/does-a-canal-cutting-across-an-isthmus-make-an-island/959682.md?page=2)