Three-Country Cairn, the boundary cairn at the tripoint, is 10 metres from the shore of Lake Goldajärvi/Koltajauri, and hence arguably a tiny artificial island. Around 14 m2. The lower limit for artificial islands is a matter of definition, because near Haparanda there are boundary poles of less than 0.1 m2.
The border between Austria and Hungary cuts across the Neusiedler See/Fertő tó, where the water level fluctuates, sometimes exposing island flats which straddle the border.
The lower reaches of the Ganges,[83]Teesta,[84] and Brahmaputra[85] Rivers, approaching the Ganges Delta, are braided and contain numerous sand islands called chars.[86] These can be large and inhabited but are impermanent. At any given time, several are likely to straddle the border between India (Assam and West Bengal) and Bangladesh, though this border is not fully specified.
Other islands have been divided by international borders in the past but they are now unified.
The definite borders of modern nation states do not apply in other forms of societal organisation, where "divided" islands may consequently be less noteworthy. For example, in Ancient Greece, the island of Euboea was divided among several city-states, including Chalcis and Eretria; and before its settlement by Europeans, the Island of Tasmania was divided among nine indigenous tribes.
Boundary Islet – divided between the colonies of Victoria (part of New South Wales until 1851) and Tasmania (known as Van Diemen's Land until 1856); remained separated between two Australian states
Ternate – divided between the Spanish Empire allied with Tidore, and the Dutch Republic allied with the Sultan of Ternate from 1607 through 1663. Later, Ternate has successive been owned by the Netherlands, the Japanese Empire (1942–1945), Netherlands again, and the independent country of Indonesia, beginning in 1949.
Saint Kitts – Divided between Great Britain and the French Empire in 1628. "The island fell to the French in April 1666, but by the Treaty of Utrecht, April 11, 1713, it was yielded entirely to the British crown."[94] Then it became part of the British Empire for about 250 years, and finally part of the independent country of Saint Kitts and Nevis. At various times of war in the Caribbean Sea, either France or Great Britain occupied all of Saint Kitts both before and after 1713.
Frijoles Island within Gatun Lake in the former Panama Canal Zone was split between the United States and Panama on 1 October 1979, the date that the 1977 Panama Canal Treaty took effect. Much of the former Canal Zone area was transferred to Panama on that day. The Panama Railroad served as the new border in an area where it crosses Gatun Lake via a causeway, with the railroad bisecting Frijoles Island. The entire island transferred to exclusive Panamanian jurisdiction on 31 December 1999.[97][98]
The small middle island of Las Tres Hermanas ("The Three Sisters") off the Pacific coast of Panama City was split between the U.S. Panama Canal Zone and Panama by the Taft Agreement on 12 December 1904. The entire island was placed in the Canal Zone on 11 February 1915. Today the Cinta Costera lies on top of it.
Popes Folly Island in Passamaquoddy Bay between the United States (Maine) and Canada (New Brunswick) had been divided prior to the 1908 border treaty between the U.S. and Great Britain.[99][100]
The small Bogomerom Archipelago of islets in Lake Chad was formerly divided between Chad and Nigeria.[101] The water level of Lake Chad has historically varied a lot, but this level has fallen so low that these islets are now part of the mainland of Africa.
Subnationally divided islands
There are islands that lie across different provinces or states of the same country.
The tip of Cape Muzon was established as the "point of commencement" of the international boundary with Alaska in the Anglo-Russian Convention of 1825. A Court of Arbitration in 1903 ruled that Point "A" (54°39′43.993″N132°41′3.093″W) was the initial point of this boundary. Canada has accepted this as a demarcated boundary; however, the U.S. disputes that Point "A" is a boundary point.
Margedant, Udo; Thomas Ellerbeck (1991). Politische Landeskunde Mecklenburg-Vorpommern (in German). Mecklenburg-Vorpommern: Landeszentrale für politische Bildung. p.89.
Giosan, Liviu; Donenelly, Jeffrey P.; Vespremeanu, Emil; Bhattacharya, Janok P.; Olariu, Cornel; Buonaiuto, Frank S. (2005). "River Delta Morphodynamics: Examples from the Danube Delta"(PDF). River Deltas—Concepts, Models, and Examples (Special Publication No. 83). Society for Sedimentary Geology: 403–405. ISBN1-56576-113-8.
Jacques Boisvert. "Province Island". Retrieved 2006-11-04. It is the largest island in Lake Memphremagog, being 77 acres, of which 7 acres, are in the United States.
International Boundary Study No. 74, page 22. ""The frontier follows the creek down to Lake Onkamojarvi, intersects the small island of Siiheojansuusaai and proceeds in a straight line to the small island of Tossensaari."
"World Lakes Database: LAKE DRUKSIAI". International lakes environment committee. Archived from the original on 2007-03-12. Retrieved 2006-12-10. Number of main islands (name and area): Zamok (0.26 km2), Sosnovec (0.048 km2), Utovec (0.0088 km2) and 5 nameless islands.
The northern shore of Corocoro is on the open ocean, but it is not truly a sea island as the southern boundary is a freshwater channel. The island is claimed in its entirety by Venezuela. 8.517°N 60.083°W / 8.517; -60.083
Chowdhury, Sifatul Quader; Chowdhury, Masud Hasan (2012). "Char". In Islam, Sirajul; Jamal, Ahmed A. (eds.). Banglapedia: National Encyclopedia of Bangladesh (Seconded.). Asiatic Society of Bangladesh.
Office of the Geographer, Bureau of Intelligence and Research (1964-11-23). International Boundary Study No. 41: Greece – Turkey boundary(PDF). United States Department of State. p.7. Archived from the original(PDF) on 2009-03-16. Returning to the median of the Maritsa, [...] the boundary continues [...] to boundary marker No. 24 on the northern end of an island designated "Q". Thence, the boundary line extends a distance of 800.5 feet to marker No. 25 near the center, thence a distance of 1,804 feet to marker No. 26 on the southwestern extremity of island "Q".
A treaty between Great Britain and the United States providing for the more complete definition and demarcation of the international boundary between the Dominion of Canada and the United States. 1908. pp.1–3. hdl:2027/hvd.32044086241809.
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