A recursive island or lake, also known as a nested island or lake, is an island or a lake that lies within a lake or an island.^[1] For the purposes of defining recursion, small continental land masses such as Madagascar and New Zealand count as islands, while large continental land masses do not. Islands found within lakes in these countries are often recursive islands because the lake itself is located on an island.

Recursive islands

Islands in lakes

Only a few notable examples are given.

Islands in lakes on islands

There are nearly 1,000 islands in lakes on islands in Finland alone.^[6]

Islands in lakes on islands in lakes

Islands in lakes on islands in lakes on islands

Until 2020,^[15] Vulcan Point was an island that existed in Main Crater Lake on Volcano Island in Lake Taal on Luzon in the Philippines.^[16] Main Crater Lake evaporated during the 2020 Taal Volcano eruption,^[15] but the water in Taal Lake has returned and has a new island. Vulcan Point became a peninsula.^{[citation needed]}

Islands in lakes on islands in lakes on islands in lakes

Moose Boulder was claimed to exist in the seasonal pond of Moose Flats on Ryan Island in Siskiwit Lake on Isle Royale in Lake Superior in the United States.^[17] In 2020, an expedition to the island found that it is potentially a hoax, along with the aforementioned seasonal pond.^[18]

Recursive lakes

Lakes on islands

Only a few notable examples are listed.

Lakes on islands in lakes

Lakes on islands in lakes on islands

Lakes on islands in lakes on islands in lakes

Only one such lake is known.^{[citation needed]}