Third Order Islands

Caitlin Dempsey

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The world has a lot of islands. There are about 900,000 official islands in the world and hundreds of thousands of unnamed islands.

In geographical terms, an island is any piece of land that is completely surrounded by water. Islands come in all sizes and shapes. There are landmasses completely surrounded on all sides that they aren’t technically islands but are continents — Australia is the most prominent example.

The largest island in the world that isn’t classified as a continental landmass is Greenland with an area of 822,700 square miles (2,130,800 kilometers). On the flip side, the smallest islands, like Landsat Island, are tiny rocks that jut up above the surface of the water.

In between these two extremes of areas are most islands. These islands can be quite complex geographically. One area of classification among islands is their order.

What are recursive islands?

Recursive islands are islands that contain bodies of waters such as lakes or ponds that have smaller islands in those bodies of water. This creates a nested or “recursive” pattern of islands within islands. It’s like a nesting doll but with islands.

What causes recursive islands to form?

The formation of lakes on islands requires specific geographical and climatic conditions. Often recursive islands are found in areas where the landscape has been formed by the effects of glacial movement. Glacial retreat leaves behind thousands of depressions that fill up with meltwater and rainfall.

Another geographic phenomenon that creates recursive islands is the collapse of volcanoes which forms a depression known as a caldera. The caldera is then filled in by water, create a lake around the remnant peak.

Understanding the Orders of Islands

First Order Island

This is a piece of land surrounded by a body of water.

A small rock island with some trees growing on the top of it.  The island is surrounded by water.
A first order island: A small rock island in the middle of Lake Superior. Photo: Scott Dwyer, USGS, public domain.

Second Order Island

If an island has a lake and there is another piece of land within that lake, that island is a second order island. This is popularly called “island in a lake on an island” or a sub-sub-island.

A satellite image of an island within an island
A second order island. Krenitzyn Peak located in Kal’tsevoe Lake on Onekotan Island. Satellite image: NASA, public domain.

Third Order Island

Should that island in a lake on an island also have a lake that has another island, this is a third order island. These islands are called “island in a lake on an island in a lake on an island.” A shorter way of referring to this type of an island is a  “sub-sub-sub-island.”

A diagram showing the different order of recursive islands.
A diagram showing the different orders of recursive islands. Diagram: Caitlin Dempsey.

World’s largest third order island

The largest third order island is an unnamed island found on Victoria Island in Canada’s Nunavut Territory. Victoria Island, one of over 36,000 islands in the Canadian Arctic Archipelago, is the the eighth-largest island in the world. Victoria Island contains an unnamed seahorse-shaped island that sits within a lake. That seahorse-shaped island also contains a lake. And within that lake lies a third order island that measures about 1,000 feet (300 meters) from east to west.

In 2007, island geographer Josh Calder was the first person to discover that this particular island in a lake on an island in a lake on an island is the world’s largest third order island after painstakingly reviewing Google Maps.

A satellite image of green areas and dark blue waters in Canada.
The world’s largest third order island on Victoria Island in Canada’s Nunavut Territory. Image: Landsat 8, NASA, public domain.

The third order island that disappeared and reemerged

Vulcan Point in the Philippines is one of the most famous of the “island in a lake on an island in a lake on an island.” Vulcan Point is a remnant of the old crater floor that juts out near the middle of Main Crater Lake on Volcano Island which lies in Taal Lake on the Luzon, the largest island in the Philippines.

A satellite image of an island with a lake filled crater in the middle.
Vulcan Point, a third order island in the Philippines. Photo: Landsat 8 satellite image, February 7, 2014, NASA, public domain.

In 2020, a volcanic eruption temporarily dried out Main Crater Lake. Taal Volcano eruption on January 12, 2020 and blanketed the entirety of Volcano Island in ash and evaporated the water that was in Main Crater Lake.

A satellite image of a small island covered in tan ash after an eruption with glowing lava in the middle.
The European Space Agency’s Copernicus Sentinel-2 captured this image on January 23, 2020 showing the after effect of the January 12, 2022 volcanic eruption of Taal. Image: ESA, CC BY 4.0.

Rainfall has since refilled the lake, allowing Vulcan Point to once again become a third order island.

A colorize 1911 originally black and white photography of a crater lake with a cloudy sky in the background.
A 1911 photograph of Taal Volcano with Vulcan Point, the third order island. The original black and white photography has been colorized. Photo: loc.gov, public domain.

More island geography

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About the author
Caitlin Dempsey
Caitlin Dempsey is the editor of Geography Realm and holds a master's degree in Geography from UCLA as well as a Master of Library and Information Science (MLIS) from SJSU.

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