Archipelago – Concept, formation, types and examples

We explain what an archipelago is, how the islands that compose it are formed, their types and examples from different parts of the world.

The islands that form an archipelago are usually very numerous.

What is an archipelago?

In geography, the archipelago is called a set of islands grouped in a relatively small maritime portion, that is, not too distant from each other, although they tend to be very numerous. In addition to the islands themselves, in the archipelagos there may also be other types of islets, keys and reefs.

The term archipelago comes from the Greek arch (“Superior”) and pelagos (“sea”). It was the term used in classical antiquity to refer to the Aegean Sea (“upper sea” or “main sea”), since it was full of islands. In later times it came to be used to call the islands of the Aegean Sea, and by extension, the groups of islands that resemble them.

Archipelagos are numerous in the world, although most are concentrated in Southeast Asia and between the northeast coast of the United States and Greenland.

Why are islands formed?

Many archipelagos include large expanses of coral.

The islands are the product of different geological processes, that is, of the changes that the earth’s crust undergoes over time. Just as continents are formed, islands of different types are also formed. In that sense, we can talk about:

  • Continental islands, which have the same origin as the rest of the continent, and are in fact connected to it by the continental shelf, although they are separated on the surface by a shallow body of water (no more than 200 meters deep). Many of them were part of the continent itself in past times when the ocean water level was lower.
  • Volcanic islands, which are the result of the action of underwater volcanoes, that is, of the deposition of subterranean materials on the surface, where they cool and become solid soil. They are the most recent type of islands of all.
  • Mixed islands, in which seismic or volcanic action is combined with the continental plate itself, giving rise to a combination of the two previous cases.
  • Coral islands, usually flat and low, formed due to the accumulation of coral material in a shallow underwater platform, usually of the volcanic type.
  • Sedimentary islands, that is, the result of the accumulation of sediments, generally at the mouth of large rivers that carry significant amounts of sand, gravel, mud and other materials, which over time compact and solidify. They generally form a delta at the mouth of the river.
  • River islands, which are formed in the middle of the rivers due to changes in their course or their channel, which allow the emergence of solid ridges, shoals or floodplain swampy depressions.

Types of archipelagos

Similarly, archipelagos are classified according to their geological origin, but in this case only two categories are differentiated:

  • Oceanic archipelagos, made up of islands generally of volcanic origin, and that are not part of any continental plate.
  • Continental archipelagos, made up of continental islands, that is, islands that are part of a continental plate, although they are separated from it by shallow extensions of water.

Examples of archipelagos

galapagos archipelago ecuador
The Galapagos Islands are home to the second most important marine reserve in the world.

The following are examples of archipelagos in different parts of the world:

  • The Hawaii Archipelago, located in the North Pacific and belonging to the United States, is made up of nine islands and atolls, the largest of which is precisely the Island of Hawaii. It is the most isolated archipelago on the planet.
  • The Galapagos Islands, belonging to Ecuador and located 1000 km from its coasts, in the Pacific Ocean. It is made up of thirteen islands of volcanic origin and another 107 small islets, which are the second most important marine reserve on the planet, declared a World Heritage Site by UNESCO in 1978.
  • The Canary Islands archipelago, located on the northwest coast of Africa and politically belonging to Spain, it is made up of eight islands, five islets and eight rocks. It is a group of volcanic islands that sit on the African continental plate, and are part of the natural region of Macaronesia.
  • The Chiloé archipelago, located in the south of Chile, is made up of a large island (Isla Grande de Chiloé) and a significant number of smaller islands, distributed in groups of three and four around the largest. This archipelago corresponds to the foothills of the Chilean coast mountain range, submerged except for its peaks.
  • Los Roques archipelago, belonging to Venezuela and located 176 km from its capital city, in the Atlantic Ocean, and is where the largest coral reef in the Caribbean Sea is located. It has an unusual form of atoll, more common in the Pacific Ocean, and comprises about 42 keys with an internal lagoon and 1500 km of coral reefs.
  • The Malay Archipelago, also called Insulindia, is the insular region of Southeast Asia, located between the Indian and Pacific Oceans, and covering totally or partially the territory of seven countries: Brunei, the Philippines, Indonesia, Malaysia, Papua New Guinea, Singapore and East Timor. There are more than 25,000 different islands, grouped into three groups: the Sunda Islands, the Moluccas and the Philippine Islands.