Island – Concept, characteristics, origin and plastic islands

We explain what an island is, what types exist, their characteristics and how they are formed. Also, what are plastic islands.

The islands can be of very diverse origin, shape and topography.

What is an island?

An island It is a portion of land that is naturally surrounded by water, and that is smaller in extension than a continent, but bigger than an islet. The islands are very common in the world geography, and have different shape, topography and geological origin. When several of them are together in the same region of the ocean, they are known as an archipelago.

The separation of the islands from the mainland usually influences the life that develops on them, giving rise to endemic species that have evolved in isolation and independent of their continental counterparts. For many centuries, mankind’s maritime exploration consisted of searching for secret and mysterious islands.

In fact, the islands have been very present in the imaginary of humanity since ancient times. Entire countries consist of one or more islands grouped politically, and many of them were formerly used as prison destinations or as initiatory places in which to test the warriors of the tribe, who had to survive on their own.

In this way, the islands gained a prominent symbolic value in myths and literary stories of all times, generally as an unpublished place, where treasures and wonders can be found, but it can also be abandoned and isolated, as in the stories of castaways. In the texts of Ancient Greece the islands used to be populated by deities and mythological beings, such as the sorceress Circe or the daughter of the titan Atlas, Calypso.

Characteristics of the islands

In a general sense, the islands are characterized by the following:

  • They consist of a portion of land surrounded by water on all sides. This may mean that you are in the middle of the ocean, a river, or a lake or lagoon.
  • According to international standards of the Millennium Ecosystem Assessment must exceed 0.15 km2 surface area and be separated from a continent by at least 2 km of water. However, otherwise they have a very diverse topography, climate and geography, but
  • Very small islands are known as islets and they are rarely populated. Instead, when it comes to many islands together, they are referred to as one archipelago.
  • The largest island in the world is Greenland, with 2,175,000 km2 total surface area, and is located in the North Atlantic Ocean.

Formation of the islands

Islands are formed as a consequence of different geological processes. Some are due to volcanic and / or sedimentary activity, which slowly accumulates materials until they harden and form a solid territorial platform.

Therefore, in theory, it is not impossible to witness the appearance of new islands after major tectonic movements or large underwater volcanic eruptions. However, these processes usually occur in very long periods of time.

Other islands are due to historical changes in ocean water level, since the sea has not always been at the same level as we see it today. Increasing or decreasing water can cover or expose entire portions of the continental shelf, respectively, and thus create islands or, conversely, link them to the mainland.

Types of islands

island sedimentary types
Large rivers can create sedimentary islands, forming deltas.

The classification of the islands responds precisely to the mechanisms that led to their appearance. So we can talk about:

Continental islands. Those that are part of the continental shelf, and therefore have the same materials, the same textures and are located in the relative proximity of the coast, although separated from the mainland by extensions of water that are not too deep (200 meters deep). depth or less). This occurs when the ocean water level rises and submerges portions of land, “creating” islands by separating them from the rest of the continent. Examples of this type of island are:

  • The Malvinas or Falklands Islands, in the South Atlantic off the Argentine coast.
  • The island of Greenland, separated from North America by the Atlantic Ocean.
  • The British Isles, a territory of the United Kingdom, separated from Europe by the North Sea and the English Channel.

Volcanic islands. Those that are formed due to the eruption of underwater volcanoes, which pour magma and liquid rocky materials out of the subsoil, where they cool and solidify, settling until emerging from the water. They can be of three types: insular arches in subduction zones, mid-oceanic ridges, and intraplate hot spots. Volcanic islands are the youngest islands in geological terms, and they are not part of any continental shelf. They are examples of them:

  • The Antilles, a group of islands in the Caribbean Sea.
  • The islands of the archipelago of Hawaii, in the Pacific Ocean.
  • The Galapagos Islands, located in the Pacific off the Ecuadorian coast.

Mixed islands. Those that are the result of the combination of volcanic and continental processes, that is, that combine both previous types. They are examples of them:

  • The islands of the Aegean Sea, between Greece and Turkey.
  • The islands of Japanese territory.

Coral islands. Those that are formed in tropical and subtropical seas due to the accumulation of biological residues of corals: primitive marine organisms, whose calcareous shells are capable of reaching large proportions. When deposited on shallow underwater platforms or volcanic cones, they produce recognizable islands. Such is the case of:

  • The Maldives islands, about 1,200 islands located in the Indian Ocean, 450 km off the Indian coast.
  • The Los Roques archipelago, on the Venezuelan Caribbean coast.
  • The Chagos Archipelago, in the Indian Ocean, 500 km south of the Maldives.

Sedimentary islands. Those that occur due to the gradual accumulation of materials as a result of the flow of larger rivers, which drag gravel, mud or sand in large quantities. Where the current loses speed, these materials settle and an island begins to form, generally around the river delta. This occurs in the cases of:

  • The islands of the Orinoco delta, in eastern Venezuela.
  • The islands of the Ganges river delta in India.
  • The island of Marajó, at the mouth of the Amazon River, in Brazil, the largest in the world, with a size equivalent to Denmark.

River islands. Those that are formed from barriers in the central channel of a river, as its course changes historically, exposing flood-prone coastal ridges and platforms, such as sandbanks and marshy depressions. Such is the case of:

  • The island of Bananal, in Brazil, considered the largest river island on the planet.
  • The “ait”From the River Thames in England, such as Eel Pie Island in Twickenham.

Plastic islands

garbage plastic islands
Plastic islands can be made up of very small pieces.

Plastic islands, garbage islands or toxic islands are a recent and painful phenomenon, which is not due to natural geological processes, but to the lifestyle of human beings in the last century of their existence.

These are gigantic agglomerations of floating garbage that has been dumped into the sea by human societies and that, due to the action of the elements, its particles are reduced to small sizes, close to that of a grain of rice. For the most part they are made up of plastic and non-biodegradable materials.

These immense islands of garbage are formed due to the circulation of oceanic water, which gradually accumulates the floating microfragments in patches of variable extension. The largest of all varies between 710,000 and 17,000,000 km2 Of surface, larger than the territory of many countries, and is located in the heart of the Pacific Ocean.

The garbage contained in them is not only difficult to detect from the air and by means of radars, due to their small dimensions, but also gradually destroys the marine ecosystem.

Since plastic does not biodegrade, when ingested by animals it causes their death, and also obstructs the flow of plant species, preventing them from accessing sunlight. The mere existence of this type of phenomenon should be a reason to stop the consumption and manufacture of plastics throughout the world.