An island is a piece of land naturally surrounded by water, smaller in area than a continent but larger than an islet. Islands are very common in world geography, with different shapes, topographies and geological origins. When several of them are found together in the same area of the ocean, they are called archipelagos. geology explains how islands are formed.
For this reason, we are going to dedicate this article to telling you how islands are formed, what their characteristics and types are.
what are the islands
The separation of islands from the continents often affects the life that develops on them, resulting in endemic species that evolve independently of their continental counterparts. For many centuries, human exploration at sea has involved finding mysterious islands.
In fact, these islands have existed in the human imagination since time immemorial. The entire country consists of one or more politically grouped islands, many of which were previously used as prison destinations or as places to train tribal warriors who must survive alone.
In this way, the islands have acquired an outstanding symbolic value in mythology and literary stories of all times, often being an unprecedented place where treasures and wonders can be discovered, but also abandoned and isolated like stories of shipwrecks. In ancient Greek texts, the islands were once inhabited by gods and mythical creatures, such as the witch Circe or Calypso, daughter of the Titan Atlas.
Key features
In general terms, the islands have the following characteristics:
- They consist of a piece of solid land surrounded by water on all sides. This could mean that you are in the middle of an ocean, river, lake, or pond.
- According to the international standards of the Millennium Ecosystem Assessment, they must be more than 0,15 square kilometers in size and at least 2 kilometers away from the mainland. Beyond that, however, they are very diverse in topography, climate, and geography, but
- The very small islands are called islets and are rarely inhabited. Instead, when many islands are involved, they are called archipelagos.
- The largest island in the world is Greenland, with a total area of 2.175 million square kilometers, located in the North Atlantic Ocean.
how islands are formed
The islands are the result of different geological processes. Some are due to volcanic and/or sedimentary activities that slowly accumulate material until they harden and form solid territorial platforms.
So, in theory, it's not impossible for new islands to arise after a major tectonic shift or major underwater volcanic eruption. However, these processes usually take place over a long period of time.
Other islands are due to historical changes in sea levels, as sea levels are not always the same as what we see today. Rising or falling water can cover or expose entire parts of the continental shelf, respectively, forming islands or, conversely, connecting them to the mainland.
Types of islands
Large rivers can form sedimentary islands, forming deltas. The classification of the islands responds precisely to the mechanisms that led to their appearance. So we can talk about:
mainland island. They are parts of the continental shelf, and therefore have the same material, the same texture and are located relatively close to the coast, although they are separated from the continent by not too deep waters (200 meters deep). or less). This happens when the sea level rises and floods parts of the land, "creating" islands by separating them from the rest of the continent. Examples of these types of islands are:
- The Malvinas or Malvinas Islands, located in the South Atlantic Ocean off the coast of Argentina.
- Greenland, separated from North America by the Atlantic Ocean.
- The British Isles is a British territory separated from Europe by the North Sea and the English Channel.
Volcanic island. Volcanic rocks were formed as a result of underwater volcanoes pouring magma and liquid rock materials from underground, where they cool and solidify until they emerge from the water. They can be of three types: island arcs in subduction zones, mid-ocean ridges, and intraplate hot spots. The volcanic islands are geologically the youngest islands and do not belong to any continental shelf. They are an example of this:
- Antilles, a group of islands in the Caribbean Sea.
- An island in the Hawaiian archipelago, located in the Pacific Ocean.
- Galapagos Islands, in the Pacific Ocean off the coast of Ecuador.
mixed island. They are the result of a combination of volcanic and continental processes, that is, a combination of the two previous types. They are an example of this:
- Island in the Aegean Sea, between Greece and Turkey.
- Islands in Japanese territory.
Coral Island. Those that form in the tropical and subtropical oceans as a result of the accumulation of coral biological debris: primitive marine organisms whose calcareous shells are capable of reaching a large proportion. When deposited on shallow underwater platforms or volcanic cones, they create recognizable islands. details as follows:
- Maldives archipelago, about 1.200 islands are located in the Indian Ocean, 450 kilometers from the coast of India.
- Los Roques Islands, off the Caribbean coast of Venezuela.
- The Chagos Islands are located in the Indian Ocean, 500 kilometers south of the Maldives.
sedimentary island. These arise from the gradual accumulation of material due to the flow of larger rivers that carry gravel, mud or sand in large quantities. When the flow of water decreases, the material settles and begins to form an island, usually around a river delta. This happens when:
- Islands in the Orinoco Delta in eastern Venezuela.
- Islands in the Ganges delta of India.
- Marajo Island, at the mouth of the Amazon River in Brazil, is the largest island in the world, the size of Denmark.
river islands. Those formed by obstructions in the central river channel, as history changed, exposed submersible coastal ridges and platforms as staging areas and marshy depressions.
I hope that with this information you can learn more about how islands are formed and what their characteristics are.