An island may be described as such despite the presence of an artificial land bridge, for example Singapore and its causeway, or the various Dutch delta islands, such as IJsselmonde. Some places may even retain “island” in their names for historical reasons after being connected to a larger landmass by a wide land bridge, such as Coney Island. Conversely, when a piece of land is separated from the mainland by a man-made canal, for example the Peloponnese by the Corinth Canal, it is generally not considered an island.
A desert island is an island with no people. Typically, a desert island is denoted as such because it exists in a state of being deserted, or abandoned. An arid desert climate is not typically implied; one dictionary uses the phrase ‘desert island’ to illustrate the use of ‘desert’ as an adjective meaning “desolate and sparsely occupied or unoccupied”. According to another, “A desert island is a small tropical island, where nobody lives or an undiscovered island.
Oceanic Islands
Oceanic islands are ones that do not sit on continental shelves. The vast majority are volcanic in origin. The few oceanic islands that are not volcanic are tectonic in origin and arise where plate movements have lifted up the deep ocean floor to above the surface. Examples of this include Saint Peter and Paul Rocks in the Atlantic Ocean and Macquarie Island in the Pacific.
One type of volcanic oceanic island is found in a volcanic island arc. These islands arise from volcanoes where the subduction of one plate under another is occurring. Examples include the Aleutian Islands, the Mariana Islands, and most of Tonga in the Pacific Ocean. Some of the Lesser Antilles and the South Sandwich Islands are the only Atlantic Ocean examples.
Tropical Islands
There are approximately 45,000 tropical islands on Earth. Among coral tropic islands for example are Maldives, Tonga, Nauru and Polynesia. Granite islands include Seychelles and Tioman. The socio-economic diversity of these regions ranges from the Stone Age societies in the interior of Madagascar, Borneo or Papua New Guinea to the high-tech lifestyles of the city-islands of Singapore and Hong Kong. International tourism is a significant factor in the local economy of Seychelles, Sri Lanka, Mauritius, Réunion, Hawaii and the Maldives, among others.
Natural vs Artificial Islands
Most of the Earth’s islands are natural and have been formed by tectonic forces or volcanic eruptions. However, artificial (man-made) islands also exist, such as the island in Osaka Bay off the Japanese island of Honshu, on which Kansai International Airport is located. Artificial islands can be built using natural materials (e.g., earth, rock, or sand) and/or artificial ones (e.g. concrete slabs or recycled waste). Sometimes natural islands are artificially enlarged, such as Vasilyevsky Island in the Russian city of St. Petersburg, which had its western shore extended westward by some 0.5 km in the construction of a new sea terminal.
Source: Wikipedia