Island, the general term for islands, refers to a naturally formed land area surrounded by water and exposed at high tide, which can maintain human habitation or their own economic life.

The island has territorial sea, contiguous zone and exclusive economic zone. More than two islands are concentrated in a narrow area, which is called "island group". Larger island groups are called "islands" or "islands", and islands arranged in rows are called "islands". If all the territory of a country is located on one or more islands, it can be called an island country, or "island country" for short.

volcanic island

The volcanic island of Bird Island in Qinghai Lake was formed by the continuous eruption of submarine volcano, the gradual accumulation of magma, and finally exposed to the water. For example, the Hawaiian Islands are formed by a series of submarine volcanic eruptions, which are long and straight after emerging from the water.

Volcanic islands can be divided into two types according to their attributes. One is an ocean volcanic island, which has nothing to do with continental geological structure. The other is a volcanic island in the continental shelf or slope, which is related to the continental geological structure, but not the same as the continental island, and belongs to the transitional type between the continental island and sea island.