その理由は次のとおりです。
* 火山諸島： Many underwater mountains are formed by volcanoes. When the volcano erupts and builds up enough material, it can eventually breach the surface of the ocean, forming an island.
* Continental Islands: Some underwater mountains are part of the continental shelf. As sea levels drop or the land mass rises, these underwater mountains can become exposed, forming islands.
Let me know if you'd like to know more about the different types of islands!
