There are various methods by which islands are formed and the prime among them is the volcanic eruption.
When a volcanic eruption happens it releases lava and several other substances from the crater. In due course of time the lava cools down and it turn into a solid. And the accumulation of all these solids is what makes an island. But it is not a process that is being done in a year or two but takes millions of years to form an island. There are several examples of the formation of the islands through this method and the prime among them is the islands of Hawaii. In some areas of Hawaii you can still find the volcanic eruption going on and it may happen that the size of some islands get increased or some other island may also formed soon.
When a volcanic eruption happens it releases lava and several other substances from the crater. In due course of time the lava cools down and it turn into a solid. And the accumulation of all these solids is what makes an island. But it is not a process that is being done in a year or two but takes millions of years to form an island. There are several examples of the formation of the islands through this method and the prime among them is the islands of Hawaii. In some areas of Hawaii you can still find the volcanic eruption going on and it may happen that the size of some islands get increased or some other island may also formed soon.