Page "Archipelago" Paragraph 6

By its geological origin, islands forming archipelagos can be referred to as oceanic islands, continental fragments and continental islands.

Oceanic islands are mainly of volcanic origin.

Continental fragments correspond to land masses that have separated from a continental mass due to tectonic displacement.

Finally, sets of islands formed close to the coast of a continent are considered continental archipelagos when they form part of the same continental shelf so islands are just exposed continental shelf.