a string of islands can simply be called an archipelago, I used to forget all the time too! :)
reword the question to get a better answer
A chain, string or group of islands is called an archipelago.
an archipelago
A string or group of islands is called an archipelago.
Japan is a string of island called kuril. The islands stretches around 1,300 km.
It is called an archipelago.
A string of islands formed from a collision of two oceanic plates is called an island arc.
A cluster or chain of islands is called an "archipelago", which specifically applies to islands created by the same volcanic or tectonic source.
Archipelago
Volcanoes at the boundaries where two oceanic plates collide will create a string of islands called an archipelago. An archipelago is also linked by land areas that are below the sea.
An "archipelago".
Known as an archipelago - an extensive group if islands
The Hawaiian Islands could be described as string of islands. A random string of notes does not make a tune.